Effective control of microbial populations in polysulfone ultrafiltration membrane systems

Sanitizers currently used in the food industry are not efficient in destroying bacterial populations in polysulfone UF membrane systems. A new sanitizer composition that releases chlorous acid and chlorine dioxide from sodium chlorite at pH 2.7 was evaluated. Polysulfone UF membranes were soiled for 2.5 h by circulating and concentrating Cheddar cheese whey and skim milk. A cleaning regimen was established whereby acid and caustic cleaning solutions were circulated to clean the UF membrane system. Restoring permeate flux to initial values did not indicate that the system was effectively cleaned. The UF system was sanitized by recycling sanitizer solutions. Stainless steel and membrane surfaces were examined by swabbing to determine bacterial populations and sections of membranes were removed for examination using a scanning electron microscope. The new sanitizer appeared to control microbial populations effectively in UF membrane systems.