Effect Of Exogenous Additives On Anaerobic Digestion Of Sulfate Wastewater

A large amount of sulfate organic wastewater will be discharged in the production process in the fields of chemical industry,pharmacy,papermaking,food processing and mining.This kind of wastewater contains high concentration of sulfate,which will cause acidification of water quality and soil structure,and then affect the growth of crops.Anaerobic digestion technology has been widely used because it can degrade sulfate and produce biogas at the same time.However,there are still a series of problems in the anaerobic digestion of sulfate wastewater,such as slow and insufficient hydrolysis rate,accumulation of organic acids,low yield of hydrogen sulfide and methane.In this paper,the anaerobic digestion performance of sulfate organic wastewater is improved by adding exogenous additives(biochar（BC）,zero valent iron（n ZVI）and biochar loaded nano zero valent iron（BC/n ZVI）.The effects of BC,NZVI and BC/n ZVI materials on anaerobic digestion performance are systematically analyzed;The main work and conclusions are as follows:（1）The effect of sulfate concentration on anaerobic digestion is discussed.The results show that an appropriate amount of sulfate can promote anaerobic digestion.When SO₄^2-/COD=0.1,compared with the blank group,the cumulative methane and COD removal rates are increased by 0.45%and 0.21%respectively.With the continuous increase of sulfate concentration,anaerobic digestion is inhibited;（2）The effect of BC dosage on anaerobic digestion of sulfate wastewater is discussed.The results show that biochar selectively enriches hydrogen methanogens and increases the relative abundance of anaerobic microorganisms.Under the condition of high sulfate concentration,biochar can also promote methanogenesis and reduce sulfate,indicating that biochar can alleviate the inhibition of sulfate to a certain extent;（3）The effect of n ZVI dosage on anaerobic digestion of sulfate wastewater is discussed.The results show that when SO₄^2-/COD=0.1,the effect of 2g/L n ZVI is the best.At this time,the removal rates of COD and sulfate are 75.24%and 91.30%respectively.Increasing the amount of n ZVI do not improve the anaerobic digestion performance,and a large amount of n ZVI have a certain toxic effect on anaerobic microorganisms;（4）The effect of BC/n ZVI dosage on anaerobic digestion of sulfate wastewater is discussed.The results show that the cumulative methane production of BC/n ZVI group is 30.2%-36.4%higher than that of BC group and n ZVI group.BC/n ZVI also promotes the degradation of organic matter and sulfate,showing the synergistic effect of BC and n ZVI mediate interspecific electron transfer.In addition,BC/n ZVI can significantly improve the abundance of hydrogen methanogens.