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Today’s sophisticated wastewater treatment processes require highly effective operations. It all starts in the headworks where optimal performance is largely determined by effective screenings capture ratio (SCR). There are three major design principles for maximizing SCR through tailored screen design: type, size and grid opening. Let’s talk about wastewater screen types and how they support the mission of wastewater treatment plants.
Through the decades, we’ve seen a variety of screen types emerge, each in their own way aligning to the performance that plant operators need for their facilities to run effectively. In this overview, we’ll look at the different types of screens for wastewater treatment plants, and the benefits and challenges that each of them present.
Single Rake Mechanical Bar Screen
This design features a stationary bar rack with large openings, greater than 1”, that is anchored within the channel. A rake arm engages the screening materials and lifts it up and out of the channel.
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Step Screen
This design includes two vertical stainless-steel plates shaped like steps; one of the plates is stationary, while the other rotates. The plates alternate across the width of the channel opening to form the step screen face, elevating solids one step at a time to the discharge point.
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Through Flow Continuous Belt Screen
This design signaled the birth of fine screens and is known for being both a filtering and removal mechanism. Usually there is a rotating or static brush to knock the screenings off. A spray wash is also commonly used for offloading materials.
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Center Flow Screen
These screening systems became popular in the U.S. in the 2000s. The center flow screen provides a solution to the limitation of the drum screen design by elongating the screen opening, which allows for a higher flow into the equipment. It features an all stainless steel construction.
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Multi-Rake Bar Screen
The single rake type bar screen has evolved into a design that includes all or mostly stainless-steel construction with multiple rakes.
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Spiral Screw Screen
This design, which originated in Europe, includes a trough with a ¼” perforated hole basket. The screening is cleaned by a rotating screw which transports solids up into the compaction area. The design includes a stainless-steel housing.
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Inclined Drum Screen
Developed by screw screen manufacturers for screening, washing, and handling in single unit. Inclined rotating drum screen in the channel replaces the static basket. Spray bars offload solids into a trough containing a rotating screw.
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Finding the right screens for your wastewater operations
We’ve looked at several screening systems that can be matched to municipality wastewater treatment needs. Independent testing will help with the process of selecting the right screen type for your operations, and on-site sampling will help optimize the proper screen size and screen grid opening. If you’d like to discuss your specific needs, connect with Hydro-Dyne’s highly experienced professionals for more information about determining the right screen – type, size, and grid opening — for your wastewater treatment facility.
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