Treatment, purification, secondary treatment, disinfection, decontamination, decolloidation and pollution control of sludge; services of dewatering and pollution control of sludge; Fixed and movable, apparatus, devices and installations used in a purification plant, namely, a main reactor, in the nature of industrial chemical reactors for treatment, purification, secondary treatment, disinfection, decontamination, decolloidation and pollution control of sludge; fixed and movable apparatus, devices and installations used in a purification plant, namely, a main reactor, in the nature of industrial chemical reactors and in a process for dewatering and reducing in volume the treated sludge; Building, commissioning, repair and maintenance of fixed and movable apparatus, devices and installations for treatment, purification, secondary treatment, pollution control of sludge; services of building, commissioning, repair and maintenance of fixed or movable apparatus, devices and installations for dewatering and pollution control of sludge; Engineering services, namely, designing, calculating and dimensioning of facilities used for treatment, purification, secondary treatment, disinfection, decontamination, decolloidation, and pollution control of sludge, dewatering sludge