Water purification of lake water using progressive freeze concentration method

Abstract

Progressive freeze concentration method using stainless steel coil crystallizer was performed to concentrate and purify water from lake in Universiti Teknologi Malaysia, UTM. The study focused on the effect of operation time in range of 5 to 25 min and coolant temperature in range of -5 to -17 °C with constant pump rotation (450 rpm), initial biological oxygen demand (16.83 mg/L), total suspended solid (566 mg/mL) and turbidity (300 NTU). In water treatment using this progressive freeze concentration setup, a layer of pure ice crystal is produced on the inner wall of the crystallizer, leaving behind concentrated mother liquor. In order to determine the efficiency of the process, values of parameters such as biological oxygen demand (BOD5), total suspended solids (TSS) and water turbidity were measured. High system efficiency was observed at coolant temperature of -11 °C and operation time of 10 min giving BOD: 2.23 and 2.47 mg/L TSS: 28 and 36 mg/L and turbidity 1.22 and 1.25 NTU, respectively. The current technology of crystallizer design was found to be relevant to reduce BOD5, TSS and turbidity of water lake.