Viscous heating by extrusion of faecal material obtained from ventilated improved pit (VIP) latrines can be used to deactivate soil-transmitted helminth (STH) eggs by increasing the temperature of faecal sludge uniformly. Viscous heating can deactivate STH eggs present in sludge to make the material safer to transport, dispose of, or use in agricultural applications or as an energy source. The mechanical energy required to generate the shear rate can originate from any source. No other heat source or additive is required. Here we determined a baseline for the deactivation of STH eggs using viscous heating. To characterize equipment performance, three parameters were investigated: (1) minimum temperature required for deactivation; (2) local maximum temperatures for various flow rates and moisture contents (MCs); and (3) thermal efficiency. Excess water is undesirable since low viscosities require extended residence time and increased energy input. The minimum temperature to achieve greater than 90% helminth egg deactivation is 70 °C. For the laboratory-scale equipment tested, the maximum allowable mass flow rate for VIP sludge with 77% MC was found to be 3.6 g/s.
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Research Article|
June 18 2015
Viscous heating effect on deactivation of helminth eggs in ventilated improved pit sludge
D. Belcher;
D. Belcher
1School of Chemical Engineering, Oklahoma State University, Stillwater, OK 74078, USA
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G. L. Foutch;
2Computing and Engineering, University of Missouri, Kansas City, MO 64110, USA
E-mail: garyfoutch@outlook.com
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J. Smay;
J. Smay
3Materials Science and Engineering, Oklahoma State University, Tulsa, OK 74106, USA
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C. Archer;
C. Archer
4School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Westville 3630, South Africa
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C. A. Buckley
C. A. Buckley
5Pollution Research Group, University of KwaZulu-Natal, Howard College Campus, Durban 4001, South Africa
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Water Sci Technol (2015) 72 (7): 1119–1126.
Article history
Received:
March 01 2015
Accepted:
May 27 2015
Citation
D. Belcher, G. L. Foutch, J. Smay, C. Archer, C. A. Buckley; Viscous heating effect on deactivation of helminth eggs in ventilated improved pit sludge. Water Sci Technol 1 October 2015; 72 (7): 1119–1126. doi: https://doi.org/10.2166/wst.2015.300
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