Decolorization Efficiency And Key Influence Factors For Anaerobic Digestion-bioelectrochemical Enhancing Dye Wastewater Treatment

Printing and dyeing wastewater has the characteristics of large discharge,complex pollutants,large fluctuation of water quality and poor biodegradability,which accounts for a large proportion of industrial wastewater in China.Azo dye is one of the most widely used refractory pollutants in printing and dyeing wastewater which are difficult to be treated and decolorizedwith high chromaticity.The traditional anaerobic treatment has disadvantages of long treatment time and low efficiency.The technology of bioelectrochemical system(BES)has been proved to be capable of directionally converting various refractory pollutants.In this paper,a new anaerobicbioelectrochemical system coupling reactor(AD-BES)was constructed by combining BES with traditional anaerobic process.Two operation modes of continuous stirred reactor and continuous upflowed reactor were used.The latter was combined with anoxic process into a modular stacking combined process,followed by aerobic tank and sedimentation tank.A complete set of wastewater treatment process(AB-A-O)was constructed.In order to evaluate the ability of coupling reactor for dye wastewater treatment and the enhanced performance of BES,the current,potential,decolorization,product generation and COD consumption were compared between the AD-BES and the traditional anaerobic reactor(AD)when treating orange II wastewater of 50 mg/L.Bio-electrochemistry could speed up the start-up of reactors and improve the treatment efficiency.Electrochemical system(ES)was added to the comparison.The decolorization rate in 8 h of AD-BES reached 97.2%,which was 1.7 times and 4.3 times higher than that of AD and ES,even higher than that of the sum.The parameters of ADBES were optimized,including the proportion of domestic sewage,electrolyte concentration and additional carbon source concentration,and the response surface method was used to optimize the effect of three factors in the degradation of orange II and the significance order were as follows: electrolyte concentration > proportion of domestic sewage > additional carbon source concentration.By parameter optimization,the decolorization rate of orange II was up to 99.94% when the proportion of sewage was 59.1%,electrolyte concentration was 0.03 mol/L and additional carbon source concentration was 0.15 g/L.Based on the optimal parameters,the AD-BES was applied to enlarged continuous flow reactor(AB-A-O).The efficiency of domestic sewage as a cheap carbon source to enhance the treatment of azo dye wastewater at different dye concentrations was studied.When the influent concentration of dye was high,domestic sewage could still provide enough electrons,resulting in higher decolorization rate,product generation,COD consumption and TN removal efficiency.The concentration of orange II gradually increased from 50 mg/L to 400 mg/L,the decolorization rate increased from 93.6% to 98%,the effluent COD was lower than 60 mg/L,and the total nitrogen removal rate was higher than 55%.The dominant functional bacteria of biological electrodes were analyzed,and the key electron transfer bacteria and anaerobic metabolic bacteria were identified.The morphological characteristics of biofilm or activated sludge were observed by SEM analysis,and microbial community structure and composition was analyzed by 16 S r RNA gene Illumina sequencing.The bioanode and biocathode in the batch-type AD-BES were enriched with Desulfovibrio,Arcobacter,Acinetobacter,Pseudomonas,Geobacter,etc.,which had the function of electron transfer or reductive degradation of orange II.The continuous AD-BES reactor was dominated with various functional genera and the biofilm diversity was abundant.Desulfovibrio,Acinetobacter,Pseudomonas,Anaerovorax,Pseudorhodoferax and other functional genera were detected.This paper proved that the introduction of bio-electrochemistry could enhance the feasibility of the treatment efficiency of azo dye wastewater.Both of the two constructed reactors had good treatment effects.The design of the reactors,the optimization of parameters and the construction of the entire wastewater treatment process could provide theoretical and technological basis and process ideas for engineering practice.