Effects of metabolic uncouplers on excess sludge reduction and microbial products of activated sludge

• Three uncouplers all resulted in significant sludge reduction.
• The EPS content and composition were changed with three uncouplers.
• The PHB production was stimulated by three uncouplers.

The present study investigated the influences of three metabolic uncouplers (pCP, oCP and oNP) on excess activated sludge reduction and microbial products of extracellular polymeric substances (EPS) and intracellular storage product (polyhydroxybutyrate, PHB) in short-term tests. Results showed sludge was reduced 58.2%, 59.8% and 80.8%, respectively, at pCP, oCP and oNP concentrations of 20 mg/L. The dosage of three uncouplers had no obviously influences on COD removal and sludge settleability, but had significant inhibition effect on ammonia removal, especially for oNP. Low concentration of pCP and oNP (5 mg/L) dosing resulted in protein and polysaccharide content increased in EPS, however, they were decreased at high pCP and oNP concentrations (>5 mg/L). To oCP, the protein content in EPS was increased linearly with oCP concentration. Furthermore, metabolic uncouplers addition stimulated the production of PHB. Among three uncouplers, oCP could be an alternative uncoupler for sludge reduction in activated sludge process.