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Open AccessArticle

Decentralized Constructed Wetlands for Wastewater Treatment in Rural and Remote Areas of Semi-arid Regions

by

Ibrahim Hendy

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Martina Zelenakova

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Katarzyna Pietrucha-Urbanik

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Yasser Salama

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Mohamed Abu-hashim

Water 2023, 15(12), 2281; https://doi.org/10.3390/w15122281 - 18 Jun 2023

Viewed by 961

Abstract

Vertical-flow constructed wetlands (VFCWs) are an innovative and sustainable nature-based technology for wastewater treatment in rural areas. This work aimed to evaluate the treatment performance of VFCWs using real wastewater, which can provide more accurate and reliable results compared with field-based experiments, and [...] Read more.

Vertical-flow constructed wetlands (VFCWs) are an innovative and sustainable nature-based technology for wastewater treatment in rural areas. This work aimed to evaluate the treatment performance of VFCWs using real wastewater, which can provide more accurate and reliable results compared with field-based experiments, and to investigate the use of Paulownia trees in VFCWs for wastewater treatment. To compare the efficiency of the plants based on the treatment performance of the VFCWs, three units were prepared and composed of Paulownia, the commonly used Phragmites Australis, and an unplanted unit used as a control during the experimental program. The results show significant reductions in both the chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) levels for both planted units, with removal ratios for COD and BOD5 of 60% to 98%, respectively. Both Paulownia and Phragmites Australis significantly reduced the levels of COD and BOD5 in the effluent, with removal percentages ranging from 57.1% to 98% for COD and 49.1% to 98% for BOD5. The control unit, without plantings, showed a lower but still significant removal percentage for both COD (from 55.1% to 96.1%) and BOD5 (from 48.3% to 97.8%). Thus, the results reveal that the efficiency of constructed wetlands can be significantly enhanced by the presence of suitable plant species, such as Paulownia and Phragmites Australis, and constructed wetlands can be a viable and cost-effective option for the treatment of wastewater in various settings, with the added benefit of using the relevant biodiversity. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Open AccessArticle

Using Stormwater in a Sponge City as a New Wing of Urban Water Supply—A Case Study

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Water 2023, 15(10), 1893; https://doi.org/10.3390/w15101893 - 17 May 2023

Viewed by 991

Abstract

Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when [...] Read more.

Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when Sponge City concepts are implemented. Thus, the concept presented here addresses existing urban neighborhoods and proposes to collect rainwater from nearby rooftops and treat it in decentral treatment units called “City Water Hubs” (CWH) equipped with modular coupled low-energy technologies to produce various customized “City Water” qualities, and store it until it can be used or distributed. A feasibility study with a focus on the campus area at the main building of the Leibniz University of Hannover, the determined rainwater qualities, and the results from investigations with two laboratory test plants provided the basis for the technical design of the pursued concept. The feasibility study showed how sufficient rainwater for irrigation purposes can be made available for the listed large university park even under extreme dry and heat wave conditions. If large portions of the roof area (11,737 m²) of the university’s main building were activated, even in a dry year with only 49.8% of the average precipitation, only 19.8% of the harvested stormwater would be needed for irrigation. The rainwater samples showed TSS concentrations of up to 7.54 mg/L, COD of up to 58.5 mg/L, and NH₄ of up to 2.21 mg/L, which was in line with data reported in the literature. The treatment technologies used for the two pilot plants are proven approaches for stormwater treatment and were composed as follows: (1) gravity-driven membrane filtration (GDM) and (2) slow sand filter with integrated activated carbon (AC) layer. The treatment with both (1) and (2) clearly improved the rainwater quality. The GDM reduced turbidity by 90.4% and the Sand/AC filter by 20.4%. With regard to COD, the studies for GDM did not show a clear elimination trend; the Sand/AC filter reduced the COD by 77%. Taken together, decentralized low-energy rainwater treatment can reliably provide quality-assured City Water for any specific use. Regarding the treatment design, GDM is preferable and can be better operated with downstream UV disinfection, which might be needed to reduce the pathogenic load, e.g., for local heat control measures. The research steps presented here will pioneer the development of a city-wide rainwater harvesting infrastructure on the way of establishing stormwater as a resource for a new wing of urban water supply. The presented findings will now result in the implementation of a full-scale CHW on the campus to ensure long-term irrigation of the listed park, relieving the public drinking water supply. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Open AccessArticle

Extensive Green Roofs: Different Time Approaches to Runoff Coefficient Determination

by

Cristina M. Monteiro

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Cristina Santos

and

Paula M. L. Castro

Water 2023, 15(10), 1852; https://doi.org/10.3390/w15101852 - 13 May 2023

Cited by 1 | Viewed by 880

Abstract

Stormwater runoff in green roofs (GRs) is represented by the runoff coefficient, which is fundamental to assess their hydraulic performance and to design the drainage systems downstream. Runoff coefficient values in newly installed GR systems should be estimated by models that must be [...] Read more.

Stormwater runoff in green roofs (GRs) is represented by the runoff coefficient, which is fundamental to assess their hydraulic performance and to design the drainage systems downstream. Runoff coefficient values in newly installed GR systems should be estimated by models that must be feasible and reproduce the retention behavior as realistically as possible, being thus adjusted to each season and climate region. In this study, the suitability of a previously developed model for runoff coefficient determination is assessed using experimental data, and registered over a 1 year period. Results showed that the previously developed model does not quite fit the experimental data obtained in the present study, which was developed in a distinct year with different climate conditions, revealing the need to develop a new model with a better adjustment, and taking into consideration other variables besides temperature and precipitation (e.g., early-stage moisture conditions of the GR matrix and climate of the study area). Runoff coefficient values were also determined with different time periods (monthly, weekly, and per rain event) to assess the most adequate approach, considering the practical uses of this coefficient. The monthly determination approach resulted in lower runoff coefficient values (0–0.46) than the weekly or per rain event (0.017–0.764) determination. When applied to a long-term performance analysis, this study showed no significant differences when using the monthly, weekly, or per rain event runoff, resulting on a variation of only 0.9 m³ of annual runoff. This indicates that the use of monthly values for runoff coefficient, although not suitable for sizing drainage systems, might be used to estimate their long-term performance. Overall, this pilot extensive GR of 0.4 m² presented an annual retention volume of 469.3 L, corresponding to a retention rate of 89.6%, in a year with a total precipitation of 1089 mm. The assessment of different time scales for runoff coefficient determination is a major contribution for future GR performance assessments, and a fundamental decision support tool. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Open AccessArticle

Feasibility Studies of Rainwater Harvesting System for Ablution Purposes

by

Fadhlul Wafi Awg Kapli

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Fatin Amanina Azis

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Hazwani Suhaimi

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Norazanita Shamsuddin

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Pg Emeroylariffion Abas

Water 2023, 15(9), 1686; https://doi.org/10.3390/w15091686 - 26 Apr 2023

Viewed by 1145

Abstract

For countries with an abundance of rain, there is definite potential to implement a rainwater harvesting system for different applications. This paper describes feasibility studies of an open-pond rainwater harvesting system for ablution purposes, analysing the quality of harvested rainwater and formulating a [...] Read more.

For countries with an abundance of rain, there is definite potential to implement a rainwater harvesting system for different applications. This paper describes feasibility studies of an open-pond rainwater harvesting system for ablution purposes, analysing the quality of harvested rainwater and formulating a rainwater harvesting model with suitable performance measures. The formulated model can be used to analyse the feasibility of the system in any locality by inputting local meteorological data. Quality analysis has shown that the harvested rainwater can be used safely for ablution purposes, albeit with a slightly acidic pH below 6.5. At a depth of 1.0 m and using the current pond configuration of a local mosque, the reliability of the system is 62.5% (228 days per year), and the amount of water saved is 345 m³, which is 60.7% of the water demand. It has been shown that a pond surface area of 60–70 m² provides optimum reliability and water saving, and more water savings can be expected with a more economical usage of water during ablution. These results indicate the feasibility of implementing a rainwater harvesting system for ablution purposes in religious institutions to help curb the water shortage crisis. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Open AccessArticle

Influence of Design Variables on the Financial Feasibility of Rainwater Harvesting Systems

by

Rodrigo Novais Istchuk

and

Enedir Ghisi

Water 2023, 15(6), 1112; https://doi.org/10.3390/w15061112 - 14 Mar 2023

Cited by 1 | Viewed by 1001

Abstract

Extensive implementation of rainwater harvesting (RWH) systems can promote substantial improvement in urban water resource management. Therefore, establishing the financial feasibility of RWH systems is imperative for their dissemination. This study evaluated the influence of rainfall time series indicators (average annual rainfall, seasonality [...] Read more.

Extensive implementation of rainwater harvesting (RWH) systems can promote substantial improvement in urban water resource management. Therefore, establishing the financial feasibility of RWH systems is imperative for their dissemination. This study evaluated the influence of rainfall time series indicators (average annual rainfall, seasonality index and behaviour of periods without precipitation) and design variables (catchment area, rainwater demand, number of inhabitants, potable water demand and rainwater tank size) on the financial feasibility of RWH systems in eight Brazilian cities. Correlations between rainfall indicators and financial feasibility were introduced, along with sensitivity analysis of design variables. Financial feasibility was obtained in 30% to 70% of the simulated scenarios. Initial investment and operating costs varied significantly among the eight cities according to local prices. Systems with a catchment area of 200 m² were capable of supplying, on average, 90.5% of the maximum rainwater consumption observed in this study. Local variation of potable water tariff schemes affected the financial feasibility of RWH systems. The number of inhabitants was the most influential design variable on the financial feasibility of RWH systems, followed by the rainwater tank size. Places with lower rainfall seasonality indexes and lower incidence and duration of dry periods are likely to lead to greater financial feasibility. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Open AccessArticle

Capacity Optimization of Rainwater Harvesting Systems Based on a Cost–Benefit Analysis: A Financial Support Program Review and Parametric Sensitivity Analysis

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Water 2023, 15(1), 186; https://doi.org/10.3390/w15010186 - 02 Jan 2023

Cited by 2 | Viewed by 1617

Abstract

Water risk has been continuously rising due to climate change and ownership disputes of water resources. Dam construction to secure water resources may lead to environmental problems and upstream immersion. On the other hand, rainwater harvesting systems can effectively supply water at a [...] Read more.

Water risk has been continuously rising due to climate change and ownership disputes of water resources. Dam construction to secure water resources may lead to environmental problems and upstream immersion. On the other hand, rainwater harvesting systems can effectively supply water at a low cost, although economic efficiency of these systems is still debatable. This study evaluates financial support programs to promote installation of rainwater harvesting systems, increasing economic feasibility. Based on a cost–benefit analysis, capacity optimization methods are further suggested. A sensitivity analysis is performed to determine the relative importance among uncertain parameters such as inflation and discount rates. In doing so, priority factors to consider in the design of rainwater harvesting systems are ultimately identified. A net present value, although it is sensitive to the inflation rate, is shown to be more appropriate to estimate the economic efficiency of rainwater harvesting system, compared to the typical cost–benefit ratio. Because the high future value overestimates the economic feasibility of rainwater harvesting systems, proper inflation rates should be applied. All in all, a funding program to promote rainwater harvesting systems significantly increases the benefits. Thus, national financial support policies are recommended to ensure economic feasibility of rainwater harvesting systems. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Review

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Open AccessReview

The Importance of Rainwater Harvesting and Its Usage Possibilities: Antalya Example (Turkey)

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Water 2023, 15(12), 2194; https://doi.org/10.3390/w15122194 - 11 Jun 2023

Cited by 1 | Viewed by 3537

Abstract

The significance and effective use of water, one of the most basic requirements for sustaining vital activities, is gaining importance every day. Population growth and unprogrammed industrialization accelerate the consumption of available water resources. However, drought, as a result of climate change, poses [...] Read more.

The significance and effective use of water, one of the most basic requirements for sustaining vital activities, is gaining importance every day. Population growth and unprogrammed industrialization accelerate the consumption of available water resources. However, drought, as a result of climate change, poses a threat to water resources. Factors such as the exhaustibility of water resources, rapid population growth, unscheduled industrialization and drought increase the tendency towards alternative water resources. Rainwater harvesting is based on the principle of using the rainwater falling into the regions after it is stored. Water collected through rain harvesting can be utilized in many different areas, such as agricultural irrigation, landscape irrigation and domestic use. Among agricultural activities, the idea of water harvesting in greenhouse areas comes to the fore. Due to the gutters on the greenhouse roofs, water can be stored. In Antalya, which has about half of the greenhouses in Turkey, the amount of water in the rain harvest that can be obtained in greenhouses is 224,992,795.8 m³ per year. Monthly calculations throughout the year showed that the minimum water can be harvested in August (938,447.53 m³) and the maximum (54,771,210 m³) in December. Therefore, it is thought that some plant water consumption can be met by building sufficient storage in areas close to the greenhouse. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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Open AccessReview

Rainwater Harvesting and Treatment: State of the Art and Perspectives

by

Anita Raimondi

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Ruth Quinn

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Gopinathan R. Abhijith

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Gianfranco Becciu

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Avi Ostfeld

Water 2023, 15(8), 1518; https://doi.org/10.3390/w15081518 - 13 Apr 2023

Viewed by 5238

Abstract

Rainwater harvesting is an ancient practice currently used for flood and drought risk mitigation. It is a well-known solution with different levels of advanced technology associated with it. This study is aimed at reviewing the state of the art with regards to rainwater [...] Read more.

Rainwater harvesting is an ancient practice currently used for flood and drought risk mitigation. It is a well-known solution with different levels of advanced technology associated with it. This study is aimed at reviewing the state of the art with regards to rainwater harvesting, treatment, and management. It focuses on the environmental and social benefits of rainwater harvesting and links them to the Sustainable Development Goals. The review identifies characteristics of laws and regulations that encourage this practice and their current limitations. It presents methodologies to design a rainwater harvesting system, describes the influence of design variables, and the impact of temporal and spatial scales on the system’s performance. The manuscript also analyzes the most advanced technologies for rainwater treatment, providing insights into various processes by discussing diverse physiochemical and biological technology options that are in the early stages of development. Finally, it introduces trends and perspectives which serve to increase rainwater harvesting, water reuse, and effective management. Full article

(This article belongs to the Special Issue Rainwater Harvesting and Treatment)

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