Biological treatment of saline wastewaters in an aerobic sequencing batch reactor

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The influence of different chloride salts (sodium, potassium, calcium, and magnesium) on wastewater biological treatment performance was investigated. Long term assays were performed (30 d) operating aerobic sequencing batch reactors (SBR) with a 24-h cycle (23 h of reaction and 1 h of sedimentation and draining). Salt content varied from 0% to 6% m/v in different assays, using synthetic wastewater with an average COD of 2000 mg/L. When salt was not added to the SBR influent chemical oxygen demand (COD) removal averaged 95%. For the higher salt concentration tested (6% m/v), average COD removals for NaCl, KCl, MgCl2, and CaCl2 were, respectively, 81%, 92%, 83%, and 87%. Some deleterious effects caused by salt concentration were: reduction of protozoa population and diversity and sludge deflocculation, which caused a rise on the SBR effluent turbidity. © 2011 American Institute of Chemical Engineers Environ Prog, 32: 198-205, 2013