Toxicity identification and reduction of wastewaters from a pigment manufacturing factory

In this study, major toxicants in pigment wastewaters (i.e. raw wastewater and effluent) were determined by toxicity identification evaluations (TIEs), and changes in their toxicities due to combined gamma-ray (γ-ray) and ozone treatments were evaluated. From TIE results using Daphnia magna, Cr(VI) and o-toluidine were identified as major toxicants in the raw wastewater with concentrations of 2.47 and 25.3 mg l−1, respectively. This was confirmed by subsequent spiking and mass balance approaches. For effluent, TIE results suggested that organic anions were likely responsible for the observed toxicities. Toxicity reduction tests showed that γ-rays with ozone treatment after coagulation was more efficient in reducing toxicities in the raw wastewater (3.9–2.0 TU) than γ-ray treatment alone (3.9–3.1 TU). For pigment effluent, γ-ray/O3 treatment resulted in a complete removal of the acute toxicity.