Influence of Imidazolium Ionic Liquids on Dehydrogenase Activity of Activated Sludge Microorganisms

Imidazolium salts are one of the most often used and investigated groups of ionic liquids (ILs). The research concerning their ecotoxicity comprised many test organisms representing different trophic levels; however, their impact on mixed cultures of microorganisms such as activated sludge has been hardly ever investigated. Thus, in this work, the effect of imidazolium ionic liquids on dehydrogenase activity of activated sludge was estimated. Three activated sludges of different properties and origin were tested. It occurred that 1-alkyl-3-methyl imidazolium bromides do not inhibit dehydrogenase activity of sludge, if the alkyl chain contains up to six carbon atoms. The values of IC50 for these ILs were above 100 mg l(-1). At the same time, the inhibitory effect on dehydrogenase activity of activated sludge increases with the increase in chain length of the alkyl substituent. The degree of inhibition of dehydrogenase activity of sludge microorganisms is dependent on activated sludge properties.