Water lost is water wasted
Water loss is a key issue for water management. David Field, marketing manager for HWM and a member of the International Water Association's Water Loss Task Force, explains the latest initiatives and technologyWater loss management is of fundamental importance in the application of efficient and effective strategies for reducing water losses from distribution networks.
In recent years, the International Water Association's Water Loss Task Force has made several significant steps towards its goal to provide leadership in the field of water loss management through effective and sustainable international best practices.
The group's Water Balance and Performance Indicators methodology, used for the quantitative monitoring of water use and water loss in drinking water systems, has already been adopted as the basis for many global water utilities.
Members of the task force have also assisted the World Bank Institute in producing a series of training manuals designed for use in developing nations, where making the most of scarce existing water resources can be especially valuable.
Currently, the main initiatives being worked on are:
- Acoustic Noise Principles and Applications
- Repair of Replace Dilemma for Services and Mains
- Apparent Losses Principles and Applications
- Training on Water Loss Management
- Target Setting and Strategy for Water Loss Management
- Pressure management
- Decreased response time for fixing leaks
- Active leakage control
- Improving infrastructure conditions
Although the actual physical leak repair and maintenance of pipe infrastructure are two important factors in water loss reduction, pressure control and leak detection are arguably easier to improve effectively and have greater immediate impacts on efficiency of water supply.
The turnaround time between a leak occurring, its detection, location and repair is crucial to reducing losses. More time equals more water lost, with a direct, linear relationship - although an unattended leak has the potential to get worse, which then could turn it into an exponential equation.
Pressure management is important for several key reasons: with higher pressure, more water is lost per time period through a leak or break of any given size. Higher pressure also leads to a higher frequency of break and leaks, as the pipes and fittings are being put under greater stress.
Calculating the optimum system pressure for any given time is relatively easy once flow and pressure data have been gathered. However, to date the problem has been in physically adjusting it to the optimum level.
The good news is that equipment is now available that can help: pressure reducing valves (PRV) and PRV controllers can be fitted to limit the pressure of water supplied to a zone at different times according to a pre-programmed plan.
Some PRV controllers even allow remote programming for optimisation control, making the operation even easier.
This also allows for the potential to have an automated system which uses remotely gathered flow (and even noise-based leak) data to programme the unit on the fly, which would make the basic infrastructure optimise its own efficiency at any given time.
Leak detection follows the principle of LLP - locate, localise, pinpoint. The installation of dataloggers at points throughout the water network, dividing it up into district metering areas (DMAs), and then analysis of the night flow through each area, relative to total water flow at supply, is the established method of detecting and locating unreported leaks.
DMAs with unexpectedly low flow rates are then targeted by leak localisation teams, who will carry out acoustic surveys of the area. Noise loggers, which listen out for and record possible sounds of leakage, are affixed to the pipes at set intervals.
These can be permanent or temporary deployments, as they are typically attached externally by magnet so installation is usually quick and easily reversible. Leak detection teams would then patrol the area, picking up readings from each logger in order to find the local area of the leak.
A faster process
Technological advances have been made which make this process quicker. Firstly, with certain noise loggers, came local wireless transmission capability. Leak detection teams could simply drive or walk past in the vicinity of a logger, and have the data transmitted to a PDA or similar handheld device.
The next step is already approaching rapidly. Sophisticated noise loggers with long-range transmitters can be installed in a permanent network, to automatically record and collate noise logging data and send it straight to a remote location - typically a personal computer.
This creates an active system that is always listening out for any leak within its perimeter; it can be set to send the acoustic data both on a regular basis (daily perhaps), and also immediately when it detects that certain programmed parameters have been met which would indicate a leak.
With immediate detection and location of leaks, time is saved and resources are freed up to repair the leak with maximum expediency.
Once a leak has been located, it needs to be localised. To do this, leak noise correlators are employed. These typically use two or three listening outstations positioned along the pipe in question, and a centralised device to correlate the data gathered to quickly provide a precise location from only one deployment.
Now there are digital correlator systems which make the process even easier. In the past, correlation was highly dependent upon the quality and veracity of information provided to the system - and in many cases the essential variables could be unknown.
Wireless connectivity, the integration of presets for pipe and flow specific details, the use of a three-outstation system for subjective velocity checks, and automated digital data processing and graphing all reduce the onus on the operator and provide the capability for even faster and more accurate leak localisation (even bordering on pinpointing).
Finally, the leak needs to be confirmed and/or pinpointed, and this is still largely done with the use of listening sticks - albeit electronic ones now.
Noise amplification, automatic or manual filtering, minimum noise level profiling and visual analytical displays all speed up and ease the process from the days of literally putting one's ear to the ground.
These latest developments always work to reduce the overall turnaround time, make the job easier, and improve efficiency by decreasing the incidence of costly dry holes.
Training and information sharing at all levels of service is essential to achieving success, and personal experience is still invaluable to a leakage engineer. But the use of up-to-date technology and methodology can ease the entire process. When time and resources have gone into building an effective system - any system - those investments are saved many times over when the system is implemented.
This is particularly evident in largely automated (typically computerised) systems, where the burden of processing is placed with devices specially designed to do them. By separating and specialising responsibilities not just between people but also by sharing them with technological systems, each aspect becomes more efficient - and the whole benefits greatly as a result.
This article was prepared with the aid of information from several sources, including Bambos Charalambous Chair WLTF and Stuart Hamilton Secretary WLTF.