A novel technology to improve drinking water quality using natural treatment methods in rural Tanzania.

Introduction

Provision of clean and safe water in rural areas is a great challenge for the developing countries of the world since most communities rely on poor traditional sources that often provide unsafe domestic water. It is estimated that world over, about three million people die annually from water-borne diseases (World Health Organization [WHO], 1999). This situation is a source of great concern and makes water purification at the household level especially desirable and important. In Tanzania, over 80 percent of the population live in rural areas, of which only 30 percent are reported to have access to safe potable water (World Bank, 1994). The reliance of the majority of the population on polluted water supply sources poses a great risk to health. These sources are heavily polluted by animal excretions, human excreta, and sewage effluents. Fecal pollution of water supplies is attributed to poor disposal of excreta and a low standard of community hygiene.

Conventional water treatment relies on the addition of chemicals such as alum (aluminium sulfate) as coagulants and the addition of chlorine as a bactericide. The availability of these chemicals, which depends on foreign exchange, is unreliable and unpredictable. Because of economic and political constraints, the universal provision of piped water is not currently feasible. This circumstance leaves millions without access to safe drinking water (WHO, 1999). Interim solutions are clearly needed. For these reasons, the Chemistry Department of the University of Dar es Salaam is looking at alternative water purification methods (Mbogo & Malunga, 2003; Mbogo & Othman, 2000). One approach has been the on-site generation of sodium hypochlorite solution with an electrochemical hypochlorite solution generator (EHSG) as a simple method of producing a drinking-water disinfectant (Mbogo & Othman, 2000). The EHSG can be constructed and operated easily at any place and at any time in rural areas with just a chemical battery and kitchen salt. The second approach has been the use of indigenous or natural treatment methods using plant materials and solar radiation as alternatives to conventional chemical treatment methods. A majority of Tanzanians in rural areas still rely on traditional indigenous technologies for their daily needs--hence the need to study the viability of some of the indigenous technologies applied in various areas with a view to scientifically validating and promoting them.

Plant materials have for many centuries been used as coagulants in developing countries to clarify turbid water (Jahn, 1988; Schulz & Okun, 1984). In India, crushed seeds of the Nirmali tree have been used for centuries to clarify muddy water (Tripath, Chaudhuri, & Bokil 1976). Jahn and Diar (1979) have reported that in Sudan seed powder from the indigenous plant Moringa is added to drinking water to remove turbidity.

Studies have shown that synergies from the combined application of radiation and thermal treatment have a significant effect on the die-off rate of microorganisms (Wegelin, Canonicas, Michener, Pesaro, & Metzler, 1994). Although the technology of solar disinfection of water is not practiced in Tanzania, the country falls within favorable latitudes (35[degrees]N and 35[degrees]S) in terms of solar radiation intensity.

The purpose of my study was to evaluate the potential of traditional treatment methods (i.e., those based on local knowledge inherited from previous generations). The study used plant materials (seeds) from five Tanzanian plants for turbidity removal and used sterilization of water by solar energy for destruction of bacteria, and it compared the results with those of standard treatment practices.

Methods

Study Area

The study involved survey work that covered the Iramba and Bariadi districts, in the Singida and Shinyanga regions, respectively; these regions belong to the semi-arid areas of Tanzania, where scarcity and pollution of water are serious problems.

Data Collection

The study involved a field survey that collected information on the indigenous uses of plant materials for water purification and collection of materials for laboratory analysis. The survey used a pre-designed questionnaire administered randomly to community members in the specified areas.

Data Analysis

Analysis of the information obtained through the questionnaire was performed with Microsoft Excel.

Plant Materials Used as Coagulants

Five types of natural coagulating plant materials were collected from Iramba and Bariadi districts and labeled accordingly. Botanical samples such as twigs, leaves, and pods were collected from the target plants, along with the seeds, and were examined in the Herbarium Unit of the Botany Department, University of Dar es Salaam, for identification. Five plant varieties were collected and identified as Vigna unguiculata, Phaseolus mungo, Glycine max, Pisum sativam, and Arachis hypogea.

Preparation of Seed Extracts

The seeds were dried for a day in an oven at 40[degrees]C. The dried seeds were then ground in a kitchen blender and sieved through an iron sieve (200 [micro]m) to yield a fine powder. Ten grams of resulting natural coagulant powder was blended for 10 minutes with a kitchen blender. This blended mixture was made into 1 liter (1,000 mL) through the addition of distilled water, which gave a coagulant strength of 10 mg/mL. The resulting 1 percent w/v solution was used throughout this study. When the extract was ready for use, it was stored in a refrigerator.

Coagulation Tests

Coagulation tests were conducted with jar-test equipment (Phipps & Bird, Richmond, Virginia), which has a base floc illuminator. Flash mixing time (at 100 rpm) was 1 minute and flocculation time (at 40 rpm) was 15 minutes. The samples were then allowed to settle for 30 minutes, after which the water samples were examined for physical and chemical quality parameters and the lowest dose of coagulant that gave satisfactory turbidity reduction of the water was established.

Physical and Chemical Parameters of Raw and Clarified Water

Physical and chemical parameters of raw and clarified water--pH, conductivity alkalinity, and total hardness--were determined according to standard methods (APHA, 1992). Turbidity was determined by the adsorptometric method with a turbidity meter.

Determination of Microbial Numbers

Five plastic 1,000-mL bottles were filled to the 1,000-mL mark with water clarified by natural coagulants, and the lids were put on. The bottles were then put on a black-painted roof, where they stayed for different periods of time, after which the water samples were examined for microbial numbers according to the standard plate count method (Holden, 1970).

Results

Questionnaire Analysis

The plants from which the seeds were taken have traditionally been known to the communities in the two districts for their use in water purification. Parents were named as the main source of knowledge about these plants by 68 percent of the respondents. This result indicates that the species are familiar to the people living in the communities. Respondents identified the main water sources for their communities as follows: river (48 percent of respondents), shallow wells (18 percent of respondents), bore-holes (8 percent of respondents), dams (6 percent of respondents), springs (12 percent of respondents), and other sources such as rock catchments (8 percent of respondents). Only 41 percent treated water during the rainy season, and only 11 percent treated water during the dry season. The difference could be attributed to the fact that during the rainy seasons, the rivers, wells, and dams have very high-turbidity water, while during the dry season people can dig the river bed to obtain clean water. The respondents classified the main water treatment technologies as plant species (38 percent), boiling (42 percent), sedimentation and decantation in pots (56 percent), other technologies such as ashes and clay (8 percent) and no treatment (16 percent).

Water Quality

Raw water (482 nephelometric turbidity units [NTUs]) was flocculated with different concentrations of the extracts. The observed optimum dosage, which is the minimum dosage corresponding to the lowest turbidity, varied by plant species (Table 1). Residual turbidity after clarification with seed extracts used as the primary coagulant (100 percent natural coagulant) indicated removal of 97 percent to 100 percent. There was a significant increase in the efficiency of seed extracts when they were used as coagulant aids (80 percent natural coagulant + 20 percent alum); residual turbidity of clarified water decreased from 482 NTUs to 0 NTUs, which indicates 100 percent efficiency for all plant species tested (Table 2). To test the laboratory results at a household level, I conducted another jar test with some modifications to the test design. Five plastic containers with a capacity of 2 liters each were filled with 1 liter of turbid water (482 NTUs); plastics of this type are readily available in many houses in villages as they are used to contain cooking oils. Seed powder at the optimum concentration (Table 1) was poured into the turbid water in the five plastic bottles. The water was stirred with a spoon and left to settle to clarity, after which the precipitation time was noted (Table 3). Precipitation time varied between 7 and 25 minutes for the different plant species. At optimum concentration, none of the seed powders affected the pH or the conductivity of the water. Alkalinity (CaC[O.sub.3]) and total hardness (CaC[O.sub.3]) remained almost constant and were within acceptable levels according to WHO standards for drinking water. When alum ([Al.sub.2]S[O.sub.4]) was used, however, the pH, conductivity and alkalinity changed significantly at optimum concentration, which necessitated intervention measures to correct these parameters to the acceptable levels.

Bacterial Removal from Water Clarified with Natural Coagulants

The use of solar radiation to remove bacteria was tested in water clarified by the most efficient natural coagulant, Phaseolus mungo (Table 4). The test was conducted on water with turbidity of 0 NTUs and bacteria counts per 100 mL of 25 for white colonies and 7 for yellow colonies. The species present in the water in both disinfected samples (solar radiation) and non-disinfected samples (water purified with natural coagulants) were predominantly yellowish-red colonies (Pseudomonas/Enterobacter spp.) and white colonies (Bacillus spp.). Bacteria colonies appeared to decrease with time of solar radiation in the disinfected water samples compared with the non-disinfected sample. Because of the limitations of currently available identification schemes, it was not possible to classify the yellowish-red organisms as Pseudomonas or Enterobacter spp. As indicated by the results given in Table 4, after 8 hours of solar radiation--during which the sun was assisted by the black roof, which helps absorb heat--removal of both white (Bacillus spp.) and red-yellowish (Enterobacter/Pseudomonas) bacteria was 100 percent.

Discussion

My study indicates that clarification of turbid water with natural coagulants from plant material (seeds) combined with use of solar radiation (on a black-painted roof for 8 hours) could provide a simple low-cost water treatment method for rural communities in Tanzania. High levels of turbidity can protect microorganisms from the effects of disinfection and can stimulate bacterial growth. The residual turbidity of water clarified with seed extracts from five Tanzanian plant species fluctuated between 0 NTUs and 15.73 NTUs, which constitutes efficiency of 97 percent to 100 percent. The degree of disinfection can be inferred from the bacteria counts before and after application of solar radiation. When the numbers of colonies fall appreciably, some amount of disinfection has occurred. When the number of cells is zero, adequate disinfection has occurred. The residual-turbidity values of the clarified water complied with WHO's standards for drinking water (WHO, 1998). Using the sun to sterilize water by leaving the water on a black-painted roof for 8 hours and subjecting it to a combination of ultraviolet rays and heat inactivated 100 percent of both white (Bacillus spp.) colonies and red-yellowish bacteria isolate (Enterobacter/Pseudomonas spp.) colonies. This finding is particularly significant as there has been some limited success in the use of natural coagulants alone as a household water disinfectant. It has been shown that neither alum nor natural coagulants can yield water free from coliforms (Jahn, 1988; Tripath, Chaudhuri, & Bokil, 1976); coliform-free water can be achieved only by chlorination. Disinfection by sun could be a cost-effective and environmentally friendly technology compared with the boiling of water--which uses firewood--and could conserve forests. When water is disinfected by boiling, the smoke from the firewood can have an impact on health and on the taste of the water. The results from the combination of natural treatment methods using plant seeds and solar radiation indicate that this method can effectively clarify and disinfect household drinking water. More work needs to be done, however, if more people are to enjoy the benefits. More outreach programs should be made available to people in rural areas to create awareness of natural treatment methods. Further studies should be conducted to assess the possibility of extending these findings to other applications, like oil production and medicinal plant uses.

Conclusion

Access to clean and safe drinking water is difficult in rural areas of Tanzania. Water is generally available during the rainy season, but it is muddy and full of sediments. Because of a lack of purifying agents, communities drink water that is no doubt contaminated by sediment and human feces. So the use of natural coagulants that are locally available in combination with solar radiation, which is abundant and inexhaustible, provides a solution to the need for clean and safe drinking water in the rural communities of Tanzania. The findings show that 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 this technology can reduce poverty, decrease excess morbidity and mortality from water-borne-disease infections, and improve overall quality of life in rural areas.

Acknowledgements: I owe great thanks to the community members in the surveyed areas for their cooperation and honesty in giving all the indigenous information on the plant species used for water clarification during the field survey. The author thanks the University of Dar es Salaam, which provided financial assistance through the Swedish International Development Agency, the Tanzania Commission for Science and Technology, and the African Institute for Capacity Development, Japan.

Corresponding author: Professor Shaaban Aman Mbogo, University of Dar Es-Salaam, P.O. Box 35061, Dar Es-Salaam, Tanzania. E-mail: [e-mail], [e-mail].

REFERENCES

American Public Health Association, (1992). Standard Methods for the examination of Water and Wastewater (18th ed). Washington, D.C.: Author.

Holden, W.S. (1970). Water treatment and examination. London: Churchill.

Jahn, S.A., & Diar, H. (1979). Studies on natural water coagulants in the Sudan with special reference to Moringa oleifera seeds. Water S.A., 5(2), 90-97.

Jahn, S.A., (1988). Using Moringa oleifera seeds as coagulant in developing countries. Journal of the American Water Works Association, 96, 43-50.

Mbogo, S.A., & Othman, O.C. (2000, July). Study on the enhancement of hypochlorite yield in electrochemical hypochlorite generator to serve as a simple rural water disinfectant production. Paper presented at the Proceedings of the 1st Tanzania Chemical Society International Conference.

Mbogo, S.A., & Malunga, D. (2003, July-August). Studies on the use of locally mined kaolin (china clay) in the preparation of aluminium sulfate used for water purification. Paper presented at the 7th International Chemistry Conference in Africa Dar es Salaam Tanzania.

Schulz, C.R., & Okun, D.A. (1984). Surface water treatment for communities in developing countries. New York: John Wiley & Sons.

Tripath, P.N., Chaudhuri, M., & Bokil, S.D. (1976). Nirmil seed--A naturally occurring coagulants. Indian Journal of Environmental Health, 16(4), 272-281.

Wegelin, M., Canonicas, S., Mechsner, F., Pesaro, F., & Metzler, A. (1994). Solar water disinfection: Scope of the process and analysis of radiation experiment. Journal of Water Supply Research and Technology--Aqua, 43(3), 154-169.

World Health Organization. (1998). Guidelines for drinking water quality (2nd ed.). Geneva: Author.

WHO. (1999). The World Health Report 1999. Geneva: Author.

World Bank. (1994). World Development Report. Oxford: Oxford University Press.

Although most of the information presented in the Journal refers to situations within the United States, environmental health and protection know no boundaries. The Journal periodically runs International Perspectives to ensure that issues relevant to our international constituency, representing over 60 countries worldwide, are addressed. Our goal is to raise diverse issues of interest to all our readers, irrespective of origin.

Shaaban Aman Mbogo, Ph.D.

TABLE 1 Turbidity Removal by Traditional Plant Materials Used Alone, by
Comparison with Alum

Treatment  Residual NTUs in Water (a) After Treatment
Dose       Glycine  Phaseolus  Arachis  Pisum    Vigna
(mg/L)     max      mungo      hypogea  sativam  unguiculata  Alum

   0       482      482        482      482      482          482
 200        26.4      8.4       34.5     11.6     14.6         34.6
 400        18.2      6.9       23.4      9.7      7.9         25.7
 600         8.6      2.9       19.7      7.8      6.2          3.93
 800         9.5      0.00      23.15     7.15     3.67         1.62
1000         5.63     1.58      15.73     4.48     5.42         0.00

(a) The raw water had the following parameters:
* original turbidity: 482 NTUs,
* temperature: 35[degrees]C,
* alkalinity (as CaC[O.sub.3]): 80.2.mg/L,
* total hardness (as CaC[O.sub.3]): 88.5 mg/L,
* conductivity: 1.25 mS/cm, and
* pH: 7.6.

TABLE 2 Turbidity Removal by Traditional Plant Materials Used as
Coagulant Aids, (a) by Comparison with Alum Alone

Treatment  Residual NTUs in Water After Treatment
Dose       Glycine  Phaseolus  Arachis  Pisum    Vigna
(mg/L)     Max      mungo      hypogea  sativam  unguiculata  Alum

   0       482      482        482      482      482          482
 200        23.68     7.86      24.6     10.4     11.68        34.6
 400        17.23     6.63      20.21     9.03     6.95        25.7
 600         4.42     0.00       8.64     2.54     3.66         3.93
 800         0.00     0.00      11.17     0.00     0.00         1.62
1000         0.00     0.00       0.00     0.00     0.00         0.00

(a) 80% natural coagulant and 20% alum.

TABLE 3 Water-Purifying Plant Species (Seed Powder) and Flocculating
Time (a)

Plant species      Optimum Dosage(g/L)  Precipitation Time (min)

Glycine max        1                    14
Phaseolus mungo    0.8                   7
Arachis hypogea    1                    25
Pisum sativam      1                    12
Vigna unguiculata  0.8                  10

(a) 1 liter water.

TABLE 4 Removal of Bacteria by Solar Radiation from Water Clarified with
Phaseolus mungo (a)

Time (Hours)  Plate Count per 100 mL

0             25 (W), 7 (Y)
1             22 (W), 6 (Y)
2             20 (W), 5 (Y)
4             12 (W), 3 (Y)
6              4 (W), 1 (Y)
8             nil (W), nil (Y)

(a) W = white colonies. Y = yellow colonies. Original plate counts were
25 per 100 mL (W) and 7 per 100 mL (Y). Water turbidity was 0 NTUs.