The application of Moringa oleifera as a coagulant for water treatment in developing countries

The focus of this study has been on the ability of crushed seed suspensions of the pan-tropical tree Moringa oleifera Lam. to clarify turbid waters. Information regarding the coagulant effect of the seeds was first published in 1979. Since then a number of studies have been carried out to establish the effectiveness and nature of the coagulant effect. These are reviewed. The coagulation effect has been attributed to water soluble, low molecular weight cationic proteins contained within the seed kernel. The mode of activity has been proposed to be charge neutralisation via the patch mechanism. In an attempt to further the understanding of coagulation behaviour, four water sources in Malawi and Zimbabwe have been examined. A modified theory of protein coagulation that involves a combined charge neutralisation and protein precipitation mechanism is presented. Further work required to fully determine the mechanism of activity is discussed.;In order to establish whether seed solutions could be considered for use within continuous flow water treatment systems a pilot plant was designed and constructed in Malawi. Details of the design are presented. Studies undertaken over a three-year period demonstrated that, as a coagulant, seed solutions were effective. Subsequent to these trials, an evaluation of the efficacy of using seed solutions on an operational treatment works was undertaken. Factors that might be potential constraints to utilisation at this scale, for example seed processing and dosing solution preparation, were investigated. Although effective as a coagulant, it has been concluded that the use of powdered seed suspensions is not a viable option for large-scale applications. Amongst those constraints identified, problems with the preparation of dosing solutions, the potential for increasing Total Organic Carbon levels in treated water and regulatory issues are considered.