Abstract

Rainwater can be a safe and sustainable source of drinking water. Progressive freeze concentration has been identified to be a suitable freeze treatment process to treat rainwater into drinking water. In this work, the harvested rainwater quality was evaluated based on atmospheric conditions and the subsequent purification process was carried out and reported on the respective supercooling phenomena and effect of operating parameters.  Statistical analysis found the total dissolved solids of rainwater to negatively correlate with rainfall amount (r = -0.32) and the range was found to be workable for our progressive freeze concentration system. The supercooling effect in the falling film freeze treatment system was found to be non-existent, showing rainwater can be purified to a relatively high purity without excessive precaution to prevent contamination caused by supercooling. Experimental results and statistical analysis showed higher circulation time (26 min) and lower rainwater total dissolved solids (6 ppm) improved the purification efficiency of rainwater by giving higher concentration factor (3.4). A simple energy consumption analysis also signifies this system to consume a significantly lower energy compared to distillation. This work can serve as a preliminary study for future research to explore freeze treatment as a viable process to produce drinking water from rainwater.