Originally Appeared in: Amaranth to Zai Holes, Chapter 11
We learned of another use for the multipurpose tree Moringa oleifera from Dr. Samia Al Azharia Jahn with the Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ) in Germany. Suspensions of the ground seed of the moringa tree are used as primary coagulants to clarify Nile water. At high turbidities their action was almost as fast as that of alum, and at medium and low turbidities >30 FTU it was comparable with the optimum dose and proper stirring technique. The doses required did not exceed 250 mg/l.
Coagulating the solid matter in water so that it can be easily removed can remove a good portion of the suspended bacteria. "River water is always faecally polluted. At our sampling site the total coliforms amounted during the flood season to 1600-18,000 per 100 ml. Turbidity reductions to 10 FTU were achieved after one hour, reducing the coliforms to 1-200 per 100 ml. Good clarification is obtained if a small cloth bag filled with the powdered seeds of the moringa is swirled round in the turbid water." "With raw water turbidities below 30 FTU no satisfactory removal of suspended matter can be achieved unless the seed suspension is used in combination with alum."
The material can clarify not only highly turbid muddy water but also waters of medium and low turbidity which may appear milky and opaque or sometimes yellowish or greyish (showing annual turbidity fluctuations between 50-300 FTU, such as the White Nile or several African lakes). During the cool season, complete clarification, which takes only one hour in warmer water, may take two hours unless the water is left in the sun for some time to raise its temperature."
The number of seeds required for treatment depends on the local average weight of their white kernels, found to range from 130-320 mg in different clones. "In the case of the Blue Nile, for example, water of low turbidity in the initial and final flood season needs doses equivalent to about one quarter of a 200 mg seed per liter, water of medium turbidities needs half a seed per liter and at high turbidities the dose should be 1-1.5 seeds per liter." Water from a different river will require different quantities of clarifier because of variable characteristics of suspended material. Simple experiments in a jar will determine the best dose.
To prepare the seed for use as a coagulant, remove the seed coats and the "wings." The white kernel is then crushed to a powder, using a mortar or placing in a cloth on top of a stone and crushing. The powder should be mixed with a small amount of clear water (about a 2% suspension) in a small bottle. Close the bottle, then shake at least 5 minutes to obtain a good water extract. This milky extract is then poured through a tea strainer before being added to the turbid water. It is even better to put some thin clean wide-mesh cotton cloth on the strainer.
"The milky white suspension has to be added to the turbid water and stirred fast for at least one minute. If a wooden soup whisk is used, the nails sometimes present in these gadgets should be replaced by small wooden sticks. After that the floc will not form unless it is stirred slowly and regularly (15-20 rotations per minute) for about five minutes." "After stirring the treated water should be covered and left to settle for at least an hour." If moved or shaken before then, clarification will take much longer or fail to reach completion. The GTZ is planning implementation projects in Indonesia and Kenya. Dr. Jahn has retired, but you may still write her at GTZ, Abt. 414; Postfach 5180; D-65726 Eschborn, GERMANY.
Dr. Samia Al Azharia Jahn has written a 539-page book, Proper Use of African Natural Coagulants for Rural Water Supplies. (Chapter titles: Annual fluctuations in raw water quality, Water treatment with traditional plant coagulants, Special microbiological and toxicological studies on water purification, Cultivation of moringa trees, Introducing domestic water treatment to rural people, Practical guide to domestic water coagulation and hygienic water storage). Much of the book is devoted to moringa. French and Spanish translations are in preparation. The book may be available from the Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ) at the address above; fax 06196-79-73-17. Dr. Jahn has sent us seed for two related, more drought-tolerant species which, if we get them to produce, we will offer to you. Dr. Jahn would like to hear from you if you are working with moringa in a major way.
She also sent us an article from the East African Medical Journal that investigated whether water treated with moringa seed powder might be toxic to people. Pounded seeds were fed to rats for 6 weeks with no toxic effects. "As the plant material acts as a flocculent [makes solids come together and settle], one might assume that most of it will get trapped in the sediment and only easily dissolvable substances will be present in the water." Furthermore, moringa "seeds are used for food; they are roasted like peanuts, pounded for tea and curries are prepared from the green pods." [I have not heard of the mature dried seeds being eaten, and at least the variety we have is quite distasteful, so I wonder if these food uses are not all for green seeds.]
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