Effect Of Tetracycline On The Growth And Nutrient Removal Of Chlamydamonas Reinhardtii In Reclaimed Water

Microalgae have been regarded as model organisms in aquatic ecological risk assessments and play an important role in wastewater treatment,because these microalgae not only are unicellular and sensitive to environment,but can also grow rapidly and are widely distributed.Therefore,sewage treatment-microalgae culture system has been become a focus of research in the domestic and overseas,but it is aimed at high concentration wastewater treatment.Additionally,The environmental problems which been caused by the abuse and improper disposal of antibiotics have been a global crisis that threatens human health,and antibiotics are widely detected in water environment.In order to explore the response mechanism on the toxic effects of tetracycline and the feasibility of sewage retreatment by Chlamydomonas reinhardtii,this paper chose tetracycline as target compound,used Chlamydomonas reinhardtii as tested subject,investigated the effect of tetracycline on the biomass,chlorophyll,carotenoids,antioxidant system,polysaccharide and nutrient removal capacity of Chlamydomonas reinhardtii in simulated reclaimed water.The experimental results are as follows:(1)Tetracycline has an inhibited effect on the growth of Chlamydomonas reinhardtii.The tetracycline concentrations of 0-0.05 mg/L have an indistinctive inhibition on the biomass,chlorophyll a,chlorophyll b,total chlorophyll,carotenoids of Chlamydomonas reinhardtii,while the maximum inhibition rates of biomass,chlorophyll a,chlorophyll b,total chlorophyll,carotenoids(71.0%,68.3%,62.8%,66.7 % and 72.9%,respectively)occurred at 0.25 mg/L tetracycline.(2)The activity of antioxidant enzymes(SOD,POD,CAT)could been stimulated under 0-0.25 mg/L tetracycline.The tetracycline concentrations of 0-0.05 mg/L have an indistinctive effect on the SOD activity,POD activity and CAT activity,while the final activities were 7.05,1.53 and 3.54 times those of the control groups occurred at 0.25 mg/L tetracycline,respectively.Besides,the tetracycline concentrations of 0-0.25 mg/L have an indistinctive effect on the MDA content of Chlamydomonas reinhardtii,and the corresponding contents were 1.02,1.16,1.21,1.18,1.24 and 1.47 times those of the control groups.(3)The polysaccharide of Chlamydomonas reinhardtii increased at first and then declined.The maximum polysaccharide content and promotation rate(2.06 %)occurred under0.05 mg/L tetracycline,while the minimum content and maxium inhibition rate(65.16%)occurred at 0.25 mg/L tetracycline.(4)Chlamydomonas reinhardtii was successfully cultured,with a high-efficiency rate of nutrient removal.The nutrient removal decreased with increasing tetracycline concentration in the reclaimed water,when the tetracycline concentration reached 0.25 mg/L,the removal of total phosphorus,total nitrogen and chemical oxygen demand decreased from 100% to 92.5%,80.8% to 55.0% and 36.5% to11.5%.