Study On The Removal Of Heavy Metals From Metallurgical Wastewater By Etig Electrocoagulation System

The fourth smelter of Hunan Shui Kou Shan Nonferrous Metals Group Co., LTD.emitted cadmium, zinc, arsenic, and lead into the Xiangjiang River for a long time,which brought serious heavy metal pollution load to the Xiangjiang River, affectedthe safety of the ecological environment and posed a serious threat to the quality ofdrinking water of people of the middle and lower reaches of Xiangjiang River. In thispaper, ETIG electrocoagulation system was employed to treat wastewater containingheavy metals from the fourth smelter. The main objective of this study was to providenecessary operational parameter for widely spreading of the ETIG electrocoagulationsystem through the piolet test.The experimental results showed that through the treatment of ETIGelectrocoagulation system various index were stable, and the effluent pHs were in therange of7-9, with an average of8.65. Concentrations of heavy metals in the effluentwere extremely low, which were far lower than the national emission standards.Before the treatment of ETIG electrocoagulation system, the average concentration ofPb, Zn, Cd, and As in the wastewater were6.79mg/L,169.13mg/L,2.23mg/L, and0.54mg/L, respectively. After treatment, the average concentration of Pb, Zn, Cd, andAs in the effluent were0.019mg/L,0.034mg/L,0.018mg/L, and0.011mg/L,respectively. The calculated remove efficiency were99.19%,99.98%,99.17%, and97.48%, respectively.In the process of electrolytic flocculation treatment, the conductivity and pHvalue of the original water sample as well as the voltage and current value of therectifier played a decisive role on the treatment effect of the wastewater. We hadfound that the treatment effect was better when the pH of the fourth smelterwastewater was controlled between7.5and9. For wastewater with high concentrationand high electrical conductivity, the pH should be adjusted to8.5-9. The Current andvoltage of the rectifier was respectively advised to be75A and18V. When theConductivity is too low, the voltage of the rectifier increases and the current valuedecreases, leading to a adverse affects to the treatment effect. Therefore, we need toturn up the pH of the raw water first, thus its conductivity could be decreased beforetreatment. The economic benefit analysis of the electrolytic flocculation treatmentproject of the fourth smelter in ShuiKouShan non-ferrous metal co., LTD showed that the total present value of cash outflow was30.3455million without the reform ofelectric flocculation technology, and it was30.2825million with the reform ofelectric flocculation technology. Although the total present value of cash outflow wasabout the same with or without the reform of electric flocculation technology, itsenvironmental benefits and social benefit is very considerable.