Ultraviolet (UV) light in sunlight has been used in a continuous process for the disinfection of drinking water in a family-sized continuous solar disinfection (SODIS) unit for drinking water purification in low-income settings. The "SODIS Family" is completely fabricated from food-grade polyethylene (PE) film, and can be made locally with minimal infrastructure. Total cost is expected to be less than $2 CAD per unit, which can treat 50 L of water per day. Fluid mechanic design required 44 photoactive serpentine channels of a 2 cm width, and negligible friction losses. Experimental testing showed a hybrid-vertical/horizontal orientation to be the most desirable. Disinfection tests show a 3.22-log removal of fecal coliforms after a 3 hour residence time in a 4 cm characteristic depth test chamber, and a 4.5-log removal in a 2 cm depth (complete disinfection). Thin PE (2 mil spec.) was used to maximize UV penetration. Stress analysis showed that hoop stress caused by water pressure in the photoactive channels had the highest failure risk, with a safety factor of only 1.3 for 2 mil PE. Stresses caused by incomplete seals led to the development of novel sealing methods to prevent leakage.
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