User perceptions and practical considerations for implementation of advanced sanitation technologies: a case study of the nano membrane toilet from Kumasi, Ghana

In response to the growing need for sustainable urban sanitation, technologies are being developed that will be completely novel to their target context. The successful adoption of such technologies will be dependent on their acceptability to end users and their adaptability to local settings. As part of the development of the Nano Membrane toilet, a design team conducted a field study in Kumasi, Ghana, to gauge acceptability of the design and to assess the perceived value of the designed outputs of the toilet. In addition, a physical survey was conducted of the residences of the interviews. Overall, the surveys provided information about site-specific attitudes and physical limitations which would need to be considered by designers. These types of survey can be used by technology developers to assist design or to identify areas that are appropriate for their technology. Conversely, similar surveys could be used as a community assessment tool to identify technologies that are best adapted for a specific circumstance

User perspectives to direct water reuse from the Nano Membrane toilet

The Nano Membrane toilet is a response to the Bill and Melinda Gates Foundation ‘Re-invent the Toilet Challenge’. The Nano Membrane toilet has many design aspects that will involve interaction by the end-user, including water reuse from the membrane treatment system which produces treated water directly available to the user at household level. In order to maintain a user focused design development, a survey was carried out on potential end users in Kumasi, Ghana, in order to understand their attitudes to direct reuse of water from the toilet, and how the attitudes may be affected by aesthetic changes to the water. It was found that end users would be willing to use the product water for a wide range of household purposes, with cleaning being the most likely. Odour was found to have the greatest effect over taste and colour on user’s willingness for all potential purposes, including drinking, cooking, and teeth cleaning

Social and economic factors influencing the choice of water supply in rural Karnataka, India

India is an enormously diverse country, although the challenges of water scarcity and quality are almost ubiquitous. This paper focuses on two villages in Karnataka state where a mixed methods qualitative research approach was applied. This revealed that decision - making about water supplies was made in a top-down fashion and there was little opportunity for village members to contribute. The policies and tariff systems were extremely complex. Communities had their own social and religious beliefs about their water supplies as well. Together these may be contributing to their rejection of the government supplied water and their use of alternative, often unimproved sources and of water filters in their houses. These decisions and the reasons behind them will be further explored in an additional fieldwork campaign

Testing decentralised treatment solutions for portable home toilet waste - Kumasi, Ghana

Water and Sanitation for the Urban Poor (WSUP) and Unilever have developed Clean Team, a business providing portable home toilets that are attractive and branded. Customers pay for their waste to be collected two to four times per week. Three “off-the-shelf” technologies are being tested to treat this waste and allow Clean Team to scale up to other cities. The three technologies are Sistema Biobolsa, which uses flexible tubes as anaerobic digesters, and aerobic planted gravel filter; Biorock, where an anaerobic pre-treatment tank is followed by an aerobic tank containing synthetic filtration media, pretreated with enzymes that stimulate the growth of aerobic bacteria and ventilation executed by natural draft; and Biofil, which will receive the sludge from the Biorock system, and digest it using macrofauna. The paper will present the initial trial results

The impact of hydraulic retention time on the performance of two configurations of anaerobic pond for municipal sewage treatment

Anaerobic ponds have the potential to contribute to low carbon wastewater treatment, however are currently restricted by long hydraulic residence time (HRT) which leads to large land requirements. A two-stage anaerobic pond (SAP) design was trialled against a single-stage control (CAP) over four HRTs down to 0.5 days, to determine the lowest HRT at which the ponds could operate effectively. No statistical differences were observed in particulate removal between the ponds over all four HRTs, suggesting solids loading is not a critical factor in AP design. Significantly higher biogas production rates were observed in the SAP than the CAP at 1.5 d and 1.0 d HRT, and microbial community profiling suggests the two-stage design may be facilitating spatial separation of the anaerobic digestion process along reactor length. Hydrogenotrophic methanogensis dominated over aceticlastic, with acetate oxidisation a likely degradation pathway. Experimental tracer studies were compared to CFD simulations, with the SAP showing greater hydraulic efficiency, and differences more pronounced at shorter HRTs. Greater flow recirculation between baffles was observed in CFD velocity profiles, demonstrating baffles can dissipate preferential flow patterns and increase effective pond volume, especially at high flow rates. The study demonstrates the potential of APs to be operated at shorter HRTs in psychrophilic conditions, presenting an opportunity for use as pre-treatments (in place of septic tanks) and primary treatment for full wastewater flows. Two-stage designs should be investigated to separate the stages of the anaerobic digestion process by creating preferential conditions along the pond length