Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations

摘要

The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency,and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined.At DO of 0.5 and 1.5 mg O2 /L during the aeration phase,the efficiency of ammonia oxidation exceeded 90%,with nitrates as the main product.Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes.The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2 /L.Total bacterial diversity was similar in all experimental series,however,for both COD/N ratios of 6.8 and 0.7,higher values were observed at DO of 0.5 mg O2 /L.The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8.For both COD/N ratios applied,the AOB population was not affected by oxygen concentration.Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.