Utilization of a metabolic uncoupler, 3,3′,4′,5-tetrachlorosalicylanilide (TCS) to reduce sludge growth in activated sludge culture

This paper studies the feasibility of using 3,3′,4′,5-tetrachlorosalicylanilide (TCS) as a metabolic uncoupler to reduce the sludge growth in activated sludge cultures. The results have confirmed that TCS is an effective chemical agent in limiting the sludge growth when its concentration is >0.4 mg/L. It was demonstrated that TCS was able to reduce sludge growth rate by around 40% when the TCS concentration was 0.8 mg/L. It was also revealed that substrate removal capability was not affected adversely by the presence of TCS when TCS was continuously dosed in a range of 0.5–1.0 mg/L during the 30-day operation of activated sludge batch cultures. Such a sludge growth reduction is associated with the enhancement of microbial activities and an increase in the percentage of active bacteria over the total microbial population. In the 30-day operation of the cultures, the TCS dosing at a 1-mg/L level did not undermine the treatment performance in terms of the substrate removal efficiency. This work has demonstrated that it might be feasible to apply TCS in activated sludge systems to limit the excess sludge production.