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.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 2.1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 8 |
| Published : | 09/01/2007 |
