The PFP flotation unit is a compact built plate separator, which is designed for efficient removal of settling as well as floating particles.

 

The waste water is mixed with aerated, re-circulation water before it enters the flotation unit. The micron-sized air bubbles are mixed with the solid particles or oil and fat droplets. This results in a good adherence of air to the particles. After entering the flotation unit the water flow is distributed in a set of flow distribution baffles.

 

After the first compartment where fast settling and flotating particles are already separated, the water flows in vertical direction through the parallel plates. The corrugated plates are installed under an angle so that settling solids will slide down and flotating particles are moving upwards.

The plate distance between the corrugated plates is selected to ensure a laminar flow pattern between the plates. The laminar flow is essential for the separation of the small particles.

The clarified water leaves the separator via an underflow and an overflow baffle system.

 

The floating sludge layer is de-watered with a designed thickener and removed by a skimmer device. Settled particles are collected in the sludge cone under the plate pack. The sludge can be removed regularly through the de-sludging valve. This valve can either be an automatic or a manual valve.

 

The de-sludging will result in a downward motion of the liquid in the separator. This causes particles which are stuck to the plates to be released and to continue their path. Due to this "selfcleaning" system the plate pack will usually not clog-up.

 

Part of the treated water is recycled for aeration purposes. The special 2-phase re-circulation pump is ingesting air at the suction side. The pump not only delivers the 2 phases, but also works as a dynamic mixer. At the pressure side an excellent saturation of the water with air is obtained. This saturated water is dosed to various points of the unit. The de-pressurization takes place in specifically designed devices. As a result fine air bubbles of 30 - 50 micron are formed. The size of the air bubbles is essential for the efficiency of the flotation unit. Small bubbles easily adhere to equally sized or larger particles.

The sludge removal by the sludge de-watering/skimming device can be adjusted by level. An adjustable outlet weir is provided to set the level in the flotation unit in the optimum position.

 

Automatic sludge drain valves are optionally installed, subject to application. These valves are time controlled and pneumatically operated.

The water enters the inlet compartment via a distribution system. Dissolved air is already dosed before the water enters this compartment. The water will pass an water distribution flap while flowing into the flotation.. Dissolved air is dosed at the beginning of this compartment to provide sufficient air bubbles to give buoyancy to the particles and to create an aircushion under the floating layer.

The particles are collected in the floating layer (sludge) and the water leaves the separator via an underflow and an overflow baffle system. The relative dry sludge is removed by a sludge skimmer.

Heavy particles will settle down and are collected in the V-shaped bottom.

Part of the treated water is recycled for aeration purposes. The special 2-phase recirculation pump is ingesting air at the suction side. The pump not only delivers the 2 phases, but also works as a dynamic mixer. At the pressure side an excellent saturation of the water with air is obtained. This saturated water is dosed to various points of the unit. The de-pressurisation takes place in specifically designed devices. As a result fine air bubbles of < 50 micron are formed. The size of the air bubbles is essential for the efficiency of the flotation unit. Small bubbles easily adhere to equally sized or larger particles.

 

The sludge removal by the sludge skimming device can be adjusted by level. An adjustable outlet weir is provided to set the level in the flotation unit in the optimum position.

 

Heavy sludge is removed from the bottom by a screw conveyor and an automatic, pneumatic valve at the end. The screw conveyor and the valve are time controlled.