| Nowadays, traditional water flooding can't meet the need in oil field, followed by the main oil fields going into high water-cut in our country. And polymer flooding technique becomes an important method in enhanced oil recovery. But the application of polyacrylamide in oilfield meets many environmental problems. On one hand, partially hydrolyzed polyacrylamide (HPAM) increases the difficulty in oil-water separation and makes oil content in sewage exceed the standard greatly when it was applied to enhance the oil recovery. The cost and the difficulty to deal with produced water increase, and some wastewater containing high concentration HPAM is discharged to the local surface water. On the other hand, when HPAM goes into the oil reservoir with injecting water, it can hardly avoid infiltrating groundwater horizon in connection with stratal configuration. The residual HPAM degrades slowly in the environment, and the toxic acrylamide monomer is given off. As HPAM is held up in surface water and groundwater for a long period, it would endanger human health. Therefore, it's necessary to transformed HPAM into innocuous substance effectively and rapidly.Biodegradation is an efficient treatment to deal with environmental pollutant, which has many advantages, such as non secondary pollution and cheap operation expense. It will become one of effective measures to solve the problem of potential toxicity in HPAM's transformations and transports processes.In this paper, the biochemical treatment of wastewater containing HPAM is discussed. Based on explored HPAM degradation influence factors, HPAM determination methods are optimized, which are suitable for evaluating HPAM biodegradation, polymer-degrading bacteria are screened and degradation conditions are optimized, the degrading mechanism of polyacrylamide is explored, and the simulation biochemical treatment of wastewater is done by added the polymer-degrading bacteria. The conclusions are as follows: 1. It showed that pH value, light and mineralization affect viscosity of HPAM apprantly, but do slight effect on concentration of HPAM. Low temperature and shear intensity affect viscosity and concentration of HPAM slightly, but high temperature and shear intensity did apprant effect on viscosity and concentration of HPAM. The determination methods of HPAM were optimized. Concentration detection method is the main means to evaluate the degree of degradation, viscosity and molecular weight detection methods are assistant way. The concentration of HPAM is measured by starch-cadmium iodine method. The pH of buffer solution in conditions of detection was optimized. The suitable pH value is 3.5.2. Three aerobic bacteria strains, PM-2, PM-3 and PM-4, are isolated from producing water in Shengli Oilfield. Through morphology observation, physiological and biochemical experiment and 16Sr DNA analysis of the three strains, it indicated that PM-2 and PM-3 were affiliated to Bacillus sp. and PM-4 was affiliated to Ochrobactrum sp.. PM-4 showed antagonism to another two strains. While PM-2 and PM-3 indicated synergetic effect, the degradation rate of 300 mg·L-1 HPAM was up to 42%.The optimal primary degradation conditions on mixed of PM-2 and PM-3 were as follows: 4 of continuous activating times, 3 % amount of inoculation, 35°C - 45°C of degradation temperature, 6.0-6.5 of pH, 140 r·min-1 of shaker rotate speed and 2500 -10000 mg·L-1 of mineralization.3. The degrading mechanism of polyacrylamide was preliminary researched. The utilization of HPAM by the bacteria was explored. It showed that microbes could partly utilize HPAM as either carbon or nitrogen source, and when it served as nitrogen source, better utilization by the bacteria occurred. Based on the SEM, IR, UV and HPLC analysis of HPAM samples before and after biodegradation, a hypothesis about the biodegradation of HPAM in aerobic culture is put forward. The HPAM was utilized as the nitrogen source firstly, which was obtained by hydrolysis of the amide groups from HPAM, using an amidase enzyme produced by the bacteria. During bacteria's developing and metabolism progress, the main carbon backbone was cleaved and the HPAM was transformed into smaller molecular organism, which could serve as the carbon source. 4. Based on water analysis and biodegradability analysis of polymer-bearing wastewater, biodegradability improvement of the wastewater was done. The laboratory simulation treatment on wastewater was done by biologic contact oxidation method. There are two parts in simulation experiment, one is static, and the other is dynamic. After 7 d static biochemical treatment, the degradation ratio of polymer in wastewater was up to 80 %, oil was 95 %, CODCr was 86 %. And in dynamic simulation experiment, after 3 d treatment, the quality of the water reaches stable. The degradation ratio of polymer was up to 67 %, oil was 93 %, CODCr was 80 %.
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