Natural coagulants at pilot scale

Crushed seeds of the tree Moringa oleifera Lam. (M.oleifera) are a viable alternative to aluminium sulphate as a coagulant for water treatment applications in the developing world. Supporting cases, in both technical and economic terms are presented based on a recently completed field study in Malawi. A pilot scale treatment works operating at a flow rate of 16.51 min-1 reduced raw water turbidity from 1000 NTU to below 1 NTU (header/ mixer tank, gravel bed flocculator, sedimentation tank and rapid gravity filter). The filter was operated as a contact flocculator -filter during periods of low raw water turbidity. 20 NTU inlet values were reduced to below 1 NTU with this treatment unit. Successful M.oleifera plantation trials are briefly reported as is an economic analysis of establishing M.oleifera as a 'coagulant crop' in the Malawi context.