Loss In Carrying Capacity of Water Mains due to Encrustation and Biofouling, and Application to Walkerton, Ontario

摘要

Encrustation and biofouling causes loss in carrying capacity of water mains and impacts water quality. Encrustation is a build-up of a slimy orange-brown deposit due to precipitation of calcium, iron and magnesium carbonates. Biofouling is the undesirable accumulation of a microbiological deposits in a biofilm layer. Biofilm accumulation is the result of physical, chemical, and biological processes, which play a major part in the microbial characterization of drinking water quality in distribution networks. In this work, the decrease in pipe diameter and increased pipe roughness are computed as a function of service age of water mains. The method is then applied to the water distribution network in Walkerton, Ontario and the effects of encrustation and biofilm build-up with age and their effects on the hydraulics are investigated. Hydraulic analysis was performed by simulating the flow through the water supply network, assumed to be 100 years old, using EP ANET2. The results indicate that changes in the hydraulic parameters of a network can cause: 1. a change in a flow pattern from reservoirs, 2. water to take a longer time to reach the far end of network, and 3. increased energy cost. It is also concluded that the available empirical model to compute pipe roughness and decrease in pipe diameter after a certain service time cannot be standardized, because of its dependence on the local and transient quality of water from various supply sources.