Washing wastewater is the washing wastewater generated from bedding, work clothes, medical linen and functional surgical linen, and contains a small amount of domestic sewage; it mainly includes pre-washing sewage, main washing sewage, washing sewage and drying sewage.

It has the following characteristics: the washing sewage contains surfactants, carboxymethyl vitamins, oil stains, dust particles and various microorganisms. It has a turbid appearance with containing a large number of short fibers, bacteria, viruses and other potentially infectious bacteria as well.