Nitrate Nitrogen And TOC Removal From Groungwater By A Three-bioelectrochemical Reactor

Three-dimensional electrode biofilm reactor is used to degrade groundwaternitrate nitrogen, and trace organics, which makes up for the shortcomings of theconventional water treatment methods, it has many advantages such as goodmass transfer effects, operating under normal temperature and pressure, and simpleoperation. This reactor has unique advantages and good prospects for developmentin low concentrations of groundwater and drinking water treatment.However, previous studies have shown many shortcomings to traditionalthree-dimensional electrode biofilm reactor, for example, the contact area of thecathode and particulate electrode is small, cross section is uneven, utilization of theanode is low. This study will rebuild a new three-dimensional electrode biofilmreactor to solve these problems, and to treat contaminated groundwater.1.The study use the removal of nitrate nitrogen and phenol single-factor test todetermine the reactor operating conditions: influent nitrate concentration was25mg/L, phenol influent concentration of about0.08mg/L, temperature27℃, testcurrent is40mA, the residence time is10h,pH=7.9.Under this condition, the resultis nitrate nitrogen removal rate reached to40.07%, TOC removal rate reached to60.47percent.2.The single factor affect experiment of NO3--N remove results shows that: a、The vertical distribution of NO3--N in the reactor, from the cathode to anode，withthe increase in current intensity，the NO3--N concentration decreases gradually. Withthe increase of current, NO3--N concentration in anode region shows a rising trend,but the cathode area of NO3--N concentration shows a downward trend. This matchthe phenomenon of negatively charged ions nitrate moving towards anode in theelectric field conformity. b、Influent concentration affected the conductive mediumconcentration in solution further affect the mass transfer rate, in the waterconcentration is25mg/L,the nitrogen removal rate reached a maximum value of 37.27%.From Nitrate nitrogen removal rate、total nitrogen removal efficiency andthe accumulation of NO2--N can be seen, when water concentration is25mg/L,reactor had the best effect for removal of NO3--N. c、Current intensity has someeffect on nitrogen removal, on one hand, current stimulus the microbial growth, onthe other hand, the changes of current strength will also change the number ofelectron donor. d、HRT has a certain effect on oxygen concentration. When HRT isless than6h, while DO value is large, it will not conducive to denitrification.3.The reactor has removal effect of organic pollutants phenol in the process ofremoving nitrate nitrogen. Reactor for phenol removal single factor experimentalresults show that: a、the research was conducted to scan the spectrum of inlet andoutlet water in running reactor to judge whether the removal of phenol in reactor isdegradation or fully activated carbon adsorption. The absorbance peak and valley ofinlet and outlet water were quite different. Combined with TOC removal in thereactor it can be further explained that the reactor may be decomposed phenolorganic into small molecules and makes the pH alkaline. b、 During theelectrochemical anodic oxidation of phenol, the current increases with increasing theconcentration of hydroxyl radicals that the phenol removal rate rises and it willreduce the number of microorganisms andphenol removal. c、The reactor cansimultaneously remove nitrate and phenol, removing the solution of nitrates cancause slow rate of mass transfer which will make the reactor for removal of organicmatter reduction. it shows a longer residence time in the reactor will not suitable forthe simultaneous removal of nitrate and phenol.