Determination of permissible industrial pollution load at a municipal wastewater treatment plant

Industrial wastewater discharged to a municipal sewage system may often be a source of valuable organic substrate for biological processes at a municipal wastewater treatment plant (WWTP). In such situations, the pretreatment of wastewater at an industrial plant should be minimized, in order to maintain the favourable structure of organic material in influent to a WWTP. A frequent problem is how to determine the maximum industrial pollution load that can be discharged, without compromising the treatment capability of a WWTP. This article presents a method based on computer simulation that can be used for this purpose. As a result, the method produced the permissible industrial pollution load that could be discharged safely, and the relationship between chemical oxygen demand (COD) load and required biomass concentration as a function of process temperature. The method was tested at a fruit-processing plant and municipal WWTP, located in Poland. The results of this study have shown that the bioreactor should be operated at a biomass concentration varying between 3,600 and 5,400 g m^-3 in function of the process temperature. Under such operational conditions, the WWTP would be able to accept the permissible industrial COD load of above 9,000 kg COD d^-1 for a wide range of temperatures, namely 14–19 °C. If the WWTP was operated at a constant biomass concentration, its permissible industrial COD load would be reduced to 7,500–9,000 kg COD d^-1. The method can be applied to other municipal WWTPs with activated sludge that receive industrial effluents.

Keywords
Industrial wastewater; Wastewater treatment plant; Activated sludge; Nutrient removal; Modelling; Computer simulation