Positron emission particle tracking (PEPT): A novel approach to flow visualisation in lab-scale anaerobic digesters

YesPositron emission particle tracking (PEPT) was used to visualise the flow patterns established by mixing in two laboratory-scale anaerobic digesters fitted with mechanical mixing or gas mixing apparatus. PEPT allows the visualisation of flow patterns within a digester without necessitating the use of a transparent synthetic sludge. In the case of the mechanically-mixed digester, the mixing characteristics of opaque sewage sludge was compared to a transparent synthetic sludge at different mixing speeds. In the gas-mixed apparatus, two synthetic sludges were compared. In all scenarios, quasi-toroidal flow paths were established. However, mixing was less successful in more viscous liquids unless mixing power was increased to compensate for the increase in viscosity. The robustness of the PEPT derived velocities was found to be significantly affected by the frequency with which the particle enters a given volume of the vessel, with the accuracy of the calculated velocity decreasing in regions with low data capture. Nevertheless, PEPT was found to offer a means of accurate validation of computational fluid dynamics models which in turn can help to optimise flow patterns for biogas production.The first author was funded via an EPSRC CASE award in conjunction with Severn Trent Water. The second author was funded via a University of Birmingham Postgraduate Teaching Assistantship award

Lessons learned from operating a pre-commercialisation field-testing platform for innovative non-sewered sanitation in Durban, South Africa

The Engineering Field Testing Platform (EFTP) was designed to provide an opportunity for technology  developers (TDs) to test non-sewered sanitation prototypes in the eThekwini Municipal Area (Durban), South Africa. Between 2017 and 2020, 15 sanitation systems were tested in informal settlements, peri-urban households, and other ‘real world’ settings. This paper illustrates the lessons learned from establishing and managing this testing platform. Costs and timelines for testing are dependent on several factors, including the aims of testing, the development stage of the prototype, whether testing takes place in a community or household setting and if a testing site is shared between prototypes. Timelines were routinely underestimated, particularly for community engagement and commissioning of prototypes to reach steady-state operation. Personnel accounted for more than half of the EFTP’s costs. The presence of the municipality as a platform partner was vital to the success of testing, both for gaining political support and for enabling access to testing sites. It is noted that working in communities, with test sites in public spaces, requires technical and social sensitivity to context. It was important to ensure testing supported future municipal decision-making on service provision, as well as longer-term development within communities. The high number of stakeholders, locally and internationally, raised management challenges common to any large project. However, the EFTP added value to TDs, the eThekwini Municipality, and communities requiring improved sanitation services; this was amplified through the platform approach

Why shit happens : amplifying the voices of frontline WASH professionals to reduce failure in the sector

This record includes an extended abstract and MP4 presentation. Presented at the 42nd WEDC International Conference

Research brief : amplifying local voices to reduce failure in the water, sanitation and hygiene sector

There needs to be a culture shift towards greater responsibility, and particularly shared accountability, for water, sanitation, and hygiene (WASH) failures and challenges

Amplifying local voices to reduce failure in the water, sanitation and hygiene sector

This is a poster briefWASH endeavours regularly fail. Sometimes this means that entire programmes do not achieve their stated aims, sometimes these failures are setbacks which can be rectified with sufficient reflection and action. This research aimed to develop an evidence base of how and why field-based WASH professionals in four sub-Saharan African countries believe failures occur, their experiences when sharing and discussing them within their organisations, and how they believe a culture conducive to publicly sharing and learning from failures could be nurtured