Evaporators; Purification installations for sewage; Sewage disposal plants; Sewage purification apparatus; Sewage purification installations; Sewage treatment plants; Thickening and dewatering machines for use in treatment of liquids including water, industrial effluent and sewage; Waste disposal incinerators; Waste processing machines using heat and chemical breakdown processes; Waste water purification apparatus, installations and tanks; Waste water purification units