Treatment of chemical cleaning wastewater and cost optimization by response surface methodology coupled nonlinear programming. (1st August 2017)

• Record Type: Journal Article
• Authors: Yang, Yang; Zhou, Zhen; Lu, Chenjie; Chen, Yunke; Ge, Honghua; Wang, Libing; Cheng, Cheng
• Is Part Of: Journal of environmental management. Volume 198:Part 2(2017)
• Page Start: 12
• Page End: 20
• Publication Date: 2017-08-01
• Subjects: Cleaning wastewater -- Neutralization -- NaClO oxidation -- Coagulation -- Response surface methodology -- Nonlinear programming; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2017.05.009
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: The real alkaline cleaning wastewater (ACW) was treated by a process consisting of neutralization, NaClO oxidation and aluminum sulfate (AS) coagulation, and a novel response surface methodology coupled nonlinear programming (RSM-NLP) approach was developed and used to optimize the oxidation-coagulation process under constraints of relevant discharge standards. Sulfuric acid neutralization effectively removed chemical oxygen demand (COD), surfactant alkylphenol ethoxylates (OP-10) and silicate at the optimum pH of 7.0, with efficiencies of 62.3%, >82.7% and 94.2%, respectively. Coagulation and adsorption by colloidal hydrated silica formed during neutralization were the major removal mechanisms. NaClO oxidation achieved almost complete removal of COD, but was ineffective for the removal of surfactant OP-10. AS coagulation followed by oxidation can efficiently remove OP-10 with the formation of Si-O-Al compounds. The optimum conditions for COD ≤100 mg/L were obtained at hypochlorite to COD molar ratio of 2.25, pH of 10.0 and AS dosage of 0.65 g Al/L, with minimum cost of 9.58 $/m 3 ACW. This study shows that the integrative RSM-NLP approach could effectively optimize the oxidation-coagulation process, and is attractive for techno-economic optimization of systems with multiple factors and threshold requirements for response variables. Highlights: Real cleaning wastewater was treated by neutralization-oxidation-coagulation process. Response surface methodology coupled nonlinear programming (RSM-NLP) was developed. 62.3% of COD and most of surfactant were removed from cleaning wastewater at pH 7.0. Coagulation was effective for the removal of surfactant alkylphenol ethoxylates. The RSM-NLP approach effectively optimized cost of the oxidation-coagulation process.