Combined Sewer Overflow Control Research Articles

Experience with Vortex Separators for Combined Sewer Overflow Control

In 1987 the first vortex solids separator facility in Germany was installed for combined sewer overflow (CSO) control. The separation efficiency was optimized in the hydraulic laboratory using scaled down models with artificial tracers to simulate typical sewage particulates. The station has two parallel operating vortex separators and serves a connected and impervious area of about 11 hectares (ha) and 1,500 people. The specific storage volume of the station is 7.2 m3 per ha. Two evaluation programs were conducted. The first evaluation phase noted the operational reliability, hydraulic loads, overflow frequencies and water mass balances. The second phase monitored separation efficiencies. The evaluation showed that vortex solids separators are now ready for use in CSO control.

Strategy of stochastic real-time control of wastewater treatment plants

The paper describes fundamentals of stochastic real-time control (RTC) of wastewater treatment and disposal facilities operating under dynamic wet weather/dry weather conditions. Similar models are also applicable to the control of combined sewer overflows (CSO's). Objectives and goals, components, strategy, and operation of RTC systems are delineated. RTC systems can be incorporated into an expert system to assist the operator of wastewater treatment and disposal facilities, and/or into semior fully automated systems. The stochastic transfer functions used for prediction of the inputs and response of the system belong to the class of ARMA stochastic models. Neural network models are also applicable. Such models can be shown to be consistent with traditional deterministic transfer functions. A review of existing RTC systems concludes the paper.

State‐of‐the‐art update on combined sewer overflow control

Control and treatment of stormwater discharges and combined sewage overflows from urban areas are problems of increasing importance in the field of water quality management. Over the past decade much research effort has been expended and a large amount of data has been generated. The purposes of past research were to quantify urban overflow pollution problems and develop countermeasure controls. This review presents an updated state‐of‐the‐art overview of those efforts emphasizing the combined sewer overflow aspects.

Two‐Stage Urban Runoff Forecast Model

Storm‐related pollution in general, and combined sewer overflows in particular, have been found to contribute significant amounts of pollutants to receiving water bodies. Control of pollution from these nonpoint sources of pollution is very costly. Accordingly, integrated real‐time control of combined sewer overflow is being considered as a possible alternative to the more traditional forms of pollution control. The basic features of suggested control combined sewer overflow control strategies are reviewed, including simple local control, reactive control, and anticipatory control. Because water quantity forecasts are essential to any integrated real‐time control strategy, the application of a simple microcomputer‐based two‐stage urban runoff forecast model is examined. Runoff forecasts from this deterministic‐stochastic model are provided for lead times ranging from 1–12 time steps (5–60 min). The two‐stage approach is found to be particularly useful for lead times of up to 30 min.

Prédiction des débits de ruissellement pour le contrôle des réseaux d'égouts unitaires

As point sources of pollution are being eliminated others, less apparent, are becoming increasingly threatening to many water users. Non-point sources of pollution generated by combined sewer overflows have been found to be responsible for many of our water quality problems. The purpose of this paper is twofold: (a) to offer a summary of the combined sewer overflow control problem, and (b) to suggest a methodology for the anticipation or prediction of runoff flows from an urban catchment.Two types of regression models designed to predict urban runoff are presented and compared with the calibrated runoff model ILLUDAS. The simplicity of regression models and their ease of application to the real-time automatic control of combined sewer overflows make their use very promising.

Worth of short‐term rainfall forecasting for combined sewer overflow control

Real‐time, short‐term rainfall forecasting is gaining recognition as a valuable input to more effective performance of a variety of urban water management activities, including controlling the incidence of untreated combined sewer overflows. An important question is, What levels of forecast error can be tolerated before it is better to abandon adaptive control policies utilizing forecast information in favor of simple reactive control methods? Experiments with an autoregressive‐transfer function model for shortterm forecasting are presented, utilizing the San Francisco North Shore Outfalls Consolidation Project as a case study. A split data technique is used to gain insight into expected forecast errors for selected overflow‐producing storms varying from high intensity‐low duration to low intensity‐high duration. These results are then compared with the performance of the planned system, utilizing automatically controlled gates in a large shoreline tunnel, for various levels of forecast error. The results of a limited number of simulation runs indicate that expected forecast model errors are generally lower than the error threshold above which reactive policies become more attractive.

National Needs for Combined Sewer Overflow Control

The national extent of the combined sewer overflow problem is investigated in terms of (1)Regional populations and acreages served; and (2) a range of potential costs for the control of overflows. Combined sewers in the United States serve approx 37 million people and 2.7 million acres (10.9 × 109 m²) of urban land. Cost estimates are presented for the control of runoff from combined sewer service areas based on a single design storm and eight hypothetical control strategies. Capital costs range from $1.2 billion - $68 billion (June 1973 dollars), and vary with the amount of storage and degree of treatment provided. Annual operation and maintenance expenses for the eight options range from $46 million - $400 million. These costs are compared with similar estimates for new and upgraded municipal wastewater collection and treatment systems required under Public Law 92-500.

Detention Storage Control Strategy Development

Simulation and optimization techniques were employed in developing strategies for the operation of detention reservoirs for the control of combined sewer overflows. A single subbasin reservoir system in the San Francisco Plan for Wastewater Management was used as a case study. A simulation model was constructed and used in conjunction with both artificial and long-term historical rainfall data to develop and evaluate various general control strategies. It was demonstrated that control strategies can produce significant reductions in number and volume of overflows.

Combined Sewer Considerations by Philadelphia

City of Philadelphia's experience and study of the combined sewer overflow pollution problem are described. Water quality legislation and pollution abatement philosophy are considered. The needs for problem definition are delineated along with pertinent constraints of existing methodology and measuring instrumentation. Costs and economic analysis of some abatement schemes are evaluated. Complete separation of stormwater and sanitary wastes, storage in conduit or detention basins, a total systems concept and the microstraining, chlorination, and ozonation of discharges are some of the principles reported for the control and treatment of combined sewer overflows, or both. Emphasis is directed to the determination of priorities in resolving the overall national pollution problem and the need for a systematic approach.

Characterization and control of combined sewer overflows, San Francisco

Characterization and control of combined sewer overflows, San Francisco