Commercial laundries process a variety of different items including rental garments, floor mats, print or ink towels, and shop towels. Many applications produce a large amount of oil or other hydrocarbon waste product, particularly laundering shop towels. The purpose of the detergent composition is to remove this oil along with other dirt and soil from the items being laundered. This is accomplished by using a combination of surfactants, alkaline agents, as well as antiredeposition agents and various sequestrants to achieve maximum cleaning efficacy. The surfactants in particular function to keep the oily soils emulsified and suspended in the wash water. In general, the more stable the emulsion generated in the wash water, the better the cleaning performance of the detergent system.
At the same time, it is frequently necessary to remove this oily soil from the wash waste water prior to disposing of this waste water to the sewer. Thus, it is necessary to counteract the effect of the wash solution in order to separate the oil from the emulsified wash solution before disposing the wash water. However, the more stable the emulsion generated in the wash water, the more difficult and costly separation becomes.
There have been many attempts to accomplish this. For example, amphoteric surfactants have been used. At an alkaline pH these are effective surfactants for emulsifying oil, but at an acid pH, their ability to function as a surfactant is reduced. This effectively enables one to lower the oil and grease content of the waste water to several hundred ppm. But this is not adequate to meet most current standards. This application also increases the potential of solubilizing heavy metal contaminants in the acidic pH required to destabilize the emulsion.
Many laundries treat the wash solution subsequent to the wash process in order to remove emulsified oil and grease. This requires the addition of various water treatment chemicals and the use of expensive water treatment systems in order to counteract the effects of the surfactants. Even with the chemical treatment one must design the wash solution to optimize water purification using whatever post treatment is available.
Many companies have changed surfactant systems resorting to less water soluble surfactants, or have actually lowered the amount of the surfactants in order to minimize emulsion stability. The net overall effect of these actions is the reduction of cleaning efficacy of the detergent.