Effective Biological Nitrogen Removal Treatment Processes for Domestic Wastewaters with Low C/N Ratios: A Review

Abstract

Effective Biological Nitrogen Removal Treatment Processes for Domestic Wastewaters with Low C/N Ratios: A Review Discharge of nitrogenous components to water bodies can cause eutrophication, deterioration of water quality, toxicity to aquatic life, and pose a potential hazard to human and animal health. Biological nitrogen removal can remove nitrogenous components via conversion to harmless nitrogen gas with high efficiency and relative low costs. However, the removal of nitrogen from domestic wastewater with a low carbon/nitrogen (C/N) ratio can often be limited in municipal wastewater plants (WWTPs) because organic carbon is a limiting factor for denitrification. The present work reviews innovative bacterial nitrogen removal pathways such as shortcut nitrification/denitrification, simultaneous nitrification/denitrification, and the nitritation Anammox process, which can remove nitrogen with low or zero dosage of organic carbon sources. We conclude that advanced process control and some new biological treatment processes including the modified anaerobic/anoxic/oxic (A(2)/O) process, the step-feed multistage anaerobic/ oxic (A/O) process, and new reactors like the membrane bioreactors (MBRs) and the membrane-aerated biofilm reactors (MABRs) can support the innovative biological nitrogen removal pathways. They can effectively be used for nitrogen removal from low C/N domestic wastewater without external carbon addition. In addition, conventional and alternative carbon sources for enhanced biological nitrogen removal were also reviewed. We conclude that alternative carbon sources such as wine distillery effluent, the leachate of food waste, digested piggery manure, hydrolyzed molasses, biologically hydrolyzed or mechanically disintegrated sludge offer the same or better performance for nitrogen removal at reduced costs. Finally, we suggest that (1) these new processes and technologies are implemented at large scale for nitrogen removal from low C/N domestic wastewater, (2) further method logic are explored to introduce the Anammox pathway into domestic wastewater treatment, and (3) alternative carbon sources are explored and optimized for supporting the denitrification. With these efforts, cost-effective nitrogen removal from low C/N ratio domestic wastewater can be obtained in the near future.

Seasonal microbial community shift in a saline sewage treatment plant

“…However, CA is more suitable if samples containing counts of taxa or counted taxa across samples are compared [22], or if the bio-community is expected to have unimodal responses to environmental factors [21]. CCA showed that microbial community of activated sludge was significantly affected by influent wastewater quality characteristics, e.g., COD, NH þ 4 -N, TKN, TP and PO 3 -4 -P. Ratio of carbon, nitrogen and phosphorus is known as an important limiting factor for microbial growth [1] and DO is a crucial factor for the microbial community shift [2]. Flow rate showed a weak impact on the microbial structure in this study, because of the relatively stable influent flow in Shatin STP (216000-256000 m 3 $d -1 ).…”

“…Activated sludge process is being widely used for treatment of municipal sewage, including the saline sewage in Hong Kong. Previous studies showed that microbial community of activated sludge in sewage treatment plants (STPs) were affected by particular external factors, e.g., influent C∶N∶P ratio [1], dissolved oxygen (DO) [2] and hydraulic retention time (HRT) [3]. However, few researches were conducted to investigate the combined effects of these factors on microbial community structure in saline sewage treatment systems [4].…”

Treatment of turtle aquaculture effluent by an improved multi-soil-layer system

“…When the influent C/N ratio is lower than 3.4, extra carbon should be added to the system to remove redundant N (Kuba et al, 1996). Influent with a low C/N ratio is deficient in organic carbon, and a low carbon source can limit biological denitrification (Kim et al, 2008;Sun et al, 2010). Chu and Wang (2011) reported that, under the average influent of TN 52.6 mg/L, TN removal was only 1%-20% when using a moving bed biofilm reactor to treat low C/N ratio wastewater (3.7-4.2).…”

“…These key processes require sufficient organic matter as the carbon source for bacterial growth (Ostace et al, 2011). Wastewater with a low C/N ratio is not able to supply bacteria with sufficient carbon, resulting in low nitrogen removal efficiency (Kim et al, 2004;Sun et al, 2010). Several processes have been developed to address this problem.…”

Simultaneous methane production and wastewater reuse by a membrane-based process: Evaluation with raw domestic wastewater

“…For example, shortcut nitrification-denitrification technology can save 25% of oxygen and 40% of organic carbon source compared to full nitrification-denitrification process [17,18]. Furthermore, recent studies demonstrated that aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic (or anaerobic) ammonium-oxidizing bacte- ria (AnAOB or anammox bacteria) could cooperate in low-organic partial nitritation/anammox systems to remove ammonia from wastewater [19][20][21]. There was an approximate linear relationship between HRT U and nitrate removal from the HRT U of 6 h to 1 h, but such linear trend seemed not suitable for HRT U of 8 h, because TN removal efficiencies at HRT 8 h and 6 h were close to each other.…”