Biological pre-treatment system for ammonia removal from slightly contaminated river used as a drinking water source

A pilot-scale biological pre-treatment reactor filled with porous polyurethanes carriers (BioNET) was operated over 500 days under different hydraulic retention times (HRT) (1.3 to 0.5 h) to evaluate the feasibility and efficiency of ammonia removal for a slightly contaminated source water. Under 0.5 h HRT, 84 % nitrification efficiency and 0.42 kg-N/m³/day ammonia removal rate could be achieved with influent ammonia concentration of 10.4 mg N/L. Results of batch tests indicated that the effect of aeration on nitrification of BioNET was more significant than temperature and components in raw water. Specific ammonia oxidization rate for batches with aeration were 4.5–9.1 times higher than those without aeration. In addition, simultaneous nitrification and denitrification were observed with batch tests using BioNET obtained from the reactor. Ammonia monooxygenase subunit A (amoA) gene of ammonia oxidizing archaea and bacteria (AOA and AOB) and 16S rRNA gene of total bacteria, Nitrospira, and Nitrobacter were quantified using real time quantification polymerase chain reaction (qPCR). AOB and Nitrospira were dominant in the bioreactor. Higher nitrification efficiency (>60 %) could be achieved at AOB abundance higher than 1.25 × 10⁸ copy/BioNET and AOB/TB higher than 1.2. This study demonstrated that the BioNET system can be a promising technology for removing ammonia from slightly polluted river water at a low HRT condition.