The Biological Safety of Model Distribution Systemfollowing UV

摘要

Water distribution system biofilms is a public health concern as they are potential sources of pathogenic bacteria and indicator organisms. UV's inability to have an enduring disinfecting effect on the distribution system is one of the most important factors which limit its applications in drinking water treatment. In this experiment, it used biological annular reactor (BAR) to simulate the model distribution system. For the measurement of biofilm, it used molecular biology methods such as PCR-DGGE and FISH to analysis the microbiological composition and other characteristics of biofilm. The results showed that: (1) The residual chlorine of 0.35mg/L could control the HPC concentration of bulk fuild below 500CFU/mL. On the other hand, when HPC was above 3.5 log, the chlorine residual was 0 for adding chlorine systems. Likewise, the biofilm could keep growing with a low residual chlorine level. (2) For 4 different coupon materials (U-PVC, PVC, copper, stainless steel), the number and composition of biofilm was different. PVC had the most of microbe species while stainless steel had the least for the model distribution system following UV. UV disinfection could control the microbe species of biofilm in the model distribution system, (3) Even though the chlorine residual concentration is 0.8mg/L, there were still hundreds of HPC in the biofilm and fluid of model distribution system. These species of microorganism might be very chlorine resistive. The inactivation rate for one species of bacterium which was separated form the model distribution system was under 10% even the chlorine CT value above 700mgmin/L. However, UV had good controlling effect for it.