Screening And Application Of Denitrogenation Strains For Rural River Water Bioremediation

Water environment has been suffering unprecedented damage with the development of agricultural and industrial economy. Especially in the rural river systems, water quality is mainly in categoryⅤand inferior categoryⅤdue to serious pollution and ecological degradation. The nitrogen element is regarded as the major factor for the rural water pollution and eutrophication. Fortunately, microbial-based biological nitrogen removal technology, as an efficient and economical ecological restoration technology, has been widely used in the treatment of water environment pollution. Therefore, screening denitrifying strains and exploring their application conditions become an extremely important fundamental work.This research procced from the isolated strains of laboratory for water purification, combined technology of molecular ecology DGGE and traditional method of screening bacteria, and selected a strain W14 that was suitable for growth in sewage and has function of ammonia-oxidizing. In addition, an oxygen-tolerant denitrifying strain designate as ADZ1 was screened from the collection of water sample. We studied deeptly the strain’s characteristics and effect of aerobic denitrification, and explored the effect that strains ADZ1 and W14 added into rural river for water purification under laboratory conditions. Moreover, according to the characteristics of surrounding river water on Zhejiang Academy of Agricultural Sciences in Hangzhou, the effect of degradation of ammonia and sewage purification by W14 on small-scale experimental river scene. The results were showed as below:1. PCR-DGGE profiles were used to analyze the growth of strains and the change of microbial community in polluted water after inoculating the microbial consortium from our lab. Based on the results, strain W14 was isolated with the capability of growing in sewage. Then, both strain W14 and the microbial consortium were added into synthetic water, measuring the variation of chemical parameters of water simultaneously. In the synthetic water, the ammonia removal efficiency by strain W14 was 75.94%, and nitrite nitrogen increased from 0.0107 mg/L to 0.1306 mg/L. Nitrite accumulation occurred in water, while the accumulations by the other three strains were weak. This indicated that strain W14 has function of ammonia-oxidizing. The strain W14 was finally identified as Bacillus sp. based on 16S rDNA sequence analysis.2. An high efficiency aerobic denitrifying bacterial strain ADZ1 was isolated from the rural river by enrichment culture and BTB (Bromothymol Blue) plates. ADZ1 was identified as Pseudomonas putida. Under the optimal growing conditions with ethanol as carbon source, C/N ratio of 12:1, speed 170 r/min, pH 7, and temperature 30℃, strain ADZ1 reached stable growth phase at 12 h. At the same time, nitrate concentrations decreased from 34.026 mg/L to 0.3733 mg/L, removal efficiency of more than 98%. In the first 6 hours, nitrite nitrogen concentration accumulated from 0.01245 mg/L to 1.51885 mg/L, followed by the degradation of nitrite nitrogen. At the end of experiment, the concentration of nitrite nitrogen was 0.0196 mg/L, and the degradation rate of total nitrogen reached to 47.29%.3. Jiashan rural river sewage was used as basic sewage samples under laboratory conditions. The effect of treatment was measured after the addition of strains W14 and ADZ1. The result indicated that nitrate and total nitrogen have a high degree of degradation in the experimental group, in which the nitrate and total nitrogen removal efficiency were 68% and 12.59%, respectively. While the accumulation of nitrate and nitrite occurred in the control group, with total nitrogen removal efficiency of 7.26% and 10 times of the concentration of nitrite higher than the original one. The later in experimental group was only 1 time higher than the original. This indicated the added strains inhibited the incensement of nitrite. PCR-DGGE profiles showed the decreasing of microbial diversity in water environments in both two group, and the increasing of some indigenous microorganisms. Those demonstrated the strains added could change the composition and abundance of microbial community in water environment.4. The solid fermentation culture of W14 to was used to treat the rural river in Hangzhou, adding every three days. After 30 days of experimentation, the concentration of ammonia nitrogen in the position of strain-adding was significantly reduced with the degradation efficiency of 48.29% compared to that in aeration points. The sensory effect of water body was greatly improved, transparency has increased and bad smell disappeared.