Solar pasteurizer for the microbiological decontamination of water

Abstract

Proposing solutions for potable water supply in semiarid regions such as Brazil's Northeast region is of great importance. In addition to the water shortage, the lack of chemical and biological quality in the water is another difficulty to be faced. Taking advantage of the high levels of solar irradiation in those regions, the use of solar systems for water treatment is possible. In this paper, an automated solar pasteurizer system was used for the microbiological decontamination of water. The main characteristics of the solar pasteurizer are energetic self-sufficiency and robustness, the ability to promote decontamination regardless of the turbidity or pH, absence of production of trihalomethanes, local biome preservation (Caatinga), control of treatment time and the absence of secondary contamination derived from the mixture of contaminated water with water in treatment. The system was able to treat the water in pre-programmed temperatures and time intervals of 3600 s at 55 °C; 2700 s at 60 °C; 1800 s at 65 °C; 900 s at 75 °C; and 15 s at 85 °C. The microbiological analysis performed (presence/absence of Total Coliforms and Escherichia coli) indicated the efficacy of the system, making it suitable for water treatment. It was found that productivity (batches' frequency) is directly proportional to accumulated irradiation. The pasteurizer is able to treat the water starting at the solar irradiation level of ≥12.2 MJ/m2 for systems without a heat recovery exchanger. The use of a heat recovery exchanger in this system, to pre-heat the water at the collector's inlet, is of great importance because it induces an increase in productivity of approximately 50% (highest productivity reaching 30 L in a day) and lowers the minimum level of solar irradiation 8.3 MJ/m2.