| Summary: | The feasibility of Metformin hydrochloride (MH) as a metabolic uncoupler to reduce excess sludge production was studied. This study was performed to more methodically study the effects of different concentrations (10 mg/L, 20 mg/L, 40 mg/L, 60 mg/L and 80 mg/L), high dosage (120 mg and 240 mg), and operating conditions such as pH, temperature and Chemical oxygen demand (COD) load on sludge yield, substrate removal, sludge settling performance, and sludge activity in a laboratory scale sequential batch reactors (SBR) fed with synthetic wastewater. Results showed that the amount of sludge produced decreased sharply with increasing MH concentration in all cases. Among the five concentrations of MH studied, 40 mg/L was the most effective in reducing sludge production by 58%. The addition of 40 mg/L resulted in the increase in specific oxygen uptake rate (SOUR) and dehydrogenase activity (DHA) values of the sludge by 32% and 25% compared to the control system. Sludge settling performance was good and effluent quality was not affected. When the MH high dosage effect was compared laterally, it was found the average residual sludge yield in the system for MH dosage 120 mg per day and 240 mg every two days was less than 38% and 57% compared to the control system. The effect of MH on sludge reduction had a great relationship with the operating conditions of the system. The optimal pH, temperature and influent load was 7.0, 25 °C, and 0.25 gCOD/(gMLSS·d), respectively. Economic evaluation for the wastewater treatment per ton (including excess sludge) was also estimated.
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