Sulfate-reducing anaerobic ammonium oxidation as a potential treatment method for high nitrogen-content wastewater

Abstract

After sulfate-reducing ammonium oxidation (SRAO) was first assumed in 2001, several works have been published describing this process in laboratory-scale bioreactors or occurring in the nature. In this paper, the SRAO process was performed using reject water as a substrate for microorganisms and a source of NH(4) (+), with SO(4) (2-) being added as an electron acceptor. At a moderate temperature of 20°C in a moving bed biofilm reactor (MBBR) sulfate reduction along with ammonium oxidation were established. In an upflow anaerobic sludge blanket reactor (UASBR) the SRAO process took place at 36°C. Average volumetric TN removal rates of 0.03 kg-N/m³/day in the MBBR and 0.04 kg-N/m³/day in the UASBR were achieved, with long-term moderate average removal efficiencies, respectively. Uncultured bacteria clone P4 and uncultured planctomycete clone Amx-PAn30 were detected from the biofilm of the MBBR, from sludge of the UASBR uncultured Verrucomicrobiales bacterium clone De2102 and Uncultured bacterium clone ATB-KS-1929 were found also. The stoichiometrical ratio of NH(4) (+) removal was significantly higher than could be expected from the extent of SO(4) (2-) reduction. This phenomenon can primarily be attributed to complex interactions between nitrogen and sulfur compounds and organic matter present in the wastewater. The high NH(4) (+) removal ratio can be attributed to sulfur-utilizing denitrification/denitritation providing the evidence that SRAO is occurring independently and is not a result of sulfate reduction and anammox. HCO(3) (-) concentrations exceeding 1,000 mg/l were found to have an inhibiting effect on the SRAO process. Small amounts of hydrazine were naturally present in the reaction medium, indicating occurrence of the anammox process. Injections of anammox intermediates, hydrazine and hydroxylamine, had a positive effect on SRAO process performance, particularly in the case of the UASBR.

S115 Characteristics of Sulfate Reduction–Ammonia Oxidation under Anaerobic Conditions

“…Sulfate reduction-ammonia oxidation is found to be a new type of biological process similar to ANAMMOX. It, however, can be seen from Figure 4 that pH in effluent was lower than that in the influent which was similar to the findings from Samubon [20] and Rikmann et al [19].…”

“…While other researchers considered S 2-should not be the intermediate product [17] due to no S 2-observed in autotrophic environment. pH value increased in autotrophic environment [17] but decreased in heterotrophic environment [19,20]. Only Samubon [20] and Rikmann et al [19] reported NO 3 --N was produced obviously in heterotrophic environment.…”

“…pH value increased in autotrophic environment [17] but decreased in heterotrophic environment [19,20]. Only Samubon [20] and Rikmann et al [19] reported NO 3 --N was produced obviously in heterotrophic environment. In summary, sulfate reduction-ammonia oxidation reaction would be changed if organic matter presented or not.…”

“…But there are many unanswered questions related to the characteristics of this reaction. For instance, some researchers considered that S 2-should be the intermediate product [10,[18][19] due to S 2-detection in heterotrophic environment. While other researchers considered S 2-should not be the intermediate product [17] due to no S 2-observed in autotrophic environment.…”

“…Some researchers tend to support this assumption because HS -/S 2-was detected in their heterotrophic experiments [18,19]. It could be analyzed that sulfate-reducing bacteria (SRB) might reduce sulfate into HS -/S 2-using organic or hydrogen as electron donor under organic anaerobic conditions.…”