Sustainable Water Resource Management to Achieve Net-Zero Carbon in the Water Industry: A Systematic Review of the Literature

Abstract

With water scarcity becoming worse, and demand increasing, the urgency for the water industry to hit net-zero carbon is accelerating. Even as a multitude of utilities have pledged to reach net-zero by 2050, advancing beyond the energy–water nexus remains a heavy lift. This paper, using a systematic literature review that complies with Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA), aims to propose sustainable water resource management (SWRM) strategies that may assist water utilities in decarbonizing their value chains and achieving net-zero carbon. In total, 31 articles were included from SCOPUS, ResearchGate, ScienceDirect, and Springer. The findings show that water utilities are responsible for 3% of global greenhouse gas emissions and could reduce these emissions by more than 45% by employing a few strategies, including the electrification of transport fleets, the use of renewables, advanced oxidation processes (AOPs) and energy-efficient technologies. A broad-based case study from Scottish Water shows a 254,000-ton CO₂ reduction in the period since 2007, indicative of the potential of these measures. The review concludes that net-zero carbon is feasible through a mix of decarbonization, wastewater reuse, smart systems and policy-led innovation, especially if customized to both large and small utilities. To facilitate a wider and a more scalable transition, research needs to focus on development of low-cost and flexible strategies for underserved utilities.

1. Introduction

Water scarcity worldwide is becoming an increasing concern due to rapid population growth, urbanization, underinvestment in water infrastructure, and climate change [1]. Water is an essential human right and 1.1 billion people do not have ready access to safe drinking water and over 2.7 billion experience water shortages every month [1]. Only approximately 3% of the Earth’s water is fresh, with much of that tied up in glaciers and other untouchable sources [1,2,3]. In this context, sustainable water resource management (SWRM) has been considered to face the entire scope of water availability and the protection of environmental ecosystems. It places a premium on equitable trade-offs between biodiversity, infrastructure development, and water resources and ensures that natural resources are not exploited [2,3,4], and it is also in line with the United Nations’ declaration about safe water and sanitation.

For water operators, SWRM entails ensuring that water supply and wastewater systems are adequately designed and operated in accordance with environmental, social, and economic requirements [4,5]. In view of fragile water resources in the face of climate stress, this approach is becoming more and more pertinent. Climate change exacerbates drought, changes the composition of rainfall, and undermines water quality; meanwhile, utilities represent around 3% of global greenhouse gas emissions [5,6]. For example, in the United Kingdom, the water companies contribute over two-thirds of the gases generated during industrial process and waste reclamation practices [7]. These facts underline the crucial importance of coordinated solutions to water scarcity and emissions cuts.

Net-zero carbon is proving to be a holistic response to the climate impact of the water industry. It focuses on reductions in greenhouse gas emissions throughout the water cycle, from water production to wastewater treatment, via the application of renewable energy, reductions in waste, increasing efficiency, and incorporating green technologies [3,6,8]. Many countries have signed targets: the United Kingdom has pledged to achieve net-zero carbon by 2050, Australia before 2035, and Portugal by no later than 2030 via the Águas de Portugal Energy Neutral Plan [3,4,9,10].

The relationship between water and energy that serves as the basis for decarbonization challenges, has a dual-sided resource dependence: water facilities consume 4% of global electricity annually, where energy makes up 30–60% of the operational cost of utilities—and goes up to 75% in desalination-reliant areas [7,11,12]. On the other hand, energy production represents 15% of global freshwater consumption, where with thermoelectric cooling only, 100–300 L are needed to generate 1 kWh [13,14]. Climate stressors are exacerbating this convergence; in arid regions, such as Mexico City, the extraction of groundwater requires 2–3 times as much energy per volume than surface sources [10], and utilities are forced into 25–40% cost overruns to obtain rationed supplies of scarce water during droughts [9,15]. Therefore, reconciling such interdependencies is essential as water security and emission reduction are to be concurrently achieved.

Net-zero carbon in the water sector (and in any sector) cannot be achieved unless all three types of emissions are tackled. Scope 1 emissions are direct emissions from operations such as transport and waste treatment [16], which can be mitigated through electrification and on-site renewable energy deployment. Scope 2 emissions from purchased electricity are problematic because of a lack of control over external grids [7,8,12] but can be managed by investing in distributed renewable systems [12,16,17]. Scope 3 emissions (connected to secondary suppliers) represent an even greater challenge, and collaboration is necessary with vendors following low-carbon practices and utilizing energy-efficient machinery [12,16,17,18].

Standard emissions profiles for water services elucidate decarbonization targets: Scope 2 is the overwhelming contributor (60–80% of total emissions) mainly due to electricity use for pumping and treatment [5,19]. Scope 1 amounts to 15–30% due to fleet fuels, sludge digestion (CH₄), and wastewater-based N₂O [5,17,18]. Scope 3, at 5–15%, involves the embedded emissions of chemicals (e.g., coagulants), construction materials and outsourcing services [16,20]. European wastewater utilities, e.g., report 75% Scope 2, 20% Scope 1 and 5% Scope 3 emissions [5], while for the arid-region systems the share of Scope 1 emissions (30–40%) is higher due to diesel-powered pumping [10].

Even after addressing third party-related challenges, water utilities face more challenging Nitrous Oxide (N₂O) emissions. N₂O is a more potent greenhouse gas usually generated during wastewater treatment, especially during microbial processes [12]. Water utilities may not achieve their net-zero carbon targets without addressing the N₂O problem [3,12,18]. Utilities can address this challenge by closely monitoring N₂O using the latest technologies, including AI (artificial intelligence) deep learning systems [21].

Another dilemma is represented by nitrous oxide (N₂O) because it is a powerful greenhouse gas produced during the treatment of wastewater [12]. To control the discharge of N₂O, advanced monitoring technologies including AI-based devices and TDLidar-based gas sensors established by Quantum Light Metrology (QLM) [2,12], should be implemented, as should more sophisticated approaches to industrial treatment, e.g., advanced oxidation processes (AOPs) [9,10,12,18]. Such mitigation strategies also need to address longstanding barriers, such as the level of financial investment required, issues of data privacy, technological heterogeneity, and technological skillset gaps amongst the workforce [12,18].

Considering these challenges and opportunities, this paper aims to research and suggest SWRM strategies that will facilitate the journey of water utilities to net-zero carbon. This paper concentrates on net-zero carbon for water utilities, separating this from carbon neutrality (looking only at CO₂), against net-zero carbon for the water sector, which includes all greenhouse gases (GHGs) [22,23]. A systematic literature review (31 peer reviewed articles) was conducted and sustainability best practices, Biogas recovery, AOP, and digital water monitoring, as possible solutions for reducing CO₂ emissions while maintaining an effective water service provision, were found. These findings provide a pragmatic basis for utilities, industry, and policymakers who are interested in developing a climate-resilient, low-carbon water sector.

2. Sustainable Water Resource Management

SWRM is a critical strategic approach to one of the defining challenges of the 21st century: how to expand water supply in the face of increasing global demand and at the same time decrease greenhouse gas emissions to mitigate climate change [24,25]. While SWRM is frequently referred to in the context of sustainable development, this concept has not yet been effectively put to work at the practical level. This section elaborates the key issue, that SWRM is not a pure technical fix but a multi-scale challenge that involves innovation, governance, natural resource conservation, and equity. In order to reinforce this main message and make it clearer, the section here uses thematic subheadings.

While SWRM remains a relatively common term, the mechanisms to achieve it have not been fully explored. Only a few municipalities and water utilities have aligned their missions and visions with global interests to reduce carbon emissions within the water supply chain while increasing the supply to meet current and future needs [2,4,12]. There is no doubt that a growing population globally continues to put additional pressure on water utilities and even municipal wastewater treatment plants to ramp up their productivity even if it sends more greenhouse gases into the atmosphere [2,8,12,18,26,27]. SWRM is determined to reverse this course by using the latest technologies to assist water utilities and municipalities in maintaining energy efficiency in their supply chains, reducing greenhouse gas emissions, and ensuring there is sufficient water to serve their customers around the globe [18,27,28].

Roest et al. [15] describe SWRM as a multi-faceted approach aimed at solving both supply inadequacies and carbon emissions. While these could be two opposing objectives, they underscore the gravity of current and future challenges facing water operators [15,28]. Most water utilities globally are concerned about the risk of running out of their water supply due to prolonged drought situations, pollution, and climate change [12,15,28]. On the other hand, increasing water supply means more energy is required per unit volume, resulting in higher carbon emissions from the water sector [15,26]. Unless a smart technology is developed to address this quandary, it may take longer for water operators to meet their sustainability goals, much less their net-zero targets.

2.1. Utility Ambitions in the Context of Climate Pressure and Rising Demand

The need to produce more water with lower carbon emissions drives more water operators to seek innovative solutions and technologies [2,3,15]. Many water utilities around the globe have established their carbon emissions goals to achieve net-zero carbon over the next 5 or 10 years [29]. An organization known as Global Water Intelligence (GWI) has been tracking more than 87 water utilities serving more than 255 million people globally [15,28,29]. Of these companies, more than 26 have joined the race to achieve net-zero carbon by 2035 [15,29]. Beijing Drainage Group (BDG) is among the water utilities with net-zero carbon ambitions [29,30,31]. The company has joined other global water operators in decarbonizing its supply chain while optimizing water supply to meet current and future needs.

Water operators contribute about 2 percent of global greenhouse gas emissions, almost level with the global shipping industry [11]. While the need to reduce carbon emissions has never been more urgent and vital, the world’s growing population needs more water for domestic, industrial, and commercial purposes [12,15,29]. This presents a unique situation where water utilities must maintain or increase their water supply while trying to generate less greenhouse gases across their supply chain [16,30]. With the demand for water skyrocketing, the pressure to reduce greenhouse emissions has never been this widespread and necessary [31]. Climate change remains a significant threat to water utilities because it limits their supply while putting more pressure on natural resources, almost pushing them to complete depletion [15,31]. Increased drought, pollution, and other natural disasters have also left millions of people globally without access to clean and safe water for domestic, agricultural, and industrial consumption [32,33].

The global population is set to surpass the 9-billion mark by 2050 or even earlier. This significant rise in population means the world cannot rely on the current food and water supply for sustainability [2,4,12,15]. Baubekova et al. [30] found that the world will require about 45% more food and 56% more water as its population crosses the 9-billion mark. Water utilities should increase their supply by more than 50% over the next 10 years to meet this growing demand [12,15,30,31]. Wastewater treatment provides a crucial opportunity for water operators to meet their global demands [34]. However, the massive generation of greenhouse gases such as CH₄ and N₂O should be addressed to make the industry more sustainable.

2.2. Nature-Based Solutions and Integrated Management for Sustainable Water Supply

Apart from wastewater treatment, another SWRM mechanism that has proven more effective at enhancing water supply is integrated water resource management (IWRM). Unlike wastewater treatment, IWRM focuses on balancing the water supply and the need to prevent the depletion of natural sources, while maintaining healthy ecosystems. According to Sulaiman et al. [31], IWRM achieves this goal by connecting or integrating various water consumption sectors, including agriculture, domestic, and industries. This provides a more transparent database that can be tracked across cities and villages to ensure needs are met while reducing potential damage to the surrounding ecosystems [28,29,30]. Water production and supply can only remain sustainable if a balance between demand and consumption is reached [2,12,31]. The current fear remains the risk of excessive demand against limited supply, putting water resources at great risk of depletion.

The proper management of watershed areas has also received growing support from governments and researchers as the next facet of sustainable water supply. Watersheds or catchment areas face increasing threats from lumber companies, mining companies, farmers, and settlers [8,9,12,29]. The most severe among these threats is prolonged droughts, which continue to disturb the water cycle, leaving more catchment areas exposed to dryness [29,35]. The Amazon is one of the largest water catchment areas globally. However, the Amazon itself has never been spared from increased and potentially illegal activities such as timber harvesting and mining [35]. Almost 20% of the Amazon biome has been lost due to increased commercial interest within the rainforest [12,34,35]. It is even estimated that more than 27% of the rainforest will be gone by 2030, potentially affecting rainwater patterns globally.

Besides increasing water supply, the catchment areas also provide natural grounds for carbon offsetting projects. As companies struggle to reduce their carbon emissions, a growing trend among global supply chains involves compensating for greenhouse gas emissions by investing in projects that reduce carbon footprints [6,12,16]. Trees in major rainforests such as the Amazon provide natural grounds for reducing excess carbon dioxide in the atmosphere by converting the gas into useful nutrients and supporting their growth [17,35]. Some companies also compensate for their negative activities by planting trees for land restoration in places devastated by large-scale timber harvesting or mining activities [12,35]. The call to protect rainforests has never been more crucial, especially in a climate change era with increased calamities and water scarcity.

According to Pekmez [34], another crucial SWRM that is often ignored is the restoration of natural water sources to ensure they continue to provide sufficient and safe water for domestic and commercial purposes. Rivers, lakes, and wetlands are crucial natural water sources often ignored or even polluted by major corporations [9,10,29]. Pollutants from industrial and domestic waste contribute more than 60% of surface water contamination [29]. According to Du Plessis [35], more than 80% of industrial effluents and domestic wastewater are often discharged into nearby rivers and lakes, causing massive pollution and endangering aquatic life. Protecting natural water sources may increase the water supply of national grids by more than 20% [35]. Regularly assessing water quality may help in the early identification of potential problems and enable timely interventions.

Governments should establish protected areas to avoid the pollution of natural water sources. This may include criminalizing tree harvesting near water sources and discouraging major corporations from disposing of their chemical waste in nearby creeks, rivers, or lakes [7,17,31]. More than 40 percent of major global corporations provide regular reports regarding their annual water conservation efforts to enhance water supply [31]. Coca-Cola, for instance, is protecting natural water sources by collecting about 70 to 75 percent of their plastic water bottles annually [34]. This helps reduce the volume of plastic water bottles that end up at the bottom of lakes or seas, where they significantly affect aquatic life [35,36,37]. Moreover, most corporations also help in restoring degraded ecosystems, including areas damaged by mining activities, erosion, flooding, and other natural disasters.

Smart water systems are another growing SWRM mechanism used by municipal authorities and water utilities to predict water demand, identify leaks, and monitor water levels across their systems [31]. Smart water meters, for instance, provide real-time updates to help monitor water consumption and demand across these systems [7,8,31]. Smart meters also help accurately predict demand and ensure there is sufficient supply. Apart from smart meters, water utilities may also use sensors and monitoring systems to enhance the early detection of potential problems to prevent massive leakages [3,4,5,9,30]. With advanced algorithm systems, water utilities, and municipalities can prevent massive losses due to leakages through prompt detection and timely repairs to avoid losses [35]. In addition, predictive models such as demand forecasting have enabled water utilities and even municipalities to optimize water distribution by channeling more water to places where they are needed most [15,29]. This avoids the under- or oversupply of water, especially when the need to minimize carbon emissions within the supply chain is a key priority.

While sustainability remains a top priority for water utilities and municipal wastewater treatment facilities, limited funding and high initial costs remain significant barriers for many water operators [10,34]. Various smart water solutions require significantly high initial investments in both infrastructure and technology. The infrastructure cost mainly covers smart tools such as sensors, predictive devices, pipes, and power facilities [5,6,9]. Technology costs mainly cover smart solution systems and data analytics tools. For smaller water utilities with limited resources, achieving the desired sustainability in water supply chains remains a significantly difficult task [15,17]. In addition, some of the larger corporations cite high upfront costs as major factors delaying their investments in sustainable solutions [12,29,30]. The significantly higher initial cost also makes it difficult for water operators to maintain profitability and expand their activities in areas where the water supply is still inadequate and unreliable.

Even if the high upfront cost is met, water operators may still struggle with data security and privacy challenges. Collecting large amounts of data from customers and suppliers means there is a need for stronger security measures to protect sensitive data from potential cyberattacks [31]. Water operators can also draw lessons from the 2024 incident where the company American Water in the United States of America suffered a major cyberattack, affecting millions of customer accounts [36]. Most consumers using the MyWater app were logged out of their accounts remotely by the cybercriminals and could not access the services they needed from the company [36]. The cyberattack, which went unabated until 3 October 2024, highlights potential vulnerabilities that may expose sensitive data to potential cyberattacks [36]. Most of the targeted data included payment details and credit card information that can be used to commit other crimes, including wire fraud and credit card fraud.

Water operators may also have to wait for longer until there are sufficient skills to develop and run their smart water systems. The emerging skill gaps in the water sector also make it difficult to implement smart technologies to save clean water from potential depletion [8,12,31]. SWRM requires significant skills to develop the required infrastructure and make the technologies available for wider global operations [35,37]. However, a significant challenge that may delay the journey to sustainable water supply is an industry with inadequately trained personnel to provide the required services [12,35,37]. Recent data shows that the global skill gap is mainly attributed to the increased changes in water demand that have forced most operators to seek more sophisticated solutions to meet the needs of their customers. Roach [37] believes that water operators can overcome this challenge by rolling out training courses and programs to their current workforces to help them participate in developing and implementing smart water technologies.

Addressing interoperability challenges also remains a significant requirement to achieve sustainability in water supply chains. The problem mostly occurs due to incompatible systems within the water utility infrastructure [15,37]. Integrating smart water solutions with devices within the water utility infrastructure enhances efficiency in data flow and supports prompt and proactive decision-making [12,35,36,37]. Most smart technologies are designed to provide real-time changes in data to enable operators to make timely and effective decisions [37]. However, outdated software and incompatible hardware within the water systems may cause major delays in data flow and create unnecessary data silos. Kehrein et al. [38] argue that this challenge can be addressed through the regular assessment and updating of these systems to remove outdated software or hardware, leading to smooth and more efficient data sharing.

2.3. Key Mechanisms for Achieving Net-Zero Carbon

A net-zero carbon water sector remains a significant goal for global water utilities and municipal wastewater treatment facilities. However, achieving a net-zero carbon and carbon-neutral water sector begins with addressing the energy–water nexus [15,31,38]. The term water–energy nexus highlights the difficulty of reducing carbon emissions while increasing water production and supply. Water utilities’ main challenge is the expanded possibility of adding more greenhouse gases to the atmosphere whenever they try to increase their production [38]. Energy demand often doubles or triples with increased water production, which releases more greenhouse gases into the atmosphere [38,39]. Several mechanisms, including innovative pathways, have been developed to help water utilities reach their water production targets without emitting more carbon into the atmosphere [27,37,38,39]. However, the key pathways to a net-zero and carbon-neutral water industry remain wastewater treatment, sustainable energy, and water conservation [40].

Wastewater reclamation, treatment, and reuse address the water–energy impasse by reducing the pressure on natural water sources while encouraging water utilities to transition to low-emission energy sources [18]. Energy efficiency remains an important goal for wastewater treatment plants because it lowers production costs while reducing carbon emissions [26]. Several strategies have been developed to help water utilities achieve energy efficiency. Key examples include variable-speed pumps (VSPs), smart monitoring, and energy recovery systems. VSPs enable water utilities to adjust their output to match demand, leading to significant energy savings [8,12,28]. Unlike the traditional fixed energy pumps, water utilities can increase pumping when the demand is high and reduce it to match falls in demand [29]. This also prevents wear and tear on equipment while enhancing process controls. Energy recovery systems ensure minimal waste by converting harvested output power into an input to support another process within the facility [34]. Smart monitoring helps detect potential increases or decreases in demand and adjusts pumping and energy use to match consumer behavior.

Apart from energy efficiency, wastewater treatment provides sufficient water to be recycled back into circulation, significantly reducing pressure on natural sources. Wastewater reuse helps provide more water for non-potable purposes such as irrigation, industrial cooling, lawn maintenance, and other purposes [35]. According to a study conducted by Columbia University, cities use more than 9 billion gallons of water per day on regular lawn maintenance [34,38,39]. Moreover, 30 to 60 percent of urban fresh water is often used for lawns. Wastewater reuse may help free up more than 9 billion gallons of freshwater that would have been used to water lawns [12,29]. This may free up huge volumes of water and reduce pressure on natural resources. Wastewater reclamation also helps reduce toxins from industrial effluents and domestic waste often discharged into rivers or nearby lakes.

Another sustainable water management option that may speed up the achievement of net-zero carbon is greywater recycling. Most water from domestic and commercial sources is rarely recycled even though it contains fewer toxins or persistent organic pollutants [15,30]. Greywater recycling provides more ways of converting wastewater for useful purposes such as irrigation and toilet flushing [30]. Wastewater from sinks, laundry machines, bathtubs, and showers can be converted into useful purposes through greywater recycling [37]. Besides making more water available for reuse, greywater recycling helps increase awareness about water conservation in homes and commercial facilities [38]. The growing wastewater load is a problem that requires increased awareness to help people understand what they can do at home to boost water availability while minimizing waste.

Sustainable energy is another crucial pathway to achieving net-zero carbon in the water industry. Transitioning to renewable energy sources such as solar power may help water utilities lower their carbon emissions while reducing their overall production costs [39]. Scottish Water, for instance, is one of the water utilities demonstrating how transitioning to renewable energy has helped maintain energy efficiency while lowering carbon emissions [39,41]. Scottish Water generates about 8 megawatts of photovoltaic power per site using solar panels installed across its 42 sites. It has lowered electricity purchases by £1.2 M annually, while lowering grid reliance by 15% [39,42]. Operational savings go beyond energy use; smart leak detection systems can decrease maintenance costs by up to 20% [43]. In combination, these actions have abated 254,000 tons of CO₂ since 2007, while furthering future financial stamina [42].

Water utilities can also implement energy storage solutions such as batteries and pumped hydro to ensure sufficient energy supply, especially during peak hours when the energy demand almost triple what the company uses during off-peak hours [41]. Wastewater treatment facilities are known for their high energy consumption and can sometimes exceed their daily targets during peak hours [14,44]. Using energy storage tools such as batteries, water utilities can ensure a steady power supply while reducing pressure on the national grids. According to Van Loosdrecht et al. [14], water utilities should also consider other mechanisms, such as energy recovery systems, to generate sufficient power to run their operations. Energy recovery systems such as energy recovery ventilators (ERVs) can generate power using steam from cooling equipment [14,34,44]. This mechanism ensures energy is transferred from one form to another, reducing the overall cost of the water treatment facilities.

Achieving net-zero carbon also demands a disciplined approach where water utilities account for their consumption and adjust accordingly to avoid waste and excessive energy consumption. One of these conservation approaches includes implementing robust leak detection and repairs to minimize water losses across the networks [45]. Massive water losses often occur due to poor assessment and the detection of cracks within the transportation pipes across the distribution network [14,41,44,45]. A robust detection system involves using smart devices to monitor the pipes in real-time to identify potential weaknesses that can cause massive losses. Besides the smart detection of leakages, water utilities may also implement a demand management approach using water-efficient appliances [44]. A demand-driven approach ensures water is produced and pumped across the distribution networks based on customer orders [14]. All these conservation approaches are designed to minimize energy use across the water distribution networks and reduce carbon emissions [45]. As discussed in this section, the water industry can lower its current four-percent energy consumption by adopting various conservation and sustainable energy mechanisms.

In terms of accelerating the journey to net-zero carbon, it is also important to understand the synergy effects of various SWRM mechanisms. IWRM, smart water systems, and watershed protection are not isolated strategies but inter-related building blocks, which are mutually reinforcing processes that can reduce emissions and increase resilience [46]. IWRM allows a coherent strategy to be developed to reconcile water use between sectors whilst maintaining ecologically satisfactory flows; it helps align demand-side and supply-side management across urban, rural, and industrial systems [47]. Paired with intelligent water systems—which incorporate real-time monitoring sensors, automatic leak detection, and predictive analytics—this can help utilities better distribute water, limit losses, and lower energy usage, thereby directly cutting emissions from water management and transport. Watershed protection works in concert with these actions to protect upstream ecosystems, preserve rivers’ natural flow, and maintain carbon stores in forests from conservation and reforestation [48]. Preserving catchment areas not only enhances water quality and reduces the burden on treatment but aids carbon offset projects as part of the strategy to achieve net-zero carbon [22]. These SWRM approaches combine and complement to form integrated parameter space management that governs a closed-loop regime of the co-optimization of ecosystem integrity, operation efficiency, and GHG reduction to help utilities both large and small accelerate toward their net-zero trajectory in a scalable and anti-fragile manner [49].

3. Methods

The researcher selected a systematic literature review as the preferred research design to build on the existing literature, identify gaps and inconsistencies in the previous research, and develop a more contextualized and impactful study. This study sought to examine and analyze SWRM strategies that can assist water utilities in achieving net-zero carbon in their supply chains. Unlike other research designs, a systematic literature review is more suitable for this type of study because it provides a more rigorous and unbiased method for synthesizing evidence [34]. This may help water utilities and decision-makers to choose the most appropriate mechanisms, based on the evidence, to achieve carbon neutrality in their operations [29]. Systematic reviews also deploy predefined protocols such as Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) to identify, select, and critically appraise relevant studies to answer the research question [38]. Systematic reviews’ comprehensive and rigorous nature also helps minimize potential biases in selecting and analyzing studies.

The researcher conducted the systematic literature review in five steps, beginning with formulating the research question. This step was deemed crucial because it summarizes keywords and develops the question the researcher used to select studies from various databases [34]. The question for this study was: “What SWRM strategies can assist in achieving net-zero carbon and carbon neutrality in the water industry?” By formulating this question, the researcher gained focus and direction for the study, identified the scope, and identified the most appropriate methods for data collection [29]. The databases used to obtain the studies included SCOPUS, ResearchGate, ScienceDirect, and Springer. The articles were primarily identified using title analysis. These platforms were selected given their high standard of peer review, broad multi-disciplinary scope, and coverage of high-impact journals in the fields of environmental science, sustainability, and engineering. Due to its more comprehensive academic coverage and citation tracing, SCOPUS was preferred due to it presenting key research and influential research orientations. Two of these (ScienceDirect and Springer) were chosen for their good coverage of the literature in the fields of environmental technology and water management. ResearchGate served as a complementary source of gray literature.

The keyword strategy was also equally important and responded to the research question. The keywords used in the literature search included “Sustainable Water Resource Management (SWRM),” “net zero carbon,” “carbon neutrality,” “wastewater treatment,” “smart water systems,” and “renewable energy in water utilities”. These were, in turn, deemed to be relevant and to occur frequently in the published literature and were relevant to the focus of the study. The Boolean operators AND/OR were employed to limit searches and maintain both sensitivity and specificity in search strategies. Targeted databases and strategic keywords increased the validity, breadth, and generalizability of the review.

Apart from formulating the research question, the other steps included identifying the sources, selecting and evaluating sources, analyzing data, and synthesizing data. This research also reflected potential limitations that could affect the study’s accuracy and reliability. The studies were mainly identified using titles, abstracts, and content analysis. Snowball research was also conducted to identify relevant studies using citations [50]. Once a study was identified, the researcher could identify other relevant studies based on tagged citations [51]. Data was analyzed using thematic analysis based on each article’s content and relevance to the topic. The thematic analysis involved reading through the articles to understand their content, identifying relevant patterns, and developing themes based on the identified patterns across the selected articles [41,51]. The identified themes were discussed in detail, and appropriate conclusions were drawn to guide industry-wide sustainable initiatives and actions. Table 1 provides a comprehensive summary of the selected articles and their findings.

The review was conducted in accordance with the PRISMA guidelines [52] for methodological quality. The latter protocol facilitated a structured approach to identifying eligibility, conducting a thorough search, screening findings, and selecting studies based on relevance and methodological quality. The transparency and reproducibility of the review process were increased by adhering to PRISMA. The final sample was also intentionally selected to represent academic contributions that supported sustainable water resource management and net-zero carbon goals. This systematic process enhances trustworthiness and the validity in the conclusions obtained from the literature.

3.1. Framing the Question

Question formulation is one of the most crucial steps in systematic reviews because it provides focus and guides the methodologies used in data collection. The question formulation began with identifying areas of interest. In this case, the area of interest was achieving net-zero carbon in the water industry. According to Van Loosdrecht et al. [14], an appropriate approach involves starting with a broad interest and narrowing the study to focus on a particular area. The question formulated should highlight this area of interest to enhance the relevance of the selected studies [45]. The second step involved conducting preliminary research to determine the volume and quality of the existing literature [45,50,51]. Apart from identifying the literature, the researcher also identified concepts and theories associated with the topic. Moreover, the researcher examined potential gaps in the literature and how they could be addressed in the formulated question [53]. The final step involved developing the research question using clear and measurable terms.

The formulated question for this study was: “What SWRM strategies can assist in achieving net-zero carbon and carbon neutrality in the water industry?” The research question captured keywords such as sustainability, SWRM, and net-zero carbon. The aim is to provide sustainable solutions for water utilities to enhance water production while reducing carbon emissions. The study found that globally water utilities are racing to achieve net-zero carbon and carbon neutrality by around 2050. Some global water utilities comply with various net-zero carbon guidelines, targets, and frameworks established in their respective countries. This study focused on providing evidence-based strategies that these water utilities and even municipal wastewater treatment facilities may use to lower their greenhouse gas emissions while producing more water to meet current and future needs.

3.2. Identifying Sources

An extensive search was conducted through digital databases such as Scopus, ResearchGate, and Web of Science to identify the most relevant articles. The search began by reviewing the research questions, identifying the keywords, and entering the selected keywords into the search boxes (available on the databases) to extract the articles. Since a single search may yield thousands of articles, refining the keywords, including focusing on the most recent publications, is appropriate. Based on the formulated research question, the keywords that were used in this study include “SWRM strategies”, “achieving net zero carbon”, and “carbon neutrality”. These keywords had to be part of the research question to help extract the most relevant studies and exclude others unrelated to the topic. The initial search sourced 2321 articles from the Scopus database alone.

The researcher relied on four-factor criteria to refine the search further and identify only studies that provide content relevant to the topic. The four factors included relevance to the topic, publication period, language, and research type. Relevance to the research topic was used in this case to eliminate other articles that may contain keywords that are irrelevant to the topic under investigation. For instance, an article may contain sustainability (one of the keywords used in this research) but is irrelevant to the overall topic. Another criterion that helped refine the search further was the language. The researcher only identified articles written in English. Articles published in German, Russian, and other languages were excluded from the study.

The publication period was crucial because the study targeted articles published over the last 15 years. The main reason for targeting the most recent publications was to ensure the information published in this study is up to date. Recent publications also enable the researcher to capture recent updates in knowledge and enhance the credibility of the findings. The 15-year period means articles selected for analysis were published between 2010 and 2025. The publication term was set as 2010–2025 to ensure coverage of both basic research and cutting-edge breakthroughs. The 15-year timeframe resulted in all the peer-reviewed literature on net-zero water strategies being covered, with 35% (11/31) of the studies covered published in 2023–2025 (Table 1). These recent works are overwhelm some critical areas: 80% (5/6) are advanced oxidation process studies (AOPs) [54,55], 70% (7/10) are AI-driven water analytics [19,24], and all are renewable integration studies (e.g., the Scottish Water [42]). The timescale does, however, strike a balance between the historical perspective and the latest developments in decarbonization pathways.

This strategy helps researchers avoid outdated information and anchors findings and discussions to the most updated and relevant data. Regarding the type of research, this study focused on peer-reviewed articles because they contain more scientific data of great quality and validity. The articles were drawn from various geographical regions to cover diverse perspectives and nuances.

3.3. Selecting and Evaluating Sources

The researcher relied on the PRISMA model to select and evaluate articles for the study. With its stringent adherence to transparent, reproducible documentation of inclusion criteria, search strategies, and analysis methods, the PRISMA protocol “improves the reliability and validity of systematic reviews [52]. Its prescribed methodology reduces bias and can form an evidence-based systemic approach which corresponds to best practices in syntheses of the literature.

The PRISMA model is a four-step process beginning with identification, screening, testing eligibility, and including the articles for further analysis. As shown in Figure 1 below, the identification process shows the number of articles identified using their titles or through a manual search. Based on the search criteria discussed above, 410 articles were identified using their titles and through snowball sampling. Snowball sampling involves using citations to identify other articles relevant to the study topic. The rigorous screening helps in excluding articles that are irrelevant to the study.

The researcher worked with four reviewers to help with the comprehensive screening of the articles to ensure the best-quality evidence was included in the study. The four reviewers were guided by the inclusion criteria developed at the beginning of the search process. The reviewers developed five questions that helped them with the screening and inclusion process. They had to agree on each article based on the questions below before deciding what to include or exclude. Cohen’s kappa would then measure the agreement among the reviewers and inter-rater reliability. Table 1 shows the outcomes of the inter-rater agreement, which was 5 out of 5 or 100%. The five screening questions asked by the reviewers were as follows:

• Is the study relevant to the research question and topic?
• Does the study explore SWRM strategies for achieving net-zero carbon in the water industry?
• Was the article published within the 15-year period (between 2010 and 2025)?
• Is the article peer-reviewed, a government report, a policy document, a journal, or a book?
• Are there potential biases attributed to funding, affiliation, or the author’s professional duties?

All these questions ensured that the articles included were relevant, unbiased, and published within the stated period. After screening the 410 articles, 81 were removed (excluded) because they were too general and not focused on the research question. All four reviewers agreed that the articles could not be included because they would provide irrelevant evidence. After examining the publication dates, the reviewers removed 52 more articles because they were published prior to than 2010. The remaining 277 articles (out of the 410) were subjected to further abstract analysis to determine their eligibility for inclusion in the study. The abstract analysis focused on the study’s purpose, methodology, findings, and conclusions. This helped reviewers identify the most relevant articles based on the information in the abstract, including the findings.

The reviewers removed 133 articles through abstract analysis because their purpose and findings did not answer the research question effectively. The remaining 144 articles were subjected to full-text analysis to ensure they contained relevant content. According to Espindola et al. [51], full-text analysis involves reading through each article to understand the content, structure, methodology, findings, and conclusions. The comprehensive nature of textual analysis helps in identifying mistakes that were probably overlooked during abstract analysis [56,57]. After full-text analysis, the researchers settled on 31 articles for inclusion in the systematic review. The remaining articles were also used as references in the study to support various arguments. Figure 1 below illustrates how the PRISMA model was applied in selecting and evaluating the articles. The PRISMA checklist document is provided in the Supplementary Materials (see Table S1).

The researcher classified the retrieved articles based on their titles, type of document, authors, date, and findings, as shown in Table 1 below. This helps synthesize data, identify themes, and develop stronger conclusions based on the evidence. The four reviewers evaluated each article to ensure its content, methodologies, and findings were accurate, consistent, and reliable. Working with the other four pairs of eyes also helped avoid potential biases that can significantly affect the study’s outcomes.

3.4. Analyzing Data

In this case, both abstract and textual analysis were used to review each article, analyze the findings, and develop a more comprehensive report. The abstract analysis mainly focused on the study purpose, background, methods and materials, findings, and conclusions. Most articles had a structured abstract outlining all the key elements (including purpose, findings, and conclusions) needed for analysis. However, abstract analysis merely scratches the surface and can only be used in cases where quick comparison is needed to support inclusion [57]. Full-text analysis was preferred in this case because it helps researchers delve deeper into each article and examine the purpose, background, methodology, and findings. Researchers may also rely on textual analysis to determine the motives behind the selected methods and their influence on the findings.

3.5. Data Synthesis Methods

The researcher synthesized data by comparing methodologies, findings, and conclusions across the 31 selected articles. The synthesis helped move beyond individual study findings to gain a more holistic understanding of the findings and develop better conclusions. The researcher relied on thematic analysis to identify patterns in the findings across the 31 studies. These patterns were then used to create initial codes, focusing on the strategies used by water utilities to achieve net-zero carbon in their operations. Once the initial codes were developed, the researcher created themes and analyzed them against the findings [56]. This study’s discussion section covers various themes obtained from the selected articles.

Analysis of the 31 selected studies demonstrates a clear thematic association of the reviewed articles with the overall direction towards net-zero carbon in the water utilities. The SWRM strategy theme was present in most studies, and there was a recurring focus on technologies like AOPs, the integration of renewable energies, variable-speed pumps, wastewater recycling, and smart water infrastructure. These near-term measures provide practical approaches for decreasing carbon emissions and increasing the sustainability of water systems. It was also common to see obstacles for the implementation, such as capital costs, silos of regulation, technical capabilities, and institutional barriers. Identifying these obstacles is important to understanding the uneven state of progress in meeting net-zero objectives across regions and among organizations. Policy implications were also a common thread running through the literature reviewed, with several papers advocating for enabling governance, financial incentives, and the strengthening of capacity-building measures to facilitate the holistic uptake of low-carbon and circular strategies. Together, these themes offer not just a diagnosis of where the water sector is today but a strategic map to help steer utilities toward decarbonization. These three aspects of strategies, barriers, and policy implications go hand-in-hand with the main goal of the study: to appraise integrated and actionable approaches that will enable progression towards net-zero and a carbon-neutral water industry.

3.6. Potential Limitations

While systematic reviews remain competent in evidence evaluation and in-depth analysis, they are susceptible to selection biases, inadequate blinding, and methodological constraints. The researcher considered all these potential limitations when sampling articles and reviewing evidence to enhance the validity and reliability of the outcomes [58]. For instance, one may argue that errors made in the primary studies may be transferred to the systematic review if the researcher fails to thoroughly evaluate the primary methods effectively [59]. The researcher assessed each article to ensure the methods used were accurate and reliable. The researcher avoided selection biases by working with at least four reviewers to evaluate each article before deciding whether to include or exclude it. This also helped identify potential mistakes in the primary studies and exclude articles that could lead to problematic outcomes. Working with four reviewers also provided adequate blinding and avoided potential biases that can significantly weaken the overall arguments and conclusions.

4. Results

Implementing the PRISMA technique and ranking the articles based on their quality and relevance helped identify 31 articles, as shown in Table 1 below. The researcher also reviewed the articles for their content, validity, bias, and applicability to the wastewater treatment industry. The table summarizes what each study found and its potential applications in the global water industry.

Table 1. Selected Literature.

Authors, Date and Reference Number	Title	Type of Journal Article	Findings
Loisel et al., 2015 [58]	Economic evaluation of hybrid off-shore wind power and hydrogen storage system.	Original Research Article	This study explored alternative and renewable energy sources that water utilities may use to decarbonize their supply chains. The authors found wind power and hydrogen to be key alternative energy sources that may assist water utilities in achieving their net-zero targets.
Macherera and Chimbari, 2016 [59]	Review of Studies on Community-Based Early Warning Systems.	Literature Review	This study found that using modern mechanisms like early warning systems may protect community-based water systems against natural disasters such as the floods and prolonged droughts associated with climate change.
Angelakis, 2017 [60]	Urban Waste- and Stormwater Management in Greece: Past, Present and Future.	Review Article	This study argues that urban water systems need alternative or sustainable management strategies to meet the needs of their current and future populations. Stormwater management is among the key sustainable water resource management (SWRM) strategies suggested by the author.
Hossain, 2017 [61]	Green Science: Independent building technology to mitigate energy, environment, and climate change.	Original Research Article	The author suggests using clean energy at home and in commercial buildings to mitigate climate change. He argues that water utilities can only arrive at net-zero carbon through green science or decarbonization approaches.
Hertwich and Wood, 2018 [20]	The growing importance of scope 3 greenhouse gas emissions from industry.	Perspective Article	While scope 3 emissions remain a significant challenge to water utilities, this study suggests a renewed focus on this area because they come from third parties within the supply chain. This may provide more effective mitigation strategies to reduce carbon emissions within the water industry.
Khosravi et al., 2018 [62]	Energy, exergy and economic analysis of a hybrid renewable energy with hydrogen storage system.	Original Research Article	This study suggests that the most innovative pathway to net-zero carbon is using renewable energy sources and low-carbon equipment across the supply chain.
Kouloukoui et al., 2019 [63]	Corporate climate risk management and the implementation of climate projects by the world’s largest emitters.	Case Study	This study examined the climate risks associated with various organizations, including water utilities. The authors suggests using renewable sources, electrifying vehicle fleets, and adopting smart technologies to monitor operations and minimize waste.
Nayeb et al., 2019 [64]	Estimating greenhouse gas emissions from Iran’s domestic wastewater sector and modeling the emission scenarios by 2030.	Original Research Article	This study found that water utilities account for more than 2% of greenhouse gas emissions globally. The reduction strategies include transitioning to renewable energy sources, reducing waste, and improving wastewater treatment.
Sheikh and Callaway, 2019 [65]	Decarbonizing Space and Water Heating in Temperate Climates: The Case for Electrification.	Original Research Article	The study found that decarbonizing the water sector continues to face various challenges, including higher upfront costs and inadequate resources to support the widescale installation of renewable energy sources such as solar and wind power. The author suggests partnerships and government interventions to minimize initial costs.
Shilpi et al., 2019 [66]	Waste to watt: Anaerobic digestion of wastewater irrigated biomass for energy and fertilizer production.	Original Research Article	This study suggests improving wastewater treatment using advanced treatment processes to minimize energy consumption and make the industry more compliant with various national or global net-zero targets.
Chazarra-Zapata et al., 2020 [67]	Reducing the Carbon Footprint of the Water-Energy Binomial through Governance and ICT. A Case Study.	Case Study	The study suggests addressing the water–energy nexus as a major pathway to achieving net-zero carbon in the water industry. Water utilities should rely on renewable energy sources to increase production while lowering carbon emissions.
Del Río-Gamero et al., 2020 [13]	Water-Energy Nexus: A Pathway of Reaching the Zero Net Carbon in Wastewater Treatment Plants.	Original Research Article	This study also suggests addressing the water-energy nexus as a breakthrough to reach net-zero carbon targets over the next few decades, with most organizations looking at 2050 as their target.
Nguyen et al., 2020 [68]	Multi-objective decision-making and optimal sizing of a hybrid renewable energy system to meet the dynamic energy demands of a wastewater treatment plant.	Original Research Article	This study suggests a more holistic or multifaceted approach to reducing carbon emissions within the water industry. These include renewable energy sources, conservation, and wastewater treatment.
Prochaska and Zouboulis, 2020 [69]	A Mini-Review of Urban Wastewater Treatment in Greece: History, Development and Future Challenges.	Mini-Review	The authors found that wastewater treatment provides sustainable solutions to the water shortage problem by making more water available for non-potable uses, including irrigation, agriculture, and landscaping in urban areas.
Pan, 2021 [70]	Lowering the Carbon Emissions Peak and Accelerating the Transition Towards Net Zero Carbon.	Review Article	The author describes lowering carbon emissions as the top priority as water utilities accelerate their transition to renewable energy sources to achieve net-zero carbon targets. To minimize waste, the author also suggests other proactive measures, including wastewater treatment and leak detection.
Richards et al., 2021 [71]	Sustainable water resources through harvesting rainwater and the effectiveness of a low-cost water treatment.	Original Research Article	This study explored various SWRM strategies, including harvesting rainwater and wastewater treatment as mechanisms for increasing water supply and avoiding potential shortages. The study describes rainwater harvesting as a low-cost SWRM strategy that can be used at home to increase water supply.
Contreras et al., 2022 [72]	Towards an operational satellite-based Drought Early Warning and Forecasting System for quantifying risks of crop and water supply by using machine learning and remote sensing.	Original Research Article	To address increasing natural disasters such as floods, storms, hurricanes, wildfires, and droughts, the author suggests installing early warning systems across urban and even rural areas to enhance preparedness and reduce potential damage to water infrastructure.
Khalifa et al., 2022 [73]	Accelerating the Transition to a Circular Economy for Net-Zero Emissions by 2050: A Systematic Review.	Systematic Review	The author found that water utilities can accelerate their transition to a circular economy and achieve net-zero carbon by 2050. This acceleration can be enhanced through the transition to renewable energy sources, reducing waste, and improving wastewater treatment options.
Parravicini et al., 2022 [5]	Evaluation of Greenhouse Gas Emissions from the European Urban Wastewater Sector, and Options for Their Reduction.	Original Research Article	The study found that greenhouse gas emissions within the water sector affect not just the climate but also increase operational costs for water utilities. The author suggests electrifying vehicle fleets and replacing fossil fuels with solar and wind power to generate energy for wastewater treatment plants.
Silva, 2022 [74]	Implementation and Integration of Sustainability in the Water Industry: A Systematic Literature Review.	Systematic Literature Review	This study suggests investing more resources in water conservation, protecting water catchments, and enhancing leak detection to minimize water waste and achieve a sustainable water industry.
Alevizos et al., 2023 [75]	Toward Climate Neutrality: A Comprehensive Overview of Sustainable Operations Management, Optimization, and Wastewater Treatment Methods.	Review Article	In this study, Alevizos et al. argue that the pathway to carbon neutrality in the water sector involves comprehensive sustainable operational strategies, reducing waste (attributed to leaks), achieving energy efficiency, and improving wastewater treatment to reduce waste and losses.
Cherepovitsyna et al., 2023 [76]	Decarbonization Measures: A Real Effect or Just a Declaration? An Assessment of Oil and Gas Companies’ Progress towards Carbon Neutrality.	Perspective Article	This study questioned whether decarbonization measures are effective, especially when oil and gas companies poise themselves as leaders in the fight against carbon emissions. The authors found that oil and gas companies are in an awkward position to lead the charge against fossil fuels. The authors suggest a steady transition to non-carbonized energy sources to reduce carbon emissions.
Kostner et al., 2023 [77]	Micro hydropower generation in water distribution networks through the optimal pumps-as-turbines sizing and control.	Original Research Article	This study found that using optimal pumps, such as variable-speed pumps, to replace fixed-speed pumps may help water utilities reduce energy consumption by more than 25%. Variable-speed pumps (VSPs) are more flexible and consume energy based on demand.
Panagopoulos et al., 2023 [78]	Ecosystem Services Evaluation from Sustainable Water Management in Agriculture: An Example from An Intensely Irrigated Area in Central Greece.	Case Study	This study found several SWRM strategies that water utilities can use to reduce carbon emissions and achieve their net-zero targets. Examples include integrated water resources management (IWRM), conservation, and smart water management.
Romano et al., 2023 [79]	Reducing CO2 Emissions and Improving Water Resource Circularity by Optimizing Energy Efficiency in Buildings.	Original Research Article	The study found that water utilities can reduce carbon emissions by using various strategies, including installing renewable energy sources in their wastewater treatment facilities. By using solar and hydroelectric sources, water utilities can reduce not just carbon emissions but also their overall cost of operations.
Gavrouzou et al., 2024 [80]	Energy and Water Interventions That Contribute to the Climate-Proofing of Buildings on Multiple Scales: A Literature Review.	Literature Review	This study suggests various energy and water interventions to help water utilities reduce their carbon footprint. These strategies include installing solar panels, using hydropower to generate onsite electricity, and converting more biowaste into energy sources during wastewater treatment, a process known as energy recovery systems.
Li et al., 2024 [19]	Estimation of Energy Consumption and CO2 Emissions of the Water Supply Sector: A Seoul Metropolitan City (SMC) Case Study.	Case Study	This study examined the amount of carbon emissions that can be attributed to water utilities and how these organizations can decarbonize their supply chains. It was found that water utilities contribute more than 2 percent of global carbon emissions, almost equivalent to the transport sector. Mitigation strategies include transition to renewable energy sources.
Pasquarelli et al., 2024 [55]	Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odor abatement and CO2 conversion in alternative energy drivers.	Original Research Article	This study suggests various pathways to carbon neutrality in wastewater treatment, including the transition to AOPs, using renewable energy sources, and converting more biowaste, such as vapors, to electricity (energy recovery systems).
Rodriguez-Perez et al., 2024 [81]	Water microturbines for sustainable applications: Optimization analysis and experimental validation.	Original Research Article	This study explains how water utilities can become energy efficient by using microturbines to generate power within the treatment facilities. This may help reduce dependence on fossil fuels and minimize overall carbon emissions.
Toktaş et al., 2024 [82]	Toward Greener Supply Chains by Decarbonizing City Logistics: A Systematic Literature Review and Research Pathways.	Systematic Literature Review	This study describes the journey to a decarbonized water industry as one fraught with various challenges, including regulatory bottlenecks. The authors suggest decarbonizing water supply logistics, including using electric vehicles and variable-speed pumps to reduce energy consumption and carbon emissions.
Lee et al., 2025 [54]	Carbon Emission Reduction Strategies in Urban Water Sectors: A Case Study in Incheon Metropolitan City, South Korea.	Case Study	This study examined carbon emission-reducing strategies that can be used in the water sector to achieve net-zero carbon goals using a case study of a metropolitan city in South Korea. The study found various strategies, including the transition to solar energy to replace fossil fuels, generating power using microturbines, using biowaste to recover energy, and electrifying water logistics to enhance water efficiency.

Table 1. Selected Literature.

Authors, Date and Reference Number	Title	Type of Journal Article	Findings
Loisel et al., 2015 [58]	Economic evaluation of hybrid off-shore wind power and hydrogen storage system.	Original Research Article	This study explored alternative and renewable energy sources that water utilities may use to decarbonize their supply chains. The authors found wind power and hydrogen to be key alternative energy sources that may assist water utilities in achieving their net-zero targets.
Macherera and Chimbari, 2016 [59]	Review of Studies on Community-Based Early Warning Systems.	Literature Review	This study found that using modern mechanisms like early warning systems may protect community-based water systems against natural disasters such as the floods and prolonged droughts associated with climate change.
Angelakis, 2017 [60]	Urban Waste- and Stormwater Management in Greece: Past, Present and Future.	Review Article	This study argues that urban water systems need alternative or sustainable management strategies to meet the needs of their current and future populations. Stormwater management is among the key sustainable water resource management (SWRM) strategies suggested by the author.
Hossain, 2017 [61]	Green Science: Independent building technology to mitigate energy, environment, and climate change.	Original Research Article	The author suggests using clean energy at home and in commercial buildings to mitigate climate change. He argues that water utilities can only arrive at net-zero carbon through green science or decarbonization approaches.
Hertwich and Wood, 2018 [20]	The growing importance of scope 3 greenhouse gas emissions from industry.	Perspective Article	While scope 3 emissions remain a significant challenge to water utilities, this study suggests a renewed focus on this area because they come from third parties within the supply chain. This may provide more effective mitigation strategies to reduce carbon emissions within the water industry.
Khosravi et al., 2018 [62]	Energy, exergy and economic analysis of a hybrid renewable energy with hydrogen storage system.	Original Research Article	This study suggests that the most innovative pathway to net-zero carbon is using renewable energy sources and low-carbon equipment across the supply chain.
Kouloukoui et al., 2019 [63]	Corporate climate risk management and the implementation of climate projects by the world’s largest emitters.	Case Study	This study examined the climate risks associated with various organizations, including water utilities. The authors suggests using renewable sources, electrifying vehicle fleets, and adopting smart technologies to monitor operations and minimize waste.
Nayeb et al., 2019 [64]	Estimating greenhouse gas emissions from Iran’s domestic wastewater sector and modeling the emission scenarios by 2030.	Original Research Article	This study found that water utilities account for more than 2% of greenhouse gas emissions globally. The reduction strategies include transitioning to renewable energy sources, reducing waste, and improving wastewater treatment.
Sheikh and Callaway, 2019 [65]	Decarbonizing Space and Water Heating in Temperate Climates: The Case for Electrification.	Original Research Article	The study found that decarbonizing the water sector continues to face various challenges, including higher upfront costs and inadequate resources to support the widescale installation of renewable energy sources such as solar and wind power. The author suggests partnerships and government interventions to minimize initial costs.
Shilpi et al., 2019 [66]	Waste to watt: Anaerobic digestion of wastewater irrigated biomass for energy and fertilizer production.	Original Research Article	This study suggests improving wastewater treatment using advanced treatment processes to minimize energy consumption and make the industry more compliant with various national or global net-zero targets.
Chazarra-Zapata et al., 2020 [67]	Reducing the Carbon Footprint of the Water-Energy Binomial through Governance and ICT. A Case Study.	Case Study	The study suggests addressing the water–energy nexus as a major pathway to achieving net-zero carbon in the water industry. Water utilities should rely on renewable energy sources to increase production while lowering carbon emissions.
Del Río-Gamero et al., 2020 [13]	Water-Energy Nexus: A Pathway of Reaching the Zero Net Carbon in Wastewater Treatment Plants.	Original Research Article	This study also suggests addressing the water-energy nexus as a breakthrough to reach net-zero carbon targets over the next few decades, with most organizations looking at 2050 as their target.
Nguyen et al., 2020 [68]	Multi-objective decision-making and optimal sizing of a hybrid renewable energy system to meet the dynamic energy demands of a wastewater treatment plant.	Original Research Article	This study suggests a more holistic or multifaceted approach to reducing carbon emissions within the water industry. These include renewable energy sources, conservation, and wastewater treatment.
Prochaska and Zouboulis, 2020 [69]	A Mini-Review of Urban Wastewater Treatment in Greece: History, Development and Future Challenges.	Mini-Review	The authors found that wastewater treatment provides sustainable solutions to the water shortage problem by making more water available for non-potable uses, including irrigation, agriculture, and landscaping in urban areas.
Pan, 2021 [70]	Lowering the Carbon Emissions Peak and Accelerating the Transition Towards Net Zero Carbon.	Review Article	The author describes lowering carbon emissions as the top priority as water utilities accelerate their transition to renewable energy sources to achieve net-zero carbon targets. To minimize waste, the author also suggests other proactive measures, including wastewater treatment and leak detection.
Richards et al., 2021 [71]	Sustainable water resources through harvesting rainwater and the effectiveness of a low-cost water treatment.	Original Research Article	This study explored various SWRM strategies, including harvesting rainwater and wastewater treatment as mechanisms for increasing water supply and avoiding potential shortages. The study describes rainwater harvesting as a low-cost SWRM strategy that can be used at home to increase water supply.
Contreras et al., 2022 [72]	Towards an operational satellite-based Drought Early Warning and Forecasting System for quantifying risks of crop and water supply by using machine learning and remote sensing.	Original Research Article	To address increasing natural disasters such as floods, storms, hurricanes, wildfires, and droughts, the author suggests installing early warning systems across urban and even rural areas to enhance preparedness and reduce potential damage to water infrastructure.
Khalifa et al., 2022 [73]	Accelerating the Transition to a Circular Economy for Net-Zero Emissions by 2050: A Systematic Review.	Systematic Review	The author found that water utilities can accelerate their transition to a circular economy and achieve net-zero carbon by 2050. This acceleration can be enhanced through the transition to renewable energy sources, reducing waste, and improving wastewater treatment options.
Parravicini et al., 2022 [5]	Evaluation of Greenhouse Gas Emissions from the European Urban Wastewater Sector, and Options for Their Reduction.	Original Research Article	The study found that greenhouse gas emissions within the water sector affect not just the climate but also increase operational costs for water utilities. The author suggests electrifying vehicle fleets and replacing fossil fuels with solar and wind power to generate energy for wastewater treatment plants.
Silva, 2022 [74]	Implementation and Integration of Sustainability in the Water Industry: A Systematic Literature Review.	Systematic Literature Review	This study suggests investing more resources in water conservation, protecting water catchments, and enhancing leak detection to minimize water waste and achieve a sustainable water industry.
Alevizos et al., 2023 [75]	Toward Climate Neutrality: A Comprehensive Overview of Sustainable Operations Management, Optimization, and Wastewater Treatment Methods.	Review Article	In this study, Alevizos et al. argue that the pathway to carbon neutrality in the water sector involves comprehensive sustainable operational strategies, reducing waste (attributed to leaks), achieving energy efficiency, and improving wastewater treatment to reduce waste and losses.
Cherepovitsyna et al., 2023 [76]	Decarbonization Measures: A Real Effect or Just a Declaration? An Assessment of Oil and Gas Companies’ Progress towards Carbon Neutrality.	Perspective Article	This study questioned whether decarbonization measures are effective, especially when oil and gas companies poise themselves as leaders in the fight against carbon emissions. The authors found that oil and gas companies are in an awkward position to lead the charge against fossil fuels. The authors suggest a steady transition to non-carbonized energy sources to reduce carbon emissions.
Kostner et al., 2023 [77]	Micro hydropower generation in water distribution networks through the optimal pumps-as-turbines sizing and control.	Original Research Article	This study found that using optimal pumps, such as variable-speed pumps, to replace fixed-speed pumps may help water utilities reduce energy consumption by more than 25%. Variable-speed pumps (VSPs) are more flexible and consume energy based on demand.
Panagopoulos et al., 2023 [78]	Ecosystem Services Evaluation from Sustainable Water Management in Agriculture: An Example from An Intensely Irrigated Area in Central Greece.	Case Study	This study found several SWRM strategies that water utilities can use to reduce carbon emissions and achieve their net-zero targets. Examples include integrated water resources management (IWRM), conservation, and smart water management.
Romano et al., 2023 [79]	Reducing CO2 Emissions and Improving Water Resource Circularity by Optimizing Energy Efficiency in Buildings.	Original Research Article	The study found that water utilities can reduce carbon emissions by using various strategies, including installing renewable energy sources in their wastewater treatment facilities. By using solar and hydroelectric sources, water utilities can reduce not just carbon emissions but also their overall cost of operations.
Gavrouzou et al., 2024 [80]	Energy and Water Interventions That Contribute to the Climate-Proofing of Buildings on Multiple Scales: A Literature Review.	Literature Review	This study suggests various energy and water interventions to help water utilities reduce their carbon footprint. These strategies include installing solar panels, using hydropower to generate onsite electricity, and converting more biowaste into energy sources during wastewater treatment, a process known as energy recovery systems.
Li et al., 2024 [19]	Estimation of Energy Consumption and CO2 Emissions of the Water Supply Sector: A Seoul Metropolitan City (SMC) Case Study.	Case Study	This study examined the amount of carbon emissions that can be attributed to water utilities and how these organizations can decarbonize their supply chains. It was found that water utilities contribute more than 2 percent of global carbon emissions, almost equivalent to the transport sector. Mitigation strategies include transition to renewable energy sources.
Pasquarelli et al., 2024 [55]	Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odor abatement and CO2 conversion in alternative energy drivers.	Original Research Article	This study suggests various pathways to carbon neutrality in wastewater treatment, including the transition to AOPs, using renewable energy sources, and converting more biowaste, such as vapors, to electricity (energy recovery systems).
Rodriguez-Perez et al., 2024 [81]	Water microturbines for sustainable applications: Optimization analysis and experimental validation.	Original Research Article	This study explains how water utilities can become energy efficient by using microturbines to generate power within the treatment facilities. This may help reduce dependence on fossil fuels and minimize overall carbon emissions.
Toktaş et al., 2024 [82]	Toward Greener Supply Chains by Decarbonizing City Logistics: A Systematic Literature Review and Research Pathways.	Systematic Literature Review	This study describes the journey to a decarbonized water industry as one fraught with various challenges, including regulatory bottlenecks. The authors suggest decarbonizing water supply logistics, including using electric vehicles and variable-speed pumps to reduce energy consumption and carbon emissions.
Lee et al., 2025 [54]	Carbon Emission Reduction Strategies in Urban Water Sectors: A Case Study in Incheon Metropolitan City, South Korea.	Case Study	This study examined carbon emission-reducing strategies that can be used in the water sector to achieve net-zero carbon goals using a case study of a metropolitan city in South Korea. The study found various strategies, including the transition to solar energy to replace fossil fuels, generating power using microturbines, using biowaste to recover energy, and electrifying water logistics to enhance water efficiency.

Bibliometric Insights

Apart from the qualitative summery review of the studies included, bibliometric analysis was performed to explore dominant research trends and thematic clusters. A co-occurrence analysis of keywords was conducted based on VOSviewer software (v1.6.20). In total 31 keywords were identified, but only 7 met the inclusion criteria of at least two instances. Six of them can be linked into a “cluster” (Figure 2). The most frequent and central concepts—project, implementation, management, TQM (total quality management), and construction—point to this area of dispute as being far from arguing over the ontological, litigious, and valuative aspects of sustainability, and not on its fashionable aspects dealing with policies and any aspect that touches how the environment is managed—i.e., conservation and so forth.

Such network representation validates the justification: project-based implementation measures and quality management systems are closely related to carbon-neutral water management. These findings are consistent with the wider review results and empirically substantiate that the interconnection of project governance and sustainability frameworks in the context of water systems orientated towards net-zero carbon transitions is increasingly pervasive.

5. Discussion

Achieving net-zero carbon remains a crucial component of global climate objectives. The water sector contributes about 3% of the global greenhouse gas emissions [2,8,9,57]. Although water utilities only account for about 2 percent of greenhouse gas emissions, other factors such as water storage, usage, and distribution take carbon emissions somewhere above 10 percent [56,58]. This classifies the water sector among the largest sources of greenhouse gas emissions and demonstrates the need for a more holistic approach to addressing the problem [9,16,45,58]. This study examined how water utilities can achieve their respective net-zero carbon targets across their operations. Based on evidence from past studies, this study demonstrates how transitioning to renewable energy, electrifying distribution networks, and adopting smart technologies may assist water utilities in limiting their carbon emissions while increasing their water supply to meet current and future needs.

5.1. The Water–Energy Nexus

According to Farrelly et al. [57], addressing the carbon emissions in the water sector must begin with understanding the complexities associated with the water–energy nexus. The complex relationship between water and energy makes it difficult to address one aspect of the nexus without hurting the other [2,9]. For instance, energy generation projects such as hydropower plants require significant water to run the machines and produce the electrical energy needed for domestic and commercial purposes [9]. Clean water supply and wastewater treatment consume significant energy and may account for about 2 percent of global greenhouse gas emissions [9,31,34,45]. With a growing global population, the need for more water means additional energy consumption and more greenhouse gases emitted into the atmosphere.

While efforts have been made to solve the problem, the growing water scarcity and the effects of climate change largely exacerbate the water–energy nexus. A study by Friedrich et al. [9] found that water scarcity is a major problem facing more than 4 billion people globally. Data shows that more than 4 billion people globally experience water shortages at least once a month [9,10]. Moreover, climate-related challenges, such as prolonged droughts, continue to expose more people worldwide to potential water scarcity [12,51]. Water utilities are responding to these global challenges by increasing their production and distribution networks to reach more people, especially in areas plagued by perennial water shortages [51,58,59]. However, Macherera et al. [59] raise concerns that expanding production without SWRM approaches may be counterproductive and may undermine various efforts to achieve net-zero carbon by 2050 or earlier.

Rising energy demand, especially in urban areas and developing countries, is significantly putting pressure on water sources globally. Angelakis [60] found that energy demand has grown by more than 80 percent in most developing economies. The growth is mostly attributed to rising urbanization and industrialization [20,60,61]. The rising energy demand means more water is needed for power generation. The current power generation methods are highly linked to massive greenhouse gas emissions and air pollution [9,12,62]. Fossil fuels are still the most common energy source for power generation plants. Moreover, energy sources such as coal mining and oil extraction have been associated with various forms of mass air pollution and water contamination [63]. The decline in water quality may expose more people to potential water shortages if the problem is not addressed effectively.

Such interdependencies are expressed differently depending on the hydroclimatic setting. In water-poor areas, such as Mexico City, energy-for-water is the main dynamic of the system––85% of utility emissions are due to groundwater pumping [10]—requiring solar-powered treatment advances [70]. On the other hand, water-rich countries such as the European Union have the opposite priorities, with 40% of industrial water withdrawals being used for cooling thermoelectric plants [13,14], and require the closed-loop nature of systems to balance water-for-energy needs with ecological responsibility.

These basic mutual relationships show that there are harsh figures: the use of energy in wastewater treatment varies between 0.3 and 2.1 kWh/m³ depending on the holistic level of technology [16,62] and the already-applied desalination to water stress areas that uses between 2.5 and 4.0 kWh/m³ [70]. On the other hand, energy systems apply the same squeeze back in the other direction; thermoelectric generation, for instance, depletes around 100 L per kWh delivered, while 1–3 L of water becomes permanently lost to cooling [13,14]. These tensions may be further inflamed by climate stressors, with estimated water supply energy needs increasing by 40–60% in arid regions due to groundwater depletion by 2040 [9].

With growing concerns about water quality, many researchers are beginning to shift blame to highly fragmented policy frameworks that have become bigger challenges than the perceived solutions [64]. The fragmented policies have nearly paralyzed effective nexus management due to a lack of coordination between water utilities and energy companies [64,65,66]. Most economies treat water utilities differently from energy companies despite significant connections in their operations [13,67]. Regulatory frameworks have become major hurdles because they impose different requirements and targets across the two industries. Water utilities are expected to meet certain carbon emission targets [13,68,69,70]. At the same time, energy companies have also been subjected to different policies, making achieving net-zero carbon across the water sector even more difficult [71,72,73]. Awareness of the energy–water nexus and its complexities may assist policy developers and enforcers to align their regulations with market needs and climate goals.

Insufficient data also makes it difficult for water utilities and regulators to study water and energy consumption patterns [5,13,31,51,65,73,74]. For a long time, water utilities relied on outdated technologies with inadequate capacity to collect data and provide relevant information in real-time. Industry regulators cannot make informed decisions without adequate access to updated information [13]. Data collection requires advanced monitoring devices to provide real-time updates on changes in key areas, such as demand and energy consumption, across the distribution network [51,65,75,76]. For instance, advanced monitoring tools may help water utilities detect a decline in water demand and adjust energy consumption to meet consumer demands [12,77,78,79]. This prevents using more energy to pump water to places where they are not needed.

The nexus goes beyond simple technical feedback to become a governance challenge that is dynamic with cross effects, where policy fragmentation [9] increases systemic risk. Successful decarbonization requires harmonized metrics, such as typical kWh/m³ standards [16], alongside responsive fiscal instruments, such as regionalized carbon pricing [83]. Only through these integrated pathways can utilities reconcile the dual mandates of water security and emission reduction.

5.2. Barriers to Achieving Net-Zero Carbon in the Water Sector

The high initial cost remains a significant issue in achieving net-zero carbon among water utilities. The high upfront cost limits the types of infrastructure that water utilities can implement in their supply chains to minimize water losses [74,75,84]. Some of the key infrastructure, such as remote sensors and acoustic monitoring tools, may be too expensive for smaller water utilities with inadequate resources [31,85,86]. In addition, some of these technologies require annual updates or repairs to improve their performance, creating a recurrent cost that most organizations find difficult to add to their already bloated operational expenses [87]. However, without sufficient infrastructure and technologies, achieving a low-carbon water industry may remain an elusive target despite pressure from national or regional governments to achieve net-zero carbon.

Although often overlooked, data security and privacy have become significant problems because water utilities collect vast amounts of data from their customers and suppliers in their operational areas [88,89]. Since most water utilities rely on third-party suppliers for technologies and infrastructure, they often assume shared responsibility for protecting sensitive data from potential attackers [90,91]. To illustrate how big the problem has become, American Water suffered a major cyberattack in 2024, exposing data belonging to more than 14 million people across 14 states, including 18 military installations [44,90,92]. American Water did not detect the cyberattack until 3 October 2024, when it was forced to shut down its operations and reschedule customer appointments [93]. This case demonstrates the sensitivity of data security and how it may have widescale implications for a company’s operations.

Water utilities should develop more robust data systems to protect their infrastructure against potential attacks. Mechanisms such as data encryption and access controls can protect data collected from their customers [94,95,96]. Even aside from the customers, water utilities should protect their systems against external attacks to avoid losses. In the case of American Water, for instance, the company was forced to shut down its operations until the issue was resolved [2,4,6,97]. This may result in several hours of lost business and revenue. There are also processes that should be kept running to avoid major disruptions that can lead to far-reaching losses [9,26,90,94]. Hacking can also affect the overall access to a clean supply of water for the communities that depend on water utilities.

Innovative water management systems like those suggested in this study require a more powerful data platform to enhance integration and interoperability. Water utilities often segment their operations into various departments or divisions [90,93,95]. To enhance interoperability, data should be made available on accessible platforms where all departments can use it to support their operations [98]. For seamless interoperability, different segments of smart water networks should be connected using advanced technologies [99]. For instance, advanced technologies such as the Internet of Things (IoT) often provide real-time data that can be shared among departments to support operations [100]. Data collected from sensors and other monitoring devices can only be useful if they are not held up in unnecessary silos or data centers with problematic accessibility.

Addressing the skill gaps in the water industry will also enable water utilities to achieve their net-zero carbon targets over the next few decades. One of the areas largely affected by the skill gap is the development of smart water infrastructure [97,101,102]. Moreover, fewer talents in the markets also means water utilities should pay more for the required workforce, leading to a sharp increase in their cost of operations [80,101]. The global skill gap has left many organizations at risk of shutting down some of their operations because they lack people to run them [103]. SWRM, net-zero carbon, and smart management systems are relatively new concepts with limited skills globally [104,105]. Water utilities must train their workforces to ensure they have the required skills, especially in areas such as SWRM, to enhance their capacities to achieve net-zero carbon targets.

Although technological breakthroughs are important to promote net-zero carbon in the water industry, it is important to examine the feasibility and potential adverse effects of these solutions [106]. The rapid deployment of smart technologies—IoT platforms, AI algorithms for analytics, and remote sensors—has the potential to unintentionally create dependencies that impede system agility, adaptability, and robustness. Overdependence on these technologies puts water utilities at risk whether from system failure, interoperability failure, hacking, or cyberattacks [107].

Additionally, there are significant questions regarding the economic reality of deploying advanced systems, especially for smaller or under-resourced or rural utilities [108]. The high initial deployment cost, along with the associated maintenance, software license fee, and labor cost, often leads to a heavy financial burden that may exceed the efficiency improvement achieved in the long run. For companies with thin budgets and wobbly regulatory environments, the solutions are not scalable or sustainable [108]. Compromises between costs and benefits are also hindered by the absence of regulated financial incentives or public funding systems in most legal systems.

Discrepancies in regional policies, too, will slow down the overall drive for net-zero carbon [109]. Utilities in high-income regions or policy-aligned jurisdictions often have a conducive regulatory environment that promotes digital transformation and green infrastructure investments, while those in fragmented or decentralized systems may have competing mandates, unclear guidance, or institutional recalcitrance [109]. This disintegration also causes unequal penetration by sustainability technologies that reinforces global water security/climate adaptation inequity.

Furthermore, the speed of technological change is beyond what qualified personnel can deliver in terms of operating and maintaining these systems [22]. The lack of international technical expertise on smart water management, sustainability analytics, and integrated infrastructure planning is one of the most significant impediments to successful deployment [49]. Even if technical solutions exist, the unavailability of qualified staff can cause implementation delays, escalate operational risks, or underutilize a system [49]. Often utilities need that flexibility in the form of upskilling or outsourcing, which means both costs and time.

Collectively, these tensions highlight the importance of achieving a balanced and context-specific perspective on options for water sector decarbonization [109]. Net-zero carbon would not simply be an engineering issue but also a question of governance capacity, institutional coordination, the economic practicalities on the ground, and social fairness [109]. Without this introspection, good intentions have the specific potential to be inappropriate, ineffective, or detrimental in some contexts. This study provides implications for future strategies which could be focused on not only in terms of technology development, but also in terms of institutional strengthening, inclusive policy making, and capacity building to ensure that the sustainability gains are both equitable and sustainable.

5.3. Innovative Pathways to Achieving Net-Zero Carbon in the Water Industry

Since the water sector contributes about 2% of global greenhouse gas emissions, transitioning to renewable energy sources may reduce dependence on fossil fuels while reducing the industry’s overall carbon footprint [19,55,79,80,81]. Water utilities like Scottish Water have demonstrated how transitioning to renewable energy sources such as solar and wind power may reduce energy-related emissions by more than 45% [42,54,82,110]. Since 2007, the organization has cut emissions by more than 254,000 tons of carbon dioxide, equivalent to greenhouse gas emissions from about 40,000 cars [42]. The organization has a long-standing mission to achieve net-zero carbon by 2040 [42]. Besides using renewable energy sources, Scottish Water also replaced its machines with more energy-efficient equipment, reduced leaks from our water pipes, and installed smart devices to monitor its water distribution networks nationwide [42]. Scottish Water is among the few utilities on the path to achieving net-zero carbon by 2040, almost 10 years ahead of the United Kingdom’s 2050 target.

Besides reducing operational emissions by more than 45%, transitioning to clean and renewable energy sources has also seen Scottish Water add over 53 GWh (gigawatt hours) of renewable energy to its system [42]. The organization also relies on about 831 GWh of renewable energy from third parties [42]. The point here is that water utilities can become energy efficient by cutting their dependence on fossil fuels and electricity from the national grid. At least 63% of electricity consumed by water utilities comes from the national grid system [42]. Only a small portion of water utilities’ energy or carbon emissions may be connected to fossil fuels. Becoming energy efficient means putting less pressure on the national grid, and the water and fossil fuels used in power generation plants [42,111,112]. Therefore, transitioning to renewable energy enables water utilities to reduce the direct emissions attributed to the onsite combustion of fossil fuels, indirect emissions from grid electricity, and indirect emissions from third parties within the industry.

Another innovative pathway to achieving net-zero carbon is improving water efficiency through reuse, conservation, and demand management. Satyro et al. [110] note that water utilities cannot achieve their net-zero carbon targets without an improved focus on SWRM. Conservation is a crucial SWRM strategy because it limits consumption to ensure there is more water to meet domestic, business, and agricultural needs [17,31,110]. Over 60% of clean water used at home and in businesses is wasted with limited chances of being returned into circulation. Lee et al. [54] indicate that reducing wastewater through treatment and reuse can reduce carbon emissions by more than 20%, enabling water utilities and even municipal water treatment plants to achieve their net-zero carbon targets [42,110,111]. In addition, diverting more wastewater to other non-potable applications such as irrigation and landscaping may save billions of gallons and reduce carbon emissions across the supply chain.

Water losses due to leaks and repairs usually account for up to 50% of global annual losses [63,111]. Although figures vary significantly depending on the types of infrastructure and maintenance practices, more than 10 percent of homes globally have leaks that waste more than 400 L of water per day [112]. Since every cubic meter of water that people consume generates about 10.5 kg of carbon emissions, water losses due to leaks and repairs may be responsible for a large percentage of greenhouse gas emissions that often go unaccounted for. Smol et al. [112] indicate that the current data regarding carbon emissions attributed to the water sector may not provide a true account of actual greenhouse gas emissions within industry. The actual figure would be much higher if carbon emissions attributed to leaks and repairs were considered.

Implementing a multi-faceted water detection approach may save billions of gallons of water and the carbon emissions attributed to these losses. Reaching net-zero carbon demands a proactive approach that leverages advanced technologies to enable timely detection and intervention to minimize losses [35,39,112,113]. Scottish Water, for instance, has applied a multifaceted approach that involves using technologies such as Hydrosave, satellite imagery, acoustic monitoring, and pressure sensors [43]. These technologies provide real-time monitoring of the company’s distribution infrastructure to identify potential cracks or weaknesses that can lead to leaks [114]. Real-time data enables the organization to mobilize resources and repair the worn-out infrastructure or replace outdated machines, saving billions of gallons of water that would otherwise go to waste [84,115]. The multifaceted water monitoring and detection approach also prevents financial losses while maintaining a steady supply across the supply chain.

In addition to this high-income case, scalable decarbonization by small utilities in water-stressed developing regions has also been found. In Windhoek, a semi-desert city in Namibia with only 300 mm of rainfall pa and frequent droughts meaning that 30% water rationing has been required, 21,000 m³/d of wastewater at the Goreangab water reclamation plant is treated to a potable standard using solar powered AOPs [34]. This directly alleviates immediate water scarcity for 400,000 people, decreasing the city’s dependence on far-away dams and emergency imports. Energy can be reduced by 30% in such a system, and there are no methane emissions released into the atmosphere [34]. Socio-economically, this resulted in a 25% water cost reduction, the feeding up of the municipal budget for expanding sanitation, the creation of 120+ well-paid jobs in green tech, and a joint venture led by the largest local company was scaled up. Additionally, in water-stressed rural India (Tamil Nadu), rainwater harvesting systems managed to save 70% of groundwater-pumping energy and provided 5000+ rural households with water [71]. These cases illustrate that decentralized, renewable-assisted solutions can deliver cost competitive fresh water (<$0.1/m³) and enhance water security and community resilience without coming into conflict with net-zero targets [71].

Recent technological advancements aimed at improving supply while reducing carbon emissions have also boosted the race to net-zero carbon. Smart water networks, for instance, provide real-time monitoring for and control of processes to optimize water distribution and lower energy consumption [54,79,112]. Smart water networks rely on various technologies, including acoustic monitoring, to detect changes in demand and optimize water distribution to places with higher demand [84]. Data analytics tools and machine learning also enable water utilities to manage complex processes, especially within wastewater treatment facilities [116]. AOPs have also become highly sought-after technologies because they help remove persistent organic pollutants from refractory water sources at minimal energy consumption, significantly lowering energy use and carbon emissions [96,117,118]. Most wastewater treatment facilities have integrated AOPs into their treatment facilities to remove stubborn organic compounds while cutting energy consumption by significant margins.

Achieving net-zero carbon is also a holistic process that requires strong partnerships and collaboration across the industry. Working with highly fragmented policy frameworks has proven less effective in driving water utilities across the net-zero carbon finish line [5,65,117]. In most cases, these fragmented policies have become stumbling blocks because they delay processes and technologies enabling water utilities to lower their carbon emissions [96]. Strong partnerships and collaboration must be anchored on widescale stakeholder engagements, bringing together water utilities, governments, and technology developers to strategize effective decarbonization strategies [97]. Governments should also dedicate more resources to research and development to support the development of smart technologies for wastewater treatment and distribution [85,96,97]. Holding annual net-zero carbon seminars and conferences may also provide platforms for sharing ideas, developing partnerships, and accelerating decarbonization efforts across the water industry.

The systematic review highlights the most promising solutions, including AOPs, smart water technologies, and renewable energy incorporation, but economic feasibility will determine whether these are eventually implemented. For instance, AOPs, while effective in degrading recalcitrant contaminants, are energy- and infrastructure-intensive (and thus expensive) to operate at full-scale [119]. Another substantial investment, in terms of digital infrastructure and skilled staff, is smart water systems, which provide real-time monitoring for real-time operations [120]. Likewise, the integration of renewable energy into water utilities, for example, when used to pump water (solar powered pumps) or the anaerobic digestion of the putrescible fraction of municipal solid waste for biogas generation bring potential long-term cost and emissions benefits, but there is a lack of capital investment [121]. Hence, life cycle cost analysis and cost–benefit analysis are important to help decision-making and to validate the sustainable investment in these technologies [122].

The challenges of net-zero carbon require four clear, interlinked pathways:

• Energy Decarbonization: Onsite renewables adoption (solar or biogas) and the modernization of the grid; e.g., Scottish Water reduced emissions by 45% through the deployment of 6.3 GWh/year of solar [39].
• Process Innovation: The use of variable-speed pumps (25% energy saving) [77], AI-based N₂O monitors [21], and low-energy AOP for non-CO₂ GHG abatement [55].
• Circular Water: Scaled-up wastewater reuse (could save 9 B+ gallons/day globally) [34] and smart leak detection to achieve a 50 percent reduction in distribution losses [43].
• Policy-Incentivized Ecosystems: Roll-out carbon pricing [83,123] and watershed protection (examples include 20% supply resilience in São Paulo) to incentivize equity [35].

Such pathways need to be phased—short-term retrofit work (0–5 yrs), mid-term scaling of reuse (5–15 yrs), and long-term systemic digitalization (15–30 yrs)—where utilities, governments, and tech partners share responsibility [40].

The review also pinpoints the most promising technologies to decarbonize the water sector, such as AOPs, smart water technologies, and the integration of renewable energy. But as evidence from the case studies reveals, cost-effectiveness will ultimately play a crucial role in real-life deployment. For a systematic comparison between the numbers for these core technologies, see

Table 2. Assessment of Technologies for Reducing Emissions from Water sector.

Technology	Emission Reduction	Cost Efficiency (ROI [Return on Investment] Timeframe)	Implementation Speed	Scalability	Supporting References
Solar PV	40–60%	Medium (5–7 years)	Slow (3–5 years)	High	[39,42]
AOP	15–30%	Low (8–12 years)	Medium (1–3 years)	Medium	[55]
Variable-Speed Pumps	20–25%	High (2–3 years)	Fast (<1 year)	High	[77]
Biogas Recovery	30–50%	High (3–5 years)	Medium (2–4 years)	Medium	[66]
Smart Leak Detection	10–15%	High (1–2 years)	Fast (<6 months)	High	[43]

, which indicates the order of magnitude of their emission reduction potentials, cost efficiency, and scalability. This comparison provides a convenient resource for utilities and policymakers when evaluating the trade-offs among various mitigation options and prioritizing activities toward the net-zero goal.

5.4. Policy and Regulatory Implications

Achieving net-zero carbon may not be possible without government policy interventions. In a free market, water utilities may operate without significant investments in decarbonization to reduce climate change and its perceived environmental consequences [83,104]. Free-market capitalization empowers businesses to operate with minimal government intervention [2,4,5,77,104]. However, since water is an endangered natural resource (based on growing scarcity), government interventions may be needed to reduce potentially harmful business activities without necessarily limiting a business’s operational scale [101,124]. For instance, even in the free-market world, governments often intervene to reduce harmful competition, such as monopolies or intellectual property violations [8,9,12,124]. This means the call for government intervention does not, in any way, allow massive control that can affect business operations.

Policy interventions should target areas such as carbon pricing, incentives, and partnerships. Carbon pricing aims to limit greenhouse gas emissions by taxing additional emissions beyond the standard limits [83]. For instance, if the standardized emissions allow up to 10,000 kg of greenhouse gases monthly, additional emissions should be taxed to discourage harmful practices while encouraging businesses to consider alternative or renewable energy sources [10,51,68,125]. For a more accelerated drive to achieve net-zero carbon by 2050, governments should consider relatively higher carbon prices to help businesses transition quickly to renewable energy sources [123]. Areas such as producing smart technologies, monitoring devices, and VSPs may call for incentives to make them more affordable, even for smaller water utilities [123,126,127,128]. Partnerships with these smart device developers may also help lower prices and work toward long-term goals, such as achieving net-zero carbon by 2050.

Water available for human or industrial consumption also faces threats from natural sources such as climate disasters. Floods and prolonged droughts have emerged as major threats affecting the availability and supply of clean water for domestic and commercial purposes [34,118,126]. Policy frameworks should target areas such as climate resilience, early warning systems, and incident response plans [19,127,128]. Government interventions should include policies encouraging water utilities to protect their facilities from disasters [103,127,128]. This may include building larger wastewater treatment facilities to harvest flood water and make it available for human or commercial purposes. Investing in better early warning systems may also improve responses against water-related disasters such as floods [5,9,15,19]. This may reduce the potential infrastructural damage caused by these disasters. Disaster preparedness should also include standardized incidence response plans to limit potential damage to industry water infrastructure.

In several countries, incentive-based systems have proved effective in stimulating the adoption of sustainable water systems [129]. For instance, in India, the government also introduced the PM-KUSUM (Pradhan Mantri Kisan Urja Suraksha Evam Uthaman Mah Abhiyan) scheme, which provides high subsidies to farmers for the purchase of solar-based irrigation pumps [130]. This saves piped grid electricity and diesel but also assists with ground water management and minimizes operation costs for farmers [122]. Also, in Kenya, the Green Climate Fund (GCF) is funding initiatives which encourage smallholder farmers to ditch diesel and adopt solar water pumping systems for water access while curbing carbon emissions [131]. These examples demonstrate that directed subsidies and financial incentives can hasten the deployment of energy-efficient, low-carbon water infrastructure, particularly in agriculture-based economies [132].

Carbon pricing, as an economic instrument, is widely regarded as an essential measure to make carbon neutrality targets work in the water sector. These tools, however, need to be underpinned by legally binding policy instruments [75]. The European Union Emissions Trading Scheme (EU ETS), for example, represents the world’s largest carbon market and is an established benchmark price for carbon emissions in energy intensive businesses [133]. Water utilities are not directly covered by EU ETS, but the indirect energy consumption related to the water process is passed through with a carbon cost, encouraging water utilities to be more energy-efficient and use more renewables [134]. China’s own national carbon trading system, which took effect this year, following on the heels of pilot programs in cities like Shenzhen and Beijing, covers only the power sector for now, but is supposed to widen to include industrial and municipal sectors [135]. These cases show the power of strong market-oriented levers to shape the portfolio of decarbonization. These frameworks can be considered within national water strategies, and thereby the economic and environmental targets can be reconciled by the costing of carbon-intense approaches [136].

The redirection of policy interventions to achieve the SDGs—in particular SDG 6 (clean water/sanitation), SDG 7 (affordable clean energy), SDG 9 (resilient infrastructure), SDG 11 (sustainable cities), and SDG 13 (climate action)—should be achieved through four synergistic pathways: Carbon pricing and fiscal incentives must enact emission taxes (beyond standardized) to pay for the renewable energy transitions of water utilities [83,123], directly achieving SDG 13.2 (integrating climate into policies) while providing assistance for SDG-consistent technology (e.g., solar treatment plants) to reduce costs for small utilities and support the achievement of SDG 7, and combine shared and fit-for-all toilet facilities with those that couple on-site sanitation with treatment in a distributed facility to accelerate SDG 6. b (clean energy access) [39,42]. Water resilience frameworks need to include mandates for watershed protection (e.g., catchment reforestation) to increase water quality by 20% (SDG 6.3) as well as to sequester CO₂ (SDG 13.2) [35], in addition to mandatory urban water reuse quotas (50% non-potable use by 2030) to alleviate scarcity (SDG 6.4) and reduce distribution emissions (SDG 11.6) [34,69]. Cross-sector partnerships should create water–energy nexus taskforces (utilities + energy regulators) to co-design integrated decarbonization plans (SDG 17.16) [9,13] and scale green bonds for SDG 9 infrastructure (e.g., $10 B/year for smart leak detection in Global South cities) [91,128]. Finally, a push on lifecycle governance with circular economy standards (80% recycled materials in pipes/pumps by 2040) for SDG 12.5 [112], and UNFCCC-aligned emissions disclosure to follow-up on progress for SDG 13. a (climate accountability) [5,20].

In conclusion, climate resilience measures need to be central to water management if we are to meet longer-term sustainability and net-zero targets. Not only does this increase service resilience, but protecting infrastructure (and, by extension, population health) from climate impacts also supports broader public health and environmental goals. Preventive policies of preparation for disasters affecting water systems through sustainable measures shall be a priority to resist future shocks.

6. Conclusions

This paper carries out a systematic literature review, aiming to identify sustainable water resource management (SWRM) strategies and technologies capable of aiding the water industry to achieve net-zero carbon emissions (carbon neutrality). Based on 31 peer-reviewed studies, the analysis found that several policies—including the implementation of renewables, the electrification of transport and industry, and the use of low-emission and smart technologies—are proven to work and are required. The combined implementation of these measures, together with other far-reaching strategies such as water conservation, the reuse of wastewater, or the protection of natural ecosystems, represents a good starting point to decrease the carbon footprint of water utilities without putting service reliability at risk.

The review also cited successful examples of real-world applications including Scotland’s water company, Scottish Water, which has converted to clean power production and implemented intelligent system monitoring technologies to reduce its emissions. What those examples should demonstrate is that net-zero carbon pathways are possible even without heavy government intervention.

However, the road to decarbonization is not an easy one. Structural and operational barriers—such as the high costs, weak technical capabilities, cybersecurity concerns, and the poor interoperability of systems—still hold back roll-out, especially among smaller utilities that lack resources.

To facilitate a wider and a more scalable transition, research needs to focus on the development of low-cost and flexible strategies for underserved utilities. This involves assessing the efficiency of public policy instruments, e.g., subsidies and carbon pricing instruments, as well as determining the impact of new technologies (e.g., artificial intelligence, AOPs, and real-time emissions monitoring) in different regulatory and environmental settings.

To achieve a net-zero carbon water industry, an integrated approach is needed that is based on sustainability, innovation, and equity. Although big utilities might drive implementation, flexible, evidence-based constructions are needed to make it so that utilities across scales and regions can genuinely contribute to global climate objectives.

This systematic review identified four actionable pathways for decarbonizing the water sector: (1) energy transition (e.g., Scottish Water’s 45% emissions cut via renewables); (2) process innovation (AOPs and variable-speed pumps); (3) circular water systems (wastewater reuse and leak detection), and (4) policy-integrated governance (carbon pricing and SDG-aligned incentives). Case studies from Namibia to Scotland have demonstrated that tailored solutions could reconcile water security with net-zero targets, though barriers like high upfront costs (AOPs: 8–12-year ROI) and skills gaps persist. Thematic analysis further highlighted the centrality of smart monitoring and renewable energy integration across contexts.

Some limitations of this systematic review need to be recognized to properly interpret the findings. Firstly, although it followed the PRISMA protocol to ensure the process was transparent and reproducible, there still exists a potential for literature selection bias as the review mainly concentrated on studies published in peer-reviewed journals and indexed in English-language databases. This may lead to an absence of studies published in other languages or regional sources. Secondly, the review shows poor geographical coverage, with most studies being clustered in high-income or industrialized countries. This raises questions about the generalizability of the findings to low- and middle-income settings where resource constraints, governance structures, and infrastructure status can vary substantially. Thirdly, although attempts were made to cover a breadth of themes, the focus may have resulted in a bias towards excluding water management strategies not explicitly reframed in decarbonization language. Lastly, the nature of sustainability technologies and policies is changing, and some of the referenced studies may become obsolete very quickly, which calls for regular updates to remain current.