An important part of wastewater management and water treatment in municipal settings is the process of wastewater screening. Screening involves retaining solids found in the wastewater, removing them early on so the rest of the liquid water can go on for further treatment in a more efficient manner. If those solids aren’t removed, the water could be contaminated, and the solids could potentially damage some of the essential water treatment equipment.
There are several primary categories of wastewater treatment screening. Let’s take a short look at each of them.
Coarse screens feature openings that range from 6 to 150 mm wide. They’re made out of bars, rods or wires, with a wire mesh or perforated plate to provide the openings in circular or rectangular shapes.
Hand-cleaned coarse screens get hand raked during the screening process at small wastewater treatment facilities. They’re most commonly used as a standby option when there are periods of high flow, or when mechanical screens are being repaired or maintained.
Mechanically-cleaned coarse screens are more common at wastewater treatment facilities, as they are much more efficient and reduce problems that are likely to occur during the screening process. These screens have subcategories that include:
- Catenary screens: These are chain-driven screens with front return and front cleaning that feature internal mechanics designed to prevent jamming when large, heavy objects are present.
- Chain-driven screens: Front and back chain-driven screens can rake upstream or downstream. An automatic chain cleans off the stream, which improves the functionality of the entire wastewater treatment system.
- Continuous belt screen: This type of screening is very high-tech and efficient. It features numerous rakes and is designed to be both continuous and self-cleaning, regardless of whether it’s dealing with fine or coarse solids.
- Reciprocating rakes: This solution features a single rake instead of multiple, which makes it less efficient against heavy loads.
The smallest type of screen option available in the world of wastewater treatment screening is the microscreen. These screens feature low-speed drum screens lined with special filtering fabrics that have openings of 10 to 35 µm. In this setting, wastewater enters the drum, and the solid waste that gets retained is disposed of after being collected.
Fine screening in wastewater treatment
Fine screens feature screens with openings of less than 6 mm. They’re typically made with wire cloth, perforated plates or wedge wire. These screens are designed for removing fine solids, with specific subcategories of fine screens including:
- Drum screens: Screens that feature rotating cylinders in the flow channel.
- Static wedge wire screens: Screens used by larger treatment plants that have much more floor space available for their operations.
- Step screens: Screens that feature fixed and movable plates spread across the channel’s width.
Interested in learning more about screening in wastewater management and the various types of screening equipment most likely to be used at water treatment plants? Get in touch with our experienced professionals at Enviro-Line Co., Inc. today with any questions you have. We look forward to working with you.
Categorised in: Wastewater Filtration