Concerns about falling fresh water resources in Britain have prompted water and wastewater companies to consider investing more in sustainable technologies to help tackle future droughts and ensure reliable supplies of good quality drinking water in the future.

Global warming, poor water management and the public's nonchalant attitude to consumption are all blamed for growing fears that the UK's fresh water supply is drying up. 

Previously, the answer might have been to build more reservoirs, but hikes in land prices, particularly in areas of the country most in need of extra resources, have put this option beyond the reach of most commercial water companies.

Alternative methods of clean water production are plentiful, but none is without financial, ethical or practical limitations.  The UK has learnt a great deal from countries where swelling populations and drying climates are exacerbating the problem of falling water supplies.  British engineers are closely involved in the development of new water treatment technologies overseas and closer to home where trials of these methods are taking shape.

Recycling effluent

Recycling effluent is not a new concept in water management.  Water-scarce countries like Australia and Mexico are already using treated sewage, mainly for irrigation.  This is a far less controversial and workable way to recycle wastewater.

In drought-hit Victoria, Australia, Earth Tech has delivered the Campaspe Water Reclamation Scheme in a public/private partnership with the local water authority.  Launched in May 2005, the $30million scheme is being used to treat 100% of the wastewater generated by a community in the town of Echua to supplement existing irrigation on privately owned farms.

Recycling effluent for human consumption means overcoming major psychological and cultural barriers.  The technology to do this already exists and its effectiveness has been proven; convincing the public that it's a safe and healthy option is a far more difficult task.  But treating wastewater to produce drinking water is by no means new to the UK.  In most areas of Britain, clean drinking water is sourced from rivers into which treated effluent has been discharged from sewage works.  The process involves clarifying, filtering and disinfecting sewage before the treated water is discharged into rivers to be extracted and treated again using normal purification processes.

The ICE's proposals would effectively remove the river stage of the process from the equation, in turn saving sewage and water companies the cost of pumping and re-treating.  Treated sewage is usually crystal clear before being pumped into rivers where it picks up mud and other sediments that add to the cost and time involved in treating to domestic standards. 

The new proposals would require major new water treatment facilities to be built alongside sewage works. The cost of this is proving a source of debate among water and sewage companies and public funding watchdogs.  Hundreds of millions of pounds have already been pumped into advanced treatment technologies for sewage works and treatment companies are understandably reluctant to inject large amounts of extra capital into expensive drinking water infrastructures. 

Desalination

Significant funding is also being invested globally in technologies such as desalination to treat sea water and brackish water for domestic and industrial use.

Desalination plants are widespread in places such as The Canary Islands, Israel and Saudi Arabia; Florida and California are also venturing down these roads.

Desalination is probably the most viable large scale alternative to effluent reuse in the UK.  The process uses reverse osmosis to draw salt from seas and estuaries, leaving clean water fit for drinking.  It works by pushing salt water through a series of ultra-fine membranes which filter out the sodium and chloride ions.

However, desalination does have considerable economic and environmental drawbacks.  The process consumes a lot of energy, creating greenhouse gases which could exacerbate the problem of climate change and drought.  One solution would be to employ energy recovery, which means designing the plant to produce its own power by converting energy created in the desalination process.  In one example of environmentally-friendly design, Perth, Australia, has just completed a desalination project powered by greenhouse neutral energy from a wind farm constructed close to the plant

Another concern is the potential for desalination plants to disrupt seawater habitats and cause pollution from the high salt levels in the wastewater pumped back out to sea.  The environmental impact of constructing major plants like these also have to be taken into consideration, particularly if long pipes are needed to pump seawater into the plant and to distribute treated water. 

Conservation

Using tighter measures to conserve the UK's natural water resources must be the priority for the water industry and government.  Calls for the widespread introduction of domestic water meters and repair and replacement works to leaking pipe networks are expected to gather pace in the coming months as the Environment Agency and OFFWAT prepare to clamp down on water wastage in line with the industry's next five-year performance plan which come into force in 2010.  These measures must go hand in hand with emerging technologies like effluent conversion and desalination if the water industry is to improve efficiency and stand up to public scrutiny.

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