Health Stream Literature Summary - Issue 50 - June 2008

A novel technology to improve drinking water quality using natural treatment methods in rural Tanzania
Mbogo, S.A. (2008) Journal of Environmental Health, 70(7); 46-50.

Providing clean and safe water to those in rural areas in developing countries is a great challenge. It is estimated that one billion people worldwide do not have access to treated drinking water and around three million people die annually from waterborne diseases. In Tanzania, over 80 percent of the population live in rural areas of which only 30 percent of are reported to have access to safe potable water. The majority of the population rely on water sources heavily polluted by animal excretions, human excreta and sewage effluents. Economic and political constrains mean the universal provision of piped water is not currently feasible therefore interim solutions are needed. One approach as an alterative to conventional chemical treatment methods is the use of indigenous or natural treatment methods using plant materials and solar radiation. This study was conducted to evaluate the potential of these traditional treatment methods. The seeds from five Tanzanian plants were used for turbidity removal, and water was sterilized by solar energy for bacterial destruction, results were compared with standard treatment practices.

The study area included two districts in semi-arid areas of Tanzania where scarcity and pollution of water are serous problems. A questionnaire was administered randomly to community members in the specified areas and included information on the indigenous uses of plant materials for water purification. Materials were also collected for laboratory analysis. Plant materials were collected from five plant varieties Vigna unguiculate, Phaseolus mungo, Glycine max, Pisum sativam and Arachis hypogea. Twigs, leaves and pods were collected from the target plants as well as seeds. Seeds were dried then ground and sieved to yield a fine powder. This powder was blended with distilled water and resulted in a 1 percent w/v solution. Coagulation tests were conducted and water samples were examined for physical and chemical quality parameters and for the lowest dose of coagulant that gave satisfactory turbidity reduction of water. Physical and chemical parameters measured of raw and clarified water included: pH, conductivity, alkalinity and total hardness. Turbidity was determined by the adsorptometric method with a turbidity metre. Five plastic 1,000 mL bottled were filled with water clarified by natural coagulants and put on a black-painted roof where they remained for different periods of time and were then examined for microbial numbers.

Parents were named by 68% of respondents as the main source of knowledge about the plants whose seeds are used traditionally for water purification. There were only 41% of respondents who treated water during the rainy season and only 11 percent treated water during the dry season, the difference attributed to very high-turbidity water in the rainy season whereas during the dry season people can dig the river bed to obtain clean water. Main water treatment technologies were classified by respondents as plant species (38%), boiling (42%), sedimentation and decantation in pots (65%), other technologies such as ashes and clay (8%) and no treatment (16%).

When raw water (482 NTUs) was flocculated with different concentrations of extracts, turbidity fluctuated between 0 NTUs and 15.73 NTUs, which constitutes an efficiency of 97% to 100%. There was a significant increase in the efficiency of seed extracts when they were used as coagulate aid (80% natural coagulant + 20 % alum) with residual turbidity of clarified water decreased from 482 NTUs to 0 NTUs, a 100% efficiency for all plant species tested. Laboratory results were tested at the household level using plastic containers commonly used to contain cooking oils. At optimum concentration, none of the seed powders affected the pH or the conductively of the water, and alkalinity and total hardness remained almost constant and were within acceptable levels according to WHO standards for drinking water. However when alum was used the pH, conductivity and alkalinity changed significantly at optimum concentrations and measures had to be taken to correct these parameters to acceptable levels.

To test the removal of bacteria by solar radiation, water was clarified by the most efficient natural coagulant, Phaseolus mungo. Tests were conducted on water with turbidity of 0 NTUs and bacteria counts per 100 mL of 25 for white colonies (Bacillus spp.) and 7 for red-yellowish colonies (Enterobacter/Pseudomonas). Bacterial colonies appeared to decrease with time of solar radiation in the disinfected water samples compared with the non-disinfected sample. After 8 hours of solar radiation on the black roof, both white and red-yellowish bacteria were 100 percent removed.

This study indicates that clarification of turbid water with natural seed coagulants combined with the use of solar radiation could provide a simple low-cost water treatment method for rural communities in Tanzania. This study shows it is possible to provide clean and safe water in the domestic rural environment through indigenous knowledge that can be adapted and supported by contemporary scientific knowledge. Use of theses methods can lessen poverty, reduce excess morbidity and mortality from waterborne diseases and improve the overall quality of life in rural areas.

Comment Bacterial solar inactivation experiments appear to have been conducted using low ambient contamination levels (around 30 CFU/100ml) rather than spiking with higher levels of faecal indicator organisms, therefore only a small log reduction could be demonstrated. Bacterial levels prior to coagulation treatment were not reported.