Norwegian wastewater treatment company Vestfjorden Avløpsselskap (VEAS) has installed equipment that is normally utilised on offshore vessels at Norway’s largest wastewater treatment plant at Slemmestad in Røyken municipality, Buskerud county.
VEAS has acquired three hydraulically driven agitators for the plant’s large sewage tank. Supplier is Vestfold-based PG Flow Solutions AS, which has delivered this type of agitator to offshore vessels and platform supply vessels in more than 20 years, used amongst other things for treatment of mud from drilling operations.
The agitator, which is named PG-Sumbix 80, is a slow moving, paddle-type propeller with high torque. The agitator is placed in tanks to prevent that sludge and additives settle at the bottom of the tank as such build-up of solids could cause problems for outlets and pumps if pieces of deposition were to detach.
The advantage with PG-Submix 80 is that it does not leave any “blind spots” in the tank, as the agitator slowly pushes sludge and waste water towards the bottom of the tank, where the highest velocity is needed, and then up against the walls of the tank. This ensures that the liquid is kept in continuous suspension and that sediments and waste products do not accumulate at the bottom of the tank.
“We have developed and supplied such agitators and associated systems to approximately 1,500 offshore vessels during the past 20 years, but this is the first time we utilise it for a land-based industrial application. However, the principle of keeping fluids in motion is exactly the same offshore and onshore. We have a product that has demonstrated its reliability over hundreds of thousands of hours, which is why we were chosen as supplier to VEAS,” says Tom-Erik Svendsen, sales manager – industry, at PG Flow Solutions.
The delivery consists of three PG-Submix 80 agitators that are mounted separately on pedestals at the bottom of a large bio-tank which has a diameter of 12 metres and is 15 metres tall. Each Submix comes with its own hydraulic system because of VEAS’ requirements to operational reliability.
PG Flow Solutions has not disclosed the value of the contract.
“This bio-tank contains excreted sludge and will, in principle, only be emptied and inspected internally every 4-5 years. It was therefore important for us to identify the most reliable product. Each of the three Submix agitators delivers a primary pump flow of 12,439 cubic metres of liquid per hour. Hence, even if one or two units fail, we will still have enough circulation in the tank to maintain operational reliability. In addition, PG Flow Solutions provides excellent operational guarantees for its Submix agigators and, as such, they became the natural choice for us,” says Kjetil Wang-Hansen, head of production, and Per Torp, maintenance manager at VEAS.
The VEAS plant is Norway’s biggest waste water treatment plant and a key contributor to keeping the Oslo fjord clean. VEAS is an inter-municipal partnership owned by the municipalities of Asker, Bærum and Oslo. Wastewater from more than 600,000 inhabitants in Oslo, Bærum and Asker are transported via the VEAS tunnel from entry points in the municipalities to the treatment plant at Bjerkås in Asker. VEAS also cleans wastewater from the municipalities of Røyken and Nesodden.
PG Flow Solutions provides proprietary solutions, systems and products for companies within the energy, maritime, aquaculture and land-based process industries. The heritage of the business is pumps and pumping systems. The company’s headquarters and manufacturing facility is located in Sande, Vestfold, Norway. Its subsidiary Calder Ltd operates out of a similar facility in Worchester outside Birmingham, UK, while subsidiary Cflow Fish Handling AS operates out of Aalesund, Norway.