Microbial structure and nitrogen compound conversions in aerobic granular sludge reactors with non-aeration phases and acetate pulse feeding

Abstract

A technological system was developed for efficient nitrogen removal from real digester supernatant in a single reactor with shortened aeration to increase the economical aspects of wastewater treatment. The supernatant (600 mg TKN/L, low COD/N ratio of 2.2) was treated in batch reactors with aerobic granules (GSBRs) to test how one, two, or three non-aeration phases and acetate pulse feeding in the cycle affect the morphological and microbial properties of biomass. Introduction of one non-aeration phase in the cycle increased nitrogen removal efficiency by 11 % in comparison with constantly aerated GSBR. The additional non-aeration phases did not diminish the efficiency of ammonia oxidation but did favor nitrification to nitrate. Acetate pulse feeding in the reactor with three non-aeration phases raised the efficiency of nitrogen removal to 77 %; in parallel, the number of denitrifiers possessing nosZ genes and performing denitrification to N2 increased. Ammonia was oxidized by aerobic and anaerobic ammonia-oxidizing bacteria and heterotrophic nitrifiers (Pseudomonas sp. and Alcaligenes faecalis) that coexisted in granules. Azoarcus sp., Rhizobium sp., and Thauera sp. were core genera of denitrifiers in granules. An increase in the number of non-aeration phases diminished EPS content in the biomass and granule diameters and increased granule density.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-016-7709-7) contains supplementary material, which is available to authorized users.

Effect of Aeration Mode on Microbial Structure and Efficiency of Treatment of TSS-Rich Wastewater from Meat Processing

“…This indicates that ammonium nitrogen oxidation is stimulated by anoxic conditions. It has been reported that increasing the number of anaerobic phases in the reactor cycle increased the total number of bacteria (as shown by abundance of 16S rRNA gene), the number of AOB bacteria involved in nitrification (amoA gene abundance) and the number of complete denitrifiers (nosZ gene abundance) [34]. In the present study, such increases were not observed; however, the share of such taxa as Thauera sp., Dokdonella ginsengisoli, and Lysobacter daejeonensis, which participate in nitrogen The average N-NH 4 concentration in each effluent was around 1 mg L −1 (Figure 4).…”

“…This indicates that ammonium nitrogen oxidation is stimulated by anoxic conditions. It has been reported that increasing the number of anaerobic phases in the reactor cycle increased the total number of bacteria (as shown by abundance of 16S rRNA gene), the number of AOB bacteria involved in nitrification (amoA gene abundance) and the number of complete denitrifiers (nosZ gene abundance) [34].…”

Appraisal of suspended growth process for treatment of mixture of simulated petroleum, textile, domestic, agriculture and pharmaceutical wastewater

“…The increase in residual nitrate (Fig 3b , phase-A) in treated effluent at start-up period could be from seed municipal wastewater as the nitrification pathway was limited due to low bacteria population. The steady reduction in nitrate which ensued at limited nitrification phase implies denitrification of the near constant residual (original) nitrate believed to have occurred within the anaerobic environment of aerobic granules and flocs created due to limited air diffusion in the biomass structure [34,35,36]. The sudden increase in nitrate concentration in treated effluent from day 28 was in tandem with the nitrification activity shown in Figure 3a, phase-A.…”

“…Similarly, seed municipal wastewater was responsible for the sudden decrease in phosphate concentration in treated effluent which gradually increased in response to increased feed dosage (Fig 3c , phase-A). The subsequent gradual reduction in phosphate in the aerated bioreactors could be by denitrifying phosphate accumulating organisms process [34,42,43].…”