Abstract
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&Q) 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&Q of faecal sludge.
Highlights
The current state of sanitation in urban areas of low- and middleincome countries is 2.8 billion people served by onsite sanitation, with the majority of excreta not safely managed
The wide variability of reported rates illustrates the lack of available data, with 30% of values reported in Fig. 2 coming from eThekwini in South Africa, the difficulty in determining rates based on individual systems, and transferring knowledge from one region to another due to the wide variety of influencing factors
Accurate fundamental models based on what is occurring at the individual household level will be difficult to achieve, based on the large number of factors that affect the sensitivity of a model, and the lack of knowledge of processes occurring within onsite systems
Summary
The current state of sanitation in urban areas of low- and middleincome countries is 2.8 billion people served by onsite sanitation, with the majority of excreta not safely managed. A simplified classification of onsite systems in Dar es Salaam, Tanzania included pit latrines that were lined, unlined, partially lined, improved, collapsed, abandoned, tanks that were fully lined (“septic tank”, “storage tank”), partially lined (“cess pit”), with no drainage, or drainage going to soakaway, open drain, overflow, water body, soakaway, or soil (Brandes et al, 2015) This status is the result of many factors, including a lack of tenure or ownership in slums, government involvement, financial resources, heterogeneous settlement patterns, and a strong focus of the Millennium Development Goals (MDGs) ending open defecation, but not developing management plans for what happens when onsite storage of sludge becomes full (Beyene et al, 2015; Günther et al, 2011; Moe and Rheingans, 2006; Oyoo et al, 2013; Tilley et al, 2014). Treatment is difficult due to wide-ranging characteristics and stabilization, which dictate selection of technical solutions, govern settling and dewatering, and influence treatment efficacy (Appiah-Effah et al, 2014; Bassan et al, 2013; Dodane et al, 2012; Gold et al, 2016; Kengne et al, 2014; Sonko et al, 2014)
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