Abstract
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 pre-treatment 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.
Highlights
Industrial effluents discharged to a sewage system may strongly affect the operation of a municipal wastewater treatment plant (WWTP)
Some industrial effluents discharged into municipal sewage systems carry valuable organic substrate that may be
In order to be able to accept the increased industrial pollution load, it was concluded that the activated sludge process at the WWTP should be operated at MLSS that vary in the range of 3,600–5,400 g MLSS m-3, in function of the process temperature
Summary
Industrial effluents discharged to a sewage system may strongly affect the operation of a municipal wastewater treatment plant (WWTP). A large variability in flow rate, extreme concentrations of pollutants and the possible presence of pollutants that are resistant to biological treatment may disturb technological processes, increase operational costs and deteriorate the quality of the effluent. Industrial wastewater is usually pre-treated before discharge to a sewage system, in order to reduce pollution loads, but even treatment processes at a municipal WWTP may be disturbed (Mhlanga et al 2009; Redey et al 2011). Similar situations may arise if organic material, present in high concentrations in industrial effluent, has an unfavourable structure, represented by a high COD:BOD5 ratio
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