The Screening Of Acrylamide Biodegradating Bacterium And Degradation Effect Study

Acrylamide (C3H5ON, for short AM) is a white crystal chemical, which is the production of polyacrylamide materials. Polyacrylamide is widely applied for the water treatment areas due to its well flocculation characteristics, including the raw water treatment, sewage treatment, industrial water treatment, urban sewage treatment, etc. In the oil industry, polymer flooding three recovery technique has entered the industrial application stage. Polyacrylamide is basically non-toxic, but its monomers, acrylamide, produced by hydrolysis is toxic. Sewage seriously polluted by high concentrations of polyacrylamide, caused great harm to the natural environment and human health, even damaged the ecological balance. Acrylamide is a toxic agent to nervous system, which damages the nervous system, causes body weakness and movement disorders and other symptoms. To avoid pollution of the environment, it is nesessary to seek acrylamide monomer removal method. Acrylamide light degradation and hydrolysis rate is very low. Biological degradation is a natural way to eliminate acrylamide pollution, with less energy consumption, low cost, wide function scope, long lasting and other advantages.From an activated sludge in the secondary sedimentation tank of wastewater treatment plant, a bacterial strain with high efficiency of degrading acrylamide was found, named as A18. Based on the result of16SrDAN sequences, this strain was identified as Delftia tsuruhatensis. Delftia tsuruhatensis is a newly discovered strain, which has also been reported as a degradation strain for phoxim, bifenthrin, PAEs and aniline. This study found this strain can also degradate acrylamide.By the comparison between growth conditions and acrylamide degradation, the optimum degradation conditions of Delftia tsuruhatensis were determined, which were acrylamide concentration1000mg/L, inoculated amount at2.0%, temperature of30℃and pH of7.0. Under the optimum conditions, the acrylamide could be completely degraded by the strain within48h in the inorganic medium. With the temperature between20to40℃, pH between 5.0～10.0, acrylamide were also degradated well, which implied the environmental requirements for acrylamide degradation was low.In the sewage treatment plant, dosing external nutrition is a kind of good method to improve biodegradation speed in normal operation. So in this paper acrylamide was degradated by Delftia tsuruhatensis adding external nutrition, with acrylamide concentration1000mg/L, inoculated amount at2.0%, temperature of30℃and pH of7.0, which added extra carbon sources, nitrogen source, metalions. Experiment results made it clear that adding the extra nutrient medium in the inorganic medium as maltose, NaNO3, Zn2+, the degradation effect of24h was significantly improved camparing with control as99.98%,98.13%and95.6%, respectively.Acrylamide degradation dynamics preliminary study showed under the best degradation condition, Delftia tsuruhatensis degradation of acrylamide process, fitted well with first-order kinetic model, with a degradation rate constants (k) of0.875d-1and half-lives (t1/2) of0.8d.This paper used photogenic bacteria and microalgae to test biotoxicity of acrylamide, catabolite, found that acrylamide could be degraded into other compounds by Delftia tsuruhatensis, the toxicity of these compounds were lower than acrylamide, which demonstrated the strain of Delftia tsuruhatensis had good application prospect.