Isolation And Identification Of Three Strains Of Degradation Of The Herbicide Atrazine And Applied Research

By using enrichment culture in liquid minimal medium or direct culture on minimal medium plates, Arthrobacter sp. AD26, AD30 and Pseudomonas sp. AD39 were isolated from a mixture of industrial wastewater and sludge from an atrazine manufacturing plant. PCR assays for degradation genes indicated that AD26, AD30 and AD39 contained atrazine-degrading genes trzN and atzBC, used atrazine as sole source of nitrogen and sucrose or sodium citrate as the carbon source for growth and degraded atrazine to cyanuric acid. The rate of atrazine degradation of these strains was fast but their degradation was not complete. Pseudomonas sp. ADP was an atrazine-degrading strain isolated by Wackett and his cooperators. This strain contains atrazine-degrading genes atzABCDEF, which uses atrazine as sole source of nitrogen and sodium citrate (not sucrose) as the carbon source for growth and degrades atrazine to NH₃ and CO₂. Although atrazine degradation of ADP is complete, the degradation rate of atrazine is slower.Co-cultivation of AD26 and ADP in minimal medium containing 200 mg/L of atrazine indicated that they exhibited cooperative degradation of atrazine and higher degradative rate. The two strains could grow quickly in the minimal medium using atrazine as sole source of nitrogen and sucrose as carbon source. They were capable of removing atrazine in the medium at 99.9% in 72 h, and 76.7% of atrazine was degraded to NH₃ and CO₂.Atrazine biodegradation experiments of AD30, AD39 and their mixture showed that the percentage of atrazine removal were respectively 92.5%, 97.9% and 99.6% after the cultures were incubated at 30℃for 48 hours in minimal media containing 200 mg/L atrazine, indicating that atrazine degradation by the mixed bacteria was more effective than the single strain.Bioreactor experiment using polyurethane foams as a carrier showed that CODcr of effluent was in less than 100 mg/L and concentration of remaining atrazine was in less than 0.2 mg/L when influent contained 1702 mg/L CODcr, 133 mg/L atrazine and hydraulic retention time (HRT) was 24 h. The effluent quality conforms to the standards of GB 21523-2008. A bioremediation trial of contaminated soil has indicated that AD30 and AD39 can degrade as high as 99% of atrazine contained in soil (200 mg/kg) after incubating for 20 d at 30℃. These results proved that AD30 and AD39 as a good candidate for use in biotreatment of atrazine-containing industrial wastewater and bioremediation of atrazine-contaminated soil.