BAR SCreen : Definition and applications
A Bar Screen is a mechanical filter used to remove large objects from wastewater. It is part of the primary filtration flow and it usually is the first level of filtration being installed at the influent to a wastewater treatment plant. They typically consist of a series of vertical steel bars spaced between 1 and 3 inches apart.
Primary treatment removes material that will either float or readily settle out by gravity. It includes the physical processes of screening, comminution, grit removal, and sedimentation. Primary treatment is a very important step within the process of water treatment, because if the primary treatment is not properly performed, all the following processes will be afffected by it.
The first step of the primary treatment of wastewater is called “screening”. The effluent passes through vertical metal bars, which block the floating debris such as fibers, plastic, wood, rags and other bulky objects that could clog pumps. The screens can be raked manually, but in modern plants, the screens are cleaned by a Mechanical Screen, most commonly called Bar Screen or Step Screen. The waste removed by the Bar Screen is then disposed into a container, a compactor or a conveyor.
Manual screening has been replaced over the years by mechanical screening, because the cleaning process could be dangerous for the operators. Another reasons is that the flow is very often quite important, as well as the amount of debris to be lifted up, and therefore only a mechanical screen is powerful enough to clean the bars of the screen.
Most Common Screening Issues
Saturated Manual Screen
Saturated Fine Screen
Clogged Aeration Pipes
Fibers in Settling Tank
The solution: the Mechanical Bar Screen
A Mechanical Bar Screen is placed across the effluent. The waste is then blocked by the bars of the screen, and a rake automatically cleans the bars, grabbing the debris and rejecting them into a container. The debris can also be rejected into a Screw Conveyor or a Screw Compactor. Thanks to use of a Mechanical Bar Screen, the effluent is regularly screened, and the pumps are protected and do not risk to get clogged.
Thanks to the Mechanical Bar Screen, screening is now efficient, regular and safe. It’s the guarantee of efficient wastewater pretreatment.
FB Procédés offers a complete range of Bar Screens meeting all efficiency and quality requirements for the pretreatment of wastewater:
- Protection of the pumps
- Reduction of wwtp waste load
- Same footprint as a manual screen
- Only the large waste if removed (not the case with a manual screen)
- Little or no modification of the civil works
- Waste directly rejected into a waste container
- Adaptable to all civil works
- Fits directly into the pump station or lift station
- Maintenance performed above grave for complete safety