Study Of Nitrogen Removal From Simulated Wastewater Using Microalgae Based Floating Permeable Nutrients Uptake System

At present,the environmental pollution caused by aquaculture is becoming more and more serious,and the treatment of aquaculture wastewater has attracted attention from all walks of life.Due to the huge amount of water in aquaculture water,how to remove nitrogen from wastewater at low cost is a technical problem.Microalgae is a single-cell photosynthetic autotrophic organism.The components required for growth are relatively simple,and the growth rate is fast and the cycle is short.Combining microalgae and aquaculture wastewater treatment is an effective way to recycle waste water and solve the problems of land use and cost of microalgae production.This article takes the simulation of aquaculture wastewater as an example to study,from the design and preparation of floating semi-osmotic reactors,the cultivation conditions of microalgae,and the relationship between the influencing factors in applications,and establishes a mathematical model to reveal the N release amount.The main research contents and conclusions are as follows:?1?Nutrients?N*?can be transmitted inside and outside the floating semi-osmosis reactor,and semi-permeable membranes with different pore sizes?1,5,10,40?m?The average mass transfer rates were 14.7,17.3,20.8,and 181.8 mg·L^-1h^-1m^-2.As long as the microalgae does not leak out,the faster the mass transfer rate,the better.When the algal-liquid ratio and contact area are the same,the biomass yield of Scenedesmus acuminatus in a 5 cm depth reactor is about 1.87 times that in a 13 cm depth reactor,which are 0.195 and 0.104 g·L^-1·d^-1,respectively.?2?The growth of microalgae and its absorption of N are affected by many factors.Scenedesmus acuminatus grows more better than Chlorella sorokiniana in this device better,has a strong ability to remove nitrate and nitrogen,and 1?m semi-permeable membrane has better interception effect.In white-red-blue light quality experiments,the biological yields of Scenedesmus acuminatus were 0.21,0.04,and0.03 g·L^-1·d^-1,respectively;under different light intensities(50,100,220 umol·m^-2s^-1).The biological yields of Scenedesmus acuminatus are 0.08,0.10,and 0.15 g·L^-1·d^-1.The average daily removal of nitrate and nitrogen is 1.85,2.42,and 2.97 mg·L^-1·d^-1.50.8%,76.9%,and 98.4%,respectively;at different initial concentrations(0.05,0.20,0.27 g·L^-1),the biological yields of Scenedesmus acuminatus are 0.173,0.186,and0.214 g·L^-1·d^-1.Nitrogen removal efficiency is 71.82%,91.26%,97.02%.In the cultivation process of microalgae,choosing suitable growth conditions is beneficial to improve biological yield and nitrogen removal capacity.?3?In the presence of the sole nitrogen source of ammonia nitrogen,the sole nitrogen source of nitrous nitrogen,and the simultaneous presence of ammonia nitrogen,nitrous nitrogen,and nitrate nitrogen,the bio-yield of Sa.algal cells is 0.135,0.151,0.179 g·L^-1·d^-1,nitrogen removal efficiency is 98.25%,85.34%,93.11%,protein content is 32.2%?±0.89%?,29.86%?±0.76%?,26.98%?±0.79%?.In the presence of trinitrogen,Scenedesmus acuminatus uses NH₄⁺-N preferentially.When the content of NH₄⁺-N is low or absent,Scenedesmus acuminatus uses NO₃^--N and NO₂^--N to meet its own growth needs.Compared with NH₄⁺-N,The removal efficiency of NO₃^--N and NO₂^--N were 98.53%,83.57%and 86.44%,respectively.?4?The effect of Scenedesmus acuminatus aquaculture on aquaculture water is good,and the comparison with the data in simulated wastewater is not large,indicating that the device has certain application value.Model analysis showed that the microalgae biological yield a,protein content b,and light intensity had a negative correlation with R?algal fluid area and pond area?,and a positive correlation with the N content released by the pond every day.When the N release rate,microalgae growth rate,and protein content were 0.001 mg·L^-1d^-1,0.15 g·L^-1d^-1,and 30%,the ratio of treated area to water area was 0.208.