Screening Of Tetracycline-degrading Bacteria And Its Ability Of Aquaculture Wastewater Treatment

With the development of economy and the growth of population,people are favoring seafood products with high nutritional value increasingly and their demand has increased significantly.In order to solve the problem of shortage of seafood,the marine aquaculture industry has developed rapidly in the past 30 years in China.For many years,the output of marine aquaculture products has ranked first in the world.However,in order to accelerate the growth of marine products and prevent pathogenic diseases when artificially cultivating seafood,a large amount of feed and antibiotics were added into the aquaculture water,resulting in prominent marine pollution increasingly.The research of marine aquaculture wastewater purification has become the focus of research gradually.In this paper,tetracycline was added as the sole carbon source in the inorganic base medium,and a tetracycline-degrading strain screening model was constructed.After repeated purification,three strains TC1,TC2 and TC3 were obtained,in which TC2 was highly efficient in the degradation of tetracycline.The removal rate of tetracycline reached 86.30% after 7 d,and the strains grew well.The dry weight increased 1.58 g/L after treatment.With TC2 as the target bacteria,the removal of tetracycline in the inorganic salt medium and the optimization of the growth conditions of the suspension were studied.The results showed that under the optimum conditions of initial pH 7,strain inoculation of 1% and tetracycline concentration of 100 mg/L,the tetracycline removal rate of suspended TC2 strain reached 86.30%,and the dry weight increased 1.58 g/L.Under the addition of sucrose,glucose,soluble starch and galactose,the growth of the strain promoted,but the tetracycline removal rate was lower than the control group.Compared with the experimental groups,20 mg/L galactose had the highest tetracycline removal rate of 64.20%,and the growth of the strain increased 1.76 g/L under this condition.The purification ability of simulating marine aquaculture wastewater by immobilized tetracycline degrading bacteria TC2 was studied.The effects of different ammonia nitrogen concentrations,different tetracycline concentrations,different initial COD concentrations,different reactor densities,and pre-immobilized strain concentrations on the removal rates of COD,tetracycline,ammonia nitrogen,and orthophosphoric acid were investigated.The results showed that under the condition of ammonia nitrogen 50 mg/L,tetracycline 20 mg/L,COD 500 mg/L,reactor density 150 beads per bottle and the immobilized bacteria of dry weight of 8 g/L.The removal rates of tetracycline,COD,ammonia nitrogen and phosphorus orthophosphate were 76.01%,50.59%,84.29% and 90.67%,respectively.The average weight gain 85.97 mg per bead.The tetracycline-degrading bacteria TC2 and Chlorella vulgaris were used to construct an immobilized bacteria-algae system.The results showed that the purification efficiency of tetracycline was better and the removal rate was 59.98% when the bacteria to algae ratio was 1:1.The removal efficiency of COD(81.20%)was highest when the bacteria to algae ratio was 4:1.The optimal ammonia nitrogen and orthophosphate removal rates were 86.50% and 94.98%,respectively after 6 d treatment.