Water & Wastewater Treatment Magazine
Issue link: https://read.utilityweek.co.uk/i/863631
• How o en water supplies are interrupted (and for how many customers, and how long) is one of the central measures of water company performance. Most water companies have an 'SI3' threshold, meaning that any interruption longer than 3 hours must be logged and counted against its annual targets. • There is also a 'SI12' threshold for interruptions lasting more than 12 hours. This is significant because water companies are legally obliged to provide an alternative supply of water, such as bottled water or a bowser in the street, a er 12 hours of interruption. • Supply interruptions are measured by the length of time water is unavailable from customer taps, so providing alternative water in the form of bottles or bowsers does not help water companies when it comes to these performance figures. However, pumping water into the network via the AiS system eliminates the interruption to those properties for these purposes. • In England and Wales in 2016-7, the average supply interruption was 11 minutes per property per year. Water company performance varied widely against this: Northumbrian Water was the best performing of the major WASCs with just 2 minutes 26 secs of interruptions on average. The worst was United Utilities (13 minutes 33 secs). Thames Water was better than average, with 7 minutes 12 secs of disruption. • Water companies typically spend a large proportion of their alternative water supply budget on bottled water, which costs them around 40p a litre when the cost of transport is included. Any system that allows them to use their own water – where the cost of water is less than 1p a litre – is therefore a big saving. Another factor is that water companies typically overestimate the amount of bottled water they need for an incident, resulting in wastage and unnecessary cost. • FactFile: Supply InterruptIonS The Works: alternative water www.wwtonline.co.uk | WWT | SEPTEMBER 2017 | 21 • WateR cOMPaNY VieW "It's a flexible solution... much better than giving out bottled water." MErIEl JoNES, ComplIanCe lead, thameS Water "Ever since I started working in our business resilience and security department, we'd always talked about having mini-reservoirs for customers: simple, alternative water that we could use for a few streets, that's easy to get around, that's cheap and isn't too complicated. "I came across these things called Arlington tanks, and felt they could be the answer, so around two years ago, we went up to Arlington to talk about the different things we could do with them. Because they are quite a small, innovative company with an engineering background, they were open to discus- sions. Could we make them pressurised? Add a pump? What about putting a weight on top? "In six months, they had come back with a proto- type with a pump; then we went through a couple of iterations, before ending with what we've got now. "It's a flexible solution. You can put the tanks in series, and have any number of them – it just depends on how long you want to use it for and how many times you are willing to top it up. We have done it for small shuts of up to about 400 houses, which is fine, especially during the day when people aren't using a huge amount of water. You can use it for about six or seven hours, then refill, and carry on like that for days if needed. "You can also have more than one pump – the pumps have Bluetooth technology where they talk to each other, to keep a continual pressure. "The customer doesn't see any change. When we first did the original trials with it, we had quite a few customers who came out and said, 'I thought you were switching my water off?' They didn't notice any change in pressure, or any spluttering, to them it was a continual service. It's very quiet as well - especially when you use electric generators - so most customers don't even hear it. "So far, we have tended to use them for emergen- cy, unplanned events, but we are now trying to build the planned work up as well. It's better than giving out bottled water, which is not very green, doesn't help with our SI4 or SI2 [regulatory targets], and from the customer's perspective, is never the same as get- ting water through your tap." Northumbrian Southern Thames Yorkshire Severn Trent Anglian Welsh Wessex South West United Utilities 02:26 07:00 07:12 09:47 10:08 11:43 12:09 12:48 13:16 13:33 Average annual mins lost to supply interruptions per property served 2016-7 (stats: Discover Water)