Comparison of toxicity induced by EDTA Cu after UV/H2O2 and UV/persulfate treatment: Species specific and technology dependent toxicity.
Advanced oxidation processes (AOPs) can degrade heavy metal complexes in wastewater to improve the removal efficiency of metals. However, the influences of AOP treatments on toxicity induced by metal complexes are not well understood. This study compared the toxicity induced by EDTA copper (Cu) after UV/persulfate (PS) and UV/H2O2 treatments on luminescent bacteria and human HepG2 cells. The results showed that EDTA Cu complexes decreased Cu toxicity in luminescent bacteria but increased the cytotoxicity in HepG2 cells, indicating species specific toxicity. The UV/PS and UV/H2O2 treatments under most pH values and [oxidant][EDTA Cu] conditions decreased the toxicity of EDTA Cu in HepG2 cells but increased the toxicity in luminescent bacteria. When the ratio of [oxidant] to [EDTA Cu] was 10, low toxicity in treated solutions was observed in both UV treatment processes. The alkaline precipitation treatment had a significant influence on toxicity reduction after UV/PS treatment; however, it had minimal influence on the UV/H2O2 treatment system. The Cu and total organic carbon (TOC) removal efficiency cannot completely explain the results of toxicity assays. EDTA Cu intermediates might play important roles in changing the toxicity of EDTA Cu after both UV treatments. This study provides insights into evaluating the treatment efficiency of UV/PS and UV/H2O2 on EDTA Cu decomplexation.
Chemosphere