Water pasteurizer

The water pasteurizer comprises of heating coils, a heat exchanger, and regulating thermostatic valve – all housed in a 60 L pot, and is designed to work with 60 L and 100 L cookstoves but could potentially be used with other biomass heat sources. Water is gravity fed from an elevated tank (3-4.5 m) and enters into the hot-side of the heat exchanger, then it passes through a coil where it increases in temperature. Next, a thermostatic valve regulates the system by only opening if the temperature of the water is above 71 °C. Water then flows through additional piping before re-entering the heat exchanger and cooling down to room temperature as it exits the system.

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Estimated 10 years^{Interview with designer}

Laboratory testing was conducted by Oregon State University and found a 99.9999% reduction in E. coli through the pasteurization unit in all samples and an average clean water production rate of 6.7 L per minute. The steady-state production of clean water required an average of 5.5 g of dry wood equivalent per liter of water pasteurized or 106 kJ of energy per liter. When accounting for system startup, it required 9.1 g of dry wood equivalent per liter of pasteurized water produced or 175 kJ of energy per liter.

Handling firewood and feeding the stove presents a reduced burn hazard compared to a typical open cooking fire. The pasteurization unit is designed to cool the water down using a heat exchanger so that the water at the outlet does not exceed 20 °C and does not present a burn hazard.