The grit removal classifier is a mechanical device used to separate heavier particles (grit) from the wastewater. Grit consists primarily of sand, gravel, and other inorganic materials that do not degrade biologically, and thus, they need to be removed from the wastewater before it undergoes further treatment. The removal of grit is crucial for protecting downstream equipment and optimizing the efficiency of the STP.

The grit removal system generally operates in the following way:

1. Inflow of Wastewater: The incoming sewage or wastewater is directed into a grit chamber or a grit channel where the flow velocity is controlled to allow the separation of grit from the rest of the water.
2. Sedimentation (Gravity Separation): In a grit chamber, the velocity of the wastewater is reduced, causing the heavier particles like sand and gravel to settle at the bottom due to gravity.
3. Grit Scraping or Conveying: A grit classifier typically includes a scraper or conveyor mechanism that collects the settled grit and moves it to the appropriate storage or disposal area. This process may include:

• Mechanical scrapers: These are typically rotating blades or augers that move the settled grit to a designated removal area.
• Screw conveyor: In some systems, the grit is conveyed by a screw-type auger to a discharge area for removal.
• Washing: A spray system often rinses the filter surface to remove accumulated solids, which can then be directed to a collection system for disposal.

4. Grit Dewatering: After the grit is removed, it is often dewatered to reduce its moisture content and volume. Some systems use dewatering bins or centrifuges for this purpose.

5. Disposal of Grit: The dewatered grit is either transported for disposal or used in certain applications, like filling or construction material,
depending on local regulations

Prefabricated grit removal systems have gained popularity due to the following benefits:

• Quick Installation: As prefabricated systems come pre-assembled, they can be installed much faster than traditional construction methods.
• Standardized Designs: These systems are often standardized and come with proven designs that can guarantee performance.
• Cost Efficiency: Pre-engineered systems are often more cost-effective because of the economies of scale in manufacturing.
• Compact and Modular: Prefabricated grit classifiers can be designed to fit various space constraints and can be easily expanded if needed.