Aerobic thermophilic treatment of sewage sludge contaminated with 4-nonylphenol.

4-Nonylphenol (4-NP) occurs in sewage sludge as a result of the breakdown of detergents which contains nonylphenol ethoxylates (NPEs). 4-NP is of environmental concern because of its toxicity to biological systems. The present paper reports results of aerobic treatment under thermophilic conditions of sewage sludge artificially contaminated with 4-NP. Experiments were carried out using three parallel laboratory-scale batch reactors operating with blank, 50 and 100 mg/l of 4-NP concentration. For the two studied concentrations up to 66% 4-NP reduction was achieved at a specific air flow rate of 16 l/(l.h) and a thermophilic temperature of 60 degrees C, within 10 days of operation. The presence of 4-NP has minor effect on the rate of sludge oxidation and the nitrogen and phosphorous content in the sludge.