Systematic and long-term technical validity of toxicity determination and early warning of heavy metal pollution based on an automatic water-toxicity-determination-system

Water toxicity determination with electrochemically active bacteria (EAB) shows promise for providing early warnings for heavy metal pollution in water. However, thus far, only idealized tests with a few types of heavy metals have been conducted. In this study, an automatic water-toxicity-determination system with high technical maturity was established, and the toxicological properties of common heavy metals were systematically assessed. The results demonstrated that the common heavy metals linearly inhibited EAB currents in the range of 0.1 mg/L to 0.5 mg/L. The toxicity ranking of the tested heavy metals was Pb²⁺ > Tl³⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ > Ni²⁺ > Hg²⁺ > As²⁺. The toxicity interaction mainly exhibited an antagonistic effect in binary heavy metal mixtures. The system can accurately determine surface water toxicity and rapidly monitor heavy metal pollution, with good repeatability and a long lifetime. Overall, this study demonstrates that EAB are capable of long-term (> 60 d) surface water quality monitoring and on-site early warning of heavy metal pollution.