HOW GETTING A BETTER VIEW OF WATER CONSUMPTION CAN HELP IMPROVE REVENUE RECOVERY
For water utilities, getting more information on non revenue water offers a great chance to improve fi nancial viability and boost the immediate and long term availability of water supplies. Alan Hunt of ABB’s Measurement & Analytics business looks at how high accuracy fl owmeters can make sure water gets to the right users and water losses are minimized.
Research by the International Water Association (IWA) divides the total volume of water supplied to a network into revenue and non revenue water (NRW), the latter being the amount of water that essentially goes missing from a pipeline and cannot be accounted for. This research shows that 24 percent of countries have a rate of NRW greater than 40 percent.
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While water companies worldwide have done a good job in improving their supply side management, there is a growing recognition that sustainability can only be achieved through a robust understanding of the demand being placed on supplies.
When coupled with the issues posed by an ever more unpredictable weather system caused by climate change, the challenges of ensuring a sustainable supply of water for all those who need it call for radical changes in the way that water is collected, distributed and reused.
As these challenges bite, the answer is to make sure that as much water as possible is legitimately consumed within water distribution systems, with as little being lost in transit as possible. While signifi cant advances have been made in reducing water losses in recent years in various parts of the world, a signifi cant amount of the clean water that utilities produce and distribute continues to be unaccounted for, either through real losses caused by leaks and burst pipes, inaccurate fl ow measurements or unauthorised extractions from pipelines.
Why every drop matters
As every lost drop represents a loss of revenue, there is a clear need to understand where and how it is being lost so that action can be taken.
These losses cause a number of problems. One of the chief issues is the waste of energy and other resources needed to replace the lost water. Every drop lost is another drop that must be processed and pumped again, using more dosing agent and energy and adding to the emissions caused by an already energy intensive industry. Another issue is the lost revenue. The World Bank has estimated that the global cost of non revenue water to utilities is around US$141 billion per year. As well as the effect on operating profi ts and the viability of the business, lost revenue reduces the capital available to invest in improving water networks.
A fi nal question affects the validity of the data used to gather these fi gures in the fi rst place. If the instruments used to gather the data are not accurate and underestimate the legitimate consumption, then in many places the overall NRW estimate may be grossly overstated.
A number of methods exist to tackle the challenge of calculating NRW, with pressure management, minimum night fl ow analysis and the IWA’s water balance methodology being chief among them.
The water balance method is widely accepted. Using it requires utilities to establish an accurate estimate of water balance, the ratio between actual loss from leaks and other physical causes and the apparent losses from human errors such as billing mistakes, inaccurate reading of manual meters or unauthorized extraction. The process of estimating the water balance components can never be exact, as it will contain uncertainties arising from factors such as inaccurate measurements and unreliable data.
Measure at night for a real picture of losses
One method widely used to get an accurate estimate of losses is through the measurement of minimum night time fl ow. At
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night, water consumption is at a minimum and pressure is high, so any losses will represent a large part of the fl ow entering the system. Using data from minimum night time fl ow measurements gives water companies the chance to accurately evaluate net night fl ow (NNF), an estimate of volume of real losses during the minimum night fl ow (MNF) period. The NNF is mostly composed of real losses from the distribution network and service connection piping between the water mains and customer meter. However, it may also include leakage on the customer side of the meter and consumption either legitimately or through unauthorized connections.
Leading water utilities have confi gured networks to continuously monitor night fl ows using district meters measuring fl ow and pressure. Flow and pressure data is recorded on meters and regularly transferred to a SCADA system. Data is analyzed to confi rm its validity and used to derive continuous night fl ow in each District Metering Area (DMA).
The night fl ow into a DMA consists of the following components:
• Customer night use, made up of exceptional, non household and household night use
• Reported burst losses, made up of bursts on supply pipes, communications pipes and mains
• Unreported burst losses made up of bursts on supply pipes, communications pipes and mains
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