Assessment of drinking water treatment using Moringa Oleifera natural coagulant - A Minor Field Study in Maputo, Mozambique

Abstract: The access to safe and clean drinking water is a major concern throughout the world. Surface water has become the most common source for raw water, when large quantities of groundwater often are inaccessible, and as surface water requires more treatment, simple, cheap and efficient process methods are necessary. Turbidity removal is essential for treatment of surface water and is often carried out with coagulation using metal salts as aluminium sulphate. This is used at Àguas de Mocambique (AdM), which provides the city of Maputo with water, but studies suggest that the metal salt can be replaced with a natural coagulant from the Moringa Oleifera tree. The Moringa Oleifera (MO) tree grows in tropical and subtropical regions around the world and its seeds have been used in drinking water treatment in small scale in Sudan and India for generations. The coagulant in the seeds is believed to be one or several proteins that act as a cationic polyelectrolyte. The soluble particles in the water attaches to the active agent, that binds them together creating large flocs in the water. Previous studies indicate that MO is an efficient coagulant and does not have an effect on most of the properties of the water, but an increase in COD has been noticed. Different ways of extracting the active agents are used and this will have an effect of the treatment efficiency. A comparison between MO and aluminium sulphate was conducted using jar test. The optimum dosage of the coagulant was investigated for different levels of turbidity, and monitoring of the properties of the water was performed. Use of MO together with roughing filter, and the possibilities to use MO at AdM was also investigated. Most efficient treatment was found when using aluminium sulphate for all levels of turbidity but the coagulant had an effect on pH and alkalinity. MO had no effect on measured parameters and was found to be most efficient at high raw water turbidity. MO extracted with tap water gave a better treatment than the MO extracted with distilled water or oil, but neither had an impact on the characteristics of the water. A prolonged sedimentation time together with MO improved the treatment and the experiment with roughing filters was successful. Treatment with MO and roughing filter led to a more efficient treatment compared to aluminium sulphate and roughing filter. Moringa is found to be a sustainable, cheap solution for coagulation in drinking water treatment. It is not considered possible to replace aluminium sulphate at AdM with MO at present time, but might be in the future. No current plantations of MO are located in the Maputo area and a stable and secure access to seeds is necessary. For best results MO is to be used together with roughing filters, which, will require reconstruction and investments at AdM. The possibilities of using MO at small scale treatment plants together with roughing filters are good, and provides a realistic alternative to conventional methods, presuming that an adequate amount of plantations are established.