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

Leandra Rhodes-Dicker,Barbara J Ward,Wali Mwalugongo,Evan Thomas,Lindsay Stradley,Katherine Junglen,Emily Gitau

doi:10.3390/su12219040

Leandra Rhodes-Dicker, Barbara J Ward + Show 5 more

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https://doi.org/10.3390/su12219040

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Abstract

The safe management of fecal sludge (FS) relies on different treatments, processes, and disposal options in different contexts. Waste transfer stations can improve FS management particularly in resource-constrained areas, including low-income urban informal settlements, by providing a safe discharge and treatment location. Low-footprint options for FS treatment are sensitive to the characteristics of incoming FS, which are typically highly variable, difficult to predict, and differ significantly from the characteristics of traditional wastewater. The success of low-footprint technologies relies on the monitoring of incoming FS characteristics, such as total solids (TS), total suspended solids (TSS), chemical oxygen demand (COD), ammonia, electrical conductivity (EC), and pH. Monitoring the characteristics of incoming FS typically relies on the use of a laboratory, which can be expensive and time-consuming, particularly in resource-constrained areas. Useful correlations between easy to measure parameters and difficult to measure parameters may provide useful information related to the monitoring of FS, while reducing the need for laboratory analysis. In this paper, we describe a sampling campaign at a waste transfer station in Nairobi, Kenya managed by Sanergy Inc., to characterize and observe settling behavior of FS collected from manually emptied pit latrines. The investigation found that easy to measure parameters (e.g., TS, turbidity) could be used to approximate difficult to measure parameters (COD, TSS). Additionally, rapid measurements (turbidity) could be used to approximate time-intensive parameters (TS, COD, TSS) to aid in the design, operation and monitoring of FS treatment facilities in resource and space-constrained areas.

Highlights

One-third of the world’s population relies on onsite sanitation, producing fecal sludge (FS) that should require safe disposal in-situ or transport and treatment offsite [1]
We examine influent FS at a waste transfer station, owned and operated by Sanergy Inc., a sanitation social enterprise operating in informal settlements in Nairobi, Kenya, where an estimated 66% of fecal waste is not safely managed and up to 80% of onsite containments are pit latrines [4,21]
This study aims to contribute to the body of knowledge of FS characterization and identify if difficult to measure parameters (e.g., chemical oxygen demand (COD), total suspended solids (TSS), ammonia) pertinent to designing, operating and/or monitoring treatment facilities can be approximated by easy to measure parameters

Summary

Introduction

One-third of the world’s population relies on onsite sanitation, producing fecal sludge (FS) that should require safe disposal in-situ or transport and treatment offsite [1]. FS includes a mixture of solid and liquid waste that contains human excreta collected in onsite sanitation systems such as pit latrines and septic tanks and not conveyed through a sewer system [2,3]. It often contains garbage, sand, or soil, and groundwater, rainwater or greywater, depending on localized conditions [4,5]. The safe management of FS is especially challenging in resource-constrained areas, including low-income urban informal settlements, where population density is high, and space is often limited. Inadequate space for exhauster trucks contributes to reliance on dangerous manual emptying practices, which often lack a safe disposal option for the FS [6,7]

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