Wasser und Entwicklung

On-site biological hand washing water treatment can improve global access to safe hand washing water, but requires a thorough understanding of the chemical composition of the water to be treated, and an effective treatment strategy. This study first presents a detailed characterization of the individual inputs to hand washing water. We demonstrate (1) that soap is likely the most significant input in hand washing water, representing ∼90% of mass loading, and (2) that inputs to hand washing water have low concentrations of biologically-essential macro- and micro-nutrients (nitrogen, phosphorus, potassium, copper, zinc, molybdenum and cobalt) with respect to carbon, which may impair biological carbon removal. This study next formulates a recipe that recreates a representative composition of hand washing water and develops a procedure to identify and supplement nutrients in which this recipe is estimated to be deficient. Batch testing of the nutrient-supplemented hand washing water with an inoculum of planktonic bacteria demonstrated improved assimilable organic carbon removal (99% vs. 86% removal) and produced lower final DOC concentrations (1.7 mg_C/L vs. 3.5 mg_C/L) compared to realistic (nutrient-deficient) washing water. Supplementing nutrients did promote cell growth (50x higher final total cell count). Full-scale testing in a biologically activated membrane bioreactor (BAMBi) system treating 75 L/day of nutrient-supplemented hand washing water showed that long-term operation (100 days) can deliver effective carbon removal (95%) without detrimental fouling or other disruptions caused by cell growth. This work demonstrates that biological treatment in a BAMBi system, operated with appropriate nutrient-balancing offers an effective solution for decentralized treatment of light greywater.

Sanitation access in urban areas of low-income countries is provided through unstandardized onsite technologies containing accumulated faecal sludge. The demand for infrastructure to manage faecal sludge is increasing, however, no reliable method exists to estimate total accumulated quantities and qualities (Q&ampQ) This proposed approach averages out complexities to estimate conditions at a centralized to semi-centralized scale required for management and treatment technology solutions, as opposed to previous approaches evaluating what happens in individual containments. Empirical data, demographic data, and questionnaires were used in Kampala, Uganda to estimate total faecal sludge accumulation in the city, resulting in 270 L/cap∙year for pit latrines and 280 L/cap∙year for septic tanks. Septic tank sludge was more dilute than pit latrine sludge, however, public toilet was not a distinguishing factor. Non-household sources of sludge represent a significant fraction of the total and have different characteristics than household-level sludge. Income level, water connection, black water only, solid waste, number of users, containment volume, emptying frequency, and truck size were predictors of sludge quality. Empirical relationships such as a COD:TS of 1.09 ± 0.56 could be used for more resource efficient sampling campaigns. Based on this approach, spatially available demographic, technical and environmental (SPA-DET) data and statistical relationships between parameters could be used to predict Q&ampQ of faecal sludge.

Unsafe water consumption is the environmental risk factor in sub-Saharan Africa contributing most to premature death. In urban slums and dispersed rural communities, where access to safe water is especially limited, water kiosks are a relevant safe water source. However, irregular use challenges their operational viability and may cause discontinuation. The present study investigated collective psychological ownership for the kiosk as a potential factor to increase regular kiosk use. Data were collected cross-sectionally in one urban and two rural kiosk sites through interviews in study households (N = 205) and analyzed by path analysis. Involvement in decision-making related to the kiosks explained collective psychological ownership for the kiosks. Collective psychological ownership, in turn, explained self-reported kiosk use through social-cognitive factors. The results emphasize the importance of community involvement in decisions related to kiosk installation and maintenance because it may contribute to regular kiosk use.

To reduce open defecation, many implementers use the intervention strategies of Community-Led Total Sanitation (CLTS). But CLTS focuses on latrine construction and does not include latrine maintenance and repair damage or collapse. Some households rebuild their latrine while others return to open defecation. The reasons why are unknown. Using data from a cross-sectional survey, this article shows how physical, personal, and social context factors and psychosocial factors from the RANAS model are associated with CLTS participation, and how these factors connect to latrine rebuilding. In 2015, heavy rains hit the north of Mozambique and many latrines collapsed. Subsequently, 640 household interviews were conducted in the affected region. Logistic regression and mediation analyses reveal that latrine rebuilding depends on education, soil conditions, social cohesion, and a feeling of being safe from diarrhea, the perception that many other community members own a latrine, and high confidence in personal ability to repair or rebuild a broken latrine. The effect of CLTS is mediated through social and psychosocial factors. CLTS already targets most of the relevant factors, but can still be improved by including activities that would focus on other factors not yet sufficiently addressed.