THE MALTHUS SYSTEM FOR BIOCIDE EFFICACY TESTING AGAINST DESULFOVIBRIO-DESULFURICANS

Microbially influenced corrosion (MIC) makes an important contribution to corrosion in various industries. Considerable success has been ach ieved by the use of biocides. Little information for controlling MIC i s, however, available on the effectivity of biocides against sulphate- reducing bacteria (SRB) due to the difficulties of culturing these org anisms using conventional techniques. Conductance changes monitored us ing the Malthus system were evaluated as an alternative method of esti mating numbers of Desulfovibrio desulfuricans for laboratory biocide e valuations. The correlation of log10) counts of Desulfovibrio cells in iron sulphite (IS)-medium using conventional techniques with detectio n times using the Malthus systems was highly significant (r = 0,974), indicating that the Malthus system can be used as an alternative metho d to conventional media for the enumeration of SRB. Growth studies of Desulfovibrio using the Malthus system were useful in the evaluation o f biocides. A 56 % and a 100 % kill was obtained when using 60 and 200 mg/l quaternary ammonium compounds (QAC), respectively.