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Water Saving Technology
Saving water has become a highly political issue of late and has received substantial media coverage.
The information below covers higher impact water saving initiatives such as desalination and groundwater use as well as more
low impact approaches such as rainwater tanks and reusing greywater.
What is Desalination?
Desalination is the process of removing dissolved minerals (including but not limited to salt) from seawater,brackish water, or
treated wastewater to create drinkable water. It results in the recovery of 15%-50% of water,the rest being waste known as
brine. A number of technologies have been developed for desalination,including reverse osmosis.
The Jubail desalination plant in Saudi Arabia is the largest in the world.
Who Uses Desalination?
Of the whole desalination capacity in the world, 50% is in the Middle East, 20% is in North America, 12% to 14% is in Europe
and in comparison to that, less than 1% is in Australia.
What are the Impacts?
- Energy use and resulting green house gas production - The energy used in the desalination process is primarily electricity and heat. Large amounts of greenhouse gasses can be produced by desalination plants due to the high energy requirements.
- Waste - A heavily concentrated brine solution. After the brine solution is discharged into the sea, it has the potential to kill marine organisms through pollution (chemical and metal content) as well as rise in the salinity and temperature of coastal waters near the outlet.
- The development of the desalinisation plant - Results in land degradation and noise and visual disturbance as well as air pollution.
- Disturbance to the aquifer - Long pipes conducting seawater and brine increase danger of leakage and penetration of salty water to aquifer
- Entrainment (sucking in) or impingement (sucked up against screens at the intake area) of marine life: molluscs, weeds, algae, fish. Fish eggs, larvae and juveniles as well as plankton are especially susceptible to entrainment. Impinged organisms, typically juvenile or adult fish, usually die or suffer injury as a result of starvation, exhaustion, descaling by screen wash sprays, or asphyxiation.
Desalination may be best looked at as one of a number of strategies examined by people in a variety of disciplines in order to
make sure we make the best use of water and all our resources. Although the impacts of desalination may be reduced through
use of best practice, risks still remain. With a variety of reasonable water saving solutions currently at hand (water reuse and
recycling, effective management strategies and education) desalination may be most appropriately viewed as a last resort.
Bore Water
Many suburbs have a good supply of shallow underground water suitable for garden use, flush toilets, wash cars and clothes.
The cost of setting up a residential underground bore depends on the type of bedrock and how deep the water lies below the
surface and can vary between $2000 - $50,000 (this includes sourcing a bore, licensing, excavation and pump and does not
include ongoing electrical charges).
Sandy soils such as those close to Randwick and Kurnell make for ideal conditions for sourcing bore water whereas soils
around Ryde are shale and sandstone based making for a difficult and expensive water sourcing procedure.
Like desalination, bore water is not without its issues, these include:
- Land disturbances from bore hole drilling.
- Inducement of salinity.
- Damage to natural water balance resulting in flooding or lowering of water table.
- Possible contaminated ground water from off-site activities.
Bore water is being used to irrigate many parks around Sydney however its residential use is limited by Council regulation
and high cost.
What is Rainwater Harvesting?
The harvesting of rainwater simply involves the collection of water from surfaces on which rain falls, and subsequently storing
this water for later use. Normally water is collected from the roof of a building and stored in rainwater tank.
This is very common in rural Australia. Water can also be collected in dams from rain falling on the ground and producing runoff.
The collection of rainwater from the roofs of buildings can easily take place within our cities and towns, not just in rural
Australia. All that is necessary to capture this water is to direct the flow of rainwater from roof gutters to a rainwater storage
tank. By doing this, water can be collected and used for various uses.
If you are reliant on collected rainwater and are not connected to a town water supply, then the water collected will be especially
important to you. If you are from the city,then it is possible to replace all or at least a substantial portion of your fresh water
requirements by the capture and storage of rainwater from your roof. Being largely self sufficient in water supply is possible
for a vast majority of Australian households and buildings.
What are the Benefits in Rainwater Harvesting?
By capturing water directly, we can significantly reduce our reliance on water storage dams.This places less stress on these
water storages and can potentially reduce the need to expand dams or build new ones (the expansion and creation of dams
causes many environmental impacts)
Collecting and using your own water can also significantly reduce your water bills.
By capturing water, the flow of stormwater is also reduced and this minimises the likelihood of overloading the stormwater
systems in our neighbourhoods.
Sizing of Rainwater Storage Tanks
If you are installing a rainwater tank you'll need to decide on the size, material, filtration devices and other requirements.
Whether you want to maintain a lush garden, supplement your home's water supply or fulfil BASIX requirements, you may have
thought about installing a water tank. There are a number of factors that will determine the type of tank you take home.
The process of selecting and installing a rainwater tank can be baffling. You should ask yourself the following questions.
But also, due to the many variables involved, it is still strongly recommended that you talk to a professional who can determine
your individual requirements. A free quote can be obtained from one of the numerous organisations specialising in
rainwater tanks.
How do water tanks work?
Regardless of the size of your tank, the basic principle of water collection (or water harvesting) is the same. Put simply,
the rain that falls onto your roof is caught by the guttering, channelled along the downpipe and filtered into your tank where
it is collected for later use (this process may require a pump depending on the gradient involved).
Can I have a tank
With the number of compact domestic water tanks on the market now, it is unlikely that a small roof area will prevent you
from owning a small tank. However every council has different regulations, therefore check with your Local Council.
What can I use the water for?
Most retrofitted rainwater tanks are designed to collect water for the garden, flush toilets and wash clothes. More complex
systems can be connected to provide "potable water" - that is, water fit for drinking and cooking with.
The size of the area of capture or roof area must also be known when estimating the amount of rainfall that is able to be
collected. The larger the roof area, the more rainfall that is able to be collected.
What size tank do I need?
Determine your required tank capacity by assessing the size of your roof catchment area and what the water will be used for -
for example, internal or garden use.
Another factor to consider is the amount of space available for the tank. A tank that holds enough water to supplement a
townhouse (about 5000 litres) will take up about 2 sq m. A tank with a capacity of 15,000 litres will occupy an area of about
6 sq m. There are a number of slimline tanks on the market designed to fit down narrow side passageways.
For domestic use Sydney Water recommends:
- A minimum size of 5000 litres for non potable (non-drinking) domestic water uses (such as flushing the toilet, washing your clothes, watering the garden, washing the car) and holding stormwater.
- A minimum size of 2000 litres for toilet flushing only; or watering a small garden area.
Harvesting Surface Runoff
The harvesting of surface runoff is a concept being considered more and more in new residential estates,where land is
available to capture and store surface runoff for future use in the landscaping of the development.
Sydney Water Rebates for Rain Water Tanks.
Sydney Water is offering a rebate of up to $800 for installing a rainwater tank from Sydney Water.
By storing rainwater run-off from your roof, rainwater tanks can provide a valuable water source for flushing toilets, in washing
machines, watering gardens and washing cars. How can you qualify for a rebate. To qualify, your new rainwater tank must:
In addition you may be eligible for a $150 washing machine rebate when you purchase a new washing machine with a water
efficiency rating of 4-star or AAAAA.
Also on offer from Sydney Water are free DIY water saving kits for your home.
Grey water Reuse:
People are now waking up to the benefits of greywater re-use, and the term "Wastewater" is in many respects a misnomer.
Maybe a more appropriate term for this water would be "Used Water".
What Can Greywater Be Used For?
Used appropriately, you can water your garden with grey water and save around 400 litres of fresh water each day.
Grey water can be diverted to your garden through domestic grey water treatment system (DGTS).
A DGTS will produce higher quality grey water to use in the garden and possibly your toilet or washing machine.
Be sure to contact your Council for their greywater reuse guidelines.
What Are The Benefits of Greywater Re-use?
Two major benefits of greywater use are:
- Reducing the need for fresh water. Saving on fresh water use can significantly reduce household water bills, but also has a broader community benefit in reducing demands on public water supply.
- Reducing the amount of wastewater entering sewers or on-site treatment systems. Again, this can benefit the individual household, but also the broader community.
How Is The Greywater Treated For Re-use?
Untreated greywater from your washing machine and shower may be reused on the garden depending on the level of chemicals
in it (dilution factor) and the sensitivity of your garden.
Use organic, natural products in your washing machine and shower to reduce the chance of chemicals placed on your lawn from
reusing greywater. This is not only good for your garden but your health as well.
A greywater treatment system collects, stores and treats greywater to a high standard. It includes components such as
wetlands, intermittent sand filters, soil filters, grey water septic tanks and aerated wastewater treatment systems.
The treatment process varies according to how the grey water is used and includes settling of solids, floatation of lighter
materials, anaerobic digestion in a septic tank, aeration, clarification and finally disinfection
As primary treatment will only reduce the solids in the wastewater, secondary treatment is necessary to remove pollutants
from the remaining liquid.
The installation of a greywater treatments system requires an approval from you local council prior to any installation.
What is the best option for our environment?
Environment groups are calling on political parties to fund the broad scale roll out of rainwater tanks across our cities to
deliver water security in the face of climate change. Rainwater tanks produce far less greenhouse gas emissions than a
desalination plant, and lose less water to evaporation than a dam.
It is also recommended that we implement low cost water saving tips in the home such as water efficient v devices like dual
flush toilets, showerheads, taps, tap aerators, trigger nozzles and tap and shower timers as well utilising greywater reuse.
For more information visit Sydney Water.
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