An Innovative Reverse Osmosis – Freeze Concentration Hybrid System On A Vertical Sewage Treatment Plant And Performance Testing

Abstract

An innovative hybrid system of membrane treatment (Reverse Osmosis) and freeze concentration was developed to remove the dissolved solids from the real urban wastewaters. The hybrid system was installed on a vertically aligned sewage treatment plant that uses both, anaerobic and aerobic treatments. The sewage treated through these two organic processes is further subjected to the membrane treatment Reverse Osmosis (RO). The concentrated brines rejected by the reverse osmosis system are further treated using a reversible heat pump-based freeze concentration (FC) system. The process involves freeze concentration followed by melting of ice alternately in each tank by reversing the refrigerant flow. Thus, the sewage treatment plant integrated with the RO FC hybrid system could recover around 75% of the input sewage as usable water. The reversible heat pump simplified the process of separation of the ice from water and reduced the energy consumption of the compressor. The pilot sewage treatment plant of capacity 10000 LPD was built, and trials were taken with actual urban sewage water.      By treating the sewage water through an RO-FC hybrid system, a 25% increase in the yield of usable water was obtained compared to the conventional RO only system.