Effect Of Calcium Ion On The Membrane Fouling Mechanism Of Algal-Bacteria Symbiosis-membrane Process For Treatment Of Livestock Wastewater

Although the algal-bacteria symbiosis can more efficiently treat livestock wastewater and effectively recycle the resources in the wastewater,the quality of its effluent still cannot meet the requirements for standard discharge or further regeneration and reuse.Ultrafiltration membranes can further optimize water quality.However,the problem of membrane fouling still limits its wide application.Therefore,this article is mainly based on the treatment of livestock wastewater based on the algal-bacteria symbiosis-membrane process,Combined with a variety of characterization methods,including FTIR,three-dimensional fluorescence,contact angle,zeta potential,particle size distribution,etc.,to explore the contribution of extracellular polymers substance to the mechanism of fouling,as well as the effect of Calcium ion on EPS components and membranes.Provides theoretical guidance and technical support for the better practice and application of the algal-bacteria symbiote-membrane process in livestock wastewater treatment.The study on the treatment of actual wastewater by the algal-bacteria symbiosis shows that the algal-bacteria symbiosis has a high treatment effect on nitrogen and phosphorus in livestock wastewater,but at the same time,the EPS secreted by the microorganisms will cause serious membrane pollution in the subsequent membrane filtration process.Among the components,the membrane fouling caused by Soluble Microbial Products(SMP)is the most serious,followed by loosely bound extracellular polymer substances(LB-EPS).In addition,the blocking of the membrane surface and membrane pores by the algal flocs is also an important reason for aggravating membrane fouling.The analysis results of membrane fouling components show that the organic pollutants that cause membrane fouling are mainly polysaccharides and protein substances.Studies on the influence of the interaction between calcium ions and EPS on membrane fouling have shown that the main component of membrane fouling is LB-EPS,which contains a large amount of organic matter.The pollution models of different components and different pollutants are different,and the type of pollutants will affect the fouling model.The addition of calcium ions will interact with the hydrophobic substances in the EPS,increase the retention rate of the hydrophobic substances by the membrane,and also change the fouling model.Studies on the effect of calcium ions on the secretion of EPS by algal-bacteria symbiosis have shown that the addition of calcium ions will not have a major impact on the COD(Chemical Oxygen Demand)and TN(Total Nitrogen)in the wastewater treated by the algal-bacteria symbiosis,but it will affect the removal rate of TP(Total Phosphorus).And calcium ions will promote the growth rate of the algal-bacteria symbiosis,so it grows quickly to a stable period.The effects of calcium ions on the EPS of the algal-bacterial symbiosis are mainly in two aspects: on the one hand,the addition of calcium ions will reduce the content of EPS secreted by the algal-bacterial symbiosis,which is also one of the factors that cause the reduction of membrane fouling;On the other hand,calcium ions can strengthen biological flocculation,which will affect the distribution of EPS to achieve the effect of reducing membrane fouling.