Coupling Process Based On Catalyzed Micro-electrolysis And Biofilm For Advanced Nitrogen Removal Of Low C/N Ratio Wastewater

Advanced nitrogen removal from low carbon to nitrogen ratio(C/N)wastewater has always been hot and difficult in the research of wastewater treatment.It is of great significance to develop new technology with high efficiency,low cost and security assurance to make up for the limitation of traditional technology in low C/N ratio wastewater treatment.The research in this article was conducted aiming at the existing problems in low C/N ratio wastewater treatment.Chemical reduction of nitrate and biological nitrogen removal of the self-develop composite catalytic bio-carrier(CCBC)were investigated to develop a coupling nitrogen removal process between the catalyzed micro-electrolysis and biological process.Firstly,Jar tests were conducted to investigate the nitrate reduction efficiency of the bio-carrier under various reaction time,aeration and pH value.Then continuous operation of the CCBC filled reactor was conducted.The start-up process,impact factors,nitrogen removal along the reactor and nitrogen removal efficiency of the coupling system were evaluated.The coupling nitrogen removal between the physicochemical reaction and biological process was experimentally verified.Finally,the economic effects of the coupling process were analyzed.The results of the research showed that:(1)The bio-carrier achieved 94.9%nitrate reduction in 180 min,which was much higher than that of zero valent iron(Fe0)under initial pH of over 7.0.The reaction order of 3 was calculated.The reaction rate and ammonia accumulation increased with the increase of the influent ammonia concentration.(2)The coupling process between the catalyzed micro-electrolysis and biological process was started in 51 days.The optimal operation conditions of HRT=3.5 h,DO=3.5±0.1 mg/L and pH=7.5±0.1 with ammonia,nitrate and total nitrogen removal of 90.08%?95.3%,90.5%?99.0%and 90.3%?96.5%,respectively,indicating that the effective nitrogen removal from low C/N ratio wastewater was achieved.(3)Effective nitrate removal in the 60?100 cm of the reactor was found and the dominant autotrophic denitrification was estimated.The kinetic equation of nitrogen removal in the coupling system was calculated as Ne=Noexp(-0.004368h·L-1.8438)based on the Eckenfelder equation,in which the K of 0.004368 and n of 1.8438 verified the suitable of the bio-carrier for attachment growth of the microorganisms and the efficient nitrogen removal of for nitrogen by the microorganisms.(4)The coupling process was not simply the aggregation of micro-electrolysis and biological nitrogen removal in the reactor,but a micro-electrolysis supported autotrophic denitrification process.(5)Cost of 3.68 yuan/kg bio-carrier was calculated.The nitrogen removal load of 0.38-0.41 kg TN/(m3·d)was verified,higher than other bio-carriers.Relatively low nitrogen removal cost of 26.74 yuan/kg·N was calculated.The CCBC based coupling process was a technology of high efficiency,low cost,easy operation and security when compared to other technologies.The proposed technology was of potential for practical use in the tail water from advanced treatment wastewater treatment plant,recycled water and polluted surface and ground water.