Heat-activated persulfate for chemical cleaning of ceramic MBR

Abstract

Irreversible membrane fouling is a major concern in the application of membrane bioreactors (MBRs), and periodic chemical cleaning is required to sustain MBR operation. However, conventional NaClO cleaning exhibited limited efficacy and caused secondary environmental risks (e.g. disinfection by-products). Therefore, it is necessary to develop safe and efficient chlorine-free cleaning methods. Here, we proposed a heat-activated persulfate (peroxymonosulfate PMS and peroxydisulfate PDS) process for efficient cleaning of fouled ceramic membrane in MBR. Results showed much higher chemical cleaning efficiency in heat-activated persulfate process (79~81%) than that in NaClO (34~52%). A medium solution temperature of 60 °C was enough to efficiently activate PMS and PDS, with the optimal persulfate concentration of 1mM and solution pH of 7. Both SO4•− and •OH were identified as the main reactive oxygen species for membrane cleaning. Compared with PDS, PMS was easier to be activated, and thus more free radicals were generated in heat/PMS system. Further investigations demonstrated radicals degraded polymers and broke microbial cell structure, thereby effectively removing foulants from membrane. This work provides a new idea for developing safe and efficient chemical cleaning method for ceramic MBR.