Frequently Asked Questions

They remove biological contaminants (germs) and solids from water, making it normally safe to drink.

At the heart of an Aquafilter is a “membrane filter” made by a specialist supplier which comprises small tubes (1 mm bore) with 0.00002 millimetre pores (holes) in their walls.

Water is fed through the system by means of a hand pump, flowing water up and down the tubes, with the microscopic holes in the filter walls allowing water to pass through, but holding back dirt, bacteria and viruses.

A washable pre filter with a gauze screen of 0.12 millimetre holes stops sand and other coarse particles from entering the membrane filter.

The remaining finer particles pass through the screen into the membrane filter, where they flow up and down the inside of the tubes, keeping the tubes free from clogging. This dirty water is periodically flushed out of the system.

Water from a well, a stream, a pond, or lake is collected and poured into a container, usually the box the filter came in, and in the case of the family unit also in a bucket or jerry can. This water is pumped through the Aquafilter which cleans it and then pours the clean water into a clean water vessel.

This method is better than pumping directly from surface water, as it allows some dirt to settle rather than going into the filter.

Also pumping directly from a well is not recommended, as it takes a lot of pumping effort just to lift the water, considerably reducing the flow rate of clean water.

No. Aquafilters have a membrane which mechanically removes germs from dirty water.

This can be done in several stages depending on the condition of the input water :

1. Coarse particles are held back by the pre filter screen, which can be periodically washed off.
2. Water flows along the membrane tubes in both directions when pumping, continually washing out the tubes.
3. Clean water can be pushed backwards through the pores, freeing the small particles stuck in them.
4. It is possible for micro organisms to grow inside the tubes, blocking some of the pores. If that occurs, the Aquafilter then needs to be treated with tablets from a pot attached to the unit.

In many applications some of these tasks are not needed.

They do not remove dissolved substances which sometimes occur in water from deep wells. Examples are salt, calcium, or arsenic. Where it is proposed to use an Aquafilter for contaminated deep well water, the water should first be analysed to find the nature of the contamination.

Aquafilters provide water which is clear and free from particles. It is possible for it to be tinted by dissolved substances, for example water may be slightly green from pond weed. This does not make it unsafe to drink.

Water from a public water supply is normally treated to kill the bacteria with chlorine, which stays in the water you drink, which means it can be stored.

Water from Aquafilters is free of chemicals, so the water should not be stored for more than about a day before the germs get back into it. (This is also the case with bottled water or clean well water).

1. Removes all solid particles such as bacteria, viruses, cysts, and protozoa.
2. Produces pure clear water free of chemicals.
3. Long lasting without the need for replacement parts.

1. The hand pump means water can be available on demand. You do not have to decide at breakfast what you will need for lunch!
2. There is continuous flushing of the membrane.
3. They are a very cost effective method of providing clean drinking water.
4. They are the right size for the job. The Aquafilter Community can provide water for a school or clinic, yet it is portable so that it can be carried to a locked room at night. The Aquafilter Family fits neatly in a bucket, box, or adapted jerry can for instant use by a family.

The life of a membrane depends on the condition of the input water used. The membrane may eventually become permanently clogged, and cause reduced water flow. We have as yet had no evidence of Aquafilters suffering any reduced water flow. None of our units in the field has yet shown reduced flow, in one case even after three years of heavy use. As a useful comparison, membrane filters in industrial use normally last over 5 years.

So far, the only part which has been replaced is the pump seal. This is a simple rubber “o” ring. Therefore we now add some spare rings, stored on the piston rod, and it is an easy task to move one to the piston.

The only way the filters can fail to clean the water is if there is a break in the wall of the membrane tube which will then allow dirty water through. The membrane tubes allow water through their walls, but not air when they are damp. This enables simple tests for air leaks to be carried out by the user. These are described in the operation manuals.

There are no international standards for point of use water purification. However, system providers tend to use American EPA (environmental protection agency) guidelines. The University of Newcastle upon Tyne has carried out tests for bacteria, and found that our Aquafilter exceeds the EPA guidelines by a large factor. Details of the tests can be found in the technical pages under the section “Supply of Safe Water”. Independent testing for viruses is also in progress.

To date, over 60 Aquafilter Communities are in use in schools, clinics, and villages in Gambia, Ghana, Haiti, India, and Honduras. At this stage, we send them only to locations where we can get feedback, which has so far been very positive. We also provide Aquafilters to Aquabox, who send out humanitarian aid Boxes to victims of disasters.

The Aquafilter Family has been developed more recently, and so far there are 100s of these smaller filters in operation in developing countries. Many of these have been in successful operation for more than 12 months.

The Safe Water Trust is a non profit making charitable company, limited by guarantee, dedicated to developing and promoting systems for clean water at the point of use in developing countries. It has evolved from and has close links with the Rotary organisation. The work is being carried out in close association with Aquabox.

Aquabox (http://www.aquabox.org/), is a Rotary linked organisation, providing emergency relief in boxes. Aquabox are our partners in the Aquafilter project, and they distribute Aquafilter Community units in their standard boxes for emergency relief. Aquabox also assemble Aquafilter Family units and incorporate them in the boxes as a replacement for the chlorine tablets and carbon filters.