Pretreatment of dyestuff wastewater by internal microelectrolysis

Internal microelectrolysis is an effective pretreatment technology for poor biodegradable industrial wastewater contaminated with dyestuffs, pesticides, pharmaceuticals, etc. In internal microelectrolysis system, numerous microscopic galvanic cells are formed between iron and carbon in wastewater, resulting in galvanic cell reaction. Products released from the galvanic cell reaction include hydroxyl, atomic hydrogen and Fe(II) which have high capacity to decompose contaminants. In this paper, the effects of internal microelectrolysis pretreatment for dyestuff wastewater were firstly studied. The degradation mechanism and influence factors of internal microelectrolysis were also investigated. Experimental results indicated that the weight ratio of iron to carbon is a key parameter during internal microelectrolysis. The optimum ratio of Fe/C was found to be 5. To obtain the maximum removal efficiency with low operation costs, reaction time of microelectrolysis was about 2 hours and the pertinent pH of influent was 2-3. Under these optimum conditions, different concentrations of dyestuff wastewater were treated by internal microelectrolysis. In the end, the removal efficiency of COD was over 45 percent, and B/C of wastewater was increased obviously from 0.2 to about 0.4.