DETERMINATION OF MICROBIAL RESPONSES TO SEASONAL VARIATIONS OF WASTEWATER COMPOSITION IN THE IZMIR WASTEWATER TREATMENT PLANT

摘要

Enhanced biological phosphorus removal (EBPR) processes are one of the most popular methods for nutrient control. In this study, effects of seasonal wastewater composition upon key characteristics of the EBPR process were investigated in a large wastewater treatment plant (Izmir WWTP). Microbial activities were determined by anaero-bic-anoxic-aerobic batch tests using fresh activated sludge. In addition to batch tests, wastewater composition, environmental conditions and operational variables of the plant were compiled in the period of the study. Quantification of microbial groups was based on a model. All of the compiled data were evaluated statistically. Decrease in the ratio of influent readily biodegradable soluble COD (rbsCOD) to total phosphorus (TP) (rbsCOD TP~(-1)) from 16 (winter) to 9 (summer) affected mass fraction of the microbial groups and intracellular phosphorus content of polyphosphate accumulating microorganisms (PAOs). Intracellular phosphorus (P) content of PAOs ranged from 10% to 30%. Average mass fraction of ordinary heterotrophic microorganisms (OHOs), glycogen accumulating microorganisms (GAOs) and PAOs were 54.3%, 21.2%, 24.4% in the winter period and 51.6%, 8.2% and 9.5% in the summer period. A positive correlation between PAOs activities (anaerobic-anoxic-aerobic) and influent rbsCOD TP~(-1) ratio was observed. Decrease of the ratio below 10 resulted with significant EBPR deterioration.