WRC final report from a research project to understand bound moisture NOW AVAILABLE at the SuSana Library

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  • SeptienS
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WRC final report from a research project to understand bound moisture NOW AVAILABLE at the SuSana Library

Dear Colleagues,

The final report for a project to understand bound moisture in faecal sludge and faeces is now available at the SuSana library  through the following link: www.susana.org/en/knowledge-hub/resource...library/details/5227.

The project was funded by the Water Research Commission.

Please don't hesitate to contact me in the case of any inquiry or question related to the report.

Kindly,
Santiago

ABSTRACT:
The aim of this project is to characterize the moisture boundness in faecal sludge, i.e. how moisture can be found in the sludge structurematrix and its interactions with the solid material. The understanding of moisture boundness will be greatly beneficial to improve the dewatering and thermal drying processes. The limit of bound-unbound moisture varies between 50 to 70% moisture content (MC), depending on the analytical technique employed and type of faecal sludge. Capillary moisture is the more abundant type of bound moisture. It can be found approximately between around 70 to 20% MC. It is responsible of the lumpy consistency and high stickiness behaviour exhibited by faecal sludge in this MC range (observed by a peak of the cohesion and adhesion forces). Below 30% MC, the remaining moisture is mostly in the form of vicinal moisture (adsorbed at the surface of the solid particles by poly-layers) and internal moisture (being part of the chemical structure of the solid material and biological bodies). The removal of this type of moisture can only be achieved by thermal drying, but this will lead to an exponential increase of the energy consumption (because the energy to remove the vicinal and internal moisture is significantly higher than the latent heat of water vaporization). In general, faecal sludge drying requires a considerably higher thermal energy input than the latent heat of water vaporization because of the moisture boundness. In order to lead to energy savings, drying could be stopped at around 30% MC. Indeed, the sludge has the form of a granular solid at this point and could be considered safe in terms of pathogens since the remaining moisture is too bound for most of the microbes  development and survival. The removal of the unbound and capillary moisture leads to significant changes in the physicochemical and  mechanical properties of the faecal material, by converting it into a granular solid from a slurry or viscoelastic consistency and passing through an intermediary sticky lumpy phase. These changes must be considered in the design of dewatering and thermal drying units. The  moisture boundness between the different types of faecal sludge differ slightly.
Dr. Santiago Septien Stringel
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+27312601122

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