Abstract
Bacterial community dynamics of the ANAMMOX reactor of an integrated “UASB + SHARON + ANAMMOX” system for treating piggery wastewater were investigated using the Illumina MiSeq method with samples obtained at ~ 2-week intervals during a 314-day period. With aerobic activated sludge as seeds and low content artificial wastewater (NH4+–N 50 mg/L; NO2−–N 55 mg/L) as influent for the ANAMMOX reactor, nitrogen removal was initially observed on day 38 with a removal rate 1.3 mg N L−1 day−1, and increased to 90.4 mg N L−1 day−1 on day 55 with almost complete removal of ammonia and nitrite, indicating a successful startup of the reactor. Increasing influent load stepwise to NH4+–N 272.7 mg/L/NO2−–N 300 mg/L, nitrogen removal rate increased gradually to 470 mg N L−1 day−1 on day 228, and maintained a stable level (~ 420 mg N L−1 day−1) following introduction of SHARON effluent since day 229. Correlation between microbial community dynamics and nitrogen removal capability was significant (r = 0.489, p < 0.001). Microbial community composition was determined by influent ammonia, influent nitrite, effluent nitrate and some undefined factors. Anammox bacteria, accounting for ~ 98.7% of Planctomycetes, became detectable (0.03% relative abundance) since day 38 and increased to 0.9% on day 58, well consistent with nitrogen removal performance of the reactor. Relative abundance of anammox bacteria gradually increased to 38.4% on day 140 with stepwise increased influent load; decreased to 0.4% on day 169 because of nitrite inhibition; increased to 19.24% on day 233 when the influent load was dropped; kept at ~ 9.0% with SHARON effluent used as influent and dropped to 3.3% finally. Anammox bacteria, only Candidatus Brocadia and Ca. Kuenenia detected, were the most abundant at genus level. Ca. Brocadia related taxa were enriched firstly under low load and detectable during the entire experimental period. Three main groups represented by Ca. Brocadia related OTUs were enriched or eliminated at different loads, but Ca. Kuenenia related taxa were enriched only under high load (NO2−–N > 300 mg/L), suggesting their different niches and application for different loads. These findings improve the understanding of relationships among microbial community/functional taxa, running parameters and reactor performance, and will be useful in optimizing running parameters for rapid startup and high, stable efficiency.
Highlights
Ammonia pollution from pig farm has steadily increased worldwide in recent decades and presents serious environmental problems (Ali et al 2013)
Effluent ammonia and nitrite levels showed no significant decrease through day 1 to day 37, nitrogen removal was initially observed since day 38 with a removal rate of 1.3 mg N L−1day−1
To date, little attention has been given to microbial community dynamics in an anaerobic ammonium oxidation process (ANAMMOX) reactor including rapid startup, increasing nitrogen load and stable performance (Costa et al 2014; Liu et al 2017)
Summary
Ammonia pollution from pig farm has steadily increased worldwide in recent decades and presents serious environmental problems (Ali et al 2013). Conventional nitrification–denitrification methods require large amount of energy and organic materials, resulting in high operational cost and limited application (Bernet et al 1996; Boiran et al 1996). The anaerobic ammonium oxidation process (ANAMMOX), a more recently developed approach for nitrogen removal from wastewater, has the advantages of high efficiency, low sludge production, and no organic material requirement (Strous et al 1999). Combined process SHARON–ANAMMOX had been applied for piggery wastewater treatment, but the nitrogen removal efficiency was not ideal due to high organic content, which would seriously inhibite anammox bacteria (Hwang et al 2005; Jin et al 2012; Tang et al 2010; Yamamoto et al 2008)
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