An experimental study probing moisture kinetics and indices of microwave dried fecal sludge with an insight on real world applications

ABSTRACT

The ever-increasing population rate, followed by resource deficiency, has made innovations crucial in sanitation. The deteriorating hygiene, particularly in the population’s low strata, is of great concern in most developing countries. As the current fecal sludge management system is linear, it needs to be transformed into a closed-loop circular system like any other waste management system. This study examines the potential of using microwaves to dry feces before transporting and reduce the spread of disease. The microwave output power; sample load; feces-urine composition, were adjusted between 100 and 300 W; 20 and 40 g; and 10% and 90% respectively. Drying kinetics were determined using empirical drying data modeling and the standard error analysis was used to select the best model. Under a range of experimental conditions, the effective moisture diffusivity of drying was determined to be on the order of 10⁻⁹, and the effect of process parameters on the effective moisture diffusivity was investigated. Furthermore, thorough tests were performed to determine the microwave drying process’ efficiency and energy consumption (6.782 MJ.kg⁻¹ to 29.268 MJ.kg⁻¹), determining its feasibility for large-scale deployment as a fecal sludge pretreatment method. This study provides a solution for modern sanitation by successfully closing the nutrient loop.

GRAPHICAL ABSTRACT

KEYWORDS:

• Human waste management
• microwave drying
• empirical modeling
• statistical approach
• water and sanitation
• resource recovery

Nomenclature

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Acknowledgements

The authors wish to acknowledge the support rendered by the Vellore Institute of Technology - VIT, Vellore, India, for performing the experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).