title: Field-scale application of spent sulfidic caustic as a source of alternative electron donor for autotrophic denitrification.
abstract: Biological reuse of spent sulfidic caustic (SSC) originating from oil refineries is a promising method for the petrochemical industry because of low handling cost. SSC typically contains high concentrations of sulfur, with the most dominant sulfur compounds being sulfide (S(2-)). SSC is also characterized by a high pH and elevated alkalinity up to 5-15% by weight. Because of these characteristics, SSC can be used for denitrification of NO3(-)-N in the biological nitrogen removal process as both the electron donor and buffering agent in sulfur-utilizing autotrophic denitrification. In this study, two kinds of SSC (SSC I, SSC II) produced from two petrochemical companies were used for autotrophic denitrification in a field-scale wastewater treatment plant (WWTP). The effluent total nitrogen (TN) concentration in this process was about 10.5 mg/L without any external carbon sources and the nitrification efficiency was low, about 93.0%, because of alkalinity deficiency in the influent. The injection of SSC I, but not SSC II, promoted nitrification efficiency, which was attributed to the difference in the NaOH/S ratio between SSC I and II. SSC was injected based on sulfide concentration of SSC required to denitrify NO3(-)-N in the WWTP. SSC I had higher NaOH/S than SSC II and thus could supply more alkalinity for nitrification than SSC II. On the other hand, additional TN removal of about 9.0% was achieved with the injection of both SSCs. However, denitrification efficiency was not proportionally increased with increasing SSC injection because of NO3(-)-N deficiency in the anoxic tank due to the limited capacity of the recycling pump. For the same reason, sulfate concentration, which is the end product of sulfur-utilizing autotrophic denitrificaiton in the effluent, was also not increased with increasing SSC injection.
authors.affiliation: SU Engineering Co. Ltd., Yangsan, 626-800, Korea.
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Jeung-Jin
authors.initials: JJ
authors.lastname: Park
authors.forename: Gi-Choong
authors.initials: GC
authors.lastname: Choi
authors.forename: Im-Gyu
authors.initials: IG
authors.lastname: Byun
authors.forename: Tae-Joo
authors.initials: TJ
authors.lastname: Park
authors.forename: Tae-Ho
authors.initials: TH
authors.lastname: Lee
mesh_terms: D052818:Autotrophic Processes; D057919:Biological Oxygen Demand Analysis; D002424:Caustics; D058440:Denitrification; D004583:Electrons; D007220:Industrial Waste; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D010578:Petroleum; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013440:Sulfides / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000378:metabolism
chemical_list: D002424:Caustics; D007220:Industrial Waste; D009566:Nitrates; D010578:Petroleum; D000644:Quaternary Ammonium Compounds; D013431:Sulfates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D009584:Nitrogen