Biofilm formed on stainless and copper in water treatment plant was investigated for sixteen weeks. Biofilm reactor was specially designed for this study. It was similar to that of a real distribution pipe. Raw water, coagulated, settled, filtered and treated water were used in this study. The average number of heterotrophic bacteria counts was 1.6 × 10 4 CFU/ml, 5.8 × 10 3 CFU/ml, 1.8 × 10 3 CFU/ml, 1.3 × 10 2 CFU/ml, 1 CFU/ml, respectively. Density of biofilm bacteria formed on stainless and copper pipes in raw, coagulated and settled water increased above 2.9 × 10 3 CFU/cm 2 within second weeks while more biofilm bacteria counts were found on the stainless pipe than on the copper pipe. In case of filtered water (free residue chlorine 0.44 mg/L), there was no significant difference in the number of biofilm bacteria on both pipes and biofilm bacteria below 18 CFU/cm 2 were detected on both pipe materials after fifth weeks. Biofilm bacteria were not detected on both pipe materials in treated water (free residue chlorine 0.88 mg/L). According to the results of DGGE analysis, Sphingomonadacae was a dominant species of biofilm bacteria formed on the stainless pipe while the copper pipe had Bradyrhizobiaceae and Sphingomonadaceae as dominant bands. In case of filtered water, a few bands (similar to Propionibacterium sp., Sphingomonas sp., Escherichia sp., and etc.) that have 16S rRNA sequences were detected in biofilm bacteria formed on both pipes after fifth weeks. Stainless pipe had higher species richness and diversity than the copper pipe.
This study investigated the recovery and absorption rates of murine norovirus, a surrogate for human norovirus, by using NanoCeram ® filters which served as a tool for recovering viruses. In the study, two types of NanoCeram ® filters were employed: one was a cartridge type and the other was a disc type ( 47 mm) whose surface area is 75 times smaller than the cartridge type. The analytical method was the real-time reverse transcription-polymerase chain reaction (RT-PCR). The study found that the average recovery rates of the cartridge type and the disc type were 30.9% and 29.5% respectively. Since these two rates were very close to each other, the adsorption rate of the cartridge type could be predicted with the disc type. Analyzing recovery and absorption rates of the disc type based on different filtered volumes showed that when the volume increased from 0.5 L to 20 L, the average recovery rate rose from 14.78% to 30.41 %, while the average absorption rate dropped from 56.33% to 10.48%. The increase in turbidity from less than 1 NTU to less than 3 NTU raised the average recovery rate from 47.23% to 82.84%.
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