Greywater recycling

31 October 2013

While efforts continue to educate the public to use less water and legislation requires new homes to be designed to reduce water consumption, newly launched technology is now enabling users to make more use of their water supply without any form of rationing or disruption to their existing lifestyle.

Designed for use in residential, commercial and municipal properties, it's a water-saving solution that enables the collection of waste-water (so- called 'greywater') from baths, showers and in some cases sinks, and then recycles it for use in flushing toilets.
 
Suitable for retrofit as well as new-build, such greywater reuse systems reduce the mains water needs of a house or building by up to 30 per cent and are designed to be easy to install and use. A revised plumbing set-up takes all waste-water from baths and showers, redirecting it through a filtration unit where it is treated with a disinfectant.

This treated water is collected in a tank and piped on, as required, to supply all the flushing water needs for multiple toilets in the building. Once fitted, the water-saving potential is compelling: based on daily usage figures of 150 litres of water per person (figures from the UK organisation, Waterwise), a family of five will typically save around 80,000 litres of water each year, the equivalent of over 1,000 baths, over 1,600 loads of washing or about 328,000 cups of tea.

An optional feature of these systems ingeniously allows heat to be extracted from the building's greywater, before it's recycled, so it can be fed back into the central heating system. Fitting a heat exchanger to the greywater reuse link between the bath, shower and toilet flush recaptures the heat energy from the bathing water, feeding it back into the building's hot water system, and reducing fuel bills as well as enabling a twofold reduction in CO2 emissions.

As most buildings in the UK have only one water supply, we have, until now, had little option but to put up with the confused logic of using drinking quality water to flush our toilets. With increasing pressure on our water supply from droughts, greywater reuse technology has the potential to make a big contribution to reducing water demand across the UK.

The technology's relevance and appeal stretches beyond those with an environmental conscience to developers faced with restrictions on water supply to a project and for householders, commercial and municipal buildings which pay for metered water. In metered areas, end users benefit from significant annual savings on their water bills.

Greywater reuse overcomes the problems associated with other demand management solutions such as rainwater harvesting. In the case of greywater, supply is predictable and constant as it is not dependent upon the weather, unlike harvesting where available rainwater is used to augment the water supply to a building.  Harvesting also requires large-scale tanks and long storage times to cope with seasonal variations, both of which create further problems of cost and water quality.

Should demand suddenly increase, the greywater solution scales accordingly - more baths and showers means more water for toilet flushing. There are other benefits too: greywater has a consistent level of acidity and, unlike rainwater, it is always just above room temperature - avoiding the formation of condensation on toilet cisterns and cooling of the room. 

We're seeing an increasing number of projects, even at the point of breaking ground, switching from rainwater harvesting to greywater reuse technology to deliver a more appropriate and cost-effective solution that meets the flushing needs of a building or new housing development. As well as offering more consistent water quality, the significantly lower capital associated with specifying and installing greywater reuse technology seem to be very compelling drivers.

Greywater reuse systems can obviate the need for fitting water rationing and flow restricting technology such as low-flow showers or low-flush toilets.  Where these measures are employed residents experience disappointingly low flow rates from showers and the potential for blocked waste pipes. Research has shown that using low-flush toilets may not provide sufficient movement in small pipes to carry away solids, leading to blockages and flooding. 

From a householder's point of view, the greywater reuse solution means they do not need to make any lifestyle or behavioural changes.  Even though water consumption is reduced, "bathing comfort" is always maintained and adequate water is available to clear drains when flushing.

As well as private homes, commercial, municipal and residential builds can all benefit from these systems where they can save up to a third of the water used per day. They are increasingly attractive to municipal and public buildings such as schools and care homes as well as to residential developers.

Using recycled greywater, as opposed to high-quality drinking water, leads to a reduction in the carbon footprint of a property. It can contribute to a project's environmental sustainability and complies with specific planning conditions as well as key standards - in particular the Code for Sustainable Homes - with benefits for the project and the wider community. As such, the client can make a healthy profit, without any capital outlay.

Stephen Bates is chief executive at Reaqua Systems