Finnish company Finnchain Oy has developed a new surface scum removal system with reduced water consumption and no energy-consuming devices.

Finnchain says that it has introduced the system as an alternative to rectangular sedimentation tanks that use traditional scum skimming with a scum pipe, which require a considerable quantity of water to carry the scum in the pipes. The development is now necessary because de-nitrification creates an increasing amount of surface scum in wastewater treatment processes.

According to Finnchain, surface scum is removed in its system by constant water flow, without the need for any external energy source. The company adds that the water consumption needed to remove the surface sludge is around 2 m3/day – up to 80% less water than that required when using a traditional system. With the new Finnchain system, treated water is led to the overflow channel and surface scum is directed to the scum box from where it is pumped away.

Finnchain adds that the most significant benefit of its new surface-scum removal system is that it does not employ motors or other energy-consuming devices. The amount of surface sludge removed is adjusted by the water flow. Water flow can be adjusted by changing the height of the level adjuster. Water flow at the surface from the clarifier tank to the overflow box is adjusted by means of a level adjuster. Normal changes (±30 mm) of the water surface level in the tank do not present a problem, because there are floats to maintain the level adjuster at the selected height. Floats change the height of the level adjuster when the water surface in the tank rises or sinks. The amount of water needed to carry surface scum in the scum pipe can be adjusted by using the adjuster in the overflow channel.

The system has already been fully field tested and is currently in use at the Hämeenlinna wastewater treatment plant in Finland. Results show that the Finnchain system is working efficiently and that water consumption has been reduced significantly compared to traditional surface scum skimming systems. The new system can also be used in potable water treatment plants and for oil separation.

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