Anammox Coupled Algal Symbiosis System Treats Swine Waste Water

After anaerobic fermentation,high concentration of organic pollutants such as NH₄⁺-N,P still remain in pig digestive juices,which will seriously pollute the natural environment and harm human health if discharged directly without treatment.The two reaction n processes of algal bacteria symbiosis and anammox do not require aeration,no additional carbon source,and low energy consumption.Therefore,the combined process of algal-bacterial symbiosis and anammox has gradually attracted attention.In this paper,chlorella,ammonia oxidizing bacteria and anammox bacteria were used as the main functional bacteria,to treat the digestive juices of pig farms through the combined process of anammox coupled with algal bacteria-symbiosis system.To explore the efficiency of nitrogen and phosphorus removal in the coupling system.（1）Firstly,the symbiotic system of algae and bacteria was constructed to explore the dephosphorization and dephosphorization effects of simulated wastewater by different chlorella-activated sludge inoculation ratios,and the optimal inoculation ratio was obtained.And through high-throughput sequencing to explore the microbial community composition and structure characteristics of the optimal inoculation ratio experimental group.The results showed that when the ratio of algae:activated sludge was 5:1,the removal rates of TN and TP were the highest,which were divided into 53.85%and 85.13%.Both NH₄⁺-N and COD achieved 100%removal rate.In addition,the results of 16S rRNA gene analysis showed that there were significant differences in the microbial community at the beginning,middle and end of the reaction in the reactor with the algal slime inoculation ratio of 5:1.With the operation of the reactor,Flavobacterium,Bacteroides,Rhizobium and Nitrobacter were enriched.（2）The algae-bacteria symbiosis system and the anammox system were respectively activated,and it was found that the algae-bacteria symbiosis system could achieve stable and efficient nitrogen and phosphorus removal performance within 20 days.The light-dark ratio of 16:8 h/h was chosen as the experimental parameter;in addition,polyurethane sponge was added as a carrier to enhance the performance of the algal-bacteria symbiosis system.The results showed that the addition of the carrier did not affect the consumption of NH₄⁺-N,and could effectively promote the removal of P.After 40 days of anammox reaction,the ratio of NH₄⁺-N consumption,NO₂^--N consumption,and NO₃^--N generation reached1:1.34:0.21.（3）An anammox coupled algal-bacterial symbiosis system was constructed to explore the nitrogen and phosphorus removal performance of the coupled system and the changes in the microbial community structure in the system.The experimental results show that the coupled system can effectively remove TP,NH₄⁺-N,and COD in wastewater with low C/N ratio（0.87-2.12）,and the removal efficiencies are 100%,91%,and 87%,respectively.The average hydraulic retention time（HRT）for 3 days.The nitrogen and phosphorus removal effect of the coupled system is obviously better than that of the single algae system.The addition of anammox effluent not only improves microbial diversity but also changes sludge community structure.The dominant bacteria at the phylum level in the algal system changed from Proteobacteria to Bacteroidota.In the coupling system and the algal system,the genus level of Nitrobacter becomes the dominant genus.In addition,the suspension growth of chlorella protects ammonia oxidizing bacteria and nitrite oxidizing bacteria from light damage.（4）Through the optimization of HRT,the effect of anaerobic and aerobic combined process on nitrogen and phosphorus removal and the change of microbial community structure in pig farm wastewater were investigated under the optimal HRT conditions.The results showed that under three different HRT conditions（HRT=3,4 and 5 days）,the nitrogen and phosphorus removal capacity of the system increased with the increase of HRT.However,there was no difference in NH₄⁺-N TN TP removal effect when HRT was 4 days or 5 days.Considering the time cost and the efficiency of nitrogen and phosphorus removal,HRT=4 days was taken as the optimal condition.Under these conditions,the removal rate of COD exceeded 75%,and the removal rates of TN,NH₄⁺-N,and TP were 90%,100%,and 83%,respectively.According to high-throughput sequencing results,microbial species increased and species abundance increased.In the coupling system,Nitrosomonas becomes the dominant bacterium.In UASB,Diaphorobacter has accumulated a large number of bacteria into the system.Rhizobiaceae was enriched to varying degrees at the end of the reaction.