PFADC Computer Controlled Dissolved Air Flotation Unit.

The Computer Controlled Dissolved Air Flotation Unit, "PFADC", has been designed to study the flotation treatment process. For that purpose, raw water with different chemical products will be treated. Flotation is achieved when a fluid with suspended solids is depressurized and bubbles appear. Solid particles adhere to the bubbles and rise with them, being separated from the fluid.

The process starts in a tank, where raw water is prepared. Water is pumped to the flocculation tank with the aid of a computer controlled pump. This tank is divided into three sections. A coagulant is added to the first chamber, impelled to the tank by a computer controlled metering pump. The coagulant neutralizes the electrostatic charge of the particles, so they tend to combine into flocs. A flocculant is added to the second chamber with the same mechanism. It facilitates the formation of larger flocs in order to make filtration easier. Caustic soda is also added to this chamber to increase water pH. The regulation of the pumps flow rate through the computer allows for changing the amount of coagulant and caustic soda. Therefore, the pH is regulated. There are two pH sensors in the first and second chambers to analyze that variation. Finally, the flow is quietened in the third chamber to prevent turbulences and favor the formation of flocs.

There is a stirrer with computer controlled speed in each chamber to control the mixture of the additives. At the outlet of the flocculation tank, water goes to the flotation tank. Part of the water is impelled by a circulation pump to other tank, where it is saturated with air under pressure. It leaves the tank, is depressurized by a valve and enters the flotation tank again. There are flow and pressure sensors at the inlet and outlet of the pressure tank to observe the process variation. When the flow enters the flotation tank, little bubbles are created and adhere to the suspended particles, so particles float and it is easier to remove them. In this case, a scraper is used to collect them.

This Computer Controlled Unit is supplied with the EDIBON Computer Control System (SCADA), and includes: The unit itself + a Control Interface Box + a Data Acquisition Board + Computer Control, Data Acquisition and Data Management Software Packages, for controlling the process and all parameters involved in the process.