Methods to reliably estimate faecal sludge quantities and qualities for the design of treatment technologies and management solutions

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.

Characterization and Prediction of Fecal Sludge Parameters and Settling Behavior in Informal Settlements in Nairobi, Kenya

“…Results in this study are comparable to previously reported median values for FS from pit latrines in Uganda [17,27] and Zambia [20], as summarized in Table 2.…”

“…The reduction in variability observed in composite samples indicates the use of reception facilities, such as holding or mixing tanks, may help reduce variability across incoming FS. This conclusion supports the proposal that understanding FS parameters at a neighborhood or city-wide scale, rather than at a containment level scale, may be more feasible and useful for designing treatment facilities [17]. This is especially helpful in decision-making in treatment design in space-constrained areas.…”

“…Lab characterization results were evaluated in four groups as summarized in Table 1-all sample results, pit samples individually, composite samples individually, and tank samples individually, as summarized in Table 1. Both median and mean values were reported because FS characteristics are typically not normally distributed [17,26]. Comparisons to previous studies are summarized in Table 2.…”

“…Limited research has been published that investigates the relationship between FS parameters. Several studies have attempted to correlate measured FS characteristics with operationally useful parameters [17,18], and examined low cost and accessible measures to predict dewatering performance [19]. A study in Zambia found that FS parameters, including TS and ammonium and settling performance, could be predicted by measurements of EC and pH, observations of color and texture and containment type [20].…”

Pit latrine faecal sludge solid waste quantification and characterization to inform the design of treatment facilities in peri-urban areas: A case study of Kanyama

“…This has resulted in the use of modified garden tools as a means of desludging (Mikhael and Drabble, 2014). Strande et al (2018) submit that governments and other stakeholders have started to acknowledge the importance of FSM. However, they observe that efforts to enhance FSM predominantly focus on FSM infrastructure development.…”