Advanced treatment of coking wastewater by coagulation and zero-valent iron processes

• Published in: Journal of hazardous materials Vol. 147; no. 1; pp. 232 - 239
• Main Authors: Lai, Peng, Zhao, Hua-zhang, Wang, Chao, Ni, Jin-ren
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 17.08.2007; Elsevier
• Subjects: Activated carbon; Advanced treatment; Applied sciences; Biodegradability; Biodegradation, Environmental; Chaos theory; Chemical oxygen demand (COD); Coagulation; Coke; Coking; Coking wastewater; Contaminants; Crack opening displacement; Education; Effluents; Esters; Exact sciences and technology; General purification processes; Industrial Waste - prevention & control; Iron; Nickel; Oxidation-Reduction; Oxygen demand; Peking; Pollution; Precipitation; Sediments; Waste Disposal, Fluid - methods; Waste water; Wastewaters; Water Purification - methods; Water treatment and pollution; Zero-valent iron (ZVI); Chemical oxygen demand (COD); Advanced treatment; Zero-valent iron (ZVI); Coking wastewater; Coagulation; Oxidation reduction; Biodegradability; Zerovalent metal; Waste water; Pollution; Flocculation reagent; Chemical oxygen demand; Flocculation; Water quality; pH; Physicochemical purification
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2006.12.075

Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal COD removal efficiency of 27.5–31.8% could be achieved under the optimal condition of coagulation, i.e. 400 mg/L of Fe 2(SO 4) 3 as coagulant at pH 3.0–5.0. On the other hand, the COD removal efficiency could be up to 43.6% under the idealized condition of ZVI upon 10 g/L active carbon and 30 g/L iron being dosed at pH 4.0. The mechanisms for COD removal in ZVI were dominated by coagulation, precipitation and oxidation–reduction. ZVI would also enhance the biodegradability of effluent by increasing BOD 5/COD from 0.07 to 0.53. Moreover, some ester compounds could be produced in the reaction. Although ZVI was found more efficient than coagulation in eliminating low molecular weight (<2000 Da) compounds in the wastewater, there were still a few residual contaminants which could hardly be eliminated by either of the process.