Major membrane companies provides conditional guarantees on membrane longevity, typically 4-7 years. However, many evidences found recently suggest that the membrane longevity can be 10+ years, if the membranes are properly installed and used under reasonable operating conditions (Nishimori, 2010; Cote, 2012).
For flat sheet membranes, only 7.8% of the original panels had been replaced with new ones in the first 10 years of operation in one of the first MBR plants built by Kubota in 1999 in Japan. In other plant built in 1998 in Porlock, UK, only 6.4% of the original panels were replaced as of 2008. On average, 6.4% of panels were replaced within the first five years based on the survey performed in Europe (Nishimori, 2010).
The life expectancy study was also performed for GE’s hollow fiber membrane (Cote, 2012). In Fig. 1, the cumulative surface areas of installed membrane, replaced membrane due to the end of service life, and replaced membrane due to premature failure covered by warranty are plotted. In addition, hypothetical membrane replacements were also plotted assuming 5 year and 10 year life expectancies, where the two curves moves parallel to the total installed area with 5 and 10 year delays, respectively. It is apparent that the total replaced membrane area due to the end of service life or the premature failure covered by warranty is much less than the hypothetical 5-year replacement, but slightly more than 10-year replacement. Therefore, it can be concluded that the longevity of this particular membrane is close to 10 years. If only the recently manufactured membranes are taken into consideration, membrane service life is likely 10 years or longer forZeeWeed membranes (Cote, 2012).
Fig. 1. Cumulative membrane installations, failure replacement, warranty replacement, and hypothetical lives in North America for all generations of ZeeWeed membranes (Cote, 2012)
© Seong Hoon Yoon