Study On The Enhancement Effect Of Immobilized Algae-bacteria Symbiotic Systems In The Treatment Of Livestock Wastewater

With the rapid development of large-scale livestock industry represented,the large amount of breeding wastewater produced by it has brought a serious threat to the ecological environment.Due to the characteristics of high nitrogen and phosphorus concentration in livestock wastewater,traditional treatment processes have problems such as poor pollutant removal effects and long processes.At the same time,it also causes the waste of valuable resources such as carbon,nitrogen and phosphorus in the wastewater.Algae-bacteria symbioses exhibits great application potential due to its high treatment efficiency,resistance to high-concentration pollutants,and the recyclability of biomass.The biosorption immobilization technology has low mass transfer resistance,stable carrier,and The advantages of high pollutant removal efficiency,this article combines adsorption and immobilization with algae-bacteria symbiosis（chlorella-activated sludge）to study its strengthening effect in the treatment of livestock wastewater,and select a suitable immobilization carrier Filler,optimized the operating parameters,studied the effect of alkalinity on the denitrification and phosphorus removal of the immobilized algae-bacteria symbiosis and the growth of algae bacteria.At the same time,on the basis of the ultrafiltration process to further strengthen the treatment effect.the alkalinity’s impact on membrane fouling was studied.The main conclusions are as follows:Compared with the density polyethylene K1 filler and braided fiber filler,Polyurethane Sponge（PS）can effectively immobilize algae-bacteria,promote the symbiosis of algae-bacteria,increase the particle size of flocs,and improve the treatment effect of pollutants.Compared with the common algae-bacteria symbiosis system,the PS immobilized symbiosis system has little effect on COD removal,but it changes the distribution and utilization of nitrogen.The immobilized system using PS filler has a removal rate of 99.81%for NH₄⁺-N,the removal rate of TN is 58.37%,the final cumulative concentration of NO₃^--N is 102.49 mg/L,the removal rate of TP is71.70%.When treating wastewater with a high concentration of nitrogen and phosphorus,it’s better to use PS fillers to enhance the effect.Select the three parameters of aeration flow,algae bacteria inoculation ratio,and PS filling rate to optimize the orthogonal experiment,and use the multi-index comprehensive weighted scoring method to comprehensively evaluate the multiple indexes,and obtain the three factors that affect the comprehensive pollutant removal rate.The primary and secondary sequence is:filling rate>inoculation ratio>aeration flow.Taking the removal rate of COD,NH₄⁺-N,TN and TP as the comprehensive inspection indicators,the optimal solution is to control the aeration flow to 0.6 L/min,add PS filler with a filling rate of 10%,and inoculate the algae:sludge ratio to 1:5.The alkalinity decreases with the nitrification of the nitrifying bacteria in the algae-bacteria symbiont,and the COD is above 85%,the gap is not big.The consumption of alkalinity at the levels of 14.28 mmol/L and 7.14 mmol/L caused the p H to drop below 7,and the removal rate of NH₄⁺-N no longer increased.The immobilized algae-bacteria system was more suitable for the alkalinity level of 21.42mmol/L,The highest Chl.a concentration reached 34.29 mg/L,the removal rate of NH₄⁺-N reached 99.99%,and the removal rate of TP was 36.83%.35.7 mmol/L and28.56 mmol/L due to excessive alkalinity,Reduced sludge activity,low algae-bacteria biomass and poor growth,TP removal rates are only 5.23%and 7.66%.Comprehensive pollutant treatment effect,21.42 mmol/L is a more suitable choice for alkalinity treatment of livestock wastewater.The ultrafiltration process can effectively enhance the quality of the effluent.The flux decline rate of the mixed solution at 7.14 mmol/L alkalinity is significantly lower than that of other groups.The membrane specific flux after attenuation is 0.081,and the membrane specific flux is 35.7 mmol/L and 14.28 mmol/L.The volume change curve is close,at 0.042 and 0.054.At 21.42 mmol/L alkalinity,the filtration flux declined the fastest,and finally stabilized at 0.037.The polysaccharide content in SMP was the highest,reaching 325.37 mg/L,and the particle size distribution of algae-bacteria flocs was uneven,and the membrane pollution was the most serious.Alkalinity affects the growth of algae-bacteria symbionts,the size distribution of flocs,and the concentration of polysaccharides and proteins in SMP,which leads to differences in the degree of membrane fouling under different alkalinity.