Combined treatment of 2,2′,5,5′-tetrachlorobenzidine (TCB) industrial wastewater

2,2′,5,5′-Tetrachlorobenzidine (TCB), an intermediate in the industrial manufacture of dyes and pigments, is classified as a human carcinogen or a probable putative human carcinogen in USA. During the production of TCB, substantial quantities of industrial effluents are generated. A lab-scale combination process, composed by micro-electrochemical oxidation, air-stripping and aerobic biological processes, was carried out for the treatment of TCB wastewater from the two-staged neutralization dissolved by methanol. Performances of the processes were mainly investigated in this study. On a condition that hydraulic retention time (HRT) 1 h and pH 2.9 in iron-chipping filtration (ICF); HRT 24 h and the gas–liquid ratio 15 in air-stripping reactor (ASR); mixed liquor suspended solid (MLSS) 2.2–3.2 g/l, HRT 24 h, SRT 30 d, F/M 0.37–0.42 kg COD/kg MLSS d in aerobic reactor, when the influent COD was 12,910 mg/l, TCB 83.5 mg/l and NH4+-N 1144 mg/l, the removals of COD, TCB and NH4+-N were 15.4%, 28% and 0.3%, respectively, in ICF; 90.2%, 71.7% and 61.9%, respectively, in ASR; 86.3%, 70.6% and 90%, respectively, in aerobic reactor. The total removal of COD, TCB and NH4+-N, respectively, was 98.9%, 98% and 88.8%, respectively. Concerning about the toxicity of TCB contained in industrial discharge, more mineralization need to be done with the treated TCB wastewater in current study.