Glass Lined Steel Sludge Tank: Holding Septicity Without Losing the Wall Sludge storage is one of the few duties where the liquid in the tank is less dangerous than the gas above it. Once sludge stands and turns septic, sulphate-reducing bacteria generate hydrogen sulphide, that gas migrates to the vapour space, and sulphur-oxidising bacteria living in the condensation film on the roof and upper shell convert it to sulphuric acid. Tanks that were specified against the liquid