THE INFLUENCE OF SYSTEM-SPECIFIC PROPERTIES ON THE POLLUTANT DISCHARGE OF COMBINED SEWER SYSTEMS

The water quality policy in the Netherlands regarding discharges from sewer systems into surface water will in the near future aim at the po llutant discharge instead of the overflow frequency. Recent practical research has shown that system-specific properties are the main influe ncing factors for the sediment behaviour of sewer systems. Based on th is knowledge the pollutant discharge concept EMOR has been developed. A detailed description is given of the background of this concept and of how to work with it. The calculation results include frequency dist ributions for the COD, peak discharges and annual load, overflow quant ities, overflow frequencies, etc. An objective calculation method is p rovided to express the influence in the so-called depositing factor, w hich can be determined for a single sewer as well as for a complete se wer systems. Application of this factor in the EMOR-concept makes it p ossible to use a schematization of the sewer system into a multireserv oir model without losing the influence of the system specific properti es. Model fitting has demonstrated that with the application of the EM OR concept a reliable prediction r-an be made for the pollutant discha rge.