A Global Solution to Protect Water by Transforming Waste
Four-in-ten people live in hazardous conditions due to poor sanitation. Indeed, with half the population of developing regions without sanitation, United Nations goals of halving, by 2015, the proportion of people without access to safe water and basic sanitation seem set to be missed.
This EPSRC project focuses on the 'peri-urban' environment, which includes areas outside cities that are characterised by poor infrastructure, and poor access to formal water and sanitation services. Here, people endure water contamination, ill-health, and lack of dignity. Despite intentions to safely contain waste, sanitation systems such as pit latrines end up as ‘holes in the ground’. Initiatives, such as 'Community-Led Total Sanitation' (CLTS), have emerged to tackle the challenge. It encourages communities to analyse their own sanitation situation and build low-cost toilets. One of the key lessons is that sanitation is a social as well as technical challenge. In light of this, we comprise a team of natural and social scientists, which has come together to address this pressing problem by pooling our talents, interests and expertise. We believe that a ‘socio-technical’ approach is required to help to quickly address this problem, and that only a mixed team of different experts can do that.
The proposed technology is based on anaerobic digestion (AD), which is the breakdown of organic matter by bacteria to methane-containing biogas, in the absence of oxygen. AD is a natural process, which occurs in soils, swamps and bogs. However, if applied in airtight tanks, AD can be used to treat wastes. AD is an established technology, particularly for the treatment of industrial wastewaters. The AD process relies of several groups of bacteria working together in a cooperative manner to break down waste. Typically, the first group breaks down large chemical molecules (like fats and carbohydrates) to simpler molecules. Another group then continues the digestion process to yet-simpler forms of the waste, until eventually the methane-makers convert the waste to biogas. The groups live very closely together in slimy communities, known as biofilms. The type of biofilms commonly found in wastewater treatment tanks are known as 'sludge granules', due to their spherical appearance. The diameter of each granule is approximately 1 mm. Each granule contains millions of bacteria and, theoretically, all of the different groups required to digest the waste will be present in each single granule. AD has many advantages over more conventional types of wastewater treatment, which are carried out in aerated tanks. The chief advantage is that AD is cheaper, as there is no need to waste energy on pumping oxygen into the AD tanks. In addition, the biogas produced by AD can be readily used for electricity generation, heat production or as a vehicle fuel. It is likely that future wastewater treatment infrastructure in the UK will rely on AD for these reasons. Thus, the objective of this project is to develop a low-cost system, based on AD, for the safe and efficient treatment of domestic wastewater (sewage and personal washing water). The system will convert waste to biogas and valuable products, such as fertilisers.
The challenges facing the team are two-fold: (1) The sanitation system in the peri-urban environment is not based on a formal sewerage network of pipes with sewage transported by flushing water. Instead, a high-solids waste will be present. A major challenge will be to 're-engineer' granules to efficiently - and quickly - digest high-solids wastewater. (2) There may be cultural and social issues impeding initial progress. The proposed system, and the way it might be used, may not be acceptable to local people. We will engage with local people and integrate the social science required, with the engineering and science involved. In this way, a 'user-centred' prototype can be developed.
The principal investigator, Gavin Collins is an environmental microbiologist affiliated to Glasgow University's School of Engineering.