Maximizing Membrane Life: Lessons Learned from a Three Year Study on Performance Recovery

Reverse Osmosis (RO) membranes are susceptible to several different types of foulants and scales. Common foulants observed in RO systems are organics, metals, clays and colloidal material. Common scales that are observed are carbonate, phosphate, sulfate and silica. Onsite cleaning is the norm to remove these foulants and scales but sometimes a desire for cleaning optimization or a requirement for process troubleshooting leads operators to undertake a more detailed investigation. Therefore, one option is to send membranes for offsite cleaning to a facility that is able to clean membranes individually or in small groups. Another common approach is a membrane autopsy which requires the sacrifice of a membrane. A membrane autopsy entails membrane dissection, foulant and/or scale sampling, identification of the foulant and/or scale and permits a detailed cleaning study on flat sheet samples harvested from the full element to be conducted. Once the cleaning method has been optimized through the lab the process can be duplicated on full membranes from the same site to observe the effects of the clean on a larger scale. This paper reviews 248 studies that were carried out over three years from 2012 to 2014. The data collected included brackish, seawater and nanofiltration membranes. This body of analytical work gives a definitive statistical representation of the most common types of foulants. It also highlights fouling patterns such as the proportion of membranes that contained multiple foulants and/or scales. The effect of each foulant and/or scale on the flow and differential pressure. Additionally, the recoverability of RO membranes was analyzed and compared to the foulants and/or scales present.

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