EVALUATION OF TWO ALTERNATIVES EFFICIENTLY AND ECONOMICALLY TREATING ELECTROPLATING WASTEWATER

Kim, Chang Gyun; Seo, Hyung Joon; Nam, Ho Yeon; Yoon, Tai II

doi:2003.8.2.82

Environmental Engineering Research 2003;8(2): 82-90. DOI: https://doi.org/10.4491/eer.2003.8.2.082

EVALUATION OF TWO ALTERNATIVES EFFICIENTLY AND ECONOMICALLY TREATING ELECTROPLATING WASTEWATER

Chang Gyun Kim^†, Hyung Joon Seo, Ho Yeon Nam, and Tai II Yoon

Division of Environmental and Geosystem Engineering, Inha University, Inchon 402-751, Korea

Corresponding Author: Chang Gyun Kim ,Tel: +82-32-860-7561, Fax: +82-32-865-1425, Email: cgk@inha.ac.kr

Received: December 11, 2002; Accepted: February 12, 2003.

ABSTRACT

Currently used neutralizer and reduction and oxidation processes in treating electroplating wastewater were comparatively refitted with two different processes because treating electroplating wastewater containing cyanides and heavy metals needs more complicated processes and increased treatment cost. Process A was performed as oxidation of cyanide, reduction of Cr" and neutralization-sedimentation finally being achieved. Process B was conducted as reduction ol'Cr'". neutralization-sedimentation, oxidation of cyanide and neutralization-sedimentation finally being accomplished. Hypochlorite could oxidize cyanides at the greatest degree by up to 0.1 mg/L at the dosage of 7,000 mg/L compared to those of hydrogen peroxide and oxygen. The proper dosing of hypochlorite to completely oxidize cyanides was 4,000 mg CI" over 400 mg CN For reducing Cr' NaHSOi was used. Its optimal dosage was 2.5 SOr/Cr" in process A, whereas it was ranged from 1.5 to 1.6 SOj'VCr1" in process B. The difference of optimal dosage reflects from the residual chlorine formed due to chlorine overdosed for oxidizing cyanides in process A. Employing Mg(OH):+NaOH for pH adjustment could reduce sludge volume up to 50% compared to using Ca(OH)? showing 25 kg in process A. For process B, it was not differently obtained among three neutralizers. Regardless of type of alkaline reagents being used, their sludge quantities in the process B were much less produced compared to that of process A. However, it was required that two extra facilities should be introduced for neutralization-precipitation processes and HCN up-taker.

Keywords: Cyanide and heavy metals removal | Electroplating wastewater treatment