Sustainable Water Management - T by fjwuxn

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									SUSTAINABLE WATER MANAGEMENT
Promoting sustainable water management within schools (1) is important because of the
planned programme of school construction and the focal position of schools in our
communities as well as the opportunity to educate students about water conservation at
a formative stage of their development.

There are a number of key drivers for sustainable water management, as follows:
    climate change;
    demographic changes;
    reduction of surface run-off and diffuse pollution;
    the environmental impact of increased water abstraction;
    potential to save costs; and
    planning requirements and potential future changes in legislation.

The business case for sustainable water management
Sustainable water management can provide schools with educational, financial and
environmental benefits. These include cost savings for either mains water or sewerage
charges, simpler management of surface water run-off or the educational benefits of
being able to demonstrate aspects of the hydrological cycle on-site. Different aspects of
sustainable water management are considered below.

Education
Water conservation is a crucial part of the increasingly important topic of sustainability,
and will help students to focus on social responsibility – a key component of sustainable
development:
    water management can promote an understanding of the hydrological cycle
    SUDS can provide amenity benefits and as a wildlife habitat may also be used as
        a teaching resource.
    an operational water policy which raises awareness of both staff and students
        together with good housekeeping can substantially reduce water consumption.

Financial/cost savings
Each year, water use in the UK continues to increase, and summer shortages regularly
occur and are likely to increase. As a result, water costs are likely to increase over the
coming years, and restrictions on the use of potable water are more likely to be imposed.

Schools spend a total of around £70 million a year on water supplies. Average annual
water consumption per pupil per year in primary and secondary schools is around 4 m³
(4,000 litres), which could be reduced to 2.85 m³ per pupil per year, a potential saving of
some 28%. It is possible for a typical 600 pupil school to reduce its water charges by up
to £5,000 every year.

Cost savings can be made by:
    reducing water use by the specification of water efficient technologies at the
       design stage eg, for toilet flushing and urinals
    good on-going water management including monitoring of water use to help
       target areas where cost savings can be made
      sub-metering certain specific water uses within schools such as garden watering,
       to provide evidence to claim reductions in sewerage charges from the water
       companies
      Sustainable Urban Drainage Systems (SUDS) which may be cheaper to build
       than traditional drainage and easier to maintain by on-site staff
      efficient plumbing design which can reduce heating costs.

Environment
    water conservation helps reduce the demand for new water resources, and the
      need for potentially damaging increases in abstractions
    education of students helps to bring awareness of critical concerns, such as the
      environment and sustainable development
    SUDS can help in the management of flood risk, the improvement of
      environmental water quality, and can contribute to increased biological and
      ecological diversity
    good plumbing design minimises energy use within the school, there are
      increased amenity and wildlife creation benefits.


 Howe Dell Sustainable Drainage Systems
 Water management in the Howe Dell School, in Hatfield under construction in 2006, is a key
 strategic issue. Quite apart from draining the land, it has the potential to provide a whole new
 range of opportunities for curriculum and non-curriculum activities. The engineers, landscape
 architects and architects on the design team have worked closely to ensure water
 management is an integral part of the scheme, rather than a superficial afterthought.
 To reduce the flooding risk, the school has a site water drainage strategy, which marries
 together water-saving and ecological advantages. First, there is a sedum roof on one of the
 buildings, which slows down and reduces run-off. Next, there is a grey-water collection system,
 which collects water from the roof to be used for flushing toilets. Water will also be harnessed
 as a resource in water butts to enable children (or staff) to have easy access to water for
 gardening or washing down surfaces outdoors.
 And finally, when the grey-water collection tank is full, excess water flows into a controlled
 access pond, which will have a fluctuating water level to deal with flooding and drought with
 aquatic and marginal planting. The pond will be fed from large areas of paving by a series of
 shallow depressions (“swales”) and filter strips which channel water to a specific location. As
 well as channelling water safely, these will also serve to enrich the school‟s ecological habitat.
Watercourse Pollution
Where rainwater run-off is from relatively low pollution risk areas such as roofs, smaller
car parks and non-operational areas, the use of permeable surfaces or infiltration
trenches will offer a sufficient means of treatment, removing the need for an oil
separator. This is likely to be the case with the majority of smaller school developments.
Where soakaways or other holding facilities are present, surface run off should be
passed through an oil interceptor device prior to discharge to the soakaways.

Where there is a high risk of contamination or spillage of substances such as petrol and
oil, then oil/petrol interceptors or filtration should be specified. Guidance on the types of
oil separators available is given in PPG 3. From 2005 Regulations(2) require all oil-fuel
installations to be provided with secondary containment. This requirement is
retrospective and includes both the oil tanks and the supply pipes. Bunding of tanks and
pipe within a pipe containment is therefore required. (2)


Water Efficient Technology
There are many water efficient technologies available that can be introduced at the
design stage to help reduce water consumption.

Urinals.

Urinals use less water than WCs when they are appropriately controlled. There are
many designs of urinal flush controller available, each using differing methods of user
detection. Most systems can be linked to control all the lighting and fans in the WC area.

Waterless urinals are now widely available. They are cheaper to install (because they do
not require water supplies), avoid scale problems in hard water areas and remove the
risk of flooding caused by blockage, frost damage or vandalism. Recent designs
overcome some of the historic problems with waterless urinals such as odour and
blockage.

Dual Flush and Low Flush Toilets
Dual flush cisterns are available and work well if the method of operation is clear and
instructions are provided. As an alternative for WC installations it may be better to
consider a low volume single flush cistern delivering 4.5 litres or less (the current legal
maximum is 6 litres).

Systems exist that achieve even lower flush volumes, however, drainage systems must
be designed (i.e. have appropriate falls, rodding points, etc.) to reflect the likely demands
and maintenance requirements for low volume cisterns.

Taps
Spray taps on hand wash basins can typically save 80% of the water and energy used
compared to a standard pillar tap. Other water saving options include push/percussion
taps which stop flowing after a pre-set interval, and electronic sensor taps which switch
on and off automatically. In hard water areas, spray taps may require regular descaling.
These forms of taps prevent wastage and flooding in situations where taps may be left
running. They can also be more hygienic as the tap does not have to be touched, to turn
them off.

To avoid long delays and to save water while the water „runs‟ hot, spray taps should be
sited close to a source of hot water – eg, point of use water heaters or a circulating hot
water supply.

Water Saving Showers
There is no agreed definition of a water efficient shower - unlike other fixed volume
devices, shower water consumption depends very much on user behaviour and water
pressure. Systems with low flow rates, good water droplet distribution, and temperature
control contribute to efficiency. Water-saving shower heads usually work by reducing the
flow whilst maintaining water surface area, by either creating finer water droplets or by
aerating the flow.

Plumbing and Heating Design
Good plumbing design can contribute to water saving. Reducing the length of hot water
pipes to a minimum cuts the volume of cold water drawn each time a tap or shower is
used. For school buildings it is generally good practice to reduce volumes of stored
water as much as possible.

In large buildings, localised water heating can often be more energy and water efficient.
Long runs of hot and cold pipes should be insulated to minimise heat loss and gain.
Pipes in unheated areas must be protected from freezing.

Drinking water should be available at various points throughout a school, and ideally
should not be available in toilet areas. Drinking water and non-drinking water supplies
should be clearly marked.


   Water use at Bradley Stoke

   The school toilets have waterless urinals, which save mains water and reduce the
   volume of waste water leaving the school. These urinals also cut the amount and
   complexity of supply pipework needed during construction.

   The design also addresses rainwater run off from the site using a tanked system,
   which gathers water from the roof, the car park and the rest of the site, and feeds it
   into an attenuating pond. The rainwater is then discharged into a brook that runs
   close to the school.




Alternative Water Sources

Rainwater Harvesting
Correctly collected and stored rainwater can be used for many purposes such as toilet
flushing, irrigation, and some washing applications such as cars or sports equipment.
The effectiveness of a rainwater harvesting system will depend on annual rainfall,
catchment area and storage capacity. The potential for savings achieved by rainwater
harvesting is greater in buildings with large roof areas.

Greywater
Greywater is the wastewater collected from showers and washbasins which can be used
for toilet flushing and irrigation. If used immediately after collection, greywater can be
used with minimal treatment. Treatment systems are more complex when greywater is
stored for a significant period prior to use.

Monitoring Usage and Leaks

Metering
Water meters do not reduce water use, but well sited meters allow water consumption to
regularly monitored. Meters should be sized appropriately for the expected water use
and positioned so that regular meter readings can be recorded as part of a water
management procedure. Sub-metering of high water use applications such as kitchens
and swimming pools can quickly identify unusual or irregular usage patterns.

Pulsed outputs on meters allow usage to be monitored automatically, and automated
water shut-off systems can be installed to control water supply systems when flow rates
are unusually high and indicate that there is a high risk of leakage. This helps to prevent
wasting water and reduces the risk of water damage when the building is unoccupied.

Infra-structure, for example Drainage Requirements / SUDs
As a result of development natural and man made water courses are continually
changing, and most have to cope with increasing water volumes. This can affect the risk
of flooding, landslides and other impacts. Sustainable drainage systems allow rainwater,
and sometimes waste water, to return to the environment at a suitable quality and flow
rate to replenish ground and surface water supplies without increasing the risk of
flooding.

Swimming Pools
Swimming pools should not be drained and refilled more than necessary therefore a
sand filter system should be specified that reduces this requirement. Swimming pools
use very large amounts of water due to evaporation and backwashing filters.

Evaporation can be controlled by the use of pool covers and maintaining appropriate
pool temperatures (and surrounding air temperatures). This will also result in significant
energy savings. Scheduled maintenance intervals should minimise water lost during
backwashing. (3)

Frost protection
Adequate frost protection is vital to prevent burst pipes. Both hot and cold water pipes
should be adequately insulated throughout the building, and the heating system should
incorporate control strategies for frost protection. See guidance in Building Bulletin 87(5).

In severe weather, caretaking staff may need to visit the school when frost is expected,
especially during weekends and holidays.
REFERENCES

1. CIRIA report CIRIA W12 Sustainable water management in schools, free download
   available on http://www.ciria.org/downloads.htm including guidance on the
   implementation of sustainable water use and sustainable drainage during both the
   design and operational phases of schools.
2. Pollution Prevention Guideline (PPG) 3 “Use and design of oil separators in surface
   water drainage systems”; Environment Agency.
3. See Pool Water, Treatment & Quality Standards, www.PWTAG.org.
4. Managing School Facilities Guide No 2, Swimming Pools, DFES, 2003 ISBN 0 11
   270871 4.
5. Building Bulletin 87, May 2003 edition available from www.teachernet.gov.uk/energy

Further References
BS EN 752-4 “Drain and sewer systems outside buildings – Hydraulic design and
environmental considerations”; British Standards Institute,1997.
BS EN 12056-3 “Gravity drainage inside buildings – Roof drainage, layout and
calculation”; British Standards Institute, 2000.
Figures for UK rainfall are available from the Met Office www.met-office.gov.uk
Digest 365: “Soakaway design”; BRE, CRC Ltd, 1991.
C523 Sustainable Urban Drainage Systems “Best Practice Manual for England,
Scotland, Wales and Northern Ireland”; CIRIA.
Pollution Prevention Guideline (PPG) 1 “General guide to the prevention of pollution”;
Environment Agency
Water in schools: www.waterintheschool.co.uk
Water Regulations Advisory Scheme. www.wras.co.uk

								
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