Optimization of CSO storage and treatment systems

Combined-sewer overflow (CSO) must be controlled by a storage-treatment system because storm flow in the combined sewerage system is intermittent and highly variable in both pollutant concentration and flow rate. A treatment facility operating without the benefit of upstream storage would need to be very large and costly in order to handle the relatively high volume and flowrate of a CSO. Similarly, if storage is used without treatment, the storage volume required would be very large and also expensive. This paper describes a strategy to optimize CSO control system. This optimized system maximizes the use of the existing system before new construction and sizes the storage volume in concert with the wastewater treatment plant capacity to obtain the lowest-cost storage and treatment system.