Sewage effluent toxicity assessment: Comparison between whole effluent toxicity (WET) and the Japanese pollutant release and transfer register (PRTR) data

Abstract

Sewage effluent plays an important role in regional water cycles and is gaining attention. Because a wide variety of chemicals are used in industry and daily life, the environmental impacts of trace chemicals in sewage effluents are a source of concern. Whole effluent toxicity (WET) testing uses biological responses to directly evaluate the toxicity of chemical substances in effluent. In contrast, the Japanese Pollutant Release and Transfer Register (PRTR) system provides estimated amounts of potentially hazardous chemicals released in effluent from factories and sewage treatment plants. The objectives of this study were to evaluate the ecological impacts of sewage effluent using WET tests and PRTR data and to compare the results from the two approaches. Of seven effluent samples tested, four demonstrated toxicities to aquatic organisms. Water analyses suggest that residual chlorine is responsible for toxicity to algae, while linear alkyl benzene sulfonates do not contribute to toxicity. The PRTR data tended to overestimate toxicity in comparison to the observed toxicity. The causes of this discrepancy are discussed, such as insufficient data. Due to the difference in calculation method, PRTR data of sewerage tends to be overestimated.