Assessment of the biodegradability of dialkyldimethylammonium salts in flow through systems.

A bacterium capable of utilizing the alkyl chains of didecyldimethylammonium salt was isolated from activated sludge. In addition, the isolate also utilized didodecyldimethylammonium salt, ditetradecyldimethylammonium salt and alkyltrimethylammonium salts (C10 to C18) as sole source of carbon and energy. The broad substrate with respect to the alkyl chain length was also demonstrated with oxidation rates of various quaternary ammonium salts by didecyldimethylammonium chloride-grown cells. The oxidation rate decreased with increasing alkyl chain lengths. The main factor impeding the biodegradation of dialkyldimethylammonium salts with long alkyl chains is probably the low bioavailability of water-insoluble chemicals. The biodegradability of dialkyldimethylammonium salts was therefore determined in flow-through columns at concentrations below their aqueous solubility. Dialkyldimethylammonium salts adsorbed on silica gel particles packed in flow-through columns were immediately metabolized by the isolate when dissolved. Microorganisms present in river water pumped through a sterile column degraded dissolved dicocodimethylammonium salts within a week.