Effects Of Biochar On The Treatment Performance And Microbial Community Of Phenolic Wastewater In SBR System

In recent years,with the wide application of biochar in various fields of production and life,its ecological effect on the environment has attracted great attention.Biochar will inevitably enter the sewage treatment plant(WWTPs)during production,application and discharge.However,there is no systematic study on the efficacy and microbial community structure of the treatment of phenol wastewater by activated sludge after short and long term exposure of biochar.Therefore,in this paper,the effects of short-term and long-term biochar exposure of different concentrations on the efficiency and microbial community structure of treating phenol wastewater in SBR were systematically studied by taking sequence batch activated sludge process(SBR)as an example,and the influencing mechanism was revealed.In this study,the effects of short-term biochar exposure at different concentrations on the efficiency of SBR in treating phenol wastewater were firstly investigated.When the biochar concentration increased from 0 to 4 g/L,the degradation efficiency of SBR could be significantly improved Biochar short-term exposure to SBR system degradation rate is significantly higher than single SBR system and separate biochar-activated sludge heat inactivated system on phenol degradation efficiency,the sum that biochar short-term exposure to SBR system exists in the biodegradable and biological carbon adsorption coupling between synergy,and the coupling effect is mainly attributed to of biochar short-term exposure can significantly improve the activity of key enzymes of SBR,thus improve the SBR for phenol and COD removal rate.The results of intracellular reactive oxygen species(ROS)and lactate dehydrogenase(LDH)showed that the short-term exposure of biochar had no negative effect on the integrity of the plasma membrane,and it could significantly reduce the toxic effect of phenol on SBR community microorganisms.On this basis,the effects of long-term exposure of different concentrations of biochar on the efficiency of SBR in treating phenol wastewater were investigated.In the 50 d experiment,the degradation rate of phenol in each SBR system reached 100%,and when the biochar concentration increased from 0 to 4 g/L,the removal rate of COD increased significantly,SBR key enzyme activity increased significantly,and Pearson correlation coefficient analysis showed that key enzyme activity and biochar concentration were significantly positively correlated.The analysis of extracellular polymer(EPS)content showed that when the biochar concentration increased from 0 to 4 g/L,the contents of proteins and polysaccharides and the ratio of proteins and polysaccharides in sludge EPS decreased significantly.UV-vis spectra(UV-Vis)and three dimensional fluorescence spectrum(3D-EEM),infrared spectra(FTIR)analysis shows that when the concentration of biochar increased from 0 to 4 g/L,significant changes in the molecular structure of sludge EPS,abundance of aromatic compounds in sludge EPS,aromatic ring number,conjugated bond as well as the associated with protein C=O,-CONH,associated with polysaccharide C-OH,C-O-C,C-O and associated with nucleic acid O-PO gradually reduce the number of functional groups.To further investigate the effects of long-term exposure of biochar on SBR,this study investigated the effects of long-term exposure of biochar at different concentrations on the toxicity and structure of the SBR microbial community.LDH and ROS analysis showed that long-term exposure of biochar had no effect on cytoplasmic membrane integrity and significantly reduced the effect of phenol on SBR community microbial toxicity.Highthroughput sequencing further demonstrated that the long-term exposure of biochar significantly changed the composition and structure of microorganisms: with the increase of biochar concentration,the biological community tended to be richer and less diverse,in order to resist the impact of phenol.When the biochar concentration increased from 0 to 4 g/L,the relative abundance of the dominant phenol degradation bacteria Comamonas and Cupriavidus increased significantly.The relative abundance was positively correlated with biochar concentration.At the same time,the results of CCA showed that,compared with the impact of phenol and COD,the long-term exposure of biochar significantly affected the change of microbial community,which may be attributed to the fact that biochar can be used as a microbial carrier to facilitate the adhesion and growth of microorganisms and effectively resist the impact of phenol on SBR.Therefore,both short-term and long-term exposure of biochar concentration in the range of 0-4 g/L has no toxic effect on SBR phenol wastewater treatment system,and can significantly improve the treatment efficiency of phenol wastewater.