Start-up of PN-anammox system under low inoculation quantity and its restoration after low-loading rate shock

Abstract

Partial nitritation (PN)-anaerobic ammonium oxidation (anammox) is a promising pathway for the biological treatment of wastewater. However, the destruction of the system caused by excessive accumulation of nitrate in long-term operation remains a challenge. In this study, PNanammox was initialized with low inoculation quantity in an air-lift reactor. The nitrogen removal rate of 0.71 kgN/(m 3 $d) was obtained, which was far higher than the seed sludge (0.3 kgN/(m 3 $d)). Thereafter, excess nitrate build-up was observed under low-loading conditions, and recovery strategies for the PN-anammox system were investigated. Experimental results suggest that increasing the nitrogen loading rate as well as the concentration of free ammonium failed to effectively suppress the nitrite oxidation bacteria (NOB) after the PN-anammox system was disrupted. Afterwards, effluent back-flow was added into the reactor to control the up-flow velocity. As a result, an aggressive discharge of sludge that promoted the synergetic growth of functional bacteria was achieved, leading to the successful restoration of the PN-anammox system. The partial nitritation and anammox activity were in balance, and an increase in nitrogen removal rate up to 1.07 kgN/(m 3 $d) was obtained with a nitrogen removal efficiency of 82.4% after recovery. Besides, the proportion of granular sludge (over 200 mm) increased from 33.67% to 82.82%. Ammonium oxidation bacteria (AOB) along with anammox bacteria were enriched in the granular sludge during the recovery period, which was crucial for the recovery and stable operation of the PN-anammox system.

The main anammox-based processes, the involved microbes and the novel process concept from the application perspective

“…N. mobilis was shown to be able to tolerate nitrite at 300 mM (Thandar et al, 2016). FA and FNA can inhibit AOB and NOB (Zhang et al, 2021). A proper high FA concentration favors AOB growth over NOB growth.…”

Research progress of anaerobic ammonium oxidation (Anammox) process based on integrated fixed‐film activated sludge (IFAS)

“…These factors have become the biggest hindrance to the application of anaerobic ammonium oxidation technology in wastewater treatment plants. Suspended sludge, granular sludge, and biofilm can all be forms of biomass to be used to operate the Anammox process (Guo et al, 2020 ; Zhang, Zhang, Han, et al, 2020 ). Both granular sludge and biofilm can effectively retain and enrich functional bacteria, and both can form different gradients of DO and substrate from the outside to the inside, creating symbiotic conditions for aerobic AOB and anaerobic AnAOB Fields (Wu, Chen, et al, 2022 ).…”

Processos de nitritação parcial e anammox em efluentes anaeróbios de esgoto sanitário doméstico para regiões de clima quente

“…O gênero Denitratisoma foi identificado como o mais abundante nas amostras coletadas, variando de 22,1 a 43,6% em R1 e de 22,8 a 40,0% em R2. Este microrganismo é conhecido por seu metabolismo heterotrófico desnitrificante, sugerindo que sua presença em reatores autotróficos provavelmente se deve ao uso de fontes internas de carbono provenientes da lise celular e da decomposição (XIE et al, 2021;ZHANG et al, 2021a). Além disso, as bactérias Denitratisoma utilizam diferentes ácidos graxos como fonte de carbono e nitrato como aceptor de elétrons (FAHRBACH et al, 2006)…”