Control of Loose Deposits in a Simulated Drinking Water Distribution System Using Ultrafiltration

Abstract

Loose deposits on water supply pipe walls easily fall off and may affect the safety of the drinking water supply, and the control of them has been a hot research issue in recent years. In this research, we used two simulated pipeline test reactors to systematically study the formation and shedding pattern of loose sediment on the pipeline, analyze its characteristics, and explore the control role of the ultrafiltration process on loose sediment in the water supply pipeline network. The results showed that the loose deposits adhered to the pipe reactor fed by filtered water formed slower than did that fed by unfiltered water, the maximum accumulation of the loose deposits was reduced from 2.17 to 1.46 g/m2. The reactor after ultrafiltration showed a reduction of more than 40% in the concentration of substances other than Ca and Si. Copper and zinc were reduced by more than 80%, while the iron content was reduced by 91.2%. When the shear force of the pipe wall of the water pipeline is less than 0.33 Pa, there are loose deposits formed on the pipe wall; when the shear force of the pipe wall of the water pipeline is greater than 0.94 Pa, it was found that the loose deposits on the pipe wall were shed more completely. Ultrafiltration removes most of the suspended living bacteria, but it is not effective in removing dissolved organic matter from the water, resulting in high peak levels of bacteria on the walls and in the effluent. The maximum bacterial content of the reactor effluent after ultrafiltration was 1.6 × 104 CFU/cm2 after 22 d. It is therefore necessary to consider the use of the ultrafiltration process in conjunction with other processes to achieve the ultimate goal of controlling microbial contamination in the pipeline network.