Removal Of Nitrogen And Phosphorus From Urine Bymicroalgae Photobioreactor

A large amount of urine enters the municipal wastewater treatment plant through the sewage pipe network system every day.About 80%of nitrogen and 50%of phosphate in municipal wastewater come from urine,which is the main source of nitorgen and phosphorus in municipal wastewater.If we can find an effective method for removing nitrogen and phosphorus from urine with a low cost,it will have a very positive significance for China,which is a developing country with serious environmental problems.And it is hopeful to be applied in ecological toilets to treat urine.Based on the analysis and comparison of existing microalgae wastewater treatment methods,this study screens some species of microalgae suitable for growth in urine.The removal of nitrogen and phosphorus from urine by microalgae was determined uder different conditions.On this basis,a microalgae photobioreactor was constructed to observe the removal of nitrogen and phosphorus pollutants during the operation.It is to provide reference for ammonia nitrogen wastewater treatment.Urine can be used as a medium for microalgae,providing them the required nutrients.In this study,Chlorella,Scenedesmus,Dunaliella,and Spirulina were separately observed in the urine.And Chlorella and Spirulina are suitable to survive in the urine environment.The experiment was carried out to investigate the growth of Chlorella and Spirulina in urine under different conditions.The results show that the suitable inoculation amount of Chlorella are 15%and 20%,and the suitable inoculation amount of Spirulina are 5%and10%.The Chlorella is more suitable for the high ammonia nitrogen urine environment than Spirulina;The effect of glucose on the growth of microalgae is limited;the higher the CO₂ concentration of Chlorella,the faster the growth rate,and Spirulina's growth will be inhibited when the CO₂ concentration is too high.Nitrogen and phosphorus are important nutrient elements for the growth of microalgae.In this study,the effects of different conditions on the removal of nitrogen and phosphorus pollutants from microalgae were investigated from different inoculum size,dilution factor,photoautotrophic and mixed nutrient,CO₂ concentration,etc.The optimal inoculum size of Chlorella and Spirulina is different.The removal rate of nitrogen and phosphorus from Chlorella and Spirulina is not significantly increased by adding glucose;the Chlorella and Spirulina have different effects on removal of nitrogen and phosphorus when the concentration of CO₂ is different;The ammonia nitrogen removal rates of Chlorella and Spirulina are 58.6%and 63%when the CO₂ concentration was 4%.The rusults show that Chlorella can effectively remove nitrogen and phosphorus from synthetic urine and actual urine.On this basis,the microalgae photobioreactor was constructed and operated.The results shows that the microalgae bioreactor has a strong ability to remove nitrogen and phosphorus in the actual urine,and the highest removal rate of ammonia nitrogen and phosphate in the reactor is 74.8%and 77.6%.It is indicated that the microalgae is suitable to be combinde with the fillers in the practical urine treatment.By analyzing the absorption kinetics and material balance calculation of the experiment,it is proved that the absorption rate of ammonia nitrogen by microalgae is higher than that in the later stage because of rich nutrients,abundant growth space.At the same time,it can be calculated that most of the ammonia nitrogen removed from the urine is used for the growth and reproduction of the microalgae itself,and a part of the ammonia nitrogen is removed by the adsorption of the filler.Therefore,the combination of microalgae and the filler can effectively remove ammonia nitrogen in the urine,and the economic cost is low.And it has certain application prospects in engineering.