The Control Of DON And Biological Stability By Biological Pretreatment In Micro-pollution Water Treatment

Source water micro-pollution is a ubiquitous phenomenon in China. It is very difficult to remove Assimilative Organic Carbon (AOC) in water by conventional treatments and will bound to make the microbe growth in water, resulting in drinking water biological safety problems. At the same time, the usage of chlorine (chloramine) will lead to the generation of Nitrogen-Disinfection by-Products (N-DBPs) and cause potential safety hazard in drinking water. In our experiment, continuous stirred tank reactor (CSTR) has been adopted for pretreatment in water and following up with ultrafiltration device to investigate dissolved organic nitrogen (DON) and biological stability of effluent.In order to understand the effects of different pretreatment methods act on the water soluble microbial products (SMPs), completely mixed and fixed bed pretreatment devices have been used and the dissolved organic nitrogen forms were analyzed respectively. In addition, PMA-qPCR and qPCR has been applied for viable bacteria and total bacteria amount analysis in the reactors. The results show that, compared with the completely mixed reactor, DON generated more in the fixed bed reactor while the ratio of viable to total bacteria is lower than that in CSTR. This phenomenon suggests that mixing regime determines DON formation by influencing the distribution of viable, total biomass, and ratio of viable biomass to total biomass.Ultrafiltration (UF) membrane combined with PVC pipe are used to study the effects of ultrafiltration membrane on pipe network biofilm formation. From the results, we can conclude that microorganisms in the water can not be utterly removed by ultrafiltration membrane and this will lead to pipe network bio-membrane formation, reducing the biological stability.CSTR is placed before traditional treatment process and following with UF, which are used to measure the quantity of AOC and BGP of terminal effluent as well as each units’effluents. AOC and BGP changes of conventional treatment process have been studied, either. As the results shown, AOC and BGP have a good linear relation. As the results shown, the AOC content of terminal effluent is less than 50 μg/L in combined process while the traditional process had a lower biological stability and AOC content is exceeded 90 μg/L...