Controlled Sewage Sludge Alkaline Fermentation to Produce Vola- tile Fatty Acids to be Used for Biological Nutrient s Removal in WWTPs

In municipal wastewater treatment plants (WWTPs), the disposal of sewage sludge accounts for 20 -50% of capital and operating expenses. Therefore, technologies tha t can simultaneously reduce sludge and generate car bon source for improving biological nutrients removal are in d emand. The application of sewage sludge alkaline fe rmentation can provide the external carbon source that is requ ired to remove nutrients via nitrite for the separa te treatment of the supernatant produced from the anaerobic digestion o f sewage sludge. Existing studies on sewage sludge fermentation use caustic soda or other chemicals to achieve the desirable pH for alkaline fermentation; this practi ce increases the cost. In this work, the anaerobic supernatant produ ced from sewage sludge was used to adjust the pH in the fermentation reactor, while the impact of temperature (30 ° C and 55 ° C), pH (8 -11), retention time (1 -8 days) and initial total solids (TS = 4.5 and 6.5%) concentration of sludge was examined. The highest volatile fatty acids (VFAs) concentration was achieved at a retention time of 6 days, sl udge TS = 6.5%, pH = 10&11 and temperature of 55 ° C. The addition of pre-aerated anaerobic supernatant achieved simil ar VFAs as the one of similar pH in which caustic s oda adjustment took place.