Experimental Study Of Unit Process Performance In Conventional Water Purification Process

Biological stability is an important aspect of drinking water safety. Biological instability of drinking water will promote corrosion in pipes, causing the bacteria regrowth in networks and thus seriously damage water quality. Therefore, study the representation of index changes in conventional water treatment processess has important practical significance. Assimilable organic carbon and biodegradable dissolved organic carbon are widely used as drinking water biological stability indexs in evaluation, only control the factory AOC and BDOC content of water can ensure biological stability of drinking water ,also effectively prevent the secondary pollution in water distribution sysytem. This paper studies the removal performance of conventional routine water quality indexes, biological stability indexes and bacterial indicators in water purification process, also their time and space variation in the purification and the removal characteristics of organic matter for each purification unit. The main contents and results are as follows:Depth study of the conventional water quality indexes, biological stability indexes and bacterial indicators of the raw water in Mopanshan reservoir,the results shows that: the year averge conventional indicators in raw water are classⅠ(based on "Environmental Quality Standards for surface water", GB3838-2002).The source water is low total organic , well biodegradable and HPC count is low. Raw water are mostly organic molecules in winter and in summer are small organic molecules.For routine water quality, pH and conductivity changes throughout the purification process is not obvious; turbidity, UV254 and TOC are gradually reduced with the process, but easily interfered by the value of the raw water and the temperature.Coagulation and chlorination have stable removal efficiency, while the removal of filtration is part affected by temperature instability. Treated water can reach the "Standards for drinking water quality" (GB5749-2006).The level of biological stability index after conventional water treatment process depends on raw water.The adaptation to AOC and BDOC changes is not good, while is less able to cope with shock loading.To ensure the biological stability of the finished water, it is necessary to control the organic matter in raw water. AOC in treated water exceeds 100μg acid carbon/L while BDOC is 0.67-1.56mg/L, the value is higher than the recommended limits in biological instability of drinking water. Filter backwash has a significant impact on DOC, BDOC and AOC, such type of biological stability indicators.Conventional water purification process can meet the equirements of microbial indicators. Method CTAB-proteinase K is used successfully to raise the DNA from the water purification unit, but DNA content of samples is not high.Use specific primers on the V3 region (357GC and R518), V6-V8 region(EUBf933 and EUBr1387) in appropriate systems and response procedures for PCR amplification , the brightness and purity are good, does not appear non-specific expansion increase. V3 fragment size is approximate 250bp, V6-V8 fragment size is about 500bp.