Greywater recycling hangs in the financial balance
Greywater recycling systems, which use water from baths, showers and hand-basins to flush WCs, are being tested in a number of projects across the UK. Peter Minting examines their potential for use in residential developments.
The systems used were supplied by Water Dynamics, manufacturer of the Well Butt system. The Well Butt system collects greywater from baths and showers in a 180 litre garden tank. The water is disinfected, passed through a simple filter and pumped to a storage tank in the loft before being re-used to flush WCs.
Mr Howarth said: "The objective was not to evaluate a particular manufacturer's unit." But a number of teething problems were encountered in the study, including: l occasional pump failure, leaving the systems to run on mains water; l filter clogging, resulting in loss of greywater by overflow to sewer; and l disinfection blocks dissolving too fast, resulting in an unexpected switch to mains supply.
Water Dynamics has now made a number of modifications. For example, a foam layer has been removed from the wire mesh filter to improve flow, and instead of chlorine, bromine blocks are being used for disinfection because they dissolve more slowly. Fortunately, as performance depends largely on the frequency of maintenance and the quality of waste inputs, diligent householders can expect to avoid most of the above problems and reduce water use by about a third.
However, significant money savings are unlikely in the short-term, especially on retrofit applications, according to Mr Howarth who said: "Our results show that unless you are prepared to do frequent maintenance, the savings made are unlikely to cover your annual maintenance charges. The systems alone cost around £1000 and the extra plumbing for a retrofit costs another £250." He added: "In economic terms, for sales of such units to be widespread, there needs to be a sharp fall in the price of the units and more confidence in the reliability of the systems." With an average water bill of £250, payback will take at least 12 years. Despite the apparent lack of a short-term financial incentive, water companies have been quick to assess long-term benefits by sponsoring greywater recycling projects at new housing developments.
Essex & Suffolk Water, for example, is working with Bovis Homes, BRE, and the Plume Housing Association at the Elms Farm development in Heybridge, Essex. Of 37 properties at Elms Farm, three have now been built with Water Dynamics' system, 12 have been fitted with water efficient appliances, such as low volume flow showers and 6-litre flush WCs, while the remaining 15 are being studied as controls.
Martin Shouler, senior scientist with BRE, who is responsible for monitoring performance at the Elms Farm site said: "The results of this study will not be available for another year, but we are hoping for savings of up to 30 per cent."
Many companies are not directly sponsoring schemes, but are offering to acting in an advisory capacity. South West Water is working with Devon and Cornwall Housing Association to assess the feasibility of a seven house project in Perranporth, Cornwall. South West¹s water conservation manager Brian Hooper said: "There are a number of issues to be resolved concerning greywater recycling, including return to sewer allowance. In the south west, this is particularly important, as the fixed sewer charge is around twice that of the actual water charge. With greywater recycling, adjustments to the charge would be necessary if savings of 30 per cent were achieved."
The majority of water companies are now involved in educational activities to inform the public about the cost-saving potential of greywater recycling. For example, Wessex Water sponsored the greywater recycling system at the Eco-Home and Garden in the Bristol CREATE centre, and Thames Water is sponsoring a large system for the Millennium Dome. The Millennium Dome system is to use treated water from 280 washbasins, along with treated rain and groundwater, to flush 400 WCs and 170 urinals.
Others discount infrastructure charges for new developments with greywater pilot schemes, such as Dwr Cymru, South Staffordshire Water and Folkestone and Dover Water Services. Steve Robinson, chief engineer with Folkestone and Dover said: "So far, none of the manufacturers have been able to persuade a developer to take this offer up."
Despite such inertia, some developers have had the confidence to offer greywater recycling to private customers. Sarah Davies of Crest Homes, who is working with Thames Water and Three Valleys Water to save water at The Pavilions development in Shenley, Hertfordshire, said: 2We have tried the Water Dynamics system in our showhouse, and the trials have proved very positive. Plans are in now place to make the system a standard feature in some of the development's smaller houses. Next month, we will be building six more houses with the same system."
Mr Paul Williams, managing director of Water Dynamics said: "We have sold at least 50 units to the self-build market. There will be a demand, because we know people consider water efficiency an important factor when choosing a home." Peter Casey of Gleeson Homes provided some evidence in Mr William's favour: "Water efficiency was rated a very important factor among potential home-buyers in our latest survey 62 per cent of potential house-buyers said they would pay more for a home with water saving features that offered long-term cost savings."
Most blackwater systems are either too big or expensive for single houses in the UK, because further treatment is required, such as membrane filtration, biological breakdown and UV disinfection.
However, a blackwater treatment system would be a logical choice for a central plant on a large housing estate, with the potential to cut sewerage allowances on water bills by up to 95 per cent.
Dr Steve Mustow, head of the Centre for Construction Ecology at the Building Services Research and Information Association (BSRIA) said: "You do not get the same economies of scale with single house systems that you can get with houses on a network with effluent treated all in one place." And Barry Holden, technical manager at Anglian Water¹s Innovation Unit said: "It would be fair to say our current leaning is towards large scale projects, mainly for economic reasons."
Anglian Water¹s Innovation Unit is now involved in a number of research projects, from greywater recycling for single houses, to large scale blackwater recycling for housing estates. When released, the results of Anglian Water¹s latest blackwater project will be of particular interest to developers working on Garden City 21, a proposed 10,000 home development west of the A1(M) near Stevenage.
Hertfordshire County Council planning officer Anna Burgess said: "We need to know exactly how many houses there will be before we can say which recycling system will be viable. So far, the council has only committed to building 3,600 of the homes, by 2011, and these plans are subject to appeal."
Nevertheless, Dr Mustow said: "A 3,600 house development would probably have potential for a blackwater system. One issue that does need to be resolved is public acceptability, in terms of system choice. Blackwater systems save a great deal more water, but they may not be accepted as readily as greywater systems."
Water quality standards for recycled water use in the home are still under review. At present, there are no specific standards for greywater. Dr Mustow said: "Our report to the Drinking Water Inspectorate on the use of greywater and rainwater in the home could be seen as a Œbest practice' guide, and for safety reasons, we have suggested that zero coliforms should be found in greywater used for toilet flushing, with less strict levels for appearance and odour." Mr Peter Williams, chairman of Water Dynamics, emphasized: "Our system would have no problem at all meeting such standards."