Nonylphenol degradation in lab scale activated sludge units is temperature dependent

Nonylphenol (NP) is considered to be a pseudo-estrogen and moreover is the most recalcitrant intermediate of the nonylphenol polyethoxylates. The latter are an important group of nonionic surfactants with worldwide applications. The behaviour and fate of nonylphenol during activated sludge treatment was studied using laboratory scale reactor units. It appeared that the NP added at concentrations of 8.33 mg/l was almost totally removed and biodegraded when the reactors were operated at 28°C. By lowering the temperature from 28 to 10–15°C, elimination capacities decreased to 13–86%, depending on the process conditions. Upon re-establishing the temperature at 28°C, the accumulation of NP in the sludge could be counteracted. It was also demonstrated that the capacity of semi-continuous activated sludge (SCAS) to degrade NP was extended when the feed was made up with effluent from a full-scale activated sludge. Yet, the latter appeared also capable of rendering small amounts (20–100 μgNP/g TSS) less bio-removable.