Effect Of Autochthonous Microorganism On Stabilization Operation Of Beac Filter

The dominant microorganisims isolated from the nature with organic matter degradation ability in combination with the GAC adsorption can improve the organic substances removal efficiency of the water treatment process. For this reason, GAC process with immobilized dominant microorganisms, which called the bio-enhanced activated carbon filter (BEAC), has received considerable attention in recent years. For open system, the autochthonous microorganism invasion on BEAC system can inhibit the development of biological activity, influence the econiche of the dominant bacteria and decrease the biodegradation ability of dominant bacteria.The results showed the growth condition range of dominant microorganism was broader than the autochthonous microorganism, the DHA activity of dominant microorganism [22.9-52.9 mgTF/(L·h)] under optimum condition was higher than the autochthonous microorganism[7.9-23.5 mgTF/(L·h)]. The TOC removal of the dominant bacteria was 9.1% more than autochthonous microorganism. Although biological activity and biodegradation function of dominant microorganism was higher than the autochthonous microorganism, the nutrients of the two kind microorganisms were the same organic substances, which resulted in the competition of the microorganism on BEAC filter.The pilot-scale test of the BEAC operation results showed autochthonous microorganism had a big influence on dominant bacteria component and distribution, biomass and biological activity, and biodegradation efficiency on the BEAC filter. A rapid growth of autochthonous microorganism was observed from 30d to 90d of operation which slowed down the increase biomass of dominant bacteria. The amount and species of autochthonous microorganism increased more than the dominant bacteria, the competition for nutrients and living spaces between autochthonous microorganism and dominant microorganisms intensively existed on BEAC system on 90-180d operation. After 180d operation, the limited nutrients were not satisfied the growth of large amount of the microorganism on BEAC filter, most of the microorganism disappeared after competition unless 4 kinds of microorganisms survived including 2 kinds of dominant microorganism and 2 kinds of autochthonous microorganism. It illustrated the autochthonous microorganism had a big influence on dominant bacteria stabilization.Study of process conditions to prevent the autochthonous microorganism results showed the dominant bacteria was efficient on biodegradation with high biological activity and the autochthonous microorganism was inhibited under the condition of the backwashing operation time with 7-10d, air backwashing ratio with 8-10 L/(m2·s), EBCT of the BEAC filter with 15min. The ozone process with sterilization function was efficient to inhibit the autochthonous microorganism invasion on the BEAC filter. The optimum operation of the ozone process was dosage with 2-2.5mg/L and contact time with more than 10min.PCR-DGGE results showed Bacillus subtilis, Pseudomonas stutzeri, Pseudomonas pertucinogena were easily adsorbed on BEAC carbon media with large growing condition. Specially, Bacillus subtilis and Pseudomonas pertucinogena dominated in competition with the autochthonous microorganism on BEAC operation, these two dominant bacteria with high biological activity belonged to hyperactivity microorganism. Pseudomonas balearica and, Pseudomonas putida were not easy to attach on carbon media and easily influenced by environmental factors. Especially the Pseudomonas balearica with low biological activity and biomass on ozone-BEAC operation was not suitable for application.