By Dr Michael Templeton, Reader in Public Health Engineering
Today, Thursday 19th November, is World Toilet Day. Sadly, it is estimated that 2.5 billion people around the world still lack access to an adequate toilet. Many others rely on only basic pit latrines which eventually fill up and can become unsanitary. Many countries failed to meet their Millennium Development Goal target for access to improved sanitation, and the recently stated Sustainable Development Goals continue to emphasise improving sanitation as a key objective towards global development.
Research at Imperial College London by the group of Dr Michael Templeton in the Environmental and Water Resource Engineering section of the Department of Civil and Environmental Engineering is investigating ways to make sanitation more sustainable and safer.
The ‘Tiger Toilet’ is an innovative, low-cost toilet design that uses tiger worms to compost human waste within latrines, thereby reducing the fill rate of the latrine. Envisioned through a collaboration with colleagues at Bear Valley Ventures and the London School of Hygiene and Tropical Medicine, the goal was to create a toilet that will last for much longer than currently available latrine and septic tank designs before needing emptying. Side benefits are that the tiger worms produce a safe and easy-to-handle compost material and treat the liquid portion of the waste. After lab- and pilot-scale testing at the Centre for Alternative Technology in Wales to determine the optimum toilet design parameters, Tiger Toilets have been trialled by Bear Valley Ventures and local partners for use in communities around the world, and have recently been launched commercially in Maharashtra province, India in partnership with PriMove. Research is ongoing to understand the factors affecting the performance of the Tiger Toilet on-site and to assess the quantity and quality of compost material produced.
Another significant challenge is how to implement safe sanitation in areas with high groundwater tables and where wells are the main source of drinking water. Many of the existing sanitation technology options are based on the principle of infiltrating the liquid portion of the waste into soils, however this may pose health risks in areas where the groundwater level approaches the level of latrines. Much attention has been paid to microbial contamination of wells by latrines, however a sometimes overlooked problem is the risk of chemical contamination from latrines, specifically nitrate pollution. Research is currently trying to understand the factors affecting the conversion of ammonia and other forms of nitrogen into nitrate within and below latrines, in different soil types and moisture conditions. The aim is that this will allow identification of cases where the risk of nitrate pollution is highest and suggest forward-planning and mitigation strategies to minimise this risk. A recent collaboration with colleagues in Senegal, Benin and Cote d’Ivoire led to a modelling framework for assessing this problem, which is being developed further.
Other recent research projects by Dr Templeton’s group have investigated the best technologies for emptying sludge from full pits, the factors that cause some pits to fill more quickly than others, the applicability and challenges facing domestic biogas plants for treating the sludge that is emptied from pits, the importance of sanitation in preventing the spread of the neglected tropical disease schistosomiasis, and the successes and challenges faced by community-led sanitation projects. Dr Templeton recently summarised his perspectives on these and other aspects of the sanitation challenge in an article in the newly launched Royal Society of Chemistry journal Environmental Science: Water Research & Technology.