The situation is much different in a laboratory where a pure culture of bacteria is on glass or stainless steel. A disinfectant doesn t have to deal with any organic matter it just kills the bacteria on the nonporous surface. In the real world, a disinfectant must be able to work in the presence of organic matter on contaminated surfaces. It must be germicidal against the pathogens encountered, and it must be biodegradable, cost effective, and relatively safe for humans and animals. The disinfectant also must be able to kill pathogens in the water you have available.
Water hardness is an indication of calcium and magnesium in the water.
Those minerals can adversely affect the potency of a disinfectant. This little fact is meaningless unless you know the hardness of the water on the farm. Although bleach commonly is used in human hospitals and laboratories, it is readily inactivated in the presence of organic matter and, therefore, is not suitable for use as the primary disinfectant on the farm. Chlorhexidine does not kill rotavirus, but is useful for disinfecting surgical instruments and is used as an antiseptic. Pine oil, often used for its fragrant smell, is not useful as a disinfectant.