Looking after the grey matter
Supplier of grey and rainwater-recycling systems Water Dynamics looks into the problem of overcoming resistance to grey-water use and alternative methods of water conservation
As a nation we have become water guzzlers and the problem is likely to grow. Between 1989 and 1991, which were not particularly dry years, 178 drought orders were issued. But even without drought, there would be cause for worry. In the UK, household water consumption has risen by 70% over the last thirty years, yet we still regard water as a cheap, abundant commodity.
In January 1992, the United Nations held a world water conference in Dublin which tried to promote water conservation, prompting various governments, including ours, to act.
The Water Supply Regulations in England and Wales and equivalent byelaws have put in place some simple and practical water conservation measures. All newly- installed WCs must use a 6-litre maximum flush compared with the 7.5 litres and above allowed previously. The 20% water savings will benefit the metered customer and the environment. Dual-flush WCs are permitted with a smaller flush of no more than two-thirds of the maximum.
It is a start. However, if the government and water industry is serious about their stated objective of sustainable development then there is still much work to be done. It is the government's responsibility to educate society about water conservation. For instance, in addition to the conservation techniques already mentioned, there are two other easy ways which house builders and designers can use to conserve and manage water: harvesting, filtering and storing rainwater and grey-water recycling. Unfortunately the government has left it to vendors of such technologies to preach the gospel. And, rightly or wrongly, UK businesses are sceptical of the salesman who comes knocking on the door with a piece of equipment guaranteed to save money.
Water Dynamics, one of the leaders in grey-water recycling, is the only United Kingdom Accreditation Service-accredited manufacturer of water recovery systems. "Unfortunately we struggle with public perception of grey-water recycling from communal sources," said Water Dynamics' marketing manager Lora Lee Brown. The argument for using grey water for flushing toilets is strong when you consider mains water used for flushing toilets is of drinking quality. It clearly does not have to be of such a high standard, although it should not pose a health hazard.
The Office of Water Reclamation of the City of Los Angeles completed a project on grey-water re-use, which involved looking at eight test systems. Health worries centred on the use of water for garden watering rather than flushing the toilet, but the project found that grey water did not present health risks as long as reasonable sanitary practices are followed.
Water Dynamics' units designed to be 'fit and forget'. Regardless of the size of building, if it uses water - particularly in large quantities - the company believes it can design a bespoke, accredited system which will achieve a 40% saving in water consumption. Maintenance requirements are minimal and the units are claimed to have reasonable pay-back periods.
Water Dynamics' system does not synchronise grey-water supply and demand, instead it ensures either grey water or mains water will always be available. Continuity of supply to the toilet is maintained independently of grey-water production by the system automatically switching to mains water if there is not enough grey water. Excess grey water is automatically discharged to the drain.
The recycling system's storage capacity is based on normal toilet operation, calculated at 180 litres for a typical day. By storing only a limited amount of water, and by storing that water for only a short period of time, it has been possible to eliminate traditional engineering, hygiene and economic problems.
Grey water is pumped from the storage reservoir to a break tank, which incorporates the mains water supply mechanism and provides a gravity feed to toilets. The break tank has been designed so that the grey water cannot contaminate mains supply. Water supplies from the storage reservoir are chemically treated as they enter the break tank by passing through a dispenser of slow-dissolving bromine tablets. This provides controlled dosage for one year, without releasing any more chemicals to the environment than are used for lavatory bowl cleaning. Under normal conditions, Water Dynamics' recycling system is self-cleaning.
A filter is used to purify the water to between 60 to 80µm. After filtration, a brominator provides residual disinfectant to ensure Legionella, E. coli, organic growth and other bacteria are prevented. The filter elements receive a spray of disinfected water from the break tank after every pumping cycle. This keeps the filter chamber clean, prevents saponification and assists disinfection of the water in the storage reservoir.
Water Dynamics has been involved in extensive water recycling trials and pilot schemes with water companies and developers resulting in WIMLAS Technical Approvals/Building Research Establishment (BRE) accreditation. The company sees this as a milestone because the National House Building Council (NHBC) has stipulated it will not cover any non-accredited water recycling systems. The field of grey-water recycling is growing in sophistication believes Brown: "In all honesty, with something as new as water recycling there are no text books with all the answers, but through extensive trials with the Building Services Research and Information Association (BSRIA), the Construction Industry Research and Information Association (CIRIA), BRE, Cranfield University, Wessex Water, Gleeson Homes, Crest Homes and Three Valleys Water to name but a few, we have learned and adapted our systems to overcome teething problems."
It also appears that public awareness and demand for water-efficient devices is growing. According to Peter Casey of Gleeson Homes: "Water efficiency was rated as a very important factor among potential home-buyers. In our latest survey 62% of potential house-buyers said they would pay more for a home with water-saving features which offered long-term cost savings."
With so many water saving techniques available, one has to wonder why the government
and water companies are not promoting them as part of the drive for sustainability.
By offering significant incentives to companies willing to invest in the recycling
technology, it is within the government's power to ensure grey-water recycling
becomes an integral part of our society.