Gently Does it with Nocturnal Pumps

Whilst workers from a landmark building in Canada are at home sleeping, Landia’s (UK) pumping and mixing equipment quietly goes to work removing highly concentrated sewage at a flow rate of just 2.2 litres per second from a 31,000 litre cistern.

In fact, due to a lack of existing sewage capacity, the authorities in this city could only allow the prestigious seven-storey CAD $100M building to go ahead if such an overnight wastewater removal system could be put securely into place.

Supplied by Engineered Pump Systems of Port Coquitlam, who have worked in close conjunction with Landia and professional services firm WSP to bring about the most effective low-flow design, Landia’s chopper pumps and mixers are in operation from 11pm until 6am, removing sewage from the cistern that serves the third to seventh floors.

Eric C. Pettit, P.Eng, Project Manager for WSP, provided consulting services through for the project.  “To meet the strict low-flow rate of just 2.2 litres per second that was required for the overnight time slot, we’ve had to throttle the Landia pumps down substantially with a Variable Frequency Drive (VFD) as part of this complex installation. We start the pumps at 100% speed, and then ramp them down to the restrictive flow rate. We then ramp them back up to 100% just before shut-off to ensure that the pump is clear”.

He added:  “We are also using an additional Landia chopper pump as a mixer. Initially a standard propeller mixer was used, but it was constantly fouling and tripping on overload due to high concentrations of sanitary products that were causing a floating matt problem. It was also causing foaming, which worsened the unwanted surface matt build-up.We use the additional Landia unit to pump up and into a manifold so as to create a spray action along the floor of the basin, moving any settled material to the pump suction area.  This also pre-chops the materials, effectively eliminating the chances of jamming when we are running the VFD-controlled pumps to discharge”.

Earl Masse for Engineered Pump Systems added: “This has been an unusual, challenging yet very rewarding project. The Landia chopper pumps have conclusively proved their non-blocking capability and their ultra-reliability. The specification of a good pumping system to the successful operation of this new building has been crucial”.