A sustainable low-cost phytodisinfectant-sand filter alternative for water purification.

Abstract

In Sub-Saharan Africa, 80-90% of all infectious diseases are water borne. Governments in these countries spend a significant proportion of their budgets importing alum and chlorine from western nations for municipal water treatment. More than 1.2 million people lack safe drinking water in developing countries. Apart from high cost of treating water in sub-Saharan Africa, waterborne microorganisms are developing resistance to currently used disinfectants such as chlorine. To meet the United Nations Millennium Development Goals (MDG) of providing safe drinking water, alternative and complimentary approaches such as the application of Moringa oleifera plant materials and sand filters are being studied. Previous research regarding the application of Moringa oleifera (MO) seeds have focused on the isolation of bioactive coagulant ingredients for more than four decades, with little attention directed toward field application in small and large scale water treatment applications. Slow sand filters take more than two weeks to generate clean water but there have been few studies directed towards integrating Moringa oleifera and other plant disinfectants with sand filters to generate clean water in a relatively short retention times at faster flow rates, generating a more compact filter unit. This research sought to fill this knowledge gap. Quantitative research techniques were applied to test a Moringa-sand filter column for its disinfection activity on separate synthetic contaminated water containing E. coli, Aeromonas hydrophila, total heterotrophic soil bacteria and fungi. The constructed Moringa-sand filter column was analyzed for its coagulant activity using synthetic turbid water made from bentonite and soil. Further research into documentation of indigenous knowledge and the use of indigenous medicinal plants in Cameroon with a history of use in purifying water was carried out at both the Phytobiotechnology Research Laboratories in Bamenda, Cameroon and the Microalgae Research Laboratory of the School of Chemical Engineering, Adelaide University. The coagulant and disinfection ability of the plants using surface contaminated water was carried out at the Phytobiotechnology Research Laboratories in Cameroon, followed by in-vitro antimicrobial activity of the organic extracts using microbial isolates from stream water in Bamenda, Cameroon. The coagulant and disinfection potential of Moringa oleifera seed extracts were superior to other plant materials. To this effect, further studies on Moringa oleifera seeds were planned and executed at the Microagae Laboratory, School of Chemical Engineering, Adelaide University. Extracts of Moringa seed powder using solvents of varying polarity revealed more than 85% in-vitro antibacterial activity against E. coli (ATCC11775) strain (indicator of faecal contamination of water) and 95% against Aeromonas hydrophila strain (known to resist chlorination) compared to control of both organisms of 65% for aluminum sulphate and 80% for sodium hypochlorite. Phytochemical screening and chromatographic analyses were carried out to elucidate the possible bioactive disinfectant ingredient in Moringa seeds. These experiments were conducted as proof of concept and were preceeded by an evaluation of the microbial content of surface water at Bambui and Mile 6 Mankon water sources used for household chores in Bamenda, Cameroon, for total bacterial counts, E. coli and coliform counts. A pilot low cost disinfectant sand filter system was set up at the Government Technical College, Njinikom, in Cameroon; to test its disinfectant and coagulant efficiency using total bacterial count, E. coli, coliform and fungal counts, pH, turbidity and to provide a capacity building on dissemination of this knowledge at household level in Cameroon. Data was collected every 24 hours for a period of a month for the bench experiments using sand filters and for field work for 12 months on the pilot plant. The mean bacterial counts, pH, turbidity and a catalogue of plant materials used in water treatment were recorded. The main findings of this research are presented as a series of six publications consisting of four peer-reviewed journal articles, a book, a book chapter as well as two manuscripts submitted for publication: The main findings of this research were applied in a pilot water project at Government Technical School Njinikom, Boyo division, Cameroon. It was found in the pilot study that Moringa pretreated water filtered through sand media met both the Australian and the World Health Organization guidelines for drinking water. The broad lessons for water purification are that the use of locally available natural coagulants and disinfectants in resource limited countries has a great potential of improving the economy and health of the people. This research has demonstrated the efficacy of both plant based coagulants, disinfectants and sand filter media through extraction, in vitro bioassay, purification and integration of the two systems. It is highly recommended that governments in poor countries should take up this technology. It will require commitment of countries to strengthen the natural water coagulation technology in a holistic, integrated approach and to support initiatives including empowering and enabling local scientists to build up this system at the grassroots level.