The Renewable Energy Centre discusses the future of water recycling

May 16, 2007

With ever increasing temperatures, less rainfall and a summer hosepipe ban a likely possibility this year, The Renewable Energy Centre discusses water recycling and how useful it will be to us in the future?

Last month the UK saw the hottest April since records began in 1840 with an average temperature of 11.2C (52.16F), breaking the previous record set in 1865 of 10.6C (51.08F).

It was also the driest April in 27 years with only 25.6mm of rain, and recent reports by the MET office show that although they are unable to accurately predict the rainfall prospect over the coming months they do expect a particularly dry summer.

The Environment Agency organisation recently announced that although water reserve levels are above average after a wet winter, the prospect of dry weather means there could be real chance of water restrictions again this year.

The UK Environment Minister Ian Pearson last month highlighted that Britain’s National Water Strategy was last revised 5 years ago and must be updated to adapt the country to a changing climate.

He said “Our previous assumptions about an old wet Britain needs to change. The new Water Strategy, to be published later this year must go beyond simply “predicting and providing” and must factor in everything from greenhouse gas emissions from water recycling to water efficiency”.

UK household water consumption
UK households play a huge part in the nation’s water consumption and on average each person consumes 160 litres of water per day, for cooking, washing and drinking. This is 30 litres a day more than the EU average of 130.

Richard Simmons from The Renewable Energy Centre said “We must raise awareness to the fact that saving water is not just necessary in periods of drought when water restrictions are imposed. River levels are normal at the moment, but even the small amount of dry weather we have just had has already caused the levels to drop”.

He continued “The dry spells will only become more frequent due to climate change so we must learn how to adjust our habits. It is vital that consumers realise that the first step should always be to consider their own water usage and look for ways they can reduce the amount of grey water they produce. Following that, practices such as rainwater harvesting and grey water recycling should be considered”.

What is Grey Water?
The Renewable Energy Centre defines ‘Grey Water’ as non industrial waste water generated from domestic processes such as washing dishes, bathing and laundry. It’s name comes from its status as being neither as fresh as potable water but not as heavily polluted as ‘Black Water’ generated from toilet waste which often has chemical and biological contaminants present.

Grey water is most useful and hygienic when it can be used immediately and if it is stored for any length of time without specialist treatment it will begin to smell. This is due to the fact that it will usually contain bacteria and combined with an often warm temperature this is an idea situation for pathogens to multiply. Although there are treatment systems available, they are designed for industrial use and the negative environmental impact they have will usually far outweigh the benefits, due to the energy consumption and chemicals involved.

Water recycling for garden use
Using fresh potable water to the standard of drinking water for garden irrigation is wholly unnecessary unless it is for edible crops, yet this is what most UK households will use. In this instance grey water is more than adequate, particularly as it can be used straight away without having to be stored.

Washing machines are a useful source of grey water as the huge amount of rinse water (approximately 40-60L per wash) used will dilute detergents to the lowest level. Many detergents also have high levels of phosphates which have nutritional value to many plants.

Using an ‘Ecologically friendly’ detergent is also useful to consider as they are free of synthetic materials, and as they are low in sodium they should have the least adverse effects on soil. Water from the bath and shower is generally useful as shampoos etc are fairly mild, well diluted and not harmful to the soil.

Although soil is very effective at filtering out many unwanted contaminants, most grey water produced in the kitchen containing normal soap or detergents, salt, grease and chemicals does have the potential to cause soils to disperse and lose their structure. However, where this type of water is used for short periods, usually only during summer months, any damage is unlikely.

When installing a grey water irrigation system it is recommended that it is installed under the ground as the recycled water may contain pathogens and be unsuitable for spraying around the garden. This is called sub-surface irrigation and is the most efficient way to water plants.

Water recycling for WC’s
Typically about a third of household water is used for flushing the WC and again this is an unnecessary waste of expensively processed potable water. In some cases it is possible for grey water to be collected in a household-scale reuse system and treated to a standard suitable for WC flushing.

However, it is important to remember that untreated grey water is not suitable for use in toilet flushing as it can start to smell after a few hours and the toilet bowl can become stained. Lightly treated grey water should be used; however it may not make economical sense to do. In this case it is usually more suitable for homeowners to consider rainwater harvesting in a water butt for flushing toilets. More information on Rainwater Harvesting can be found at

The future
Grey Water recycling is still a fairly undeveloped technology, and as such its efficiency may improve with time. Advances in water treatment technology may in the future allow heavily contaminated water like grey water to be cleaned to suitable standards for reuse fairly cheaply, but the environmental impacts might still be high and only justifiable on an industrial scale.

Shortages of water in the UK would have to become much more severe to justify domestic grey water systems in UK households. It is important therefore that homeowners are informed how to conserve and recycle water not only in times of water restrictions but in the ongoing plan to change the effects of climate change.

For more information:
Angela Gallacher (Head of Press & Marketing)
1 Alpha House, Farmer Ward Road,
Warwickshire, CV8 2ED
Telephone: 0044 1926 865835

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