Effect Of Temperature And Light Conditions On Microalgae Growth Characteristics In Treated Sewage

Dianchi Lake is one of the three major lakes in China,Although the water quality has been improved after decades of treatment,the problem of water bloom is still serious.In order to control the outbreak of cyanobacteria blooms in Dianchi Lake,Aiming at the wastewater of sewage treatment plant,this paper takes Microcystis aeruginosa and mixed algae of Dianchi Lake as research objects,and explores different temperature conditions(10 ?,15 ?,20 ?,25 ?,30 ?,35 ?)and light intensity(600 lx,2000 lx,4000 lx,6000 lx,8000 lx)on the growth characteristics of microalgae in the tail water of sewage treatment plants,Based on the logistic model,Arrhenius model and Steele model,the models of temperature,light and microalgae biomass are established.On this basis,according to the growth characteristics of microalgae,the models of microalgae growth and HRT are established to obtain the control range of HRT to avoid the outbreak of water bloom.The research results are as follow:(1)The study found that the growth potential of Dianchi mixed algae in the effluent of sewage plant is higher than that of single algae(Microcystis aeruginosa).For Dianchi mixed algae,the maximum biomass was obtained at a temperature of 30°C and a light intensity of 4000 lx,while Microcystis aeruginosa obtained the maximum biomass at 25°C and an illumination intensity of 4000 lx.Based on Logistic model,Arrhenius model and Steele model,a comprehensive model of temperature,light and microalgae biomass was established.The results show that the optimal growth conditions of typical water bloom microalgae in the effluent of Dianchi Lake sewage treatment plant were temperature 25?-30°C while the lighting conditions are 2500 lx-6000 lx.(2)When the external temperature conditions reach the optimum conditions for microalgae's growth,that is,the temperature range 25? to 30?,the utilization rate of nutrients in the water by the microalgae increases with increasing temperature;We also analiyzed the light conditions for the use of water nutrients in microalgae.When the light condition is 2500 lx-6000 lx,the nutrient salt utilization rate of the microalgae increases with light intensity.(3)Under the condition of high temperature and high light(temperature is 30 ?,light condition is 6000 LX),the hydraulic retention time of landscape water should be less than 5 days when the water quality of tail water of sewage treatment plant is grade A,and less than 8 days when the water quality is grade IV of surface water.Under the condition of low temperature and low light(temperature is 10 ?,light is 1000 lx),when the tail water quality of the sewage plant is Grade A,the hydraulic retention time should be controlled less than 20 days.When the effluent quality is Class IV,the hydraulic retention The time should be less than 30 days.According to the actual concentration of N and P(TN 15.2 mg · L-1,TP 0.114 mg · L-1)in the tail water of the sewage treatment plant,the hydraulic retention time under the conditions of high temperature and high light(temperature 30 ?,light 6000 LX)and low temperature and low light(temperature 10 ?,light 1000 LX)should be less than 6 days and 37 days respectively.