The invention concerns a bacterial preparation, a method for preparing a cleaning solution, a cleaning solution and a method for cleaning targets, which contain impurities. The cleaning solution contains at least bacterial preparations, such as portion capsules, with bacteria which are harmless to humans and animals, such as probiotics, mixed into a liquid, such as water. The used water is preferably tapwater, from which components that kill bacteria in said bacterial preparations have been removed and preferably also all or nearly all salts.
