Abstract
Continuous anaerobic ammonia oxidation (Anammox) process in multistage anaerobic baffled (MABR) reactor was investigated. The reactor was operated for approximately 150 days at constant hydraulic retention time (HRT) of 48 h and was fed with synthetic wastewater containing nitrite and ammonium as main substrates. The MABR was inoculated with mixed culture bacteria collected from activated sludge plant (41.6 g MLSS/L and 19.1 g MLVSS/L). The MABR reactor exhibited excellent performance for the start-up of Anammox process within a period of 35 days. The start-up period was divided into four successive phases; cell lysis, lag, activity elevation and steady state. Total inorganic nitrogen (TIN) removal efficiency of 96.8± 0.9% was achieved at steady state conditions, corresponding to nitrogen removal rate (NRR) of 50.2±1.7 mg N/L·d. Moreover, the effect of HRT on the Anammox process was assessed with applying five different HRTs of (48, 38.4, 28.8, 19.2 and 9.6 h). Decreasing HRT from 48 to 9.6 h reduced the removal efficiencies of NH 4 -N, NO 2 -N and TIN from 97.7±2.2 to 49.0±9.8%, from 95.7±1.9 to 71.0±8.5% and from 96.8±0.9 to 57.9±9.1%, respectively, that corresponding to reduction in NRR from 50.8±1.2 mg N/L·d at HRT of 48 h to 32.5±5.0 mg N/L·d at HRT of 9.6 h.
Highlights
Several types of wastewater such as wastewater from fertilizer industry, dewatering of digested sludge and landfill leachate have high concentrations of ammonium and low concentrations of biodegradable organic compounds
The lab scale multistage anaerobic baffled reactor MABR was used to study the treatment of ammonia rich wastewater by anaerobic ammonia oxidation (Anammox) process
The occurrence of the Anammox activity was demonstrated through a simultaneous depletion of nitrite NO2-N and ammonia NH4-N coupled to a small production of nitrate NO3-N
Summary
Several types of wastewater such as wastewater from fertilizer industry, dewatering of digested sludge and landfill leachate have high concentrations of ammonium and low concentrations of biodegradable organic compounds (low C/N ratio). Under anaerobic or anoxic conditions, Anammox bacteria, which belong to the order Planctomycetales, accomplish autotrophic ammonium (NH4+) oxidation to produce dinitrogen (N2) gas while using nitrite (NO2ˉ) as an electron acceptor and CO2 as carbon source, producing scanty amounts of nitrate (NO3ˉ) (Eq (1)) [6,7]. This process offers several advantages over conventional nitrification-denitrification systems including higher nitrogen removal rate, lower operational cost and less space requirement [4]. The application of the Anammox process in wastewater treatment results in significant reduction in energy (60%) and greenhouse gas emission (90%) compared to those of traditional biological nitrogen removal processes [8, 9]
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