Research On Advanced Treatment Mechanism Of Algal-bacteria Symbiotic Wastewater Based On Microecological Theory And Its Application In Process Optimization

At present,the demand for all kinds of ecological water,such as landscape water,is increasing,and the existing water sources can no longer meet its needs.The urban secondary water is regarded as a potential source of ecological water,such as landscape water.As it is rich in nitrogen and phosphorus and other elements,the tail water needs to be deeply treated.The advanced wastewater treatment technology based on algal-bacterial consortium has gradually matured,but the mechanism research basis based on microecology is not clear.In this thesis,by verifying the algal microecology theory in wastewater,and optimizing the wastewater advanced treatment system of algal bacteria symbiosis system,the wastewater advanced treatment system of algal bacteria symbiosis system is established,and the basic of the microecology theory in wastewater is established initially.At first,The mixed microalgae of wild strains and activated sludge were used to construct the microalgal-bacterial consortia.Plackett-burman method was used to explore the effects of six factors,including light intensity,light-dark ratio,influent ammonia concentration,influent COD concentration,p H and aeration rate,on the wastewater treatment capacity of the constructed microalgal-bacterial consortium.Experimental results show that the fitted equations are statistically significant.Since the removal of COD,NH₃-N and TP by microalgal-bacterial consortium to wastewater needs to be considered comprehensively,it can be concluded that light intensity has the greatest influence on its treatment capacity,and its p value is 0.0126,0.0465 and 0.0231,respectively.The second is the photoperiod light-dark ratio,which is 0.141,0.0587 and 0.0513,respectively,which has the greatest influence on the wastewater treatment effect of the microalgal-bacterial consortium.Therefore,two ecological factors,light intensity and light to dark ratio,were further studied as the key factors affecting the wastewater treatment capacity of MBCs.Then,response surface methodology(RSM)designed by Box-Behnken of the Central group was used to analyze the synergies and interactions of the symbiosis system under the change of multiple environmental conditions.he results showed that the highest removal efficiency of COD,NH₃-N,TP and the maximal biomass growth rate would be predicted to 95.43%,95.49%,89.42%and 99.63%,respectively,all obtained under moderate illumination intensity(5000 lx),photoperiod(12:12)and aeration rate(0.55 L min^-1).Limited to critical TP removal requirements(87.44%),however,the effluent standards can meet only in the very small usable range of illumination intensity and photoperiod,even under medium aeration.The further study based on RSM analysis indicated,fortunately,by means of aeration responding illumination,it can greatly expand the usable range of illumination intensity(4613 to 5541 lx)and photoperiod(11 to 12.93 hours)within aeration(0.4 to 0.6 L min^-1).Besides,the algal-bacterial consortia with different ratios of algae and sludge were cultured in same aerobic wastewater within 48 hours in photobioreactors(PSBRs).Community structure at start and end was texted by metagenomic analysis.Bray-Curtis similarities analysis based on microbial community showed that there was obvious convergent succession in all consortia,which is well known as“convergence”in macroecology.The result showed that Bray-Curtis similarities at End(overall above 0.88)were higher than these at Start(almost less than 0.66).In terms of community structure,the consortium with 5:1 ratio at Start are the more similar with the consortia at End by which the maximum removal of TN 73.69%,TP94.40%and NH₃-N 93.26%in wastewater treatment process and biomass production98.2%higher than other consortia,according with climax community in macroecology with the highest resource utilization than other communities.Therefore,the macroecology can be introduced into phycosphere to explain the consortium for advanced wastewater treatment and optimization community structure.And the study revealed a novel insight into treatment effect and community structure of algal-bacterial consortia for advanced wastewater treatment,a new idea for to shortening the culture time of consortium and optimize predicting their ecological community structure and predicting ecological community.In addition,The convergence phenomenon of phycosphere confirmed the existence of macroecological phenomenon in phycosphere.In this study,two different strains of microalgae were used to construct a symbiotic system of 6 strains of microalgae according to the ratio of 10:1,5:1 and 1:1.After 48 hours of cultivation,the sludge removal ratio was set to 25%every 24 hours,and the system continued to operate for 96 hours.The experimental results showed that the similarity of Bray-Curtis symbiosis system constructed by different algae strains was significantly different after 96 hours,and the wastewater treatment capacity was significantly different.However,when the symbiotic system constructed by the same algae species with different algal ratios was operated after 96 hours,the similarity gap between Bray-Curtis was small,and there was no significant difference in wastewater treatment capacity.This not only confirms the existence of"convergence",the diversity determined by algae-producers,which is defined by macroecology as"conserved".