Professional Engineering

The drought may last until Christmas or beyond, according to the Environment Agency, which added 17 counties in the Midlands and South West to its list of afflicted zones last month. 

This extension of the regions affected by drought came in the wake of a hosepipe ban imposed in South East England by seven water authorities, which affects 20 million customers. Before announcing its hosepipe ban in April, Thames Water had run a prominent advertising campaign in the capital calling on citizens to save water. 

The rationale behind the ban is stark and simple: Thames Water has seen below-average rainfall nearly every month in the area it covers over the past two years. This is the driest two-year period since records began in 1884. Rainfall for March, for example, was 43% below the long-term average.

It’s easy to forget that Britain is not a particularly wet nation. Rome experiences more rainfall annually than London. Dr Richard Coulton of Siltbuster Process Solutions says: “The UK is perceived to be a relatively wet country. It’s very wet in the West and North where the population density is relatively small – but it’s reasonably dry in the South and East where most people live.

“There’s an issue of geography and demographics. Most of the water is in the West and as population density has grown in the East the water supplies have become more stressed.” And these supplies have been further stressed by drop-offs in rainfall in certain regions such as the one covered by Thames Water. Hosepipe bans may become more regular occurrences, although the current one is the London utility’s first for six years. 

It’s important not just to focus on domestic consumers’ demand. Some 75% of water consumed in Britain is used by agriculture. Domestic consumers do have a big part to play – in July 2006 Thames Water customers saved 260 million litres thanks to the hosepipe ban. 

But Coulton says: “There’s the deeper underlying issue of how we make better use of water for growing crops. We’ve reached the point where supplies are sufficiently stressed that we need to change our culture on how we handle water. 

“We need to make better use of resources with more recycling. Industry and agriculture should be looking at how we can reuse water and use grey water for irrigation.”

Coulton’s Siltbuster systems can be used speedily to cope with sudden water shortages. He says comparable technologies could typically take three months or more to deploy in the past because they would be built to order. 

“Our philosophy is that if you ring me today you can probably have a piece of equipment tomorrow to meet requirements in terms of separating algae or suspended solids from water,” he says. This means that the technology can be used in agricultural applications quickly when there is, say, a sudden spell of hot weather. 

A typical scenario might be that a farmer collects rainwater in lagoons or reservoirs on their land. In hot weather, algae would grow quickly. Siltbuster systems remove the algae and give the farmer a source of water for irrigation of crops or feeding animals, rather than using the mains, saving money. 

The technology can also process water from algae-ridden rivers and lakes before use in treatment plants or reservoirs. Coulton says: “In industry, you can focus on treating effluent to a standard where it’s suitable for secondary use as grey water, or taking it all the way back through the recovery process where you can feed some of it back in.”

With the onus on utilities to ensure that as much water as possible is saved in the system, other technological developments that could help to combat drought include devices embedded in the water network that aid in reducing bursts and leaks. 

A spin-out company from Southampton University, i2O, has developed a technology that aims to do just that. It has been trialled by all the big water companies in the UK as well as enjoying success overseas. Last year, Severn Trent, Veolia and Yorkshire Water were the first companies to roll it out at home.