SNAD For Biological Nitrogen Removal Using Carbon Tube Membrane-aerated Biofilm Reactor

The wastewater of high nitrogen components can cause eutrophication in receiving water and lead to a serious deterioration of water environment. Some poisonous nitrogen components even endanger the health of people and other animals. So how to remove nitrogen components from wastewater has been an important and serious issue nowadays. Conventional biologial nitrogen removal processes exit some problems such as system complex, large footprint, high operating costs, ect. It is hard to meet the general requirements of sustainable development of wastewater treatment technologies. Recently, a novel and promising microbial process, entitled single-stage autotrophic nitrogen removal has been developed. This technology is carried out in one reactor combining nitritation and anaerobic ammonium oxidation and it has the advantages of facility, high efficiency and low energy requirement comparing to the traditional biological nitrogen removal process.A lab-scale membrane-aerated biofilm bioreactor (MABR) equipped with non-woven fabrics support around the gas-permeable carbon tube is developed for the removal of ammonium based on simultaneous partial nitrification, anaerobic ammonium oxidization and denitrification. (SNAD) Initially, the reactor is inoculated with nitrifying biomass. By controlling the conditions, the aerobic ammonia-oxidizing bacteria are accumulated. Subsequently, the reactor is inoculated with ANAMMOX bacteria on the non-woven fabrics. Then add the organic carbon to the reactor for the survival of denitrification bacteria to start up SNAD system in one reactor. This study was performed as follows:(1) The carbon membrane with non-woven fabrics has high ability of oxygen transfer, and the nitrifying bacteria and ANAMMOX bacteria which are of slow growth can be effectively enriched. The different concentration of oxygen in the biomass can insure the suitable conditions for three groups of bacteria.(2) The influent NH₄⁺-N, temperature, pH and HRT and C/N are controlled at 200 mg/L ,34±1℃, 7.5-8.5 ,8 h and 0.6. After 180 d of operation, 93.4 % of NH₄⁺-N removal effficiency, 92.5 % of TN removal effficiency and 97.2 % of COD removal are achieved in MABR. (3) By adding organic carbon to CANON system, three groups of bacteria are observed in one single reactor. The results showed that: The suitable C/N ratio is 0.2-0.6, and the higher COD will inhibit the ANAMMOX bacteria and make the reactor performance worsen.