The Study On Application And Mechanism Of Bacteria-algae Symbiosis And Bioaugmentation Technology In Wastewater Treatment

Currently,biological treatment is the most widely used wastewater treatment.However,the use of biological treatment technology is limited because of the environmental conditions,water quality constraints and so on,so strengthen the biological treatments will become an inevitable trend.In this paper,the promoting bacteria were screened.Then bioaugmentation and bacteria-algae co-culture techniques were used to explore the effect and mechanism in wastewater treatment.In the wastewater system,the effect may not be significant simply relying on the original microbial.The effect may be limited under the inoculation of foreign microorganisms due to the competition from the indigenous microorganisms.The results showed that the introduction of chlorella in the original water body resulted in the decrease of the biological diversity of the original water body and affect the removal of the nutrient.For COD,the removal efficiency of the microorganisms in the original water body was better,and the removal rate was 85.96%.For ammonia nitrogen,the removal efficiency of bacteria-algae co-culture was better.The removal efficiency of ammonia nitrogen under the shaking-bottle cultivation and aerated culture was 70.3%and 98.7%,respectively.There was on difference in the removal rate of NO3-N under the different cultivations,and both of them were 100%.For the removal of P,the removal efficiency of bacteria-algae co-culture was better.Under the shaking-bottle cultivation and aerated culture,the rates of removal were 84.8%,93.8%,respectively.The dry weight of Chlorella vulgaris under 1%CO2 was the largest,and the removal rate of COD,N and P was the highest compared with shaker culture.After screening,the Chlorella growth-promoting bacteria included4.1475,1.8956,CMR,H3 and H4.These strains were screened from the strains purchased by the laboratory and the strains isolated from activated sludge and primary environment with organics degradation efficiency.Among them,1.3136 and1.8956 belonged to Pseudomonas putida and soil Flavobacterium,respectively.The phylogenetic analysis based on 16S rDNA sequences showed that the bacterium CMR belonged to genus Methylobacterium,while both H3 and H4 belonged to Pseudomonas.The rates of the growth-promoting of several bacteria were 24%⁴1%,and the promotion effect of H3 and H4 was the best,whose growth-promoting percentages were 28.6%and 40.8%,respectively.Under the aeration condition,the degradation effect of organic matter and nitrogen was slightly promoted by the Chlorella-H3 and Chlorella-H4 co-culture.However,the removal efficiency was not good as the single algae system when co-cultured with the four promoters of 1.3136,1.3488,1.8956 and CMR.Municipal wastewater activated sludge?AS?and two endogenous bacteria,named H3 and H4,were co-cultured with a strain of Chlorella sorokiniana under two light intensities,i.e.,1000 and 200?mol photons m^-2·s^-1 without external aeration for wastewater COD,N and P removal.Co-culture of Chlorella and AS showed to have the best COD removal efficiency,which lowered COD from 355down to 109 mg/L in only six hours.The higher light supply did not pose significantly positive effect on COD,N and P reduction in co-culture systems compared with the lower one.H4 with the highest O2 consumption rate promoted algal nitrogen assimilation as evidenced by the liquid phase.Co-culture systems generated detectable amount of indole-3-acetic acid?IAA?,the concentration of which positively correlated with the algal proliferation and ammonia nitrogen reduction.Co-culture of microalgae with many types of bacteria usually comes out with significant different treatment efficiencies for COD,nitrogen and phosphorus in wastewater remediation,compared with the single culture.In order to understand the mechanism behind,a comparative experiment was designed in this study,using the green microalgae species,Chlorella sorokiniana,in the single culture and a consortium with a bacterium,Pseudomonas H4,for nutrients'removal.Comparative metabolome profile analysis was conducted to reveal the Chlorella cell responses to the synergistic growth with the bacteria and possible relations between the metabolic regulation of microalgae and the nutrients'degradation were discussed.The detectable differential metabolites of Chlorella belonged to several classes,including carbohydrates,fatty acids,amino acids,phosphates,polyols,etc.The orthogonal partial least squares discriminant analysis?OPLS-DA?model of the identified metabolites suggest the metabolism in this algae was significantly affected by the bacteria,corresponding to different treatment behaviors.