The water margin
Having fresh water piped in and waste taken away again has a financial bearing on all businesses, which is why more recycling schemes, that harvest rainfall and put to use the gallons that usually drain away, are coming on stream
by Maureen Moody
Businesses in England and Wales use enough water to fill over 2.5 million Olympic-size swimming pools every year, says Envirowise, the government’s business environmental impact advisor. And we all know that despite the UK’s rainy reputation, water is a finite resource. There is a financial cost too — businesses pay to receive water and have the waste taken away. Any means of getting a free supply and reducing waste is a good thing, and there are two good ways of achieving just that — rainwater harvesting and greywater reuse.
Each year in the UK around 400 rainwater harvesting systems are installed, according to the UK Rainwater Harvesting Association. And for many local authorities and developers these systems are an essential part of a frugal approach to natural resources. At Ransomwood Business Park in Sherwood Forest the objective was office accommodation which performed to the highest environmental standards. As the site develops each new building features the latest green technology. The most recent, a 20,000 sq ft office facility, designed by Henry Mein Partnership, includes a rainwater harvesting system from Stormsaver. This captures rainfall from the roof area storing it in a 20,000 litre underground tank. The estimate is an annual saving of £1,000 on mains water, and a 10-year payback period.
Envirowise reports even greater success with some rainwater systems which, when combined with water-saving devices save 40 per cent on water bills and pay for themselves within three years. And, because rainwater is soft, hand washing needs less soap and laundry and vehicle washing need less detergent. As Ross Mather, custodian of frameworks at Interserve remarks, it also reduces demand on rivers and groundwater. “Over-extraction has been shown to damage river and wetland wildlife, particularly in the heavily-populated south-east. Harvesting can also cut flood risk by reducing storm water run-off, and lower carbon emissions through less reliance on mains water.”
In fact Mather says it’s the combination of rising water prices and growing environmental concerns that has made rainwater harvesting an attractive alternative to mains water. “Our clients are increasingly enquiring about rainwater harvesting and we’d expect this trend to continue. Harvesting can involve a reasonable outlay upfront, but this investment is often recouped within four years. And with water companies aiming to hike prices by 9 per cent above inflation between 2010 and 2015, there are compelling reasons to switch.”
HMP Garth is an example. This training prison which Interserve extended in 2007 uses rainwater to flush toilets in cells. “Initial capital outlay was fairly substantial,” explains Mather, “but around 1,500 cu m per year is recovered and reused, there is a reasonable payback period, and the building earns green credentials and Breeam points.”
Many systems are retrofit but it’s cheaper to include rainwater systems in new-build projects while the site drainage system is under construction. Retrofit systems need additional pipework and drainage, and backflow protection to avoid accidental push-back into the mains, advises the UKRHA.
But these are straightforward systems. Rainwater collected from the roof is taken through sealed gullies to a pre-tank filter. This removes larger debris such as leaves, allowing the water to pass into a collection tank. If the collection tank is at ground level a submersible pump then delivers the water on demand, or into a header tank which is also fed by the mains. But because water is heavy siting the tank(s) will be an important consideration.
The 20,000 litre rainwater collection tank at Eastgate shopping centre in Essex sits on the first floor, and as building services manager Ian Clark points out, “20,000 litres of water weighs 20 tonnes.” New toilets were constructed in 2006 with the rainwater system installed simultaneously as the primary source of flushing water. Clark says: “The environmental potential was the main driver, we had a large roof area draining in the right direction, and thirdly we had space for the tank. But we had to look at the floor’s load-bearing capacity and we ended up putting some reinforcing steel work in to make sure we weren’t going to dump the water on the floor below.”
It’s also possible to capture and recycle water from wash-hand basins, showers, baths and laundries, but it will contain different contaminants — this is known as greywater recycling. In a collection tank soap, detergents and other impurities are removed by sedimentation and physical filters. Aerobic treatment then enables bacteria to break down biodegradable substances, and an ultrafiltration membrane removes remaining particles, viruses and bacteria. The resultant clean water is stored in a final tank.
Claire Sweeney, water manager at Envirowise, says grey water systems have not been as widely taken up in commercial and public buildings as in domestic dwellings. She puts this down to cost and concerns about water quality. “It usually costs over £2,000 for installation and equipment and there are ongoing running and maintenance and replacement costs, so payback is likely to be more than 10 years.”
But more systems are coming on stream. “Grey water systems are frequently specified and our environmental engineer certainly considers them for projects at design stage,” says architect Sarah Marshall at McDowell and Benedetti. “Everybody today is conscious of the need to become more environmentally aware, and legislation is reinforcing this.”
One of Marshall’s projects which incorporates a grey water system is the Springboard Business Centre at Stokesley in North Yorkshire. The local authority building, which incorporates several aspects of environmental engineering, has won four awards. One of the Springboard tenants, BIFM member Mark Cooper, MD of Anabas, says: “One of the reasons we chose the building was because of the water recycling. Grey water is ideal for systems that are not critical and don’t need drinking water. Let’s face it, water is a scarce resource, and using drinking water for flushing toilets is not sensible.”
A persuading factor is the Enhanced Capital Allowance (ECA) scheme. This enables businesses to claim 100 per cent first year capital allowances on investments in water-saving technologies and products.
Typical office buildings are good candidates for grey water reuse. But hotels, care homes, apartment blocks, leisure centres and businesses involved in food preparation or industrial processing can stand to gain even greater benefit. And a company that has done so is Cambridgeshire food manufacturer G’s Fresh Beetroot. G’s efficient membrane filtration system is designed to treat and recycle around ?70 per cent of the waste water from the beetroot processing. It comprises a pre-treatment stage which includes initial screening of the wastewater and primary settlement. At its core is an ultra-filtration membrane, and a post-treatment reverse osmosis unit ensures the desired quality for reuse applications. Following treatment, the water is ready to be reused and is circulated back to the factory while the effluent reject is discharged to sewer at a significantly reduced flow rate and cost.
Whether we think the UK is too wet or too dry, and whether we choose rainwater or grey water, we can save money and earn ourselves a pat on the back by helping to manage this precious resource.
Case study: Reliance
Reliance used rainwater harvesting systems within the police headquarters for Gloucestershire Constabulary and at North Kent Police Station, supplying water for flushing toilets and urinals. The company is a partner in the PFI projects that constructed both buildings and also provides full FM services. Alex Boddy, PFI operations director at Reliance, says: “The systems are robust and require minimal maintenance intervention for the pumping and UV disinfection system. The one in Gloucestershire has been a huge success and is largely able to feed the 50 toilets and urinals on the site from the grey water supply. In no small way this is due to the high levels of rainfall that are experienced in the area, but this is supplemented when required by mains supply. The location in Kent is not so wet and therefore the rainwater tank has to be supplemented from an external supply more regularly.”
