Study On The Treatment Of High Nitrogen And High Phosphorus Wastewater By Immobilized Bacteria-algae Symbiotic SBR

With the increasing content of nitrogen,phosphorus and other nutrient elements in water body,the eutrophication of water body becomes more and more prominent.At the present stage,the removal of nitrogen and phosphorus is more traditional.The high cost of chemical method and the incomplete removal of phosphorus by biological method and the low utilization rate of resource hinder the pace of treatment of high nitrogen and high phosphorus wastewater by traditional biochemical process.As a new raw material of biomass energy,Chlorella vulgaris can realize the resource utilization of nitrogen and phosphorus in the process of efficient nitrogen and phosphorus removal.In this paper,we studied the treatment of high nitrogen and high phosphorus wastewater by co-complement of immobilized Chlorella and activated sludge.The optimum conditions for the immobilization of Chlorella vulgaris were analyzed by orthogonal analysis,the optimum operating parameters of the algal-bacterial symbionts were determined and the effect and impact resistance of high nitrogen and high phosphorus wastewater treated by algal-bacterial symbionts SBR reactor were studied.The main findings were as follows:(1)By means of orthogonal test,the immobilized Chlorella were considered synthetically with 4%alginate solution as the stationary carrier and 3%CaCl2 solution as the stationary agent.The best performance of the Chlorella was obtained by crosslinking at 4? for 24 h.The average radius of the immobilized algae ball was 2 mm and the weight was 0.03 g,which improved the sedimentation performance of the small algae and avoided the loss of small algae in the system.The optimum purification temperature of Chlorella vulgaris was(25±1)?,and the removal rates of COD,NH4-N and PO43--P were 80.02%,90%and 80.67%under the optimal fixed conditions.(2)In the experimental study on the influencing factors of algal-bacterial symbionts system,It was found that the system had the best treatment effect when the ratio of inoculation was 1/3,and the fastest light intensity of microbial growth and reproduction was 4500lux,and the system has the best removal effect when the illumination time is 10h.The best parameters(1/3,4500lux,10h)were used to optimize the algal-bacterial symbionts system,and the effect of treating high nitrogen and high phosphorus wastewater in the system was studied.It was found that after 42 cycles of stable operation of algal-bacterial symbionts SBR system,the expansion of algae balls led to instability,and the system was gradually restored to stability by partial old algae balls replacement with fresh algae balls.After stabilization,the average removal rates of COD,NH4+-N,TN,and PO43--P reached 85.79%,89.88%,78.07%,and 88.34%,respectively.SVI fluctuated stably in the range of 82?93mL/g with an average SVI of 87.70mL/g;The average values of the optical density and dry weight of chlorella during this period were 1.994 and 1.65 g/L,respectively,and the fluctuation range was small.The average values of pH and DO were 7.1 and 2.58 mg/L,respectively.The overall trend was relatively stable,and the system was stable and had a certain recovery ability.(3)In the experiment of anti-impact load capacity of SBR system for the algal-bacterial symbionts,the salinity impact experiments were analyzed from short and long angles:under the condition of short-term salinity impact,the removal effect of system influent salinity of 20g/L was better than that of 10g/L and 30g/L,and the treatment effect of reactor under 20g/L salinity impact was better after recovery of influent;In the long-term salinity impact experiment,with the adaptation of the operation of 20 cycles,the effluent removal rate of each of the three groups of reactors could gradually return to a better level,and the whole system of algae could still maintain good activity under the high salt environment,and had a good salt impact resistance.It was found that the bacterial algae symbiosis system had better resistance to ammonia nitrogen shock,and the high concentration of phosphate was beneficial to improve the treatment efficiency of the bacterial algae symbiosis system,and had excellent bearing capacity for the influent phosphate shock.