The disclosed invention relates to a two-part liquid composition for cleaning and disinfecting a substrate, comprising: (A) a disinfectant medium comprising peracetic acid; and (B) a supplemental medium comprising a non-enzymatic cleaner, a corrosion inhibitor, and a chelator. The supplemental medium (B) may further comprise an enzymatic cleaner, a surfactant, a buffer, a pH modifier, or a mixture of two or more thereof. The substrate may be a medical device, for example, an endoscope.