11 Installations and equipment, either skid-mounted or stationary, which permit the chemical, biological, physical or physical-chemical breakdown (or lysis) of the bacteria which mediate biological processes for the treatment of municipal or industrial wastewater and which constitute liquid or semi-liquid sludge from the treatment installations; installations and apparatus, either skid-mounted or stationary, for preparing, mixing, metering and feeding oxidizing chemicals, surface active agents or enzymes intended to degrade cell walls; apparatus and installations for water purification and sedimentation, including equipment permitting a reduction in the production of biological sludge by methods involving the use of oxidizing chemical reagents, surface active agents, enzymes, radiation, electrical fields, electron beams, mechanical grinding and shredding or thermal means, as well as any combination of two or more of the above methods.