Pilot scale continuous-flow solar water disinfection system by heating and ultraviolet radiation inactivating Acanthamoeba cysts and Bacillus spores

Abstract

The consumption of biologically unsafe water and the resulting consequences persist especially in developing countries marked by resource-poor environments. Solar disinfection (SODIS) systems are the next step to upgrade SODIS for public drinking water supply on a community scale. In the present study, a continuous-flow system of solar water disinfection based on heating and ultraviolet (UV) radiation was developed and tested against Acanthamoeba castellanii cysts (1.38 ×103 cysts/L) and spores of Bacillus altitudinis 1.4 (1.8 ×104 CFU/mL). The system consists of a linear Fresnel solar collector (divided into infrared (IR) and UV radiation collector parts) coupled to a parabolic trough concentrator containing heat absorbers and quartz reactors fixed at its aperture and focus. Rotating wheels fixed at the base of the collector allow solar tracking in two axes. An apparatus composed of a secondary and heating tanks, as well as a retention and discharge pipe, allows the raw water to be heated until it overflows (at 92 ± 3ºC), flowing afterwards through the quartz reactors and being irradiated by UV (for 25 – 45 s). The system inactivated A. castellanii cysts (> 3 log/L) and B. altitudinis1.4 spores (2 log/mL), mainly due to the effect of heat. The daily productivity was 1200 L (flow rate of 3 ± 0.2 L/min, for 8 h). The system has the potential to be applied in the supply of safe drinking water on a community scale, with the cost of water being €0.0008 or €0.0004 per liter, using the version of the system with or without the UV part, respectively.