Journal
CHEMICAL ENGINEERING JOURNAL
Volume 152, Issue 1, Pages 88-94Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2009.03.036
Keywords
Molasses wastewater; Ferric chloride; Coagulation performance; Molecular weight; Floc size distribution; Mechanism
Categories
Funding
- National Natural Science Foundation of China [40830748]
- China Postdoctoral Science Foundation [20080440976]
- Ministry of Environmental Protection of China
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The pigments (melanoidins) in molasses wastewater are refractory to conventional biological treatment. Ferric chloride was used as coagulant to remove color and chemical oxygen demand (COD) from molasses effluent. Using jar test procedure, main operating conditions such as pH and coagulant dosage were investigated. Under the optimum conditions, up to 86% and 96% of COD and color removal efficiencies were achieved. Residual turbidity in supernatant was less than 5 NTU and Fe3+ concentration was negligible because of effective destabilization and subsequent sedimentation. The results of high performance size exclusion chromatography (HPSEC) show that low molecular weight (MW) fraction of melanoidins is more reactive than high MW fraction and increase in the concentration of the lowest MW organic group is related to the capacity of charge neutralization. Aggregate size measurement reveals the size effect on the settleability of flocs formed, with larger flocs settling more rapidly. Charge neutralization and co-precipitation are proposed as predominant coagulation mechanism under the optimum conditions. (C) 2009 Elsevier B.V. All rights reserved.
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