Sewer Overflow Pollution Research Articles

Unraveling the synergistic mechanisms of coagulation combined with oxidation for the treatment of sewer overflow: The interaction between iron species and NaClO

During wet weather, sewer overflow pollution can pose a serious threat to surface water. In order to reduce the impact of overflow discharge on receiving waters, ferric chloride (Fe(Ⅲ))/potassium ferrate (Fe(Ⅵ))/polyacrylamide (PAM) coagulation (Fe(Ⅲ)/Fe(Ⅵ)/PAM) combined with sodium hypochlorite (NaClO) oxidation was proposed. Different combinations were constructed, including pre-oxidation coagulation (NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM), pre-coagulation oxidation (Fe(Ⅲ)/Fe(Ⅵ)/PAM-NaClO), and synchronous coagulation oxidation (NaClO+Fe(Ⅲ)/Fe(Ⅵ)/PAM). The combined processes achieved efficient removal of conventional contaminants, and the produced byproducts were controlled, especially in the NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM. The obvious discrepancy in the sulfamethoxazole (SMX) removal was observed in different processes. NaClO affected the distribution of hydrolyzed iron species, and the proportion of active iron in the NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM significantly increased. More complexation sites were generated in the NaClO-Fe(Ⅲ)/Fe(Ⅵ)/PAM, which can complex with the coagulant and then effectively transfer to the flocs. The composition of the flocs further confirmed the differences in coagulation characteristics. The generated·OH played a crucial role in SMX removal in the NaClO+Fe(Ⅲ)/Fe(Ⅵ)/PAM, and ClO·was responsible for partial removal of ammonia nitrogen (NH4+-N). The contribution of high-valent iron species was confirmed, and the introduction of NaClO promoted the generation of iron species. This study may provide an ideal for overflow treatment to improve the urban water environment.

Retrofitting low-performance units to abate sewer overflow pollution based on mathematical model and Sobol algorithm

Retrofitting low-performance units to abate sewer overflow pollution based on mathematical model and Sobol algorithm

Microplastics discharged from urban drainage system: Prominent contribution of sewer overflow pollution

Urban drainage system is an important channel for terrigenous microplastics (<5 mm in size) to migrate to urban water bodies, especially the input load caused by overflow pollution in wet weather. Investigating how they transport and discharge is essential to better understand the occurrence and variability of microplastics in different water ecosystems. This study evaluated the abundance and distribution characteristics of microplastics in the drainage systems of typical coastal cities in China. The impacts of meteorological conditions and land use were explored. In particular, the prominent contribution of drainage sewer overflow pollution during storm events were investigated. The results showed that the microplastics abundance in daily sewage discharge from different drainage plots ranged between 13.6 and 30.8 items/L, with fibers as the dominant type of microplastics. Sewer overflow discharge can greatly aggravate microplastic abundance to 83.1 ± 40.2 items/L. Road runoff and sewer sediment scouring were the main pollution sources. Systematic estimates based on detailed data showed that the average microplastics emitted per capita per day in household wastewater was 3461.5 items. A quantitative estimation method was proposed to show that the annual emissions load of microplastics via urban drainage system in this research area was 5.83×1010 items/km2, of which the proportion of emissions in wet weather accounted for about 60%. This research provides the first full-process of assessment and source apportionment of the microplastic distribution characteristics in old drainage system. The occurrence of storm events is an important marker of increased microplastic abundance in urban rivers, with a view to urgent need for interception of surface runoff and purification of sewer overflow pollution.

Abatement of Sewer Overflow Pollution Based on Distributed Optimal Control Approach

Abatement of Sewer Overflow Pollution Based on Distributed Optimal Control Approach

Research on the Comprehensive Regulation Method of Combined Sewer Overflow Based on Synchronous Monitoring—A Case Study

Combined sewer overflow pollution has gradually become the limiting factor for the further improvement of river water quality during rain events. Setting up a comprehensive regulation method based on synchronous monitoring is essential for combined sewer overflow management. However, current studies mainly focus on single monitoring and lack a correlation between control objectives and control effects. This study establishes a new aspect of a comprehensive regulation and control method based on overflow characteristic analysis, a calculation model, and control target determination. Through synchronous monitoring of the pipe network, the sewage treatment plant, and the river course in the Liangshui River basin of China, rainfall thresholds of outlets in a combined pipe network, pre-treatment overflow, and simple-treatment overflow were 14, 9, and 16 mm, respectively, and the overflow volume was positively correlated with the rainfall. The COD (chemical oxygen demand) concentration from the pre-treatment overflow was much higher than that from the combined pipe network, and the EMC (event mean concentration) in heavy rain was higher than in rainstorms. The shortest time exceeding the water quality by overflow pollution was 1 h, and the longest time was more than 7 days. Overflow load proportions of the three links were 43.4%, 32.8%, and 23.8%, accounting for 66.3% of the total pollutant load of the river, and the best scheme of input–output ratio was to regulate the first three outlets of overflow load. Our results provide comprehensive guidance and a systematic approach for the monitoring and control of combined sewer overflow.

A city-scale fully controlled system for stormwater management: Consideration of flooding, non-point source pollution and sewer overflow pollution

An increase in severe urban pluvial flooding, non-point source (NPS) pollution and combined sewer overflow (CSO) pollution increasingly threaten human life and property. City-scale sustainable stormwater management has become alternative solutions. This research designed and evaluated a stormwater management system (sponge city) on city-scale. The differences between old and new districts, the coexistence of combined and separate drainage systems, pipeline defects and the corresponding groundwater/river infiltration were fully considered in the system design. Low impact development (LID) practices, drainage upgrading and terminal control approaches were integrated together. Sponge city implementation is a no-regrets adaption strategy that can offset the stormwater related pressures. Compared with baseline values, the maximum fraction of the conduit full depth decreased for the entire pipe network. Annual values of total inflow volume (TIV) and total flooded volume (TFV) decreased by 32.26% and 53.68%, respectively. Significant decreases in pollution release were also recorded, with reduction rates of 40.96% (chemical oxygen demand; COD), 71.18% (ammonia nitrogen; NH3-N), 41.57% (suspended solids; SS) and 50.40% (total phosphorus; TP). LID on its own allows the city as a whole to control runoff and to largely reduce NPS pollution; however, it has a limited ability to improve drainage capacity. Adopting grey approaches, such as drainage system rehabilitation and renovation, as well as storage tanks, was proved to be essential for drainage capacity improvement and pollution control on city-scale. However, final pollutant discharge depends on the relative amount of increased NPS loads and reduced CSO loads after implementing combined sewer separation projects. It is usually recommended to increase the NPS pollution control target when designing stormwater control system. Terminal facilities (such as riparian zones and storage tanks) are encouraged to better control NPS pollution. Methods and conclusions on the comprehensive consideration of urban complex conditions, systematic stormwater control and the effectiveness of different measures highlighted in this study on a city scale provide important reference for future urban sustainable stormwater management.

Spatio-temporal characteristics of non-point source and sewer overflow pollution and its impacts on water environment in Shenzhen Bay Basin

Spatio-temporal characteristics of non-point source and sewer overflow pollution and its impacts on water environment in Shenzhen Bay Basin

Uncertainty analysis in a large-scale water quality integrated catchment modelling study

Receiving water quality simulation in highly urbanised areas requires the integration of several processes occurring at different space-time scales. These integrated catchment models deliver results with a significant uncertainty level associated. Still, uncertainty analysis is seldom applied in practice and the relative contribution of the individual model elements is poorly understood. Often the available methods are applied to relatively small systems or individual sub-systems, due to limitations in organisational and computational resources. Consequently this work presents an uncertainty propagation and decomposition scheme of an integrated water quality modelling study for the evaluation of dissolved oxygen dynamics in a large-scale urbanised river catchment in the Netherlands. Forward propagation of the measured and elicited uncertainty input-parametric distributions was proposed and contrasted with monitoring data series. Prior ranges for river water quality-quantity parameters lead to high uncertainty in dissolved oxygen predictions, thus the need for formal calibration to adapt to the local dynamics is highlighted. After inferring the river process parameters with system measurements of flow and dissolved oxygen, combined sewer overflow pollution loads became the dominant uncertainty source along with rainfall variability. As a result, insights gained in this paper can help in planning and directing further monitoring and modelling efforts in the system. When comparing these modelling results to existing national guidelines it is shown that the commonly used concentration-duration-frequency tables should not be the only metric used to select mitigation alternatives and may need to be adapted in order to cope with uncertainties.

Deep Tunnel for Regulating Combined Sewer Overflow Pollution and Flood Disaster: A Case Study in Guangzhou City, China

The DongHaoChong (DHC) basin is located in the central city zone of Guangzhou City, China. Owing to the high density of buildings and low quality of the drainage pipe network in the city, diversion of rain and sewage is difficult. Waterlogging occurs frequently and combined sewer overflow (CSO) pollution is a serious problem during the rainy season. Therefore, a deep tunnel for the DongHaoChong basin has been planned and its construction is currently underway. An urban rainstorm model for the DongHaoChong basin was developed on the basis of the Storm Water Management Model (SWMM), and both the interception effect of CSO pollution and the degree of mitigation of flood were analyzed. Reasonable scenarios for the deep tunnel in terms of rainstorms with different design recurrence periods were evaluated. From the viewpoints of preventing rainstorm waterlogging disasters and protecting water quality in the region downstream of DongHaoChong River, the river flood control and drainage capacities of the region were improved to a 2-year rainstorm design recurrence period by the construction of the deep tunnel. Furthermore, the main pollutant load of the CSO is expected to be reduced by about 30%–40%.

Dry Weather Channel Impacts on Wet Weather Combined Sewer Overflow Pollution Rates

Settling solids upstream of a combined sewer overflow (CSO) have led to an undesirable odour issue in warm temperatures and elevated environment…

Parsimonious Model for Combined Sewer Overflow Pollution

The reservoir concept for flow modeling has been generalized for the purpose of the parsimonious modeling of combined sewer overflow pollution. Conceptual models have been used for the buildup and washoff of pollutants on the paved surfaces, and the transport of these pollutants in the sewer system (advection, dispersion, sedimentation, and resuspension). For the parsimonious modeling of the water quality of the sewage in the effluent of the combined sewer system, the conceptual submodels of these different processes were lumped into one single model equation. When ancillary structures such as a storage sedimentation tank are present at the combined sewer overflow, the additional effect of advection, dispersion, storage, and sedimentation is considered in a similar parsimonious conceptual way. Such a parsimonious model aims to reduce the model complexity, and therefore the number of calibration parameters. In most practical cases of urban drainage modeling, water quality data are extremely limited and consequently only a small number of parameter values can be identified from the data. The proposed model is tested on the basis of 10-min and hourly concentration measurements for total suspended solids, settleable solids, biochemical oxygen demand, and ammonia at the outlet of the combined sewer system of the village of Dessel (Belgium), which were available in this case only for six overflow events.

A Case Study of Combined Sewer Overflow Pollution: Assessment of Sources and Receiving Water Effects

Abstract Combined sewer overflow (CSO) pollution was assessed in a medium size community (the Town of Malacky) in western Slovakia by means of field monitoring and computer modelling. CSO samples were analyzed for suspended solids, total chemical oxygen demand, 5-day biochemical oxygen demand, total organic carbon, heavy metals (Cu, Zn, Ni, Cd, Pb), and biological and microbiological constituents. Study results identified CSOs as a major source of biodegradable organic pollution impacting on dissolved oxygen in the receiving streams. Cumulative effects of CSO discharges were also observed in the receiving streams, in the form of high organic content of benthic sediments, which indicated the deposition of wastewater-derived sediments flushed out from the sewer system during storm events. These findings have also been confirmed by analyses of biological constituents in the sediment samples collected from the receiving waters. A comparative analysis of various pollution sources indicated that pollution problems in the receiving waters were caused not only by the municipal effluents from the Town of Malacky, but also by diffuse agricultural pollution and release of heavy metals, especially Zn, from the native soils in the surrounding area.

Foreword: Stormwater Management and Abatement of Combined Sewer Overflow Pollution

Foreword: Stormwater Management and Abatement of Combined Sewer Overflow Pollution

POLLUTION PREVENTION AND POLITICS — THE RECENT EXPERIENCE IN SYDNEY

The New South Wales State Government has embarked on a multi-billion dollar programme of pollution abatement in Sydney, The socio-economic and political factors which have prompted this are described, These illustrate the complexities of dealing with pollution problems while social values alter, public organisations experience administrative change and financial pressures, and politicians try to balance environmental and economic objectives, The technical progress of the Sydney initiatives to reduce storm water runoff and sewer overflow pollution is also outlined.

Real Time Control in Part of Copenhagen

The application of real-time control to the sewer system in a district of Copenhagen is described. It enables the storage capacity of the sewer system to be better utilised, thus minimizing combined sewer overflow pollution.

Detention of Sanitary Sewage as a Method to Reduce Combined Sewer Overflow Pollution Loads

Sanitary sewage yields the basic and most important pollution load diverted to receiving waters during combined sewer overflow (CSO). To reduce overflow pollution loads, it is proposed to store waste water in sanitary sewage detention tanks (SST). For high efficiency those SSTs should be filled and emptied by pumps or gates, operated by control devices. Control strategies have to be worked out depending on different situations and parameters (catchment, rain and flow characteristics).

Reduction of Combined Sewer Overflow Pollution Loads by Detention of Sanitary Sewage

For mixed combined/separate sewer systems it is proposed, in times of combined sewage overflows (CSO), to store sanitary sewage at the inlet point to the combined system. Thereby, sanitary sewage (with high strength) is kept in the system for further treatment after the storm whereas less-polluted CSO are diverted to the receiving water. By using data of an existing catchment different scenarios are evaluated and the potential benefit of sanitary sewage detention is quantified. This approach is compared to current German CSO regulations. It is more effective than conventional CSO detention if more than 60 % of the population upstream of the CSO diversion are served by a separate system. A key problem of this concept is the control strategy that determines when to activate and empty the storage tanks. A number of criteria are compared. Considerations are also made on operational aspects such as chemical transformations in stored sewage, maximum allowable detention time, and cleansing of storage tanks.

Stormwater Pollution Control: Structural Measures

Combinations of storage and wet-weather treatment, integrated with dry-weather treatment facilities and nonstructural control measures on an area-wide basis, are found to provide the greatest and most cost-effective control of storm-water pollution. Case studies of three very promising, constructed and operating structural measures for controlling combined sewer overflow pollution demonstrate these concepts. Information on the design, operation, performance and costs of these facilities is provided and compared to guide future planners and designers. In Seattle, Washington, computerized control of in-line storage offers operational flexibility and inexpensive storage. At Saginaw, Michigan, off-line storage/treatment integrated with in-line storage and dry-weather treatment has achieved high performance at moderate costs. At Mount Clemens, Michigan, physical and biological wet-weather treatment processes promise very high treatment levels for combined sewage, if needed.

Stormwater-Combined Sewage Pollution Abatement

The mission of the USEPA’s Storm and Combined Sewer Pollution Control Research and Development Program is to quantify the urban storm and combined sewer overflow pollution problems and develop countermeasure controls. As a result of the Program’s efforts an advanced technology or state-of-the-art has been developed, demonstrated, and disseminated. This paper addresses the problem and characterization of stormwater and combined sewage impacts upon our Nation’s receiving waters while presenting various levels of pollution control technology. Efforts of urban runoff management examined deal with source control, collection system control, storage and treatment, and integrated (complex) systems.

EPA Research in Urban Stormwater Pollution Control

This state-of-the-art on the Environmental Protection Agency's research in urban stormwater and combined sewer overflow pollution control describes the major elements of the Urban Runoff Pollution Control Program. Problem definition, users assistance tools, management alternatives and technology transfer are covered, including some of the highlights of the Program's future direction and products from over 150 of its research projects. Capital cost comparisons for storm and combined sewer control and treatment are given, along with a specific example of cost-effect solution for urban runoff pollution control by in-line storage in Seattle. In a study done in Des Moines, using a simplified receiving water model, four control alternatives were compared, considering cost and effectiveness in terms of a frequency of dissolved oxygen standard violations. (ASCE)