Potential actions that can be taken to assit towards this objection include: minimisaing water consumption, water harvesting, greywater recycling and surface water run-off/drainage.
Minimising Water Consumption
Sanitary use of water within a building is significant and a number of steps can be taken to minimise consumption. This issue encourages the use of low-water-use WCs, taps and appliances, etc. and fittings such as flow restrictors fitted in taps and delayed inlet valves fitted in WCs. For example:
- Dual Flush Cisterns – cisterns which have the facility to provide higher flush volume for solids and paper and lower flush volume for liquids.
- Flow Restrictors – contain precision-made holes or filters to restrict flow and reduce the outlet flow and pressure.
- Delayed Inlet Valves – prevent water entering the cistern until after the cistern has completely emptied into the bowl.
- Water Softeners – remove the hard material found in water by passing the water through resin.
- Taps – spray taps on hand basins typically save up to 80 per cent of the water and energy used with standard pillar taps. Sensor and push taps can save water where taps may be left on, and they also avoid the need to touch the tap once hands are washed.
- Flow Regulation and Leak Detection Devices – as well as saving water, flow regulation offers additional benefits, such as helping to balance the available pressure throughout the system.
- Urinals – installing urinal controls can halve the amount of water used for urinal flushing in offices.
- Waterless and Vacuum Toilets – waterless and vacuum toilets are an ideal solution where the water supply is scarce or non-existent.
- Water-Efficient WCs and Retrofits – dual-flush and low-flush toilets can cut water use by up to 20 per cent, and save more than half the water used in flushing toilets.
Water Harvesting
Water harvesting is the collection and storage of rain from roofs, for example, in order to replace the use of potable water in sanitary fittings and other non-potable uses. Correctly collected and stored, rainwater can meet all the requirements of WC flushing without further treatment – rainwater harvesting simply collects the rain which fall onto roofs, then stores it in a tank until required for use. When required, the water is then pumped to the point of use, thus displacing what would otherwise be a demand for mains-water. In the process, a volume of water is kept out of the storm-water management system, thereby helping to reduce flooding risks also.
Greywater recycling is the collection of shower, bath and tap water in order to replace the use of potable water in WCs. Greywater recycling can be accomplished by the use of greywater collection systems.
Commercial greywater systems are available that reuse the slightly polluted greywater from showers, baths and hand wash basins. In contrary to the domestic process where there is a only two stepped system, this time the treatment process is more clearly divided and takes place in four steps:
• Pretreatment
• Aerobic treatment
• membrane filtration
• clear water storage
The AQUA-Recycling Control unit, for example, monitors the treatment process and supplies the treatment water to the point of application using the integrated booster pump set. If there is no treated water available, the control unit will automatically switch to mains water back-up via an AA type air gap ensuring a continuous supply of water.
Planning a site so that water is removed from it as quickly as possible is potentially harmful to the environment as it can cause water pollution, the risk of flooding – both to the site itself or elsewhere downstream – and damage to wildlife and river habitats. In areas with combined drainage systems, surface water entering the system can also cause polluting from storm discharges and overload treatment plants.
To make sure a site is not polluting the environment or increasing the risk of flooding, consideration should be made to the use of a sustainable drainage systems approach, otherwise known as SUDS. This approach provides an on-site drainage solution that takes into account the following:
• the amenity benefits
• the quantity of surface water run-off, and
• the quality of surface water run-off
Sustainable drainage is a design philosophy that uses a range of techniques to manage surface water as close to its source as possible. To produce a workable and effective scheme, SUDS must be incorporated into developments at the earliest site-planning stage. Options include:
• Permeable pavements
• Swales and basins
• Green roofs and rainwater use
• Infiltration trenches and filter drains
• Ponds and wetlands