Study On Nitrogen And Phosphorus Removal And The Underlying Mechanisms In Pickled Wastewater By Immobilized Bacteria And Algae

With the development of picked industry,the waste water produced by pickled industry in China is gradually increasing.For this kind of wastewater with high salinity,high nitrogen and phosphorus,high organic matter,the cost of ordinary biochemical process is high,the utilization rate of resources is low,and the high salinity environment will inhibit the microbial activity.Therefore,this paper selects salt tolerant microorganisms to purify the pickled wastewater,and realizes the algae recycling in the process of high-efficiency nitrogen and phosphorus removal by immobilized Haloarcula sp.-Dunaliella sp.,This study provided a theoretical basis for the treatment of pickled wastewater by immobilized bacteria and algae.First,the symbiosis system of bacteria and algae was established by Halophilic sp.and Dunaliella sp.,and the effect of bacteria and algae on denitrification and phosphorus removal of salted wastewater was investigated under different conditions;The immobilized Halophilic sp.and Dunaliella sp.microspheres were optimized by orthogonal test,and the morphology and structure of the microspheres were analyzed;The effect and mechanism of immobilized bacteria and algae on nitrogen and phosphorus pollutants removal in pickled wastewater were studied.The feasibility of recycling degradation products was discussed from the perspective of biomass and by-product yield of Dunaliella sp..The main conclusions were as follows:(1)Using free Halophilic sp.and Dunaliella sp.to remove nitrogen and phosphorus from pickled wastewater,and optimizing the relevant process parameters of the treatment of pickled wastewater by bacteria and algae:the experimental resulted show that the bacteria and algae system has a good purification effect on pickled wastewater,when the initial p H of pickled wastewater was 7,the temperature of light incubator was 30?,and the light cycle of incubator was 24L:0D,When the volume ratio of Halophilic sp.and Dunaliella sp.was 2:3 and added to the pickled wastewater according to 10%(V/V),the effect of nitrogen and phosphorus removal was better.The removal rates of ammonia nitrogen,total nitrogen and total phosphorus in pickled wastewater were 41.3%,36.9%and 86.1%respectively.(2)According to the orthogonal test results,the optimal preparation conditions of immobilized Halophilic sp.and Dunaliella sp.microspheres were as follows:the dosage of bacteria and algae was 8ml,the concentration of activated carbon was0.75%,the concentration of sodium alginate was 4%,the concentration of Ca Cl₂was4%.The microspheres prepared have better removal effect on nitrogen and phosphorus in the pickled wastewater,among which the amount of bacteria and algae was an important factor affecting the effect of nitrogen and phosphorus removal of the immobilized microspheres.The morphology of immobilized single bacteria,monoalgae and microbeads was observed by SEM.It was found that the attachment effect of bacteria and algae in the microspheres was better,among which the removal rate of ammonia nitrogen reached 67.2%,the removal rate of total nitrogen was60.1%,and the removal rate of total phosphorus was 95.2%.(3)The transformation of nitrogen and phosphorus in the process of purifying pickled wastewater by immobilized bacteria and algae was analyzed.The adsorption effect of bacteria and algae cells on nitrogen and phosphorus in pickled wastewater was higher than that of absorption effect.The adsorption amount of nitrogen in wastewater accounted for 58.34%of the total nitrogen content of cells,and the adsorption amount of phosphorus accounted for 55.25%of the total phosphorus content of cells;The change trend of nitrate nitrogen and nitrite nitrogen was consistent with the transformation path and removal effect of nitrogen and phosphorus in pickled wastewater by bacteria and algae;The kinetic analysis showed that the process of nitrogen and phosphorus removal by immobilized bacteria and algae conformed to the first-order kinetic reaction model.(4)Fourier transform infrared spectroscopy(FTIR)analysis showed that-COOH group,cyclic C-H and-OH groups participated in the nitrogen and phosphorus removal reaction;Scanning electron microscopy showed that the number of Dunaliella sp.and Halophilic sp.attached to the immobilized microspheres increased significantly after the treatment of pickled wastewater,and Dunaliella sp.reached1.55×10⁸/conical flask,the reproduction rate was 80.96%,which was 1.2 times of that of free bacteria algae system;In the process of nitrogen and phosphorus removal by bacteria and algae,many high-value microbial by-products were produced.The highest total lipid yield of immobilized bacteria and algae system was 0.879 g/L,the total sugar yield was 0.545 g/L,and the final protein yield was 0.534 g/L?-carotene yield was 6.976 mg/L.These by-products have high commercial value.