Study Of Membrane-Aerated Biofilm Reactor For Nitritation Of Autotrophic Nitrogen Removal

The accumulation of nitrogen leads to a serious deterioration of water environment, so removing nitrogen components from wastewater is an important and serious issue nowadays. However 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 no extra organic carbon is affixed, and it has the advantages of facility, high efficiency and low energy requirement comparing to the traditional biological nitrogen removal process.In this study, a novel membrane-aerated biofilm reactor(MABR), equipped with non-woven materials support around the microporous carbon tube membrane, was developed for nitritation of single-stage autotrophic nitrogen removal. Microbial community structure of the biofilm in different periods was detected. The purpose of this paper is to create a good foundation for inoculation ANAMMOX bacteria so as to realize single-stage autotrophic nitrogen removal process. This study was performed as follows:(1) The ability of oxygen transfer of carbon membrane was high, and adequate oxygen was supplied to the biofilm which attached to the carbon tube for its metabolism. The capacity of biological retention could be effectively improved in MABR with carbon membrane module wrapped with non-woven fabrics. The nitrifying bacteria which were of slow growth were effectively enriched. So, carbon tube membrane was suitable for the aeration membrane module of MABR.(2) On the conditions of influent NH₄⁺-N of 200mg/L, temperature of 34±1℃, pH of 7.5-8.3, HRT=8h, stable half-nitrification was achieved by decreasing intra-membrane pressure gradually and the effluent NH₄⁺-N and NO₂^--N ratio was about 1:1. And after 20 days' continuous operation, other indexes of enffluent were stable.(3) Fluorescent in Situ Hybridization (FISH) analysis indicated that at the end of domestication of microorganisms, nitrosobacteria and nitrobacteria occupied 33%,30% of the total bacteria number, respectively. But during stable half-nitrification period, nitrosobacteria was above 65%,and nitrobacteria was decreased to 9%,the enrichment of nitrosobacteria was realized, and it created a good microorganisms foundation for inoculation ANAMMOX bacteria so as to realize single-stage autotrophic nitrogen removal process.