We examined the behavior of nonionic surfactants and their degradation products in two municipal sewage treatment plants with anaerobic-aerobic activated sludge treatment system and seven sampling points in Tone River including tributaries in Gunma prefecture, by LC-MS.
In the sewage treatment plants, Nonylphenol ethoxylates (NPE) and alcohol ethoxylates (AE) were removed more than 80% and 90%, respectively, after primary sedimentation tank and anaerobic treatment process. NPE, AE, and nonylphenol (NP) were reduced by 99%, 99.9% and 90-95%, respectively, throughout the treatment. In contrast, nonylphenoxy carboxylic acids (NPEC) rather increased in aeration tank, and were not reduced throughout the treatment. The lengths of ethoxylates of NPE were found shortened after aerobic activated sludge treatment. From these results, NPEC was supposed to generate during degradation of NPE. Since NPE (1), NP and NPEC were detected in the extract of activated sludge, certain portion was found adsorbed into the activated sludge.
NPE, AE, NP and NPEC were detected at 0.1-16.4μg·l-1, 0.3-12.8μg·l-1, <0.08-0.2μg·l-1 and <0.008-3.2μg·l-1, respectively, in river waters. OP was detected <0.08μg·l-1 in all points. Concentrations of NPE and AE were comparably higher in downstream, in tributaries and in winter.
