LAUSR

Industrial wastewater discharge is one of major threats to the sustainability of aquatic environment. Rapid and sensitive detection of toxic wastewater discharge and appropriate control if necessary are therefore crucial. In the present study, a 1 h Daphnia magna exposure with heartbeat as an observation endpoint was developed and assessed for its utility as a rapid toxicity screening measure. Two types of metal-rich industrial wastewater, i.e., metal plating and the semiconductor industry were chosen as target samples, and the 1 h heartbeat assay was applied. Based on a literature search, four metals, i.e., Cu, Cr, Ni and Zn were identified as major chemicals of ecotoxicological concerns in these wastewaters. The effective concentrations determined for each metal from the D. magna 1 h heartbeat test were comparable to those derived from the conventional D. magna 48 h immobilization test. Copper sulfate (CuSO4) was determined as the most toxic, followed by potassium dichromate (K2Cr2O7), nickel sulfate (NiSO4) and zinc sulfate (ZnSO4). For ternary mixtures, the 1 h heartbeat test showed also comparable responses to those of the 48 h immobilization test, suggesting its utility for screening the toxicity of simple metal mixtures. For the site-sampled metal plating water, the rapid heartbeat assay showed similar responses to those of the 48 h immobilization assay. However, for the semiconductor industry wastewater, clearly different responses were observed in both the heartbeat and immobilization assays, probably due to the influence of other contaminants with different modes of action that are present in the wastewater. Our observations showed that the D. magna 1 h heartbeat test can be considered as a rapid ecotoxicity screening measure for certain wastewaters with simple metal mixtures.