| Microalgae biological treatment technology has the advantages of green and high efficiency,easy operation,etc.The use of this technology to treat ammonia nitrogen wastewater is a hot research topic in recent years.Biobacterial agent has the characteristics of simple and high efficiency to remove pollutants,and the algae-bacterial system combining biobacterial agent and microalgae has good application prospect to treat ammonia nitrogen wastewater,however,there are few studies on the treatment of ammonia nitrogen wastewater using the algae-bacterial system combining biobacterial agent and microalgae.In this study,we firstly compared the changes of the relevant indexes of microalgae,bacterium and algae-bacterial system in the process of treating ammonia nitrogen wastewater and optimized the algae species,verified the superiority of the algae-bacterial system in treating ammonia nitrogen wastewater and selected the best combination of algae and bacteria;then we optimized the influencing factors of the algae-bacterial system in treating ammonia nitrogen wastewater by single-factor experiment and response surface method,and investigated the effects of light intensity,algae-bacterial ratio and ammonia nitrogen on the treatment of ammonia nitrogen wastewater,and the process parameters were optimized.The main research conclusions are as follows.（1）The effect of the algae-bacterial system on the treatment of ammonia nitrogen wastewater is better than that of single microalgae and bacterium system,and the Chlorella pyrenoidosa+bacterium group is the best combination.The removal rate of ammonia nitrogen by the algae-bacterial system was 85.15%,which was much higher than the 18.02%and 38.75%of the single microalgae and bacterium system.The growth of microalgae in the combination of Chlorella pyrenoidosa+bacterium was the best,with the highest chlorophyll a and protein content of all groups,reaching 11.21 mg·L-1 and 34.77 mg·L-1 and the best removal of ammonia nitrogen,with 83.17%removal rate.（2）When the light intensity was 4000 lux,the algae-bacterial system had the best effect on ammonia nitrogen removal with 89.57%removal rate and the best growth condition of microalgae;the ratio of 1:3 was the best inoculation ratio for the algae-bacterial system to treat ammonia nitrogen wastewater,and the removal rate of ammonia nitrogen was 86.91%;when the initial concentration of ammonia nitrogen was 50 mg·L-1,the removal rate of ammonia nitrogen was the highest,which was 94.92%.The response surface analysis showed that the main relationship between the factors affecting the removal of ammonia nitrogen was:light intensity>initial ammonia nitrogen concentration>bacterial-algal ratio,and the results of ammonia nitrogen removal rate（87.96%）were close to the predicted value（87.31%）under the best combination of light intensity 4700 lux,algae-bacterial ratio 1:3 and initial ammonia nitrogen concentration 56 mg·L-1.（3）Chlorella pyrenoidosa and bacteria contributed to ammonia nitrogen removal to different degrees,and EPS secreted by microalgae played an important role in the system.The proportions of ammonia volatilization,nitrification and ammonia uptake by microalgae were 6.64%,17.50%and 75.86%,respectively,so Chlorella pyrenoidosa Chlorella played a major role in ammonia removal.The bacterium in the system promotes EPS secretion by microalgae,and the utilization of EPS by the bacterium slows down the growth inhibition of microalgae by excessive accumulation of EPS.（4）The community structure of the algal-bacterial system was stable,and different genera played important roles.Proteobacteria were the dominant phylum in the system,and the relative abundance of Allorhizobium-Neorhizobium-Parararhizobium-Rhizobium and Porphyrobacter remained stable.The former can promote the growth of microalgae and is a key genus for ammonia nitrogen removal and p H stabilization;the latter can promote microalgae flocculation,which is beneficial to microalgae biomass harvesting and improve water quality in the aquatic environment. |
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