It is known that seed proteins of moringa (Moringa oleifera) are useful as a natural coagulant for water purification [1]. Moringa plant is distributed in tropical and subtropical zones, and named Kangaluni in Malawi. This study was conducted to investigate the effectiveness of moringa seed extracts on clarification of turbid waters.
(1) Conditions for affecting turbidity removal
・Kaolin density in turbid water
When water-soluble fraction (1.2 mg protein/ml) was added to kaolin suspension (A600=0.157), turbidity removal was approximately 80%, which was highest reduction compared with lower densities (A600=0.027 and 0.019) .
・Protein contents of water-soluble fraction added to turbid water
Protein samples diluted in the range of 12-240 µg/mL were prepared and used for coagulation assay. Effective dose in removal of water turbidity was more than 20 µg/mL protein.
・Thermal stability of water-soluble fraction
Coagulation activity was maintained after heat treatment, ie. 82% removal in unheated and 85% in heated samples.
(2) Fractionation of powder extract
Comparative assay of different fractions was made using turbid water with high kaolin density. The turbidity removal by water-soluble, 0.5M- and 1M NaCl-soluble fractions was 82%, 57% and 77%, respectively.
The potential activity of moringa coagulant was withdrawn in a suitable combination of kaolin density and concentration of seed proteins. Water turbidity can be removed up to 80% for 2 hr incubation, and close to the level of clear water during prolonged time. Coagulant activity was found in water-, 0.5M NaCl- and 1M NaCl-soluble fractions, suggesting that active proteins would be accumulated as heterogeneous forms in seeds.
Moringa seeds can be utilized as a teaching material for learning water treatment in secondary school, and are environment-friendly coagulant with low cost in comparison with conventional coagulants such as aluminum and synthetic polymers, indicating that water clarification by moringa seeds is acceptable in the rural community of Malawi.