A solid glutaraldehyde composition is provided which incorporates a quaternary ammonium compound. The glutaraldehyde can be used in a method of treating a wellbore or a subterranean formation, by introducing the composition to a wellbore or to an injection line within a wellbore in an amount effective to reduce biodegradation of crude oil, reduce corrosion of metal surfaces from sulfur-reducing bacteria, or to reduce the introduction of bacteria into the formation, reduce microbial contamination of a fluid introduced into the wellbore, or reduce microbial contamination of a pipeline.