Delaying Calcification Of Anaerobic Granular Sludge By Biological Control Of CO₂ Levels

Papermaking wastewater has the remarkable characteristics of high-concentration organic waste pollutants and high calcium concentration.It is widely used because anaerobic biological treatment has the advantages of decomposing and converting complex organic matter into stable substances such as CH4 and CO2,while releasing heat.The treatment of papermaking wastewater is used.However,the high concentration of Ca2+ in papermaking wastewater is susceptible to pH and other factors in the anaerobic system.Inorganic precipitates are generated and attached to the surface or inside of the anaerobic granular sludge,causing the inorganic components of the granular sludge to increase,reduce activity and even inactivate alcification.The calcification of anaerobic granular sludge can easily lead to sludge loss,decreased gas production characteristics,and changes in microbial community structure,etc.,and eventually even paralyze the entire anaerobic system.Although the literature has reported the calcification phenomenon and law of granular sludge in papermaking wastewater,and even studied the structure of microbial flora at different heights,no effective strategy has been proposed for the elimination or delay of calcium deposition.Based on this,this article from the perspective of microbial community structure To explore the effect of Ca2+ on the structure of methanogenic archaea in the core microorganisms of granular sludge,and then to regulate the effect of CO2 level on the concentration of Ca2+ and the structure of sludge in the anaerobic system through the regulation of CO2 levels by microbiota.The purpose is to delay the calcification of granular sludge.The following conclusions were obtained:(1)Ca2+ is easy to deposit on the surface or inside of fresh anaerobic granular sludge(the reactor runs two the deposition rate at 6 months is 64.1%).With the extension of operation time,the calcification degree of granular sludge is continuously deepened,and the organic components in sludge per unit mass are reduced,so that the methanogenic activity of granular sludge is reduced,and the IC(Internal circulation)reactor treatment effect is showing a downward trend;The color of the anaerobic granular sludge changes from shallow to dark after drying gradually;the proportion of acetic acid-type methanogens in the system is gradually increasing,and the proportion of hydrogen-trophic type methanogens is greatly reduced.(2)Under the long-term effect of high-calcium wastewater,the relative abundance of hydrogen-trophic methanogens decreases with granular sludge,as represented by Methanoregula,Methanospirillum and Methanolinea.Methanosarcina and Methanosaeta are examples.Methanosaeta is the most dominant dominant bacteria in their respective vegetative flora types.The biodiversity of archaea in ICs of different heights from high to low is:5 m>2 m>7 m,and the archaea species at 5 m are more abundant.CaCO3 precipitation reduces the methanogenic activity of granular sludge,which is mainly manifested in its greater inhibition of hydrogenotrophic methane bacteria.(3)Before and after anaerobic enrichment,the acetic acid vegetative methanogens were Methanosaeta,and the hydrogen vegetative methanogens used Methanolinea,Methanoregula,and Methanobacterium as the dominant bacterial groups.After enrichment and cultivation,the biodiversity decreased,and the relative proportion of hydrogenotrophic methanogens in the total flora increased by 2.22%,and the mesotrophic seventh methanogenic archaea Methanomassiliicoccus was detected.(4)After the end of the control experiment,it was found that the calcium content of the anaerobic granular sludge in the experimental group with the enriched mixed bacteria group was relatively small,and there were still more bacilli and cocci microorganisms in the morphological structure,with large cavities and relatively cemented Weak,the cumulative methanogenic capacity and enzyme activity are better than the control group,the relative abundance(45.96%)of hydrogen nutrient methanogens is greater than that of the control group(43.86%);The inorganic components are all CaCO3 in the form of calcite,with similar functional groups.Therefore,the regulation of CO2 level in the system by hydrogen nutrient mixed bacteria can effectively delay the calcification of granular sludge.