Treatment Of Partially Hydrolyzed Polyacrylamide Wastewater By Combined Anaerobic And Aerobic Biological Processes

Partially hydrolyzed polyacrylamide (HPAM) contained in oilfield which is extensively used for oil extraction produced waste water entering the groundwater system and having threat to the safety of the plants and animals. Among many methods to deal with this issue, biodegradation is an efficient way to disposal oilfield waste water. In this paper, combined anaerobic and aerobic biological processes based screened bacteria (PAM-2, PAM-F1) and sludge were used due to single oxygen gradually showed its limitations. The removal efficiency of HPAM based on different methods and the microbial community structure characteristics during the biodegradation were detected, the changes of simulated HPAM wastewater parameters as the change of time and the contribution of different factors during the biodegradation were also detected. All the conclusions were as follows:(1) Standing time had influences on shear viscosity and pH of simulated HPAM wastewater, the shear viscosity had a big reduction when the standing time reached 20h while it hadly had no changes when the standing time less than 20h; the pH had the same variation tendency. The ORP had no big changes when the standing time less than 7 days, that was to say the standing time had no influence on ORP in a short period of time.Mechanical agitation had a great influence on the shear viscosity of HPAM aqueous solution, when the stirring speed is 7000 r/min, stirring time is less than 10 h, shear viscosity of HPAM solution had no obvious change, shear viscosity had significant losses when stirring time more than 10 h.(2) Shake flask experiments using the activated sludge and HPAM degradation bacteria indicated that HPAM adsorption of activated sludge accounted for 32.9%, HPAM degradation of bactearia from active sludge accounted for 19.9%, HPAM degradation of co-treating mixed bacteria accounted for 47.2% respectively in all the degradation.(3) Start the reactor under the optimum parameters of the degradation, the results indicated that the removal efficiency of HP AM could reach 86.21%.32.93%,75.75% respectively based on the starch cadmium iodide method, TOC and shear viscosity.(4) HPAM amide groups were more easily biological degraded than carbon chain in the process because of the significant difference of multiple testing means. And the HPAM molecules with a molecular weight of about 2.2×107 were biological degraded into much smaller molecules with a molecular weight of about 3.5 x 105 based on the results of HPLC, GPC and scanning electron microscopy (SEM) after biodegradation.(5) Based on the variation tendency results of biological parameters such as pH, ORP, VFA et.al, we drawed a conclusion that the bioreactor can reach a stable state, and have strong self-adjustment ability.(6) In the anaerobic reactor, microorganism concentration of the second compartment decreased, the 3rd and 4th compartments gradually restore and at last reached and exceeded the microorganism concentration of first compartment. According to the result of scanning electron microscopy method, activated sludge in biological reaction during cure, became into a porous surface area huge slaking sludge, this provided more attachment points for microorganisms.(7) Scanning electron microscopy and DGGE results show that the inoculated HPAM degradation bacteria strains (PAM-2, PAM-F1) were dominant bacteria all the time during the biodegradation. And in this process, part of bactaaria from the activated sludge gradually adapted to the HPAM environment of reactors and had synergy effect with the HPAM degradation bacteria strains.