Low technology for clean water

A British company offers hand pumps and simple techniques for extracting water conveniently and hygienically from shallow sources like sandy riverbeds.
In addition to improving the quality of, and access to fresh water sources in rural areas, the technology of SWS Filtration can also be applied to supply clean seawater from sandy beaches f {mosimage}A British company offers hand pumps and simple techniques for extracting water conveniently and hygienically from shallow sources like sandy riverbeds.
In addition to improving the quality of, and access to fresh water sources in rural areas, the technology of SWS Filtration can also be applied to supply clean seawater from sandy beaches for fish farms, prawn hatcheries, aquaria, swimming pools, small desalination plants, etc.
Many rivers have deep, sandy beds, which appear dry but are actually reservoirs of water throughout the dry season. Furthermore the water is clean, and, if extracted hygienically, safe for human consumption.
SWS Filtration has developed well-jetting techniques by which small diameter wellscreens are inserted into the sand and then connected to either a hand or mechanical pump to draw water before it is contaminated.Unlike conventional boreholes which require heavy drilling, well-jetting is done by hand, using only one or two portable engine pumps, a length of hose, some pipes and a filter screen. Well-jetting techniques vary to suit particular ground conditions.
The company also offers two types of hand pump. The first is the SWS Rower Pump, a manually operated, suction piston pump to draw the water. It is adapted from the Rower pump, which was developed in the 1980’s in Bangladesh where it is widely used.
The Rower pump looks unlike a conventional pump. Its cylinder is not upright, but placed into the ground at an angle of about 30™  º. The operator holds a wide T-handle and pulls and pushes directly on the piston rod, so that the pumping action resembles the rowing of a boat. However, the pump features all main components of conventional models, including a foot valve, piston valve and pump cylinder.
The pumps are not only easy to operate, even by children, but also to make and maintain. Their application is limited to areas where the water is within six metres (20ft) of the surface.
Rower pumps do not have to be placed directly over the water source, so they are ideal for lifting water from low level springs, shallow wells or river beds, which are often important sources of drinking water, but in many cases the water is contaminated by the use of dirty buckets or by animal access. By capping a well or water hole and using a pump instead of buckets, water remains clean. Where necessary, the pump can be connected to a sub-sand filter.
The second SWS pump is the “Canzee Pump”. This is a direct action manual pump, which lifts water from beyond suction range, commonly to eight or ten metres. It is unusual in not having piston seals and like the Rower, servicing is very simple.
SWS can either sell complete pumps or assist in setting up assembly workshops locally, where demand justifies this. The pumps cost around ™  £200, including pipes and filter while the minimum investment to start well jetting is ™  £1,000.
The company has won the 1990 IBM Award for Sustainable Development for their work in Africa. However, the techniques are also applicable in South America and in parts of Asia.
The technology for extraction and filtration of seawater from sandy beaches is essentially the same as for fresh water, says SWS director Richard Cansdale. As most sea water intakes tend to be on a much larger scale, he recommends the Liquivac pump. “This pump costs about ™  £3,500, but has all stainless steel parts which makes it ideal for pumping seawater,” he says.
In this venture SWS is collaborating with British pump engineers Tomlinson Hall, developers of the Liquivac.
The pump is used to pull combinations of liquid, air and fine solids through long suction lines and generate lifts of up to 8 metres. It can be installed up to 500 metres from the sea and still extract water continuously, even at low tide. Rower pumps could be used in small operations, for instance in small-scale salt production.
SWS FILTRATION: swsfilt@dial.pipex.com Tel +1670 772214; Fax +1670 772363
TOMLINSON HALL: stuart@tomlinson-hall.co.uk Tel +1642 675696; Fax +1642 676569
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