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Polishing Treatment of Molasses Wastewater with Iron Salts: the Role of Counter‐ions
Author(s) -
Liang Zhen,
Wang Yanxin,
Zhou Yu,
Liu Hui,
Wu Zhenbin
Publication year - 2009
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143009x447975
Subject(s) - polishing , wastewater , waste management , chemistry , sewage treatment , environmental science , ion , environmental chemistry , environmental engineering , nuclear chemistry , metallurgy , materials science , engineering , organic chemistry
The effect of counter‐ions on the coagulation of biologically treated molasses wastewater using iron‐based coagulants was investigated. Parameters such as removals of chemical oxygen demand (COD) and color, and residual turbidity, were measured to evaluate coagulation performance. Experimental results showed that ferric chloride and ferric nitrate were more effective than ferric sulfate at optimal dosages, achieving 89 to 90% and 98 to 99% of COD and color removals, respectively, with residual turbidity of less than 5 NTU. High‐performance size exclusion chromatography (HPSEC) results revealed differences in the removal of the molecular weight fraction of organic compounds using iron salts. Scanning electron microscopy (SEM) showed randomly formed coagulated flocs characterized with irregular, sheet‐like shapes. Nitrate and chloride counter‐ions had similar effects on coagulation performance compared to sulfate. Both FeCl 3 and Fe(NO 3 ) 3 yielded better results than Fe(SO 4 ) 2 under underdosed and optimum dosage conditions. Coagulation efficiency was less adversely affected in the overdosed regions, however, if sulfate rather than chloride or nitrate was present.