Sodium metabisulfite (SMBS) is not a disinfectant. SMBS dissolved in water converts to sodium bisulfite. When dosed online at high dosages, it is an oxygen scavenger and many biofilm forming bacteria are anaerobic, making oxygen scavenging useless. In many cases, such high dosages have been associated with increased biological growth, especially where the water contains high TOC levels.
SMBS does however prevent fungal growth in membranes when used as a storage solution, because most fungi can’t grow without oxygen. It goes without saying that growth of aerobic bacteria is also inhibited under these storage conditions.
Fungus requires nitrogen for growth making polyamide membranes especially susceptible to deterioration should fungal growth not be prevented. Fungi and heterotrophic bacteria obtain their energy from organic compounds, so it’s important to clean the membranes well and remove all organic foulants from the membrane surface prior to long term storage in bisulfite solution.