Search Results (177)

Rapid urbanization in China has overwhelmed traditional drainage systems, resulting in frequent flooding and water pollution in densely populated urban areas. This study focuses on the East Lake core area of Wuhan, proposing a deep tunnel drainage system to improve sewage storage and conveyance capacity. A pilot-scale pipe model was employed to determine the critical non-silting velocity for full-pipe sewage flow. Based on projected dry-season inflows and intercepted combined sewer discharges, the design capacities for pumping stations and pretreatment facilities were defined. A three-dimensional gas–liquid two-phase numerical model was used to simulate inflow shaft hydraulics at Erlangmiao, Luobuzui, and Wudong pretreatment stations. Simulation results confirm that all shafts meet energy dissipation and ventilation requirements, with uniform flow and velocity distributions that could be obtained by a vortex-type shaft. The system not only mitigates regional environmental challenges but also shows significant social, environmental, and economic benefits. Overall project design, applied methodology, simulation study, and outcomes could provide a valuable reference to deep tunnel drainage design and research. Full article

Fats, oils, and grease (FOG) deposits are hardened, sticky, insoluble solids that accumulate in sewage systems globally. These deposits contribute to pipe blockages and sanitary sewer overflows, releasing pathogens and pollutants into the environment, posing significant environmental and public health risks. Current removal methods are labor-intensive and costly, emphasizing the need for alternatives. While biological strategies offer a viable alternative, the microbial breakdown of FOG is poorly understood. In this study, we evaluated the potential of individual microbial strains and synthetic microbial communities to biodegrade wastewater-derived FOG deposit samples. These biological agents were applied to a range of FOG samples, and biodegradation was assessed through visual observations such as color change or gas bubbles, particle size, cell counts, pH, weight loss, and changes in fatty acid profile. Results demonstrate that microbial augmentation can enhance FOG degradation, offering an alternative or complementary approach for reducing maintenance burdens and preventing sewer blockages. Full article

Styrene is an aromatic compound widely used as a reactive monomer in polyester resins, which are among the most utilized resins in cured-in-place pipe (CIPP) technology, the most widely used trenchless pipe renewal method. Given that styrene is classified as a suspected human carcinogen, this study aims to evaluate styrene concentrations emitted into the air during sewer pipe rehabilitation using CIPP. This study included developing a comprehensive methodology to collect data from six different CIPP installations across the U.S. and document styrene emissions before, during, and after the curing process. The air samples were collected and analyzed using the USEPA method TO-15 and TO-17. Measured styrene emissions were then compared with exposure limits established by USEPA, NIOSH, and OSHA to assess potential occupational and worker health impacts. The result confirmed that high styrene concentrations, exceeding the established threshold, can be observed within the CIPP work zone. The result also indicated a considerable reduction in styrene concentration within five feet downwind of the work zone. In conclusion, while the health risk to the public appears to be low, there is a potential for health impact for the CIPP crew. Therefore, implementing real-time air quality monitoring during CIPP installation to mitigate these health risks is recommended. Additionally, the use of appropriate personal protective equipment (PPE) by the crew is essential. Full article

Pressure on fresh water resources has been aggravated in recent decades, basically due to population growth, rapid urbanization, and global warming. Integrated engineering solutions and the circular economy, considering the urban water cycle as a whole, are becoming fundamental, particularly in arid and semi-arid regions under permanent or recurrent hydric deficit. This study aims to develop and present an integrated engineering solution for water supply, wastewater collection, and treated wastewater reuse for landscape irrigation in a large, topographically complex, and arid to semi-arid coastal urban region at the south of Santiago Island, Cape Verde. The region is one of the driest and most arid of the Island, with a current average annual precipitation between about 100 and 200 mm, and has very limited underground water resources. The main study area, with about 600 ha, has altitudes ranging from values close to sea level up to about 115 m and has several topographic difficulties, including several relatively rugged zones. The devised water supply system considers four altimetric distribution levels, three main reservoirs connected to each other by a serial system of pipelines with successive pumping, a fourth downstream reservoir for pressure balance in one of the levels, and desalinated water as the source. The sanitary sewer pipes of the urbanizations drain to an interceptor system that operates predominantly in open channel flow in a closed pipe. The long interceptor crosses laterally along the coast several very dug valleys in the path to the Praia Wastewater Treatment Plant in the east, and requires several conduits working under pressure for the crossings, either lifting or governed by gravity. The under-pressure pipeline system of recycled water is partially forced and partially ruled by gravity and transports the treated wastewater from the plant in the opposite direction of the interceptor to a natural reservoir or lake located in the region of urbanizations and the main green spaces to be irrigated. The conceived design of the interceptor and recycled water pipeline minimizes the construction and operation costs, maximizing their hydraulic performance. Full article

Urban flooding and the management of stormwater present significant challenges that necessitate innovative and sustainable solutions. This research examines the effectiveness of green stormwater infrastructure (GSI) for resilient storm sewer systems using the Storm Water Management Model (SWMM), based on customized local climate scenarios. Daily climate data downscaled by four CMIP6 models—CESM2, GFDL-CM4, GFDL-ESM4, and NorESM2-MM—was used. The daily data was disaggregated into 15 min temporal resolution using the HyetosMinute R-package. Two GSI types—bio-retention and rain gardens—were evaluated with a maximum coverage of 30%. The analysis focuses on two future climate scenarios, SSP2-4.5 and SSP5-8.5, predicted under the Shared Socioeconomic Pathways (SSPs) framework. The performance of the stormwater network was assessed for mid-century (2041–2060) and late century (2081–2100), both before and after integration of GSI. Three performance metrics were applied: node flooding volume, number of nodes flooded, and pipe surcharging duration. The simulation results showed an average reduction in flooding volumes ranging between 86 and 98% over the area after integration of GSI. Similarly, reductions ranging between 78 and 89% and between 75 and 90% were observed in pipe surcharging duration and number of nodes vulnerable to flooding, respectively, following GSI. These findings underscore the potential of GSI in fostering sustainable urban water management and enhancement of sustainable development goals (SDGs). Full article

Over the past 30 years, the City of Portland, Oregon, USA, has emerged as a national leader in green stormwater infrastructure (GSI). The initial impetus for implementing sustainable stormwater infrastructure in Portland stemmed from concerns about flooding and water quality in the city’s two major rivers, the Columbia and the Willamette. Heavy rainfall often led to combined sewer overflows, significantly polluting these waterways. A partial solution was the construction of “The Big Pipe” project, a large-scale stormwater containment system designed to filter and regulate overflow. However, Portland has taken a more comprehensive and long-term approach by integrating sustainable stormwater management into urban planning. Over the past three decades, the city has successfully implemented GSI to mitigate these challenges. Low-impact development strategies, such as bioswales, green streets, and permeable surfaces, have been widely adopted in streetscapes, pathways, and parking areas, enhancing both environmental resilience and urban livability. This perspective highlights the history of the implementation of Portland’s GSI programs, current design and performance standards, and challenges and lessons learned throughout Portland’s recent history. Innovative approaches to managing runoff have not only improved stormwater control but also enhanced green spaces and contributed to the city’s overall climate resilience while addressing economic well-being and social equity. Portland’s success is a result of strong policy support, effective integration of green and gray infrastructure, and active community involvement. As climate change intensifies, cities need holistic, adaptive, and community-centered approaches to urban stormwater management. Portland’s experience offers valuable insights for cities seeking to expand their GSI amid growing concerns about climate resilience, equity, and aging infrastructure. Full article

Ground subsidence is a significant geotechnical hazard in urban areas, leading to property damage, casualties, and broader societal issues. This study investigates the mechanisms of cavity formation and ground subsidence through laboratory model tests using Korean standard sand and marine clay under controlled conditions. A transparent soil box apparatus was fabricated to simulate sewer pipe damage, with model grounds prepared at various relative densities, groundwater levels, and fines contents. The progression of cavity formation and surface collapse was observed and quantitatively analyzed by measuring the time to cavity formation and ground subsidence, as well as the mass of discharged soil. Results indicate that lower relative density accelerates ground subsidence, whereas higher density increases cavity volume due to greater frictional resistance. Notably, as the fines content increased, a tendency was observed for ground subsidence to be increasingly suppressed, suggesting that cohesive clay particles can limit soil loss under seepage conditions. These findings provide valuable insights for selecting backfill materials and managing subsurface conditions to mitigate ground subsidence risks in urban infrastructure. Full article

Microbially induced concrete deterioration (MID) poses a significant and urgent challenge to urban sewerage systems globally, particularly in tropical coastal regions. Despite the acknowledged importance of biofilms in MICC, limited research on sewer pipe biofilms has hindered a comprehensive understanding of their deterioration mechanisms. To overcome this limitation, our research employed multiple staining techniques and digital volume correlation (DVC) technology, creating a new method to analyze the microstructure of biofilms, precisely identify the components of EPSs, and quantitatively examine MID mechanisms from a microscopic viewpoint. Our results revealed that the biofilm on concrete surfaces regulates the types of amino acids, thereby creating an environment conducive to microbial aggregate survival. Additionally, salinity significantly influences biofilm component distribution, while proteins play a pivotal role in biofilm mechanical stability. Notably, a high salinity fosters microbial migration within the biofilm, exacerbating deterioration. Through this multidimensional inquiry, our study established an advanced echelon of comprehension concerning the intricate mechanisms underpinning MICC. Meanwhile, by peering into the biofilms and elucidating their interplay with concrete, our findings offer profound insights, which can aid in devising strategies to counter urban sewer system deterioration. Full article

The inspection of sewer pipes in the UK is costly, and if not inspected regularly, they are costly and disruptive to repair. This paper presents the Mega-Joey, a novel miniature, tether-less robot platform that is capable of autonomously navigating and assessing confined spaces, such as small-diameter underground pipelines. This paper also discusses a novel decentralized event-based-broadcasting autonomous exploration algorithm designed for exploring such pipe networks collaboratively. The designed robot is able to operate in pipes with an inclination of up to 20 degrees in dry and up to 10 degrees in wet conditions. A team of Mega-Joeys was used to explore a test network using the proposed algorithm. The experimental results show that the team of robots was able to explore a 3850 mm long test network within a faster period (36% faster) and in a more energy-efficient manner (approximately 54% more efficient) than a single robot could achieve. Full article

Tree root intrusion can cause failures of underground sewer pipes and thus represent a major water asset management issue. If tree root intrusion is not detected early, this may lead to the interruption of wastewater services and high costs of repair to the pipeline. The objectives of this review are to assess the existing maintenance strategies, explore suitable strategies for Australia and similar settings around the world, and identify possible factors and predictive tools. Maintenance strategies can be divided into two categories: reactive and proactive approaches. The current reactive approaches are (1) mechanical techniques to clean the root mass in pipe networks and (2) chemical techniques to remove the root mass and control future growth. The literature suggests that the reactive approaches often provide only partial solutions. The proactive approaches, guided by a predictive model of tree root intrusion and its related factors, showed the potential to improve maintenance and limit the risk of the damage from re-occurring. Predictive models could help to evaluate the risk of planting trees in different conditions and minimise the damage of tree root intrusion after further multifactor investigations. Full article

This paper presents the study of decision variables selection in the optimization of sewer network systems. A mathematical model is presented that considers an objective of minimizing the total cost of sewer network comprising all pipe costs, manhole costs, and excavation cost. The mathematical model is solved by using an artificial protozoa optimizer bio-inspired algorithm for the first time in this domain. This work compares ten alternative decision variable sets obtained by systematically varying factors related to the pipe diameter, the slope or cover depths, and nodal elevations. The results display extreme variation among the alternatives. The alternative using only node elevation as a decision variable, that is, Alternative 6, had the lowest average cost, 81345.91, with a very low standard deviation, 28.35, showing maximum consistency. On the other hand, alternatives involving higher numbers of decision variables, such as Alternative 1, resulted in faster computation but with greater variability and cost. Running times ranged from 466 s in Alternative 1 to 66700 s in Alternative 10. The generated alternatives are statistically compared using Friedman and Wilcoxon tests to assess their impact on solution cost and algorithm performance. The results show large variability in the performance consistency and computational efficiency of the alternatives, thus providing indications on the most suitable configurations of decision variables for the sewer network optimization. The alternative which has the nodal elevation as the decision variable performs the best in terms of solution quality. These findings clearly demonstrate that selecting fewer, hydraulically meaningful decision variables can enhance solution quality, although at the expense of increased computational effort. Full article

Aiming to solve the problem of clearing obstacles in narrow and complex sewers, this paper introduces a visually assisted Sewer Cleaning Robot (SCR) for cleaning sewers with diameters ranging from 280 to 780 mm. The main work is carried out as follows: (a) A mobile platform is equipped with a pressing mechanism to press against the pipe walls in different diameters. The arm uses high-load linear actuator structures, enhancing load capacity while maintaining stability. (b) A Detection–Localization–Cleaning mode is proposed for cleaning obstacles. The YOLO detection model is used to identify six types of sewer defects. Target defects are then localized using monocular vision based on edge detection within defect bounding boxes. Finally, cutting is performed according to the localized defect positions. The feasibility of SCR in cleaning operations is validated through a series of experiments conducted under simulated pipeline conditions. These experiments evaluate its mobility, visual detection, and localization capabilities, as well as its ability to clear hard obstacles. This paper provides technical reserves for replacing human labor that use vision algorithms to assist in cleaning tasks within sewers. Full article

Carbon emission fluxes in urban sewer systems and the microbial community structure in sewer sediments remain unclear. In this study, a sewer system located in southern China was utilized to investigate the water quality characteristics. The results showed that the chemical oxygen demand loss rates in the branch pipe and sub-main pipe were 27.1% and 14.1%, respectively. The estimated carbon emission flux was estimated by the carbon emission factor method. The results revealed that the total carbon emission flux from the sewer system was 1.39 kg CO₂-eq/m³ and the emission fluxes of methane and carbon dioxide were 0.87 kg CO₂-eq/m³ and 0.51 kg CO₂-eq/m³, accounting for 62% and 36.4%. The microbial community structure was analyzed by 16S rRNA. The results indicated that the methanogenic archaea in the sediments of the branch pipe and sub-main pipe were Methanobacterium, Methanosaeta, and Methanobrevibacter. The methanogenic activity of the sewer sediments was further assessed. This study further confirmed that the branch pipe and sub-main pipe were the main sources of carbon emissions and methane and carbon dioxide are the main greenhouse gases in the sewer system. This study furnishes novel insights for the control of carbon emissions in municipal sewage systems. Full article

The Active Radar Interferometer (AcRaIn) represents a novel approach in secondary radar technology, aimed at environments with high reflective clutter, such as pipes and tunnels. This study introduces a compact design minimizing peripheral components and leveraging commercial semiconductor technologies operating in the 24 GHz ISM band. A heterodyne principle was adopted to enhance unambiguity and phase coherence without requiring synchronization or separate communication channels. Experimental validation involved free-space and pipe measurements, demonstrating functionality over distances up to 150 m. The radar system effectively reduced interference and achieved high precision in both straight and bent pipe scenarios, with deviations below 1.25% compared to manual measurements. By processing signals at intermediate frequencies, advantages such as improved efficiency, isolation, and system flexibility were achieved. Notably, the integration of amplitude modulation suppressed passive clutter, enabling clearer signal differentiation. Key challenges identified include optimizing signal processing and addressing logarithmic signal attenuation for better precision. These findings underscore AcRaIn’s potential for pipeline monitoring and similar applications. Full article

Sanitary sewer pipelines frequently experience blockages, structural failures, and overflows, underscoring the dire state of U.S. wastewater infrastructure, which has been rated a D-, while America’s overall infrastructure scores only slightly better at C-. Traditional open-trench excavation methods or excavation technology (ET) for replacing deteriorated pipes are notoriously expensive and disruptive, requiring extensive processes like route planning, surveying, engineering, trench excavation, pipe installation, backfilling, and ground restoration. In contrast, trenchless technologies (TT) provide a less invasive and more cost-effective alternative. Among these, cured-in-place pipe technology (CIPPT), which involves inserting resin-impregnated fabric into damaged pipelines, is widely recognized for its efficiency. However, a comprehensive life cycle cost analysis (LCCA) directly comparing ET and TT, accounting for the net present value (NPV) across installation, maintenance, and rehabilitation costs, remains unexplored. This study aims to establish an LCCA framework for both CIPPT and ET, specifically for sanitary sewer pipes ranging from 8 to 42 inches in diameter. The framework incorporates construction, environmental, and social costs, providing a holistic evaluation. The key costs for ET involve pipe materials and subsurface investigations, whereas TT’s costs center around engineering and design. Social impacts, such as road and pavement damage, disruption to adjacent utilities, and noise, are pivotal, alongside environmental factors like material use, transportation, project duration, and equipment emissions. This comprehensive framework empowers decision makers to holistically assess economic and environmental impacts, enabling informed choices for sustainable sewer infrastructure renewal. Full article