Sustainable Modernization of Wastewater Treatment Plants

Abstract

This analytical study was conducted on the basis of statistical data from the Russian Federation and technological requirements for WWTP operation. As a case study, a virtual WWTP, which serves a residential area of 31,500 PE (personal equivalent), was considered to solve a task of their potential upgrade. According to the initial data, within modernization, the existing infrastructure of the WWTP should be considered in order to receive wastewater with a reduced flow rate and increased values of pollutant concentrations. Within the analysis, treatment efficiency should correspond to current regulations. Special focus was put on secondary treatment facilities, as they ensure the removal of major contaminants (organic pollution) and nutrients (nitrogen and phosphorus). The results showed that even in the case of a lower flow rate, higher pollutant concentrations demanded a doubled volume of activated sludge reactor to provide the required efficiency. An increase in oxidizing capacity may be ensured through the growth of mixed liquor suspended solids (MLSS) value with simultaneous transition from gravity to membrane sludge separation. A study revealed that an MLSS raised from 3 to 8 g/L allows treatment in the existing tanks to be performed with necessary efficiency. In this case, significant costs for the purchase of membranes are offset by the need for zero additional construction. On the other hand, such a transition leads to an increase in operating costs of 60% (from EUR 0.078 to EUR 0.12/(m3/d)).