Effect of heat-alkaline treatment as a pretreatment method on volatile fatty acid production and protein degradation in excess sludge, pure proteins and pure cultures

► Investigate the effect of heat-alkaline treatment on volatile fatty acid production and protein degradation. ► Quantify bacteria present in the activated sludge by quantitative PCR. ► HAT enhances VFA production only in excess sludge, albumin, and Gram-negative bacteria. ► Gram-negative bacteria are predominant in the activated sludge used. ► Bacteria present in activated sludge comprise only 10% of mixed liquor suspended solids by qPCR.