NGO "ANOTHER WAY" (STICHTING BAKENS VERZET), NETHERLANDS, SUSTAINABLE INTEGRATED SELF-FINANCING DEVELOPMENT PROJECTS AND ADVANCED DEVELOPMENT TECHNOLOGIES

The digging of duly protected well to permanently supply communities with water is preferred to the drilling of bore-holes. From the economics point of view there is a big difference, as hand-dug wells can be prepared using labour under the local money systems. This would lead to a reduction in the formal money costs involved.

Where water tables are deep, bore-holes will have to be drilled. It is unlikely there be drilling companies active in the project area itself who are willing to work under the local money systems. This means that drilling costs are generally expressed in formal money terms. These costs are high. The costs of drilling 200 wells would represent a large part of the budget.

Large savings can be made where just 35-45 large diameter bore-holes are drilled instead of 200 4’’ ones. The 35-45 large diameter bore-holes would cost a fraction of what would otherwise be necessary. The amount provided in item 70101 of the typical project budget to drill 3500m of 8-10’’ internal diameter borehole is Euro 525.000. The amount need for 20000m of 4” diameter boreholes would be about Euro 2.600.000. The difference is Euro 2.075.000, or 55% of the typical formal money (Euro 3.750.000) of individual integrated development projects.

For detailed information on the siting of wells, see Carter R. et al, Siting of Drilled Water Wells – A Guide for Project Managers, Field Note 2010-5, Rural Water Supply Network (RWSN), St. Gallen, June 2010.

For information on nine basic principles relating to cost-effective boreholes, see Danert K, et al, Code of Practice for Cost-Effective Boreholes, Rural Water Supply Network (RWSN), St. Gallen, 2010.

Solar pumps.

If several pumps are to be installed in a single large-diameter bore-hole, a high efficiency solar pumping is needed which can both pump water over high heads and force it over several kilometres is necessary to the water tanks installed near users’ houses.

Taking the high purchasing costs of solar panels into account, high efficiency pumps should be chosen. This implies the choice of positive displacement pumps in preference to centrifugal pumps. Obviously all reliable pumps meeting the basic technical requirements are in principle acceptable. The one with the lowest number of inherent design errors should in principle be acceptable.

The technology recommended is the solar submersible balanced horizontal axis piston pump technology.

Click here for the complete installation manual. The manual includes information on the factors influencing the installation of solar submersible pumps.

Click to see a drawing of a solar submersible pump installation.

Another potentially usable technology is the progressive cavity (or helicoidal rotor) pump., such for example as the HR series marketed by Bernt Lorentz Gmbh, or the Mono Pumps design. The inherent problem with the helcoidal rotor system is that the rotor turns inside a stators made of flexible materials such as rubber. Where there is sand in suspension in the water, the contact between the rotor and the stator becomes less tight with consequential loss of efficiency.

A «classic » manual on solar pumping is Kenna J and Gillett W. Solar Water Pumping – A Handbook , Intermediate Technologies Publications, London, 1985 ISBN 0 946688 90 7. Unfortunately this publication is not available on the internet.

Click to see a drawing of drinking water structures at well commission level.

Subject always to the borehole capacity, several solar pumps can be installed in the one bore-hole. The solar panels for each pump are installed next to the bore-hole. Te bore-hole area is controlled by guards answering to the Well Commission. Each solar pump with its photovoltaic system belongs to the tank commission it serves.

Water is fed to the water tank served by a flexible polyethylene feed pipe, which can be several kilometres long.

Back-up hand-pumps.

Take another look at the drawing showing drinking water structures at well commission level.

On condition that the static water level in the bore-hole is not deeper than 45 meters, a triple hand-pump system can be installed next to the bore-holes. The hand-pumps serve as back-up in case of break-down of a solar pump, or in case of long periods of poor weather, or in case of emergencies. Because of the quantity of pumps installed in the well and the need to have access to the well for pump maintenance, installation near the well head rather than on top of it is preferred.

This means that the hand-pump feed-pipe systems must be flexible.

Two types of hand-pumps respond to these requirements. They are the so-called «hydraulic » pumps.

The recommended technology is the inertia or water oscillation pump. Click here to see the special features of water oscillation pumps. These pumps have just one single length of flexible feed-pipe.

Another appropriate technology is the pedal-driven hydro-pump or, eventually its , hand operated version. This pumping system needs two flexible feed pipes, one for the hydraulic operating system and an outlet pipe for water delivery.

1. Research.

Multiple pump systems are preferred to one large system. Explain on one page the reasons for this choice. Don’t forget to mention, amongst other things, the concepts of decentralisation and maintenance. You can draw a parallel with aircraft on intercontinental flights which have several engines instead of just one.

2. Research.

Make a one-page summary of the reasons for using single lengths of flexible feed pipes. You might wish to mention, amongst other things, the lack of joints, pipe flexibility eliminates need for verticality, the weight of systems when full with water, and the speed of pump maintenance.

3. Research.

On one page explain why a tracker is important, and why manual tracking systems have been preferred.

4. Research.

The recommended hand-pump technology has all parts in relative movement including the pistons placed above ground level.Give a one-page explanation of the advantages of that solution.

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◄ Fourth block : Section 5: Services structures.

◄ Fourth block : The structures to be created.