Early testing of new sanitation technology for urban slums: The case of the Blue Diversion Toilet

Abstract

The toilets used most in informal urban settlements have detrimental consequences for the environment and human health due to the lack of proper collection and treatment of toilet waste. Concepts for safe, sustainable and affordable sanitation systems exist, but their feasibility and acceptance have to be investigated at an early stage of development, which is difficult due to the high costs of building working models. In this paper, we present an approach to estimate acceptance in a valid and representative form with only one working model, and apply it to test an innovative zero-emission toilet with recycling of wash water. Four basic principles were specified for investigation and nine hypotheses formulated to test the feasibility and acceptance of these principles: source separation of urine and feces with subsequent collection for resource recovery; provision of wash water in a separate cycle with on-site recovery through a membrane bioreactor; a convenient and attractive overall design; and a financially sustainable business plan. In Kampala (Uganda), in 2013, data was collected from 22 regular users, 308 one-time users and a representative sample of 1538 participants. Qualitative data was collected from the users, who evaluated their likes, perceived benefits, social norms and expected ease of use based on verbal and visual information. Most of the hypotheses were confirmed, indicating the feasibility and acceptance of the basic principles. Source separation and on-site water recovery were found to be feasible and accepted, provided users can be convinced that the emptying service and water recovery process work reliably. In the survey, the toilet was evaluated favorably and 51% of the participants agreed to be placed on a bogus waiting list. However, some design challenges were revealed, such as the size of the toilet, hiding feces from view and improving the separation of urine and water.

Assessing clogging of laminated hydrophobic membrane during fecal sludge drying

“…Although alternatives to pit latrines have been proposed in the developing world in the last decade, finding alternatives in urban slums is challenging due to the lack of money, space, and access, as well as a sense of ownership that is often absent in public facilities ( Tobias et al, 2017 ). Biogas latrines and the Urine Diverting Dry Toilet (UDDT) have been suggested as replacements to pit latrines in urban areas ( Katukiza et al, 2010 ; Katukiza et al, 2012 ).…”

Field testing of a prototype mechanical dry toilet flush

“…The prototype was mainly produced from polyurethane. This is not an unusual choice: portable chemical toilets tend to be made from polyurethane, the UDDT pedestals used in the eThekwini municipality are made from polypropylene (Personal communication with Jacques Rust, Envirosan, Republic of South Africa), and the ‘Blue Diversion Toilet’ developed by EAWAG, 2014, Tobias et al, 2017 is largely made from LLDPE plastic. Given that plastics are cheap, light, durable, and easily available materials, this is unsurprising.…”

Generation of sanitation system options for urban planning considering novel technologies

“…Option generation is complicated by the emergence of many novel technologies in the recent years, especially for on-site sanitation and semi-centralized systems (e.g. Amoah et al 2016, Larsen et al 2016, Parker 2014, Tilmans et al 2015, Tobias et al 2017. While novel technologies increase engineering flexibility and allow resource recovery, they also substantially increase the complexity of creating decision options.…”