Microporous clay and colloidal silver: physics of domestic water purification
Assessment of mechanical retention and bacteriostatic performance in clay gravity pots for rural households.
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Across the mountain territories of Quiché, scattered settlement makes piped supply with central chlorination economically untenable. Point-of-use treatment through gravity-fed ceramic pots is the most dependable low-impact alternative.
Local clay, mixed with pine sawdust at a 60:40 volume ratio and fired at 900 degrees Celsius, forms a microporous matrix with pore diameters between 0.6 and 3 microns. That texture physically blocks protozoa, Giardia cysts and parasitic worms.
A 0.2% colloidal silver nitrate solution applied to the inner wall adds a lasting bacteriostatic action that deactivates gram-negative bacteria such as Escherichia coli by binding to the sulphydryl groups of their respiratory enzymes.
Microbiological sampling across 150 households after six months of continuous use records no faecal coliforms in 98.7% of the samples analysed on field Petri plates.