Abstract
Optimization of running parameters in a bioreactor requires detailed understanding of microbial community dynamics during the startup and running periods. Using a novel piggery wastewater treatment system termed “UASB + SHARON + ANAMMOX” constructed in our laboratory, we investigated microbial community dynamics using the Illumina MiSeq method, taking activated sludge samples at ~2-week intervals during a ~300-day period. Ammonia-oxidizing bacteria (AOB) were further investigated by quantification of AOB amoA genes and construction of gene clone libraries. Major changes in bacterial community composition and dynamics occurred when running manner was changed from continuous flow manner (CFM) to sequencing batch manner (SBM), and when effluent from an upflow anaerobic sludge blanket (UASB) reactor for practical treatment of real piggery wastewater was used as influent; differences among these three experimental groups were significant (R2 = 0.94, p < 0.01). When running manner was changed from CFM to SBM, relative abundance of the genus Nitrospira decreased sharply from 18.1 % on day 116 to 1.5 % on day 130, and to undetectable level thereafter. Relative abundance of the genus Nitrosomonas increased from ~0.67 % during the CFM period to 8.0 % by day 220, and thereafter decreased to a near-constant ~1.6 %. Environmental factors such as load ammonia, effluent ammonia, effluent nitrite, UASB effluent, pH, and DO levels collectively drove bacterial community dynamics and contributed to maintenance of effluent NH4+-N/NO2−-N ratio ~1. Theses results might provide useful clues for the control of the startup processes and maintaining high efficiency of such bioreactors.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0245-5) contains supplementary material, which is available to authorized users.
Highlights
Ammonia, a common aquatic pollutant, is a cause of numerous environmental problems
When effluent from upflow anaerobic sludge blanket (UASB)-treated piggery wastewater was used as influent on day 220, NH4+-N/NO2−-N ratio was maintained at ~1 without pH adjustment, indicating the stability and efficiency of the reactor
AOTU-4, aOTU-1, and aOTU-2 were respectively predominant during the continuous flow manner (CFM) period, sequencing batch manner (SBM) period, and SBM period when UASB effluent was used as influent (Fig. 6b). aOTU-4 was phylogenetically consistent with operational taxonomic units (OTU)-99 (Fig. 3a) and had 77.2 % similarity to N. nitrosa
Summary
A common aquatic pollutant, is a cause of numerous environmental problems. Wastewater from piggeries (pig farms) contains high levels of chemical oxygen demand (COD) and ammonia (Bernet et al 2000; Zhu et al 2013) and is a major source of ammonia pollution (Bernet et al 1996; Li et al 2012). Application of anammox bacteria for treatment of wastewater containing high ammonium and low organic matter level was shown to result in operational cost savings up to 90 % (Jetten et al 2001). For this purpose, a single reactor system for high activity ammonium removal over nitrite (SHARON) reactor is necessary to transform ammonia into nitrite and ensure an effluent NH4+-N/ NO2−-N ratio ~1 to meet the requirement of anammox bacteria (Kuenen 2008). AOB, but not NOB, are expected to grow in a SHARON reactor, because nitrate accumulation is not acceptable in the process
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