Study On Selection And Characteristics Of High-Effected Strains For Nonylphenol Polyethoxylates (NPEOs) Biodegradation

Nonylphenol polyethoxylates(NPEOs) is a widely used nonionic surfactant in the world.NPEOs can be degraded into intermediates, such as NP1EO,NP2EO,NP1EC,NP2EC and NP via microbial degradation after let out into nature. These intermediates show the estrogenic activity to the organism and have been proved as Environmental Hormones.Researches showed that nonylphenoxyethoxyacetic acid(NPEC), soluble and easy to be transferred in the nature, which is more harmful, can be formed under the conditions of aerobic degradation of NPEOs. NPEC can't be formed under conditions of anaerobic degradation, however, it led to long biodegradation cycle and accumulated short-chain NPEOs and NP. This paper is supported by National Natural Science Foundation project " The environmental estrogen effect in the biodegradation process of alkylphenol polyethoxylates", and studied on selection and characteristics of high-effected strains for NPEOs biodegradation. It focused on studying biodegradation characteristics of NPEOs under conditions of aerobic biodegradation, conquering shotcomings of aerobic and anaerobic degradation and exploring strains with high-effected biodegradation characteristics. It studied the formation of intermediate biodegradation products with estrogen activity and its biodegradation pathway, and researched biodegradation mechanism under the condition of aerobic biodegradation through studying on biodegradation properties under different conditions of substrate concentrations and temperatures. All these may provide a new idea for selection of high-effected strains for biodegradation and make contribution to the biodegradation of NPEOs efficiently for urban sewage treatment. The main results are as follows:1. Bacillus sp. LY with heterotrophic nitrogen removal ability could biodegrade NPEOs largely and would not form NPEC during the process of degradation. After 14d, removal efficiency of NPEOs was 95.6% and maxium removal rates of TN was 47 mg·(L·d)^-1. At the same time no NPEC was detected in the process, illustrating Bacillus sp.LY excellent strains for biodegradation of NPEOs.2. Different factors (temperatures, initial concentrations of NPEOs and typical nitrogen pollutants) had impacts to some extent on biodegradation of NPEOs by Bacillus sp.LY. The first-order biodegradation rate constants were 0.055 d^-1,0.151 d^-1 and 0.258 d^-1 respectively under temperatures of 10℃, 20℃and 30℃, showing that the higher the temperatures was, the better the effect. Under three initial concentrations of NPEOs (1mg/L, 10mg/L, 20mg/L), removal efficiencies were 89%,79% and 50% respectively, illustrating that initial concentrations of 20mg/L had inhibitory action on biodegradation of NPEOs. The removal efficiencies of NPEOs were 0.106 d^-1,0.0306 d^-1 and 0.0237 d^-1 respectively under different typical nitrogen pollutants - NH₄Cl, NaNO₃ and NaNO₂.3. Newly discovered strain LJ-1 had good degradation effect on NPEOs and no NPEC was formed during the process. Strain LJ-1 is Gram-negative Brevibacterium. After 14d, removal efficiency of NPEOs was 98% and no NPEC was detected by GC-MS. The strain is a high-efficted strain for biodegradation of NPEOs.