11 Water purifying apparatus, devices, machines and installations for the treatment of aqueous media, such as water, river water, seawater, rainwater, wastewater and sludge, in particular using chemical, physical and mechanical processes, such as precipitation, flocculation, neutralization, coagulation, adsorption, flotation, dewatering, drying, screening, filtration, stripping, reverse osmosis and electrolysis; apparatus, devices, machines and installations for the preparation of screenings and sieved material being parts of water purification units; apparatus, devices, machines and installations for the purification of water or wastewater by adsorption processes, in particular by activated carbon filters or activated carbon adsorbers; apparatus, devices, machines and installations for the preparation of sand, in particular sand traps, sand classifiers and sand washers being parts of water purification units; apparatus, devices, machines and installations for energy recovery and energy generation from water and wastewater, namely, heat exchangers and heat pumps; apparatus, devices, machines and installations for heating or cooling water, wastewater and sludge, namely, heat exchangers; apparatus, devices, machines and installations for sludge dewatering, sludge drying and sludge incineration; apparatus, devices, machines and installations for the purification of air, in particular air filters; apparatus, devices, machines and installations for the purification of exhaust air from wastewater treatment plants and drying plants, in particular scrubbers, biofilters, activated carbon filters and installations for oxidative purification, in particular by means of UV radiation or ozone; aggregate parts and fittings for the aforesaid goods; all of the aforesaid goods as far as included in this class; apparatus, devices, machines and installations for energy recovery and energy generation from sludge by sludge incineration