Elimination Of Veterinary Antibiotics And Antibiotic Resistance Genes From Swine Wastewater In The Vertical Flow Constructed Wetlands

Veterinary antibiotics and antibiotic resistance gene residues in swine wastewater have raised significant concern; these residues have a great capacity to disturb the natural ecological balance and trigger an increase of resistant bacteria in the environment. Antibiotics have been widely applied in the livestock industry, a great quantity of antibiotics through various channels into the environment, caused a serious threat to the ecological balance. Constructed Wetlands (CWs) technology has the advantages of low-cost, high-effective, low running investment, and it has great application potential for the pig industry which is of high-risk and low-profit. Therefore, CWs were used to treat swine wastewater, investigating the removal of CWs for antibiotic and antibiotic resistance genes. And design a pilot study the impacts of soil types and plant to antibiotics and resistance genes cumulative. This study investigated the efficiency of constructed wetlands, at removing three common antibiotics (ciprofloxacin HC1, oxytetracycline HC1, and sulfamethazine) and tetracycline resistance (tet) genes (tetM, tetO, and tetW) from swine wastewater. Study the concentration of antibiotics and resistance genes accumulated in the soil、media and vegetation. The conclusions are as follows:(1) The result indicated that the two systems could significantly reduce the wastewater antibiotics content, and elimination rates were in the following sequence:oxytetracycline HCl> ciprofloxacin HCl> sulfamethazine. The zeolite-medium system was superior to that of the volcanic-medium system vis-a-vis removal, perhaps because of the differing pH values and average pore sizes of the respective media. A higher concentration of antibiotics accumulated in the soil than in the media and vegetation, indicating that soil plays the main role in antibiotics removal from wastewater in vertical flow constructed wetlands.(2) All three tet genes were detected in raw wastewater; average absolute abundances of tetW, tetM, and tetO were1.07×1010,4.03×1010and4.92×1010gene copies per litre, respectively; these values were higher than respective concentrations detected in urban wastewater.The total absolute abundances of three tet genes and of16S-rRNA were reduced by50%in CW1, and by almost one order of magnitude in CW2. However, the relative abundances of target tet genes tended to increase following CW1treatment. The removal efficiency of ARGs CW1is better than CW2, show that the constructed wetland structure might affect the ARGs removal efficiency of a treatment system. Concentration of ARGs accumulated in the CWs, different regional accumulation associated with artificial wetland configuration conditions.(3) Oxytetracycline HCl、ciprofloxacin HCl and sulfamethazine has a high accumulation in the humus soil and red soil, antibiotic accumulation are significantly higher in the humus than in the red soil. Oxytetracycline HC1accumulation is highest in the soil, sulfamethazine lowest, soil types might affect antibiotics accumulation in soil as well as their own characteristics. The absolute abundances of three tet genes in humus soil are higher than that of red soil, show humus soil has a higher ability of tet genes accumulating. Plants can affect the accumulation of antibiotics and resistance genes, the existence of the plant reducing antibiotics accumulation in the soil. Plants also reduce the tetM and tetO accumulation amount in soil, but increased the tetW amount.