Fate of Haloacetic Acids in Wastewater Treatment Process and in Water Environment.

Haloacetic acids (HAAs) in wastewater effluents from the wastewater treatment plants which are located along the Tama River system and in river waters of the river system were examined. The fate of HAAs in wastewater treatment processes was investigated. The mean concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in wastewater effluents were 0.81, 4.2 μg·l-1, respectively. In the case of river water samples, DCAA was detected in very low concentrations, while TCAA was almost always detected with the concentration range from 0.2 to 1 μg·l-1. The removal of HAAs in river water treatment facilities using the gravel bed contact-purification method was insignificant. Tap water would be one of the major sources of HAAs in wastewater influents, while the contributions of industrial wastewater were not negligible. The mean removal ratios of DCAA and TCAA by activated sludge process in aeration tank were 97% and 29%, respectively. These results can be explained by the difference in the degradability of different species of HAAs. The amount of TCAA produced by the chlorination carried out in wastewater treatment plants was insignificant compared with that remaining after the biological treatment at almost all plants examined, though a high formation of HAAs was observed in the case of an exceptional treatment plant.