Research On Anaerobic Degradation Of Phenolic Pollutants In Coal Gasification Wastewater By Magnetite Nanoparticles

Coal gasification wastewater contains high concentrations of phenolic pollutants,difficult-to-biodegrade organics,and toxic pollutants,making the disposal of this wastewater one of the most important causes of the development of the coal gas industry.Because of the poor removal efficiency of phenolic pollutants in coal gasification wastewater by the traditional anaerobic process,the anaerobic strengthening technology has become a new research direction in the field of coal gas wastewater treatment.Fe₃O₄ nanoparticles?Fe₃O₄NPs?have made some progress in enhancing anaerobic treatment process.This study proposed the introduction of Fe₃O₄NPs into the anaerobic digestion system for the treatment of coal gasification wastewater,and examines its effect on anaerobic degradation of coal through small-scale and pilot-scale experiments.Moreover,we analyzed the degradation pathways of phenolic pollutants which were strengthened by Fe₃O₄NPs,thus provided new ideas and theoretical basis for improving the anaerobic treatment process to degrade phenolic pollutants in coal gasification wastewater.The experimental results confirmed that the optimal particle size of Fe₃O₄NPs was 20⁴0nm by static experiments.The optimal dosing concentration was200mg/L.Fe₃O₄NPs could enhance the anaerobic removal effects of phenol,?o-,m-,p-?cresol,?ortho-,meta-,para-?hydroquinone and xylenol under optimal dosing conditions.The optimal dosing ratio of Fe₃O₄NPs and methanol?Fe₃O₄NPs 200mg/L?was also determined?Fe₃O₄NPs 200mg/l,Methanol 500 mg COD/L?.The optimal experimental conditions for Fe3O4 NPs obtained from static experiments were applied to the dynamic experiments.The results showed that Fe₃O₄NPs significantly increased the anaerobic removal of COD and total phenol in coal gasification wastewater by 9%and 10%respectively.After addition of Fe₃O₄NPs,the anaerobic removal of COD and total phenol achieved around 38%and 40%.Beyond that,the addition of Fe₃O₄NPs resulted in the weakly alkaline environment?7.3 to 7.5?,the reduction of ORP?-330 m V?,the reduction of biological toxicity of the effluent.Moreover,Fe₃O₄NPs could improve the stability of the system in the face of the variation of temperature,impact load,and HRT.The addition of Fe₃O₄NPs increased both the proportion and biodiversity of phenolic degradation communities,and could promote the relative abundance of phenol degrading bacteria genera such as Diaphorobacter,Stenotrophomonas,and Azotobacter.It is notably that Fe₃O₄NPs could stimulate electron transfer,therefore changed the way of contact between phenolic substances and microbial communities,and promoted the degradation of phenolic substances.At the same time,the community structure of methanogens was changed,and Geobacter and Methanosaeta promoted the process of methane production.In the pilot test,it was further verified that Fe₃O₄NPs could enhance the removal efficiency of COD and total phenol in anaerobic digestion of coal gasification wastewater.The removal rate reached 53%and 49%.Fe₃O₄NPs improved the phenol degradation by changing the system environment and microbial structure.The proportion of bacteria increased,as well as the content of enzymes involved in phenol degradation;Fe₃O₄ NPs as an electron transport carrier changed the carboxylation and benzoylation stages of the phenolic degradation process and promoted the degradation of phenols.Compared to other enhanced anaerobic processes,Fe₃O₄NPs have better economic advantages.