Bioaugmentation For Treatment Of Polyacrylamide Contained Wastewater

Polyacrylamide (PAM), a type of linear water soluble polymeric compound with high molecular weight, is wildly used in metallurgy, paper making, oil production, petroleum, chemicals, textiles, mineral processing and other fields. More and more PAM are discharged into the environment with oil extraction wastewater with the promotion of the polymer oil-displacing technology. Due to its stability under the natural circumstance, PAM is accumulated in the environment and the treatment of PAM contained wastewater in oil field has become an important issue.This work focused on the biodegradation of PAM containing wastewater. Expe-riments dealed with three aspects were designed, namely, screeing of the efficient degradating bacteria, optimization the component of the inoculant bacterial cocul-ture reagent and investigating on the performance of bioaugmentation.6 bacterial strains that can degrade PAM efficiently were isolated from the sam-ples. These samples were the soil that was long-term contaminated by oil extraction wastewater, the acrylonitrile production wastewater. The strains were grown on me-dium contained 200mgL?1 PAM as the sole carbon source respectively and more than 50% of the PAM was consumed after120 h cultivation for all the strains. The degradation efficiency was much higher when 400mg/L crude oil was added into the medium as cosubstrate, more than 75% PAM was removed in the same opera-tion condition. The 16S rDNA sequence analysis showed that a strain of Bacillus flexus has a 99% similarity with strain of W-6;a strain of Brevibacillus parabrevis has a 99% similarity with strain of W-13;a strain of Bacillus cereus has a 99% si-milarity with strain of W-16;a strain of Klebsiella has a 99% similarity with strain of B2-1; a strain of Stenptrophomonas acidaminiphila has a 99% similarity with strain of B2-2 and a strain of Aeromonas jandael has a 99% similarity with strain of B2-3.The research revealed that: PAM were more likely to be used by the isolated bac-teria as N source to achieve rapid growth. When PAM was used as the only N source, PAM removal efficiencies of different strains varied from 45% to 74% after 72h cultivation. When PAM was used as the only C source, PAM removal efficien-cies of different strains varied from 17% to 60% after 72h cultivation. A orthogonal test on single strain and coculture revealed that when the degradation time was 48h, W-16 and B2-2 coculture degradated PAM more efficient than both of the single strain does. When the degradation time was 120h, the degradation efficiency of the coculture became similar to that of the single strain.The coculture was used in the PAM bioaugmentation. The microbial community structure in the biotreatment system before and after bioaugmentation were ana-lyzed through T-RFLP. The results showed that, the coculture still existed and exert the degradation function 8 cycles after it was inoculated into the SBR system with HRT 48h, while with HRT 72h, the coculture disappeared from the activated sludge system 8 cycles after the inoculation. Mean while, bio-contact oxidation reactor was also used for treatment, the biodegradation of PAM was improved remarkably after the inoculation and the coculture bacteria grow well in the system in a long term operation.