AWWA DSS65674

The Halifax Regional Water Commission (HRWC) has documented success in water loss control through adoption of the methodology promoted by the Water Loss Task Force of the International Water Association (IWA). HRWC put the methodology into action in 1999 and formally adopted it as a best practice in April, 2000. By March 31, 2006, HRWC reduced leakage in the distribution system by 34 million liters/day with a corresponding plant output reduction from 168 to 134 million liters/day. The total leakage reduction of 34 million liters/day is reflected in an Infrastructure Leakage Index (ILI) reduction from 9.0 to 3.0 and annual savings of $550,000. In addition to direct savings, the customers of HRWC see increased public health protection (a leaking system has more potential for contamination), less service disruption and reduced property damage, as leaks are now found in a proactive manner through early intervention. Water loss control at HRWC is holistic in nature and benefits greatly from a distribution network that is subdivided into permanent district metered areas (DMAs). The HRWC has over 65 DMAs and a robust supervisory control and data acquisition (SCADA) system. These tools are used in tandem for night flow analysis for leakage assessment and to determine best achievable benchmarks in system flows. A typical DMA incorporates a zone in the distribution system with a maximum pipe length of 30 km, 150 hydrants or approximately 2500 customer connections. Building on the successful installation of DMAs, flow modulated pressure control was installed in a typical sector in Dartmouth to further control and manage leakage. The Dartmouth Central DMA was selected to evaluate advanced pressure management as a leakage management tool for AwwaRF Project 2928, "Leakage Management Technologies". By reducing system pressures during periods of low demand, flow rates through background and active leaks were expected to be reduced. Improved control of system pressures would also reduce or eliminate pressure surges that can occur within the DMA. The HRWC chose the Dartmouth Central DMA for several reasons; the DMA is supplied by two recently constructed in-ground pressure reducing and metering chambers, providing new control valves and accurate metering. Dual supplies into the DMA offered the challenge of modulating two control valves in geographically differing locations, to achieve the desired system pressure in response to the changing demand. Finally, following regular active leakage detection, the minimum night flow was considered to be significantly higher than it should be, providing the opportunity to demonstrate and measure a reduction in real losses through pressure management, and additionally, through advanced pressure management. To be considered successful, reductions in real losses through advanced pressure management had to be achieved without degrading minimum system requirements. Adequate minimum residual pressures had to be maintained during peak hourly flow or maximum day demand plus fire flows. Water quality was also a concern, with possible rapid changes in velocity, flow reversal between supply points or excessive water age. Other concerns included customer complaints from low supply pressure, and a loss of metered sales offsetting the savings gained from reductions in real losses. Includes 3 references, table, figures.