| Polyacrylamide has been widely used in enhanced oil recovery, resulting in oilfield produced water containing a large of polymer, polluted the environment of the field.Polyacrylamide sewage treatment has important meanings. Biological degradation of polyacrylamide with low cost and little secondary pollution, aroused extensive attention by the researchers. This paper studied polyarcylamide wastewater in a nested circulation biofilm reactor. Formated a nested loops, outer loop nested the inner loop, making wastewater alternatively flowing in the space of anoxic environments and aerobic environments,removing organic and nitrogen simultaneously.appropriate carrier has been selected based on the nature of the carrier should have,determined the dosage of the carrier, started the nested circulation biofilm reactor. The impacts of concentration of polyacrylamide and hydraulic retention time(HRT) in aerobic zone organic removal efficiency has been explored. Growth factor vitamin B, carbon and nitrogen sources glucose, starch and peptone have been utilized to enhance the removal efficiency of polyacrylamide in the nested loops biofilm reactor. The relationships between nested loop mode, influent manner, superficial gas velocity and denitrification efficience has been investigated. Biological phase of the carrier has been observed, polyacrylamide degrading bacteria has been screened, and the impacts of metal ions on polyacrylamide degrading bacteria degradation characteristics has been preliminary studied. In addition,nested loop biofilm hydrodynamics has been studied, nested loops biofilm biodynamic coefficient has been determined.The results show that started about 90 d the nested loop biofilm reactor goes maturing.After 60 days acclimation, the average COD removal efficiency is 70.37%. During domestication, COD removal efficiency decreased with the increase of polyacrylamide concentration. HRT<24h, COD removal efficiency increased with the rise of HRT, COD removal efficiency become stable when HRT>24h. Determine the optimum HRT is 24 h. The removal of polyacrylamide is less affected by B vitamins. Glucose and starch increase removal rates by 7% and 6% respectively. Peptone has great impact on PAM removal rate,removal rate can be increased from 60% to 75%. Nitrogen removal experiments show that influent in anoxic zone, when superficial gas velocity of inner loop is 0.003mg/L, nested loops reached the highest denitrification efficiency, ammonia removal efficiency is 85%, total nitrogen removal is 33.3%. Microscopic examination show that the structure of biologicalphase of aerobic zone biofilm carrier is stable. biofilm is made by a large number of filamentous bacteria and a small amount of bacterial components. Isolation and Screening of two rod-shaped Gram-negative bacteria polyacrylamide degrading bacteria P1 and P2. Metal ions Mg2+ and Zn2+ can promoted the growth of bacteria and PAM degradation, while Mn2+have a certain degree of inhibition effection on P1 and P2. Kinetic studies show that aerobic zone mixing matrix can be completed within 1min, is a continuous stream complete mixing type. There is a linear relationship between outer loop aeration and gas holdup, fitting equation is y=10.725x-0.504. There is linear like relationship between the square of outer loop circulation rate and gas holdup. Selecting the top of stripping pipe as the best inffuent position. Established hydrodynamic model, the minimum criculation gas velocity Ugr=0.76m/s. Yield coefficient of the nested loops biofilm particles in aerobic zone Y=0.40645(mg/m3)/(mg/LPAM)... |
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