Aerobic and anaerobic ammonium-oxidising bacterial enrichment from municipal solid waste

Abstract

Leachate from the municipal solid waste (MSW) landfills contains high concentration of ammoniacal nitrogen that is a major toxic pollutant that has a great threat to environment. Among the processes available for the removal of ammoniacal nitrogen, one process is a combination of partial nitrification and anaerobic ammonium oxidation (anammox) process. It requires aerobic ammonium-oxidising bacteria (AOB) and anaerobic ammonium-oxidising bacteria (AnAOB). This paper presents the feasibility of enriching the AOB and AnAOB in 100-mL and 2.5-L batch reactors from fresh and mined MSW and leachate under aerobic and anaerobic conditions with varying feed-to-seed ratio. The AOB and AnAOB activity was monitored by measuring the intermediates such as hydroxylamine and hydrazine along with variations in ammoniacal nitrogen, nitrite nitrogen, and nitrate nitrogen concentrations in the reactor contents. The formation of intermediates such as hydroxylamine and hydrazine and ammoniacal nitrogen transformation data confirmed the enrichment of AOB and AnAOB. Further, AOB and AnAOB were validated by most probable number test and scanning electron microscopy analysis, respectively. DNA extraction, polymerase chain reaction amplification, and sequencing analysis authenticated the AnAOB as Candidatus Brocadia anammoxidans.

Role of inoculum and feeding strategy in the preference of nitrogen removal pathway in case of the fluctuations in nitrogen loading rate

“…There was no change observed in the relative abundance of hzsA gene in the SBR3 inoculated with MSW opposite to previous studies suggesting the suitability of MSW for the acclimation of anammox bacteria. 8 In the real-time PCR analyses, relative abundance of archaeal amoA gene was not detected in any sample.…”

“…1,[4][5][6][7] Recently, the municipal solid waste and leachate were also reported as suitable inocula for the acclimation of anammox bacteria. 8 The feeding strategy was also reported as an important factor to shorten the acclimation period. 6 As the slow feeding rate reported as favorable for the growth of anammox bacteria, 9 the implementation of continuous feeding was preferred in most of the studies on the investigation of anammox process.…”

“…18,20 In recent years, the functional genes related to DNRA has been included in studies on the analysis of functional genes associated with nitrification, denitrification and anammox in combination with activity measurements. 8,17,20,21 The main functional genes belonging to bacteria taking part in the nitrogen cycle are illustrated in Fig. 1.…”