Stormwater purification via progressive freeze concentration: effect of initial concentration and stirring speed

Water is one of basic needs and is essential for every living organism on Earth to survive. With increasing population, water has become scarce resource since the water demand is more than water supply. There are several methods to treat water such as evaporation, membrane processes and ultraviolet disinfection. However, these methods have limitations. Thus, researches have to find alternative ways, and this leads to the development of progressive freeze concentration (PFC) process. In this study, stormwater is chosen as alternative resource of water. By treating stormwater, not only water can be purified, but also water pollution can be prevented. This research aims to study the effect of initial concentration and stirring speed in stormwater purification via PFC towards effective partition constant (K) value, solute recovery (Y) and concentration efficiency. The range of initial concentration and stirring speed were determined at 2, 4, 6, 8 and 10 ppm and 150, 200, 250, 300 and 350 rpm. Simulated stormwater was created by using zinc chloride instead of actual stormwater to ease the process. Each effect was run at constant coolant temperature and time, -8 ᵒC and 15 minutes. The results show at lowest initial concentration, the lowest K value was obtained with 0.25 and the highest Y value of 0.686. It was found that at stirring speed of 350 rpm produced lowest K value, 0.2305 and utmost value of Y, 0.85. Best efficiency of PFC system was achieved at 2 ppm initial concentration which is 75% and 350 rpm stirring speed which is 76.95%.