Ceramic membranes have many advantages such as durability, chemical resistance, high flux, and long life span. However, they generally require relatively high initial investment cost compared to polymeric membranes when they are used for a water treatment process. Therefore, if ceramic membranes are considered to be applied to a water treatment plant (WTP), the life cycle cost (LCC) analysis should be performed to evaluate its economic feasibility. In this study, the capital and operational expense data of selected WTPs which have membrane filtration processes were used for their LCC analysis. Production capacity of the plants, membrane flux and life span, and costs of membrane modules and electricity were considered as key analysis factors. From the LCC analyses with various conditions including membrane costs and membrane flux, the correlation of the key design parameters was obtained that can make the ceramic membrane filtration more cost-effective compared to the polymeric membrane method. At present state, WTP with a ceramic membrane should increase the permeate flux to meet the economic feasibility, but it is expected to have a bright future because of the recent development of manufacturing technologies and increase of demand in many industries.

Gas hydrate (GH) desalination process is based on a liquid (salty water) to solid (GH) phase change coupled with a physical process to separate the GHs from the remaining salty water. However, GH process exhibits less than 90% of salt rejection, so reverse osmosis (RO) process is needed to finally meet the desalinated product water quality. In order to increase the total recovery of the GH and RO hybrid system, the concentrate of the RO process should return to the feed stream of the GH process. In this work, RO simulation was carried out to find an optimal RO recovery with which the energy consumption of RO was minimized. The optimal RO recovery values for GH processes with salt rejection of 78, 84, and 90% were 0.6, 0.8, and 0.8, respectively. The minimal total energy consumption appears at higher RO recovery rates than the optimal values to minimize the RO energy consumption because the portion of the GH energy consumption is inversely proportional to the RO recovery. The simulation also reveals that the maximum allowable energy consumption of GH process is 1.4 kWh/m³ (with GH salt rejection of 78%) to overcome seawater RO process with energy recovery device, and it can be increased up to 1.9 kWh/m³ when GH salt rejection increases up to 90%.