Dortmund. Different sewage purification processes prescribe that some defined quantities are led back to preceding purification processes in order to optimise water treatment processes. Recirculation pumps by WILO SE  are designed for an energy-efficient transport of large volume flows at a low flow velocity and delivery head. The main application field of the “Wilo EMU-RZP” series is municipal sewage purification.

In this case, for example, the depositing activated sludge has to be pumped back from the final clarification into the biological phosphorus removal (Bio-P) or into the activated sludge tank. Thus, the micro-organisms of the sludge, which are necessary for the decomposition of pollutants in the sewage, are reintroduced into the purification circuit. The pumps are also used for internal recirculation between nitrification and denitrification.

The flow-optimised, self-cleaning propeller of the RZP series ensures an energy-efficient operation. In this case a special blade construction makes sure that water, sewage and activated sludge can be pumped in a particularly gentle way.

The recirculation pumps of the “Wilo EMU-RZP” series are manufactured as a modular system upon customer demand. The motor, the drive and the propeller can be combined in a way that provides a tailor-made arrangement of the pump equipment and the pump curves to meet individual requirements. This is why they have an extremely wide application range. Pumps with a motor performance between 0.5 and 22.5 kW and with connections for pipes ranging from DN 200 to DN 800 are available. Thus a performance range with a delivery head of up to 3 m and up to 1,900 l/s volume flow is completely covered. The use of frequency converters enables the recirculation pumps to operate in the desired duty points.

In addition to their high flexibility, the “Wilo EMU-RZP” series is characterised by an easy installation and maintenance. Sump constructions for the pump are not required. The pump is installed and dismantled by means of a lowering device. The recirculation pumps can be lowered into the tank or lifted for maintenance purposes. The pump is easily attached to the pipe by lowering it into the required installation position. It is not necessary to screw it because due to the dead weight of the unit, the pump housing connects to the flange of the pressure pipe and fastens it. Furthermore it is maintained steadily at the flange by means of the pressing wedge which is welded at the pressure pipe flange. Besides the horizontal installation, the Wilo recirculation pumps can also be installed vertically. Another application variant is the “Inline” version. In this case the recirculation pump is placed in the pipe. This version is applied when installation is impossible due to the pipe opening or when the volume flow requires a new impulse.

In addition to their use in sewage treatment plants, recirculation pumps are for example also applied for feeding water channels in theme parks. These attractions require a continuous water circuit and permanent flow in the channel in order to permanently supply all sections of the channel with sufficient water for an unhindered sliding of the boats.