On the history of water coagulation
One example for the rich history of TK is the use of natural coagulants for purification of turbid waters. Already as early as the 1st century A.D. One can find historical records from India describing such a practice. But in fact historians believe that oral traditions might go back even much further. However in this ancient Indian text (the Sushruta samhita) some relatively vague description of water coagulation are presented, one of which even today can be easily identified as the use of the seeds of the Kataka plant (Strychnos potatorum L.) (Jahn, 1981 & 1994).
Other records, only slightly younger and probably influenced by its Indian precursors, can be found from the 2nd century A.D. in China. These ancient traditions where adapted to the Chinese climate however, as Kataka plants do not grow very well in these harsher climate conditions: The people of China found out that apricot kernels where just as potent for this tasks as the Kataka seeds. From further historical texts it becomes clear that this technique was really a wide spread practice, especially of the poorer population which was forced to rely on the turbid waters of the main rivers.
Later Islamic traders picked up the knowledge from China and transferred it to the Arabian world. European travelers first described it in the 16th century in China, but more detailed descriptions where made from the (yet again adapted) practises in Egypt. These texts from the same time period, e.g. the end of the 16th century, describe yet again a wide spread practise of the poor, who had to rely on the turbid waters of the Nile. Some confusion exists (do to translations difficulties of the Arab trade language) whether it was almonds they used, or also the cheaper and more accessible a apricot kernels. Yet the practise was similar enough, and further south where apricot trees do not grow some other plants (mostly broad beans = Vicia faba) were used (Jahn, 1994).
It was there in Sudan where the yet most potent natural coagulant was found by a village woman in the early 20th century. A tree introduced by the English from India (yet strangely enough no record of its use as a water coagulant from there exist), Moringa oleifera (also known as the horseradish tree) has seeds with a remarkable strength in clearing turbid waters (Jahn, 1981, 1986 & 1994).
Subsequently the use of this tree (which has also a wide range of other uses, as described later) spread to many other places in Africa though local spread of knowledge (Jahn, 1986 & 1994).
On the other side of the world, in South America similar yet independently developed, techniques can be also found. Chilean historians of the 19th century describe a practise of the native Peruvians and Chileans to use tuna cactus (Opuntia ficus indica) as a natural coagulant. Even older text from the 16th and 17th century also mention Peruvian sailors using a powder called pitu as a mean to clear water. This powder was prepared from roasted grains of Maize (Zea mays) (Jahn, 1981).
However not very many communities around the world can be found still using this TK, and thus it would make sense to investigate if this lost knowledge is worth being reintroduced.
The Moringa tree
The Moringa tree (also named horseradish or drumstick tree) is a small, fast growing drought deciduous tree. It reaches heights of about 5-12m and has 1-2cm large evergreen leaflets . Its seed-pods are up to 120cm long and include small, triangular shaped seeds with three papery wings (Schwarz, 2000).
Phenotype of Moringa oleifera (from Schwarz, 2000)
The Moringa tree originates from central/south Asia, but its different varieties can nowadays be found not only there but also widely spread in Africa and to a lesser extend in South America (Schwarz, 2000). It grows in the entire tropical belt and it relatively tolerant to high temperatures (up to 48°C) but can also survive light frost. Furthermore it is relatively drought resistant (range 250mm- 1500mm p.a. Precipitation), but does not survive prolonged flooding. Optimal soil conditions are therefore well drained sandy loam soils with a pH of 5-9 (Palada and Chang, 2003).
It has been long known for it’s various uses, which include the use of its leaves and seed oil for human consumption and as animal feedstock due to the extremely high content of vitamins and other healthy substances. Its leaves contain “more beta-carotene than carrots, more protein than peas, more vitamin C than oranges, more calcium than milk, more potassium than bananas, and more iron than spinach ” (Palada and Chang, 2003). Babu et al. (2000) have extensivelyy studied the use of Moringa leaves as a food supplement to combatvitamine A deficiency in Malawi where “39.1%, 7%, and 48% of children under five years of age are under weight, wasted and stuntedrespectivelyy” (Babu et al. 2000) due to malnutrition. The leaves of the Moringa tree were shown to be superior to all other local vegetables in this study and therefore could improve people’s health significantly (Babu et al. 2000).
Other recent uses are the utilization of leaf extracts as plant growth factors on experimental fields in Nicaragua (Foidl, 2001) and the use as a powerful coagulant for water treatment. This very useful application was discovered by a rural Sudanese community early in the the 20th century and extensively studied by the German scientist Samia Al azharia Jahn (Jahn, 1981,1986,1994). Kaeser et al. (1991) even constructed an entire rural water treatment plant using Moringa oleifera seeds as the only coagulant and found that such a system is efficient at removing pathogen loads by more than 99% (Kaeser et al. 1991).
Purpose
We investigated if the seed coagulant can be easily used, and if it is possible to produce seedlings for planting in gardens or on the streets.
Method
Moringa olifera seeds were acquired from South Africa (Exotic Plants; Bernd Bordne 1,Scarteen South 6570 Knysna South Africa; www.exotic-plants.de).
Germination (adapted from Palada and Chang, 2003):
- Soak seeds in water for 24 hours; remove water afterwards.
- Put seeds in a plastic bag and store them in a warm, dark place until germination (usually 3-14 days).
- Transfer plant embryos into soil.
Coagulation (adapted from Schwarz, 2000):
- Remove seeds from pods and crush them (< 0.8mm).
- Mix powder with small amount of water to form paste; filter insoluble material with a piece of cloth.
- Add milky suspension to turbid water and stir for half a minute (powder from about 2 seeds per 1l water; depends on turbidity however).
- Continue to stir slowly for 5 minutes.
- Cover container and wait for at least one hour for the suspended particles to settle.
Results
Attempts to germinate seeds under middle European conditions were unsuccessful. Seeds might have been too old for germination however. Flocculation experiments with Rhine water (low turbidity) where inconclusive, or did not yield higher sedimentation rates than untreated control samples.