title: Investigation of solid-phase buffers for sulfur-oxidizing autotrophic denitrification.
abstract: This paper investigates biological denitrification using autotrophic microorganisms that use elemental sulfur as an electron donor. In this process, for each gram of nitrate-nitrogen removed, approximately 4.5 g of alkalinity (as calcium carbonate) are consumed. Because denitrification is severely inhibited below pH 5.5, and alkalinity present in the influent wastewaters is less than the alkalinity consumed, an external buffer was needed to arrest any drop in pH from alkalinity consumption. A packed-bed bioreactor configuration is ideally suited to handle variations in flow and nitrate loading from decentralized wastewater treatment systems, as it is a passive system and thus requires minimal maintenance; therefore, a solid-phase buffer packed with the elemental sulfur in the bioreactor is most suitable. In this research, marble chips, limestone, and crushed oyster shells were tested as solid-phase buffers. Bench- and field-scale studies indicated that crushed oyster shell was the most suitable buffer based on (1) the rate of dissolution of buffer and the buffering agent released (carbonate, bicarbonate, or hydroxide), (2) the ability of the buffer surface to act as host for microbial attachment, (3) turbidity of the solution upon release of the buffering agent, and (4) economics.
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, USA. ssengupta@UMassD.Edu
authors.forename: Sukalyan
authors.initials: S
authors.lastname: Sengupta
authors.forename: Sarina J
authors.initials: SJ
authors.lastname: Ergas
authors.forename: Erika
authors.initials: E
authors.lastname: Lopez-Luna
mesh_terms: D019149:Bioreactors; D002119:Calcium Carbonate / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D008956:Models, Chemical; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D010865:Pilot Projects; D013455:Sulfur / Q000378:metabolism*; D013855:Thiobacillus / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods; D018508:Water Purification / Q000379:methods
chemical_list: D009566:Nitrates; D013455:Sulfur; D002119:Calcium Carbonate; D009584:Nitrogen