1. Centre for Water, Sanitation, Health and Appropriate Technology Development (WASHTED), Polytechnic, University of Malawi, Private Bag 303, Chichiri, Blantyre, Malawi
2. Department of Environmental Health, Polytechnic, University of Malawi, Private Bag 303, Chichiri, Blantyre, Malawi
3. Department of Civil and Environmental Engineering, University of Strathclyde, Level 5 James Weir Building, Glasgow G1 1XQ, UK