Eau et développement

Unpredictable dewatering performance is a barrier to the effective management and treatment of faecal sludge. While mechanisms of dewatering in sludges from wastewater treatment are well understood, it is not clear how dewatering of faecal sludge fits into the framework of existing knowledge. We evaluate physical-chemical parameters, including EPS and cations, and demographic (source), environmental (microbial community), and technical factors (residence time) as possible predictors of dewatering performance in faecal sludge, and make comparisons to the existing conceptual model for wastewater sludge. Faecal sludge from public toilets took longer to dewater than sludge from other sources, and had turbid supernatant after settling. Slow dewatering and turbid supernatant corresponded to high EPS and monovalent cation concentrations, conductivity, and pH, but cake solids after dewatering was not correlated with EPS or other factors. Faecal sludges with higher EPS appeared less stabilised than those with lower EPS, potentially a result of inhibition of biological degradation due to high urine concentrations. However, distinct microbial community compositions were also observed in samples with higher and lower EPS concentrations. Higher EPS faecal sludge was comparable in dewatering behaviour and EPS content to anaerobically digested and primary wastewater sludges. However lower EPS faecal sludges had different dewatering behaviour than wastewater sludges and may be governed by different mechanisms.

The provision of basic services is falling short in informal settlements of cities in the Global South. In particular, public utilities have had difficulties expanding their services to the urban poor. Why is this the case despite utilities having improved their capabilities substantially over the last years? This paper investigates how innovation strategies of utilities are aligned or misaligned with the broader contexts in informal settlements, which are populated by different socio-technical regimes. We propose a framework to identify new capabilities needed by utilities to deal with these different regimes. The paper reconstructs pro-poor initiatives of a water and sewerage utility in a large East-African city and explains why they tended to fail in terms of livelihood improvement. We show how the alignment between capability portfolios and specific regime structures have set limits to the success of pro-poor innovation strategies in informal settlement contexts.

Container-based sanitation (CBS) within a comprehensive service system value chain offers a low-cost sanitation option with potential for revenue generation but may increase microbial health risks to sanitation service workers. This study assessed occupational exposure to rotavirus and Shigella spp. during CBS urine collection and subsequent struvite fertilizer production in eThekwini, South Africa. Primary data included high resolution sequences of hand-object contacts from annotated video and measurement of fecal contamination from urine and surfaces likely to be contacted. A stochastic model incorporated chronological surface contacts, pathogen concentrations in urine, and literature data on transfer efficiencies of pathogens to model pathogen concentrations on hands and risk of infection from hand-to-mouth contacts. The probability of infection was highest from exposure to rotavirus during urine collection (∼10^–1) and struvite production (∼10^–2), though risks from Shigella spp. during urine collection (∼10^–3) and struvite production (∼10^–4) were non-negligible. Notably, risk of infection was higher during urine collection than during struvite production due to contact with contaminated urine transport containers. In the scale-up of CBS, disinfection of urine transport containers is expected to reduce pathogen transmission. Exposure data from this study can be used to evaluate the effectiveness of measures to protect sanitation service workers.

A persistent conundrum for practitioners and researchers in the development context is that, often, newly provided and improved basic services are not maintained by users despite seemingly superior functionality and user convenience. We argue that one major reason for this is an insufficient understanding of the context in which users have to manage their daily lives. We therefore propose an approach to analysing the embedding of basic services that focuses on the users' daily practices. We do so by borrowing insights from 'socio-technical transitions' and 'practice theory' in developing our concept of oscillating domestic spaces. The concept reflects the need for people to constantly respond to quickly changing and precarious circumstances by rearranging their daily practices in time and space and developing a multiplicity of alternative options and partial solutions. We illustrate the analytical approach in a case study of sanitation access in informal settlements of Nairobi, Kenya. The analysis shows how the introduction of a container-based toilet resulted in partial embedding. The innovation anchored to only a part of the oscillating domestic spaces and was in disarray with the needs of users most of the time. The conceptual approach contributes to the understanding about how users take part in sustainability transitions as well as the added value of the time-space dimension in analysing practices in highly complex contexts. We conclude by reflecting on the potential applicability of the analytical approach to transition cases in the Global North.

Direct testing of water quality to promote drinking water safety contributes to the sustainable development goals, which call for universal access to safely-managed drinking water services by 2030. Enzyme–substrate tests offer a potentially simple and reliable approach for the detection and quantification of fecal indicator bacteria, including Escherichia coli (E. coli). The novel aquatest (AT) based on resorufin-β-D-glucuronide methyl ester (RUG™) (AT-RUG) is an enzyme–substrate test that overcomes several drawbacks of other established tests. In this study, AT-RUG was used to detect and quantify E. coli in water from temperate (Zurich, Switzerland) and tropical (Bushenyi, Uganda) regions. Quantitative results of AT-RUG were compared with IDEXX Colilert-18® (C-18), m-TEC and m-ColiBlue24®. In temperate waters, AT-RUG was found to be as sensitive as m-TEC (97.0%) and C-18 (98.5%) and showed strong agreement with the reference methods. The false-positive rate for E. coli detection in temperate waters using AT-RUG was 6%. AT-RUG performed well at incubation temperatures of 37 °C and 45 °C, but not at 24 °C. In tropical waters, AT-RUG sensitivity was 94.1% compared to m-ColiBlue24®. AT-RUG detected significantly more E. coli than m-ColiBlue24®, suggesting it is a more conservative estimate. At both field sites, AT-RUG was able to effectively indicate categorical concentrations of E. coli in water samples indicating the level of risks of fecal contamination of water supplies. This study indicates that AT-RUG is a reliable and accurate medium for the detection and quantification of E. coli in temperate and tropical waters.