|
Last Update: 05. November 2008 Description: Design and optimization of a water purifying system, with focus on reliability and low maintenance. Background: Safe drinking water is one of the most important components for improving living standards. Un-purified water can cause a large number of different diseases like diarrhoea, typhus or even cholera. In Laos, diarrhoea is the main cause of infant mortality besides malaria. Villagers in Laos often have no access to safe drinking water. The current possibilities for purifying water are: piped systems, wells, and boiling raw water. The former is often not possible in the Lao difficult terrain, especially for more remote systems. Wells have the problem that they are not well maintained so often breakdown (especially hand-dug wells), and the quality of the water is only as good as the container used. Boiling the water requires large amounts of dry firewood and time. Since not all villages have access to larger amounts of wood and a general lack of dry wood exists during the rainy season, villagers often have to drink un-purified water. Even if dry firewood is available, it first has to be cut and transported to the village which means a lot of additional work.
Another issue to consider is that since Laos is only very sparsely populated (ca. 28 persons per km2) most of the villages are off the electrical grid. Connecting the scattered villages to the grid would be extremely costly, so it is not foreseeable that the situation will change for many years. Therefore, it is important that a possible water purifying system is combined with an independent energy source.
Introduction: Two water purifying systems, WATER-PPS (pumping and purification system) and OWRD-FS-2000oz, were tested and compared. WATER-PPS was developed by the Solar-Fabrik AG, and OWRD-FS-2000oz by Our World. The former uses a ceramic filter for the water purification whereas the latter uses UV-treatment. Both disinfect the water without the use of chemical additives. They are supplied with solar electricity which allows the usage in remote areas. Depending on the local conditions the devices can use water from a cistern, groundwater or from surface water. A problem with publicly funded water systems installed in villages is that due to a lack of maintenance the system breaks down after a few years. In order to bypass this problem, a business model was set up in collaboration with Sunlabob whereby the water is sold by a village entrepreneur in 20L bottles at a reasonable price for 80-90% of the villagers. Summary of the status of work: - The two systems were tested and compared in a field test. The WaterPPS was found to be unsuitable for rural use due to the fact that it clogged up too easily.
- The OWRD-FS-2000oz unit with ozone is being field tested in a pilot village, within the commercial model
Operational Details: OWRD-FS-2000oz The OWRD-FS-2000oz system comes in various models which differ slightly in the amount of water they can purify, and the final process. It was determined that for village use, a OWRD-FS-2000oz unit is to be used which includes ozone disinfection and can purify up to 5000L/day of water. Other options include a system with a 400L tank (with UV tank disinfection), but which can only purify 2000L/day. This system consists of a drinking water pump, a water purification unit which includes an electronic control system and optionally ozone purification as well as a raw water pump. There are several filters which remove chemical contaminants. These consist of a preliminary 100µm steel filter which removes suspended particles out of the water. There are then additional filters, usually a carbon filter and fine filter(s) to absorb organic and suspended solid contaminants (more filters can be added depending on the quality of the raw water). The flow sterilisation to remove microbial contaminants consists of a 11 W UV-lamp which disinfects the water streaming through the hose. Optionally, another UV lamp also generates ozone, which also disinfects the water and disinfects the piping system. | | | | The backup battery may supply the system for one day if no solar radiation is available. The system has average drinking water output of 5000 l/d (with flow sterilization). | Sand Filter The filter is an optional extra necessary for areas where the water source is particularly turbid (i.e. river water). The tank is filled with sand, charcoal and gravel to remove large suspended particles, thus relieving the filters in the water purification systems. The system is easily maintained by weekly backwashing, meaning the actual sand only needs to be replaced biannually. | |
Current work: The OWRD-FS-2000oz unit is currently being tested in a fully commercial model in villages in Laos. The testing focuses on reliability, maintenance effort, maintenance costs and the presumed technical knowledge which is needed to run the systems, as well as the robustness of the system and the business model used. | Investigating a clogged filter |
| Expected Outcomes: - Determination of the marketability and sustainability of the systems in Laos.
- Determination of the robustness of the system and business model.
- Determination of the various operational aspects to be considered (i.e. frequency of changing the filters, etc.)
| Involved Agencies: | In cooperation with: |
|
