Effects of cleaning conditions of osmotic backwashing on the SWRO operation

摘要

The cleaning-in-place method, which is most widely used to remove foulants and maintain the performance of membrane, needs a period of downtime for frequent operation stoppage, which reduces the membrane lifetime, and creates environmental issues related to waste chemicals disposal. On the other hand, the osmotic backwashing induced by the osmotic pressure of maintenance cleaning methods in the seawater reverse osmosis (SWRO) membrane can reduce the number of chemical agents needed and reduce the load on the pretreatment. The cleaning efficiency is affected by various factors such as the total dissolved salt (TDS) of NaCl solutions, backwashing time, and cycle of backwashing during osmotic backwashing. In this study, the cleaning efficiency and the change of backwashing volume were analyzed according to the TDS of the NaCl solutions, backwashing time, and cycle of backwashing. As a result, the cleaning efficiency was improved with an increase in the TDS of NaCl solutions; however, it did not change after a certain point due to the irreversible resistance of the fouling, although the backwashing time increases. Therefore, the optimal backwashing cycle at which the irreversible resistance increase rate was the lowest was confirmed through changes of the backwashing cycle.