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); HIRT 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. (C) 2007 Elsevier B.V. All rights reserved.