Can incomplete biofilm treatment be bad?
Yes. When a biofilm is not removed completely by pigging and/or biocide dosing, sessile cells on a metal surface may survive. Usually, a pig’s brush is long and flexible enough to remove biofilms in shallow pits. However, this may not be true for deep pits. If they were previously starved of nutrients due to a thick layer of top biofilm or debris, they now have better access to nutrients (including sulfate) because of reduced mass transfer resistance. If we assume that these sessile cells are not injured by chemicals, they may actually increase pitting. MICORP simulation shows increased pit growth when the mass transfer resistance layer is reduced. By the way, incomplete treatment may enhance biocide resistance.
