High-sulfate, high-chemical oxygen demand wastewater treatment using aerated methanogenic fluidized beds

Journal Article · Tue Feb 01 04:00:00 EST 2000 · Water Environment Research

DOI:https://doi.org/10.2175/106143000X137158· OSTI ID:20014589

Zitomer, D H; Shrout, J D

Many industrial wastewaters have both high organic pollution and sulfate (SO{sub 4}{sup {minus}2}) concentrations. Although biological conversion of organics to methane may be an economical chemical oxygen demand (COD) removal option, significant inhibition of methane production results from reduction of SO{sub 4}{sup {minus}2} to hydrogen sulfide (H{sub 2}S), which is inhibitory to methanogenic microorganisms. Therefore, sulfate-containing wastewater is often not amenable to conventional anaerobic treatment. Recently, limited aeration of recycle flow to hybrid and baffled reactors has been used to treat this wastewater and has been shown to reduce aqueous H{sub 2}S concentrations by causing production of uninhibitory sulfur (S{degree}) and thiosulfate (S{sub 2}O{sub 3}{sup {minus}2}) as well as gas stripping volatile H{sub 2}S. In this study, directly aerated methanogenic fluidized bed reactors (FBRs) achieved increased methane production compared to strictly anaerobic FBRs treating high-sulfate wastewater. Oxygen transfer satisfying up to 28% of the COD load resulted in maximum specific oxygen utilization rates of 0.20 mg oxygen/g volatile solids{center{underscore}dot}min, with significant, concomitant methane production. Under typically inhibitory SO{sub 4}{sup {minus}2} loading, higher aeration caused increased effluent SO{sub 4}{sup {minus}2}, increased H{sub 2}S mass in the offgas, and lower reactor H{sub 2}S concentration. As a result, COD removal increased from 25% for a strictly anaerobic FBR to 87% for an aerated FBR. In addition, aerated systems required significantly less alkalinity supplementation to maintain a pH value of 7, ostensibly because of stripping of acidic carbon dioxide. The potential pH increase associated with aeration also shifts sulfide speciation to less toxic disulfide. Direct, limited aeration of methanogenic FBRs is described as a method for increased COD removal when treating high-COD, high-sulfate wastewater.

• OSTI ID: 20014589
• Journal Information: Water Environment Research, Journal Name: Water Environment Research Journal Issue: 1 Vol. 72; ISSN WAERED; ISSN 1061-4303
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
BIODEGRADATION
BIOREACTORS
FLUIDIZED BEDS
HYDROGEN SULFIDES
INDUSTRIAL WASTES
METHANOGENIC BACTERIA
SULFATES
WASTE PROCESSING
WASTE WATER