Study On Removal Of Nitrogen And Phosphorus In Wastewater Based On Scenedesmus Obliquus

Water eutrophication because of water pollution and water shortage have received widespread attention.The nitrogen and phosphorus pollutants in wastewater have become the main targets for wastewater treatment.The cultivation of microalgae using wastewater can not only be used as a treatment process to achieve the removal of nutrients including nitrogen and phosphorus in wastewater to purify water quality,but also can provide the possibility to reduce the cost of microalgae cultivation to achieve the resource utilization of wastewater.The obtained microalgal biomass can be extracted further for the production of new energy sources to ease the current shortage of resources and energy shortages.In order to reduce the harm of ammonia nitrogen in wastewater to the environment and reduce the cost of microalgae cultivation,the basic culture process,optimization of illumination conditions and carbon source concentration for microalgae cultivation,and nitrogen and phosphorus removal from wastewater based on Scenedesmus obliquus were investigated in this study.The main results obtained are as follows:(1)The optimal culture conditions for microalgae cultivation in wastewater were blue of light wavelength,3500 lux of light intensity and 12 h of light cycle.The maximum dry weight of Scenedesmus obliquus was 0.63±0.02 g/L,and the removal rate of ammonia nitrogen reached 92.08±0.20 %.The three factors of light wavelength,illumination time and light intensity have different effects on the dry weight of algae and ammonia nitrogen removal rate.(2)The concentration of sodium carbonate can affect the removal of nutrients in the wastewater and the growth of algae.The experimental group containing 20 mg/L sodium carbonate obtained the highest biomass 0.136 g/L after 14 days.At the same time,the highest phosphorus removal rate of the group was 67.21%.The ammonia removal rate was all around 50%.In general,when the concentration of sodium carbonate was 20 mg/L,the growth of microalgae was better and the removal rate of nitrogen and phosphorus was higher,which lays the foundation for the research on the combination of microalgae carbon fixation and the removal of nitrogen and phosphorus in sewage.(3)Microalgae grew well in synthetic wastewater with ammonia nitrogen concentration of 151 mg/L and phosphate concentration of 10.47 mg/L,achieving removal rate of 52% ammonia nitrogen and 67% phosphorus,and maximum lipid content of 25%.(4)In different nitrogen and phosphorus concentrations experiments,the highest biomass(0.319 g/L)was obtained in the effluent containing 240 mg/L ammonia nitrogen and 30.5 mg/L phosphorus phosphate.Compared with BG11 medium,although the maximum biomass is less than that of S.obliquus cultivated in BG11 medium,the growth cycle is shorter than that in BG11 medium.(5)The anaerobic sequencing batch reactor and the wastewater treatment microalgae technology are combined to make use of S.obliquus to treat the reactor effluent,and the nitrogen and phosphorus in the wastewater can be well removed.In the wastewater containing 97.7 mg/L ammonia nitrogen of and 25.6 mg/L phosphate,the highest removal rate of ammonia nitrogen was 49.1%.In the wastewater containing 48 mg/L ammonia nitrogen value and 12.4 mg/L phosphate concentration,the highest removal rate of phosphorus based on S.obliquus reached 88.8%.