Simultaneous removal of organic and inorganic pollutants in tannery wastewater using electrocoagulation technique

Abstract

Tannery wastewater can cause severe environmental problems related to its high chemical oxygen demand, high biochemical oxygen demand, high total suspended solids, high oil and grease contents together with the elevated chromium concentration and objectionable color. The one-step electrocoagulation process was carried out to simulta- neously remove chromium and various pollutants from tannery wastewater at ambient temperature in the laboratory scale. Low-cost commercial iron plates were employed in this study as anodes and cathode materials. Effects of various parameters were investigated including types of electrode configuration, initial pH of wastewater (7-9), current density (15.7-24.6 Am −2 ) and circulating flow rate of wastewater (0-3.67 lmin −1 ). The optimum condition was found by applying the mono-polar electrode in a parallel connection at the current density of 22.4 Am −2 , flow rate of wastewater of 3.67 lmin −1 and 20 min electrolysis time. The initial pH of wastewater ranging from 7-9 provided the similar removal effi- ciency. At optimum condition, more than 95% of chromium and pollutants except TKN and TDS were eliminated from the wastewater and the properties of the treated wastewater met the standard and permitted to discharge into the en- vironment. The required energy consumption at optimum condition was less than 0.13 kWhm −3 wastewater. In addition, the COD reduction was fit very well with the first-order kinetics model.