Effect Of The Tetracyclines On Biological Nitrogen And Phosphorus Removal From Wastewater

Wastewater biological nitrogen and phosphorus removal was regarded as one of the most effective solution for the problem of water body eutrophication.Nonetheless,biological nitrogen and phosphorus removal processes involve many microorganisms,which are sensitive to the harmful substances,such as antibiotics.In recent years,due to the abuse of antibiotics,it frequently detected in the influent of wastewater treatment plant.In addition,the antibiotic containing wastewater mainly treated through biological approaches.Therefore,to evaluate the effect and mechanism of antibiotics on biological nitrogen and phosphorus removal will play a great role on the removal of antibiotic contamination.Two broad-spectrum tetracycline antibiotics selected in this research,respectively,tetracycline and chlortetracycline.To explore the effect of tetracycline and chlortetracycline on biological nutrient removal,through the construction of biological nitrogen and phosphorus removal system with adding different concentrations(1 mg·L^-1,5 mg·L^-1,10 mg·L^-1)of tetracycline and(0.1 mg·L^-1,1 mg·L^-1,10 mg·L^-1)of chlortetracycline.Then,to explore the influence and underlying mechanism of tetracyclines on biological nitrogen and phosphorus removal with the analysis of the transformation of nitrogen and phosphorus,and changes of sludge activity,key enzyme activity and microbial metabolic pathway.The results showed that denitrification was inhibited when tetracycline concentration exceeded 5 mg·L^-1 in acute test.After long-term exposure,5 and 10 mg·L^-1 tetracycline inhibited both nitrification and denitrification with the total nitrogen removal efficiency decreased from 85.4%to 78.6%and 75.6%in the test of 5 and 10 mg·L^-1 tetracycline,respectively.Moreover,long-term exposure to tetracycline had a slight effect on phosphorus removal ability.Mechanism analysis suggested that tetracycline could destroy flocculent colloidal structure and inhibit the settling property of active sludge,inhibited the microbial activity.Moreover,nitrite oxidizing bacteria are more sensitive to tetracycline than ammonia-oxidizing bacteria,and the nitrite oxidation is more easily inhibited than ammonia-nitrogen oxidation,resulting in the accumulation of nitrite.1 mg·L^-1 of chlortetracycline had no significant effect on the nitrogen and phosphorus removal,while long-term exposure to 1 mg·L^-1 and 10 mg·L^-1 of chlortetracycline reduced the removal efficiency of total nitrogen from 77.4%to 64.1%and 53.4%,respectively.At the same time,10 mg·L^-1 of chlortetracycline reduced the removal rate of phosphorus from 96.3%to 78.1%.Chlortetracycline showed the inhibition on the activity of nitrite reductase and the conversion of polyhydroxyalkanate and glycogen,thus inhibiting denitrification and phosphorus uptake,which may be the main reason for the adverse effect of high concentration chlortetracycline on biological nitrogen and phosphorus removal.The aim of this research is to explore the effect of tetracycline antibiotics on biological nitrogen and phosphorus removal.It is of great significance for clarifying the impact of antibiotics on sewage treatment process and has important reference value for comprehensive assessment and elimination of environmental risks of antibiotics.