Modified biosand filter coupled with a solar water pasteurizer: Decontamination study

Modified biosand filters (MBSF) and solar pasteurizers have been used as individual drinking water treatment systems around the world. The aim of this study is to evaluate the performance of a MBSF coupled with a solar pasteurizer for effective treatment systems for source water. The MBSF was designed with an extra disinfection layer with zero valent iron (ZVI) and three layers of underdrain to remove Escherichia coli (E. coli), total coliforms and turbidity. A flat solar panel with a solenoid valve was used as a solar pasteurizer and an extra disinfection system to remove residual E. coli and total coliforms from filtered water. The pasteurizer produced an average of 4.5 l of pasteurized water per day. 75 °C was selected as pasteurization temperature. A 96.25% reduction (log 1.65) in total coliforms, 98% reduction (log 2.27) in E. coli and 94.8% reduction in turbidity was observed in the filtered water samples. After the pasteurization, 100% of the E. coli and 99.99% of the total coliforms reductions were observed in the filtered and the unfiltered water. The turbidity level of the pasteurized unfiltered water did not meet the drinking water standards. However, the water quality met World Health Organization drinking water standards for the MBSF system coupled with the solar pasteurizer.