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Drinking
Water filtration can be an incredibly complex and costly subject. We have tried to simplify it here. Use this information as a basic guide only.
Note - 1 micron (mu) = 0.001mm, 10mu = 0.01mm, 100mu = 0.1mm, 1,000mu = 1.0mm
A human hair is about is about 100 microns in diameter, while the smallest particle visible to the naked eye is about 30 microns in diameter. |
Filtration, or the treatment of water suitable for human consumption, can be broken down into 3 basic areas;
Below is an interactive display of a typical household UV water filtration and treatment installation. Hover over each component for information on the entire filtration process.
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Drinking or house water throughout the Yarra Valley is mainly obtained from rainwater catchment off roofs, but can also include water pumped from streams, rivers and aqueducts (open channels transferring water from one catchment reservoir to another). The water invariably ends up in water tanks, and is then filtered / treated as it enters the house.
The size and source of the sediment particles will vary. Catchment variants include the number of trees around your house, proximity to dirt roads, etc. and how often you clean your gutters. Each site may be different, and may have different filtration needs.
Sediment Filtration can be broken down into two steps;
• Pre-Filtration - Coarse sediment particles and plant material over 100 micron (0.1mm)
• Main Filtration - Medium or Fine sediment particles and plant material from 80mu to 20mu (0.02mm). Very Fine – dust and colloidal clay particles from 10mu down to 5mu (0.005mm)
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| Pre Filtration (sediment) |
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A Media Filter is like a swimming pool filter. It is a large container normally made of steel or fibreglass. It contains specially graded sand, or other media, which can filter out various size particles. They handle relatively large volumes of water and are therefore normally only used at commercial sites such as caravan parks, conference centres, B&Bs, school camps etc. The big advantage of media filters is that they can be back-washed to clean them, and the media should last around five years before it needs replacing.
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Disc or Screen filters are commonly used in household situations. They are normally supplied in 1” or 1 ½” pipe size, and are around 100mu (0.1mm). They are economical to install and are washable. Disc filters are the better choice, as they have a larger surface area, and can be easier to clean.
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The above filters are installed to filter out the “rocks” and plant material. They are there to protect you main filters from clogging up too quickly.
| Main Filtration (sediment) |
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Cartridge Filter Elements are the most common form of household filtration. The elements are commonly made from wound polyester, pleated paper or spun polypropylene. They are commonly available in 2 different heights – 250mm or 500mm, and 2 different diameters - 60mm or 110mm. Micron ratings include 50, 20,10, 5 & 1mu.
Wound polyester filters are older technology, and do not have the precise filtration that polyspun filters can offer. Pleated paper has the advantage of being washable, however can only be partly restored to original capacity and they should only be washed 2 or 3 times.
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Common Sizes:
20mu - for sediment removal |
Most commonly used filter element for whole-of-house use (kitchen, showers, laundry, toilet etc). Will generally remove anything that settles out of a glass of water overnight. |
10mu - for fine sediment removal. |
Will remove most colour from the water if fine colloidal clay particles in suspension are present. Also used as a pre-filter in undersink drinking water filters. |
5mu - drinking water filter |
Too fine to use as a whole of house filter, it is normally used for drinking water only. Also used as a pre-filter to UV radiation. Will remove some larger cysts. |
1mu - drinking water filter |
Will remove any possible particles that are left, and because of its very fine rating, will also remove 99.9% of protozoan cysts, such as Giardia & Cryptosporidium. |
The dirtier the water – the quicker a filter will clog up.
The finer the filter element, the quicker it will clog up.
As a guide, in normal conditions, the average person on tank water should get about 3 months use, out of a standard 10”, 20mu filter. The wider ‘maxi filters” last about 4 times as long. A 20” (taller) filter will double these figures.
Depending on the application, filters sometimes get installed in series eg; you can have a 20mu followed by a 5mu.
Click here for more information on filter elements.
Whilst the above filters can give you very clean water, no filter element can remove bacteria or viruses. Further treatment is necessary to ensure safe, healthy water.
The addition of a carbon filter will help with the removal of taste & odour, which can be caused by rotting vegetation, animal waste or bacteria.
Activated carbon is capable of absorbing or removing organic compounds, which may cause the water to smell & taste bad. It is not suitable for removing metals, bacteria, viruses or protozoa. The main drawback of activated carbon is that the nutrients and organic matter that accumulate from even fully treated water, provide a medium for bacterial growth. Flush your filter before use, particularly if it has been standing for extended periods, (i.e. such as overnight).
There are numerous designs of carbon filter elements, which offer varying degrees of absorption. The larger the volume of carbon in the filter – the better the result will be. Slower flow, or better design, means longer contact time with the carbon = a better result.
“Whole of house” carbon filtration is not particularly effective. (If you notice odour from the water in the shower or laundry, you have a major problem in the water tank that needs treatment. The use of Acquasafe would be necessary in this situation).
For best results, we suggest the installation of a separate drinking water filter at the kitchen sink.
Moulded carbon |
Used as a “whole of house filter”. Minimal contact time through carbon layer. Good flow rates, but minimal taste & odour removal performance. |
Dual Purpose |
Used as a “whole of house filter”. Minimal contact time through carbon layer. Pleated paper - cheap, offers reasonable flow rates, but only ordinary taste & odour removal performance. |
Granular carbon |
Carbon granules with top to bottom flow = maximum water contact = excellent taste & odour removal. Water flow is suitable for drinking tap only. |
Carbon Block |
the ultimate for drinking water - High tech, with accurate sediment / cyst removal, no carbon fines. Water flow is suitable for drinking tap only. |
How do the germs get into the water tank?
Animal wastes are the primary source of bacteria in water.
Insects, birds, rodents, animals and decaying leaves entering the water supply are the major threat of contamination. Their droppings on your roof are a major source. Stagnant water sits in your guttering or downpipes Bird, rat and even possum skeletons can finish up in roof gutters. Where did all the tissue & organs go – straight into your tank. Dead ducks have been found in tanks.
In the case of underground water tanks, human wastes may be a concern if the septic tank or drainage lines are on the same level or higher than the water tank. Natural soil or plant bacteria is another source. Underground plumbing in poor condition may also pose threat
Each of these sources of can lead to dangerous bacteria entering your water.
What germs are we dealing with?
| Protozoa |
| Example |
Giardia, Cryptosporidium |
| Particle Size |
1.0–4.0 microns |
| Control methods |
1mu filter element or UV radiation |
| Cryptosporidium is a waterborne parasite that lives in animals and can be passed into the water through their waste. Cryptosporidium occysts from animal wastes have been found in rivers, streams, lakes reservoirs and water tanks. |
| Bacteria |
| Example |
Cholera, Coliforms (E. coli), Salmonella |
| Particle Size |
0.2–1.0 microns |
| Control methods |
Chemical treatment or UV radiation or Reverse Osmosis |
| Coliforms are found in the intestines & faeces of all warm blooded animals.E Coli is a sub group of Coliforms found in human faeces. |
| Virus's |
| Example |
Hepatitis A, rotavirus (gastro) |
| Particle Size |
Up to 0.004 microns |
| Control methods |
Chemical treatment or UV radiation or Reverse Osmosis |
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How to Treat the Water?
Ultraviolet radiation is an effective and economical means of eliminating harmful bacteria, viruses and protozoa from your drinking water supply. It is commonly used for water disinfection by local councils and the food, dairy and brewing industries. It is a proven method of ensuring safe, sterilised drinking water. There are no chemicals, no taste, and it’s impossible to overdose. Once installed, it will consistently supply safe drinking water at an incredibly low cost.
As the water flows through the main housing, the micro-organisms are exposed to a strong dose of ultra violet light which will kill / sterilise them. There is no with-holding period and no need for holding tanks. The water is safe and ready to be used immediately.
Pre-filtration is necessary to ensure that micro-organisms are not shielded behind sediment particles as they pass through the UV chamber, and the water must have a low level of colour, so the UV can pass through without being absorbed.
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The Davey Steriflo® domestic UV water disinfection systems are an effective and economical means of eliminating harmful bacteria from drinking water supplies. They can also be used for small scale waste water disinfection at reduced flow rates.
• No chemicals
• No taste
• Impossible to overdose
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Disinfection / Chemical treatment:
.Chlorine (and its many forms), is a powerful disinfectant / oxidant that kills many micro-organisms. It is used by public water supplies to maintain a residual disinfecting agent throughout their distribution system. Effective removal of organic compounds before treatment is vital to reduce the likelihood of potentially harmful chemical by-products, which can be carcinogenic. Extreme care must be used in handling chlorine. Although chlorine is effective in killing bacteria, it has limited effectiveness against protozoa that form cysts in water (Giardia lamblia and Cryptosporidium).
Acquasafe is a revolutionary new sanitiser specifically designed to kill 99.9% of dangerous bacteria and pathogens in your water tank, and keep it protected from recontamination for up to 2 months. It is tasteless, odourless and colourless. It is environmentally safe and friendly. It has national government approval for use in drinking water both here in Australia and around the world.
Acquasafe is a non-chlorine based oxidant. It is a tier-one disinfectant that, unlike others in its category, contains a stabilised form of H2O2 that provides a residual efficacy for long lasting protection. Acquasafe can provide a 99.9% kill rate against a wide range of pathogens including bacteria, mould, viruses, bacteriophages, yeast, fungi, sporogenes, amoeba and spores.
Acquasafe is more effective than most sanitisers currently available such as bromine, iodine or chlorine-based products, and has none of the negative side effects which affect humans or the environment. It has none of the disadvantages of chlorine, and has additional synergistic effects that make it the ideal choice over any other sanitation product.
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- Acquasafe is tasteless, odourless and colourless
- Acquasafe is cost effective at as little as $0.0007 per litre
- Acquasafe has been approved for use in drinking water by the National Health and Medical Research Council
- Acquasafe is not toxic, carcinogenic or mutagenic
- Acquasafe does not form new, sometimes dangerous, compounds when it comes into contact with basic substances
- Acquasafe is not dangerous when overdosed
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Other less common options:
Ozone (O3) is a powerful oxidising agent added to the water by bubble contact, which is toxic to most water borne organisms. It is a very strong, broad spectrum disinfectant that is widely used in Europe. It is an effective method to inactivate harmful protozoans that form cysts. It also works well against almost all other pathogens. Ozone is made by passing oxygen through ultraviolet light or a "cold" electrical discharge.
Reverse Osmosis: Mechanical pressure is applied to an impure solution to force pure water through a semi-permeable membrane. It is designed to remove all chemicals, both natural and added. RO membrane filters have a pore size less than 0.001 micron, giving them the ability to separate individual ions (i.e., dissolved solids) from a solution, and to remove virtually every known bacteria, virus or protozoan. Although reverse osmosis is theoretically the most thorough method of water purification available, smaller units are slow, and are realistically only used for drinking water. A small system for drinking water costs around $1,500 to $2,000. A larger unit that could cope with all the requirements of a household, costs around $15,000 to $20,000.
Ion Exchange Filters
Ion exchange resins are most commonly used in water treatment processes to soften the water supply by exchanging sodium ions for "hardness" ions including calcium and magnesium.
Ion exchange filters exchange the major ions present in the water, removing iron, fluoride and heavy metals. They are not generally suitable for the removal of organic chemicals such as pesticides or chlorine and do not work well when total dissolved solids are high.
It is important to remember that the material absorbed from the water and the resins themselves provide sufficient organic matter and nutrients for bacterial growth. |
| Specifications & Prices are subject to change without notice. E&OE. |
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