The Effects Of Turbulent Flow And Plant Hormones On Growth Characteristics And Wastewater Treatment Efficiency Of Microalgae

Under the background of water environmental pollution and energy crisis,microalgae has become one of the research hotspots of wastewater treatment and resource utilization due to its advantages of fast growth,high photosynthetic efficiency,high economic benefit,environmental friendliness and strong adaptability,which has broad application prospects.In the study of microalgae,turbulence and exogenous plant hormones are two important factors affecting their growth and biomass composition.Most of the current research focuses on the effect of plant hormones concentration on the effect of microalgae in sewage treatment and growth characteristics,while turbulence may affect the effect of plant hormones.The effects of turbulence and phytohormones on the growth of microalgae are not clear.In order to deepen the understanding of the mechanism of turbulence and phytohormones on microalgae,it is necessary to discuss these problems.In order to solve these problems,Scenedesmus quadricauda was used as the research object,and the vibration grid system was used to generate turbulence.In the batch experiment,four hydraulic conditions(turbulent dissipation rate of 0 m²s^-3、1.69×10^-3 m²s^-3、1.40×10^-2 m²s^-3、8.32×10^-2 m²s^-3,corresponding to standing condition and low,medium and high turbulence intensity conditions respectively)and mixed plant hormones（gibberellin,indole triacetic acid,and brassinolide）were set respectively to study the effects of turbulent pulsation and mixed plant hormones on the sewage treatment efficiency and growth characteristics of microalgae.On the basis of batch experiments,a sequencing batch experiment was constructed to study the effects of turbulence and mixed plant hormones on microalgae.The main research contents and achievements are as follows:（1）In the batch experiments,moderate turbulence and mixed plant hormones treatment could promote the accumulation of microalgae biomass concentration and improve the effect of microalgae in sewage treatment.Under the effect of medium turbulence intensityand mixed plant hormones,the biomass concentration of microalgae increased by 24.58%compared with the stationary group;the treatment efficiency of ammonia nitrogen was increased by 13.81%and 12.09%respectively by adding plant hormones under medium and high turbulence intensity.（2）In the batch experiments,the addition of plant hormones in the condition of static and high turbulence intensity increased the chlorophyll content of microalgae;turbulence enhanced the potential maximum photosynthetic efficiency of microalgae,the potential maximum photosynthetic efficiency of microalgae increased by 11.89%under the effect of turbulence.（3）In the batch experiments,turbulence and mixed plant hormones changed the biomass composition of microalgae and improved the sedimentation performance of microalgae.Under medium and high turbulence intensity and mixed plant hormones,the contents of protein and polysaccharide in microalgae decreased,while the contents of lipid increased;under moderate turbulence intensity and mixed plant hormones treatment,the lipid yield increased by 70.00%;adding mixed plant hormones under static conditions can increase the sedimentation efficiency of 12 hours of microalgae from 55.12%to63.67%;the sedimentation efficiency of microalgae could be significantly improved by turbulence treatment.（4）In the sequencing batch experiment,the removal rate of COD,NH⁴⁺-N and PO₄^3--P in the experimental group was increased by 11.86%,26.37%,and 18.10%compared with the control group,and the biomass increased by 45.71%.The content of lipids has increased by 38.71%,and the total amount of lipids has approximately doubled.