Treatment of dairy wastewater using intermittent-aeration sequencing batch reactor at pilot-scale

A 3000 l pilot-scale intermittently aerated sequencing batch reactor (IASBR) was operated continuously for the treatment of dairy industry wastewater in Ireland during 5 months in 12-h cycles. Each cycle alternated between non-aeration (100 mins) and aeration (60 mins) periods to facilitate nitrogen and phosphorus co-removal. The nutrient removal efficiencies achieved were over 95 % for orthophosphate and ammonia. The bacterial composition of the pilot-scale IASBR was dominated by Proteobacteria, Bacteroidetes, Planctomycetes, Armatimonadetes, Patescibacteria and Chloroflexi phyla. Multivariate analyses suggested correlations of some influent variables analyzed with key predominant orders Fimbriimonadales, Flavobacteriales, Pirelullales and Betaproteobacteriales. The presence of not previously identified bacterial groups such as Planctomycetales, Armatimonadetes and Patescibacteria was related to high nutrient removal performance of the bioreactor. The results suggest that poorly described microbial groups may contribute to nutrient removal performance and process stability in IASBR regardless of the changes in dominant phylotypes representatives in laboratory and pilot-scale settings.