Aqualuz: a new solar disinfection device for treatment of cistern water

We conducted field, laboratory and modeling studies to evaluate the efficiency of a new solar disinfection (SODIS) device called Aqualuz for the removal of Escherichia coli (EC) from cistern water in the Brazilian semiarid, for different solar exposure-water temperature conditions. The results indicated EC contamination (100-300 MPN/100 mL) in all tests performed. As compared to the literature, lower exposure times (2.5-4.0 h) and solar radiations (250-410 W/m(2)) were sufficient for EC elimination. Then, assuming the complete-mix approach and first-order kinetics, it was possible to adjust EC decay rate constants (k) considering three different models: constant k-value, k as a function of water temperature and a new formulation for k as a function of both solar radiation and water temperature. All models performed well with normalized root mean squared logarithmic error (NRMSLE) lower than 20%, but the best fitting was obtained with the new approach. A new relationship between solar radiation and water temperature was also obtained, which allowed model simulations of EC decay for 34 municipalities in the Brazilian northeast, resulting in a color map for the region depicting the exposure periods of 1.8-5.6 h for reaching a 3-log reduction.