Dataset Information

Assessing clogging of laminated hydrophobic membrane during fecal sludge drying.

ABSTRACT: A new sanitation technology has been proposed in which a laminated hydrophobic membrane contains and enhances drying of fecal sludge in a toilet, with particular focus on application to urban regions of low-income countries. The proposed technology uses a laminated hydrophobic membrane liner as an integral component of container-based sanitation systems. The focus of this study is to quantitatively evaluate the laminate's clogging after repeated use, which will affect replacement interval and might limit the laminate's application in container-based toilets. The membrane of the laminated hydrophobic membrane used in this process is hydrophobic and only allows vapor transport. Drying of water vapor using the laminated hydrophobic membrane occurs due to moderate temperature or humidity gradients, while other constituents such as aqueous dissolved solutes of fecal sludge are retained. Controlled laboratory experiments evaluated repeated use of a laminated hydrophobic membrane for fecal sludge drying, with mild brushing/rinsing of the laminate between each application. Drying occurred at a constant rate as long as the fecal sludge moisture content exceeded 11.6 (g/g), below which water activity <1. Over five drying cycles, at a significance level of ??=?0.05 the dimensionless drying rate in the constant-rate period was not reduced. While scanning electron microscopy and energy dispersive X-ray analyses of used laminated hydrophobic membrane showed deposition of fecal sludge on the inner fabric of the laminate, particulate accumulation was never sufficient to alter the fecal sludge drying rate. Experiments with only water indicated that the fecal sludge increased the effective diffusion length through the laminate by 10-30%. These data demonstrate that clogging of the laminated hydrophobic membrane is minor over five cycles of fecal sludge drying with mild rinsing between cycles, indicating that use of the laminate may be feasible in many field applications.

SUBMITTER: Bakhshayesh BE

PROVIDER: S-EPMC5892458 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Assessing clogging of laminated hydrophobic membrane during fecal sludge drying.

Bakhshayesh Babak Ebrazi BE Imhoff Paul T PT Dentel Steven K SK

The Science of the total environment 20180202

A new sanitation technology has been proposed in which a laminated hydrophobic membrane contains and enhances drying of fecal sludge in a toilet, with particular focus on application to urban regions of low-income countries. The proposed technology uses a laminated hydrophobic membrane liner as an integral component of container-based sanitation systems. The focus of this study is to quantitatively evaluate the laminate's clogging after repeated use, which will affect replacement interval and mi ...[more]

PMID: 29426196

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Project description:Laminated hydrophobic membranes have been proposed as liners for container-based sanitation systems in developing countries. The laminate allows drying of fecal sludge, which might significantly reduce the frequency of container emptying, while containing liquids and solids. While previous laboratory tests demonstrated rapid drying of fecal sludge or water retained in laminates, experiments did not assess the effects of system dimension or scale on performance. In this study fecal sludge drying and water evaporation were evaluated in 3D laminate boxes (decimeter scale) or 3D laminate-lined 40 L and 55 gallon drums (meter scale) that are prototypes of toilet containers for field application. A stagnant film model described fecal sludge drying and water evaporation in the laminate boxes and laminate-lined drums well. The effective diffusion length (λ) for the laminate was fitted in all systems and increased with system dimension and scale: λ increased by a factor of 1.4 from 1D decimeter-scale envelopes to 3D decimeter-scale boxes, and by a factor of 1.3-1.7 from 3D decimeter-scale boxes to 3D meter-scale drums. The longer λ with increasing dimension and scale is likely due to nonuniform temperature and relative humidity in the air outside the laminate and nonuniform temperature within the laminate. Using best-fit λ for the laminate-lined 40 L and 55 gallon drum experiments conducted in a controlled laboratory, drying was predicted for an 11-day field experiment. Although the air temperature and relative humidity varied significantly in the field tests from -1 °C to 26 °C and 35% to 97%, respectively, the stagnant film model predicted drying over the 11-day period reasonably well with total error ≤ 13% using 24-h average air temperature and relative humidity. Drying of fecal sludge in laminate-lined drums in the field might be adequately described with a stagnant film model using daily-average weather conditions, if wind speeds are low.

Dataset Information

Assessing clogging of laminated hydrophobic membrane during fecal sludge drying.

Publications

Assessing clogging of laminated hydrophobic membrane during fecal sludge drying.

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