Water is at the heart of our ecology. Sustainability means using it thoughtfully, to avoid both wasting it and polluting it. We can do this in building design, and in how we develop sites.
Water Within and Around the Building
Design should promote water efficiency within buildings, and water conservation within the built environment The amount of water used in a building can be reduced by selecting low water appliances. 6-litre flush WCs are now mandatory under the Water Regulations, and further savings may be made by using dual flush 4 / 2 litre cisterns.
Water-efficient measures normally incur some initial expense, but most organisations will consider it worthwhile to implement a water-efficient measure if the 'payback' period is two years or less.
'Aquaspec' is a software program which allows architects and designers to quickly calculate the water usage of a building, both in terms of water volume and cost. The program allows the designer to assess how the water usage of a building can be reduced by installing water conservation products, such as low flush WCs, into the specification or design. It calculates the water costs (including service charges) from cost files of up-to-date costs from each water company, throughout the country.
Once the building is occupied; the users should be encouraged through an awareness campaign to carry out regular checks and maintenance to minimise leaks; and to set and publish targets to reduce consumption.
| | |
Facts
- WCs typically account for 35% of water use in homes and 43% of water use in non-domestic buildings. Low flush WCs are now mandatory.
- All mains water in the UK is of drinking standard, and yet only around 6% is used for drinking. Consider using non-potable water (e.g. rainwater, greywater) wherever possible.
- A typical bath uses 80 litres of water, compared to 30 litres for a typical shower.
- A conventional tap left running for an hour wastes one cubic meter of water (1m3). Fit tap controls.
- A rainwater collection system on the average UK house would collect 96 litres of water a day (enough for between 10-16 WC flushes).
| | |
Water Consumption within dwellings per person per day
|
 - WC (36.5 litres) 33%
 - Personal Washing (28 litres) 25%
 - Drinking & Food Preparation (19.5 litres) 18%
 - Laundry (13.5 litres) 12.5%
 - Washing Up (9.5 litres) 12.5%
 - Car Washing & Garden Use (3 litres) 3% |
Water on the site
Site planning should include a water assessment, to identify the quantity of water retained on the site and its quality. Further advice can be obtained from the Environment Agency. The information collected will depend on the size of the development, but should include:
- rainfall, seasonality and intensity (consult the Met. Office) the natural drainage layout including ditches, streams and ponds
- the extent of the watertable the extent and use of the aquifer
- evidence of flooding (consult Environment Agency, local users)
- proximity of the flood plain zones
- density and area of non-permeable cover
- presence of flora and fauna in the watercourses indicating quality
- actual and potential sources of pollution
- designated responsibilities for maintenance of watercourses
- existing surface discharging into watercourses
- existing foul water drainage discharging into a sewer or septic tank
| | |
A checklist of water efficiency measures:
Push top or spray taps - these reduce the amount of water flow, but allow enough for hand washing. The potential savings are over 1,800 litres per employee every year (£2.60 per person per year).
Tap control units - save half the water used through taps by fitting a control system. Potential savings of 1,800 litres (£2.60) per person per year.
Urinal control - fit a modern system so that the cistern only operates during office hours or after use rather than 24 hours a day. Potential to reduce the cost of water for flushing by over 50%.
Waterless Urinals - using a siphonic tap or pad impregnated with deoderising agent. Potential savings 46,800 litres (£70) per urinal.
Cistern dams - reduce the amount of water required to fill the cistern to flush. Potential savings of up to 1,700 litres (£2.50) per person per year.
Supply restrictor valves - keep the water flow constant regardless of fluctuations in water pressure. Can reduce water flows by 50% or 1,800 litres (£2.60) per person per year.
Wash room controls - provide a control which limits hot and cold water supply, lighting and ventilation. Potential savings up to 66% of water through taps, plus energy savings.
Heating and Cooling systems - consider these with maintenance in mind; it should not, for instance, be necessary to drain whole floors to repair one radiator valve. Potential saving depends on good practice and planned maintenance.
Collecting rainwater / greywater - provide rainwater collection butts and use for external watering. All new buildings are metered. So this will reduce mains consumption and water bills. Potential savings: high savings if used to clean vehicle fleet etc. Rainwater collection not only saves water, but it reduces run-off from the site. Porous paving and green landscaping can further reduce run-off and pollution. There are also sewage cost savings via non returns to sewers allowances.
(NB. Costs are based on year 2000 averages)
| | |
Natural water storage is increasingly being installed to compensate for run off from hard surfaces or increased development area by channelling surface water into soakways, swales, filter strips or detention basins. A target should be set in consultation with the Environment Agency.
| Provide and manage buffer strips between buildings and water courses.
Nutrient stripping buffers should be used to absorb excess nutrients and fertilisers, which can lead to eutrophication of the water courses, choking aquatic life. | |
On sites with existing lakes and ponds, appraisals of the following potential should be undertaken: bodies of water should be appraised for:
- hydroelectric power and other forms of renewable energy such as wind, wave and tidal energy
- a heat store, such as using heat pump technology
- amenity, educational and recreational value e.g. sailing and canoeing
- value of flora and fauna
| | 
Click on the thumbnail above to see an enlarged version of this image. Please use your browser back button to return to this page. |
Sustainable Urban Drainage
Sustainable Urban Drainage is a non-traditional, environmentally friendly, way of dealing with surface water run-off. Sometimes referred to as Source Control or as Sustainable Urban Drainage Systems (hence SUDS). It is a design approach which is equally applicable to rural and urban sites.
SUDS rely on gravity to drain the surface water run-off from hard surfaces into the drainage system or into the ground to recharge aquifers. They can be designed to slow down the flow, thereby reducing the risk of flooding. Run-off is collected and stored so that natural cleaning (sedimentation, filtration and bio-degradation occurs prior to infiltration or controlled release to watercourses. This reduces the pollutant load in the surface water run-off.
| | |
The Problem
Development has caused damage to the water environment for centuries by using inappropriate methods of drainage. At present, rain from roofs, paving, roads, car parks and other hard surfaces is collected in gullies and pipes before being discharged directly without restriction to watercourses or the public sewerage system. This causes a number of problems:
- Flooding of watercourse when rain is piped straight to rivers and streams at the same time, before it has chance to soak into the ground
- Pollution of watercourses, when silt, oils and other pollutants are carried straight to steams and rivers before they can be trapped, removed and broken down naturally
- Combined sewage pollution, when sewers designed for foul water flow become overloaded, leading to escapes during heavy rain
- Decreased efficiency of the sewage treatment process from increased flows
- Increasing cost of providing new sewers and sewage treatment - as they have to be designed for huge volumes of storm sewage
- Severe damage to watercourses
| | |
SUDS techniques allow natural drainage to function in the landscape surrounding development through four general design options:
- Filter strips and swales
- Infiltration devices
- Filter drains and permeable surfaces
- Basins and ponds
These techniques have been shown to work in a practical, cost-effective and beneficial way. Currently, the Environment Agency has two demonstration sites; one at the M40 Motorway Services Area in Oxford, and another at Hopwood on the M42. | |
The Benefits to Developers
The use of SUDS helps to meet planning objectives, therefore smoothing the path through the planning process by helping to meet sustainability targets and the demands of statutory consultees, particularly the Environment Agency. They are much less dependent upon the conventional building materials used in pipeline construction, thus reducing the demand for quarried aggregates. Sustainable Drainage Schemes also benefit the developer in many ways:
Capital costs:
- Construction costs are reduced by 10% - 50%
- Expensive connection to storm sewers is often avoided
- Environmental engineering on the surface is cheaper than drainage structures below ground
Value:
SUDS use natural features in the landscape to create attractive surroundings which add value to development. Provides community, environmental and image benefits. | |
Maintenance and Management:
Simple to use and cheap, can be undertaken by landscape contractors or site personnel. Maintenance costs are reduced as they can be managed as part of normal landscape care, and avoids the need for expensive specialist contractors. However, commitment to long-term maintenance and management is essential, and must be negotiated early with the local planning authority and water utility company.
Reed Beds: Absorbing Waterborne Waste
Planting beds of wetland reeds is an effective way to treat or de-water various types of noxious effluents, including sewage sludge, leachates from landfills, and wastes from chemical plants and oil-drilling operations. More than a dozen types of waste can be treated by means of reed beds.
If an existing foul water drainage system is full or near capacity, new development can use on-site treatment by reed beds, to:
- reduce the energy consumption of sewage treatment and disposal systems
- reduce the risk of pollution from conventional treatment plants which concentrate pollution in one location
- make use of by-products - including fertiliser and materials for crafts
- increase the diversity of flora and fauna
- decrease maintenance, because of few moving parts
Reeds act in two ways to alter the character of metals present in the sludge. Firstly, their root system provides oxygen, which boosts the population and activity of naturally occurring micro-organisms which, in turn, mineralise the sludge. Secondly, the plants grow rapidly in this nutrient-rich medium and absorbs some of the minerals, as well as drawing water from the sludge.
Construction of the reed bed system is fairly simple and operation and maintenance are straightforward and inexpensive. It requires the installation of a water-tight liner and the only mechanical components are pumps for sludge and filtrate. Reed beds are safe to operate and require the presence of one person for a few hours per week (depending on the capacity of the system). Similar protective gear is required as for workers in a conventional sewage treatment plant.
- Horizontal reed beds should be approximately 0.6m deep and require approximately 5m3 of water per occupier / user of the development.
- Vertical reed beds require a fall of at least 1.5m and a volume of between 1 and 2 cubic meters per person.
| |
The Environment Agency can advise if a reed bed will be a satisfactory means of treating the effluent given the local circumstances. The Agency can also provide a list of consultants who design reed bed systems.
Rules of Thumb
Sources of Info
Case Studies
