Rapid screening for ecotoxicity of plating and semiconductor wastewater employing heartbeat of Daphnia magna

Abstract

Several countries have developed effluent discharge control measures based on ecotoxicity endpoints to protect ecosystems from adverse consequences of industrial wastewater discharge. However, these ecotoxicity tests often take a long time, and therefore may not be appropriate for rapid screening of toxicity. In the present study, we employed Daphnia magna heartbeat as an observation endpoint and investigated its utility as a rapid toxicity screening tool for industrial wastewater, by comparing with the results of conventional D. magna acute 48 hr immobilization test. Two major industries for which wastewater discharges are of potential concern were selected, i.e., metal plating and the semiconductor industry. In these industrial wastewaters, several target chemicals were identified, based on a literature search, i.e., Cu, Cr, Ni and Zn. Following 1 hr exposure to each chemical, the D. magna heartbeat decreased significantly in a concentration-dependent manner. The effective concentrations of the target chemicals determined from D. magna 1 hr heartbeat test were comparable to those derived from conventional D. magna 48 hr immobilization test (OECD TG 202) in the following order: copper sulfate (CuSO4), potassium dichromate (K2Cr2O7), nickel sulfate (NiSO4) and zinc sulfate (ZnSO4). Similar comparable results were observed also for ternary mixtures of target chemicals which are representative of each selected industrial wastewater. However, for the site-sampled wastewater especially for semiconductor industry, the correlation between two test results was not as good as the manufactured wastewaters with single or ternary metal(s). This discrepancy might be due to the influence of other contaminants that may exist in the semiconductor wastewater, which may have different modes of action. Our observations showed that D. magna 1 hr heartbeat test can be used as rapid ecotoxicity screening measure for wastewaters of simple composition with inorganic compounds. However, in order to apply to complex industrial wastewater, studies on different chemicals and their interactions on D. magna heartbeat are warranted.