The invention relates to methods and liquid compositions suitable for high level disinfection ("HLD") of medical instruments at close to ambient temperatures. The methods and compositions are also effective for digesting biological contaminants, and, surprisingly, can be used to clean and disinfect concurrently. Both cleaning and disinfection efficacy meet the criteria for cleaning and disinfection of medical devices. Use of compositions according to the invention enable reprocessing of instruments more quickly with greater energy efficacy, and greater convenience than prior art reprocessing methods. Compositions according to the invention are also useful for simultaneous cleaning and disinfecting other surfaces, for example in hospitals, food preparation areas and the like, or fabrics and the like such as are treated in hospital laundries.
