The internal flow screen is a precision mechanical device developed by our company for fine solid-liquid separation in wastewater and water treatment processes. Named for its unique "inside-out" filtration path, this equipment primarily intercepts and removes small suspended particles, floating debris, and fibrous impurities such as hair, plastic fragments, and fiber strands. Typically installed as a fine screen unit after coarse screens and before sedimentation tanks or biological treatment units, it protects critical components like pumps, aerators, and membrane modules from clogging and entanglement, thereby enhancing the overall operational stability of the treatment process.
- Structure and Working Principle
- Core structural composition
The device is typically an integrated box-type structure, with the main components including:
- Grating drum (rotary drum): The core filtration component, which is a horizontally placed cylindrical drum. The drum wall consists of a series of parallel arc-shaped grating bars or perforated plates, with the grating gaps customizable as required (commonly 1-6mm).
- The drive device is located at one end of the drum, and the whole grid cylinder is driven by the speed reduction motor to rotate slowly and continuously around its horizontal axis.
- Backwash system: located on the central shaft inside the drum, equipped with one or more high-pressure backwash nozzles.
- The screw conveyor (or slag collection trough) is positioned above the rotating drum, designed to collect and transport the removed screen slag.
- The treatment water enters the drum from the front center, and the filtered water flows out through the gaps of the filter bars into the tank, then into the outlet channel.
- Working Principle
The device achieves a continuous cycle of "water intake-filtration-sludge removal":
- Internal-external filtration: The wastewater to be treated enters the drum from the central front opening. Under hydraulic pressure, the water flows outward through the gaps of the arc-shaped perforated bars into the equipment chamber, completing filtration. Particles larger than the bar gaps are retained on the inner surface of the drum.
- Rotary lifting and flushing: The retained debris on the drum's inner wall gradually rises to the top as the drum rotates slowly. When reaching a specific position at the top, the built-in backwash system activates, ejecting high-pressure water from the inside out to flush off impurities adhering to the inner side of the bars.
- Grate residue collection and discharge: The washed-down grate residue falls into the screw conveyor above the drum and is conveyed to a side collection hopper for unified discharge. The entire filtration and cleaning process is synchronized and continuous.
- The innovative filtration channel employs an 'internal intake, external discharge' design. Water enters through the drum's center, enabling a streamlined process that minimizes head loss while trapping impurities internally, resulting in a visually clean appearance.
- Efficient online self-cleaning: The internal backwash device in the drum enables synchronized, high-pressure cleaning of the filter surface, ensuring consistent filtration performance while minimizing manual cleaning.
- Compact structure and sealing performance: The equipment adopts an integral box-type design, which occupies relatively small space and operates in a fully enclosed manner, effectively controlling odor emission and wastewater splashing.
- Interception effect: The arc-shaped grating or orifice plate design exhibits a certain interception effect on easily entangled substances such as fibers and hair.
- Automatic operation: Typically controlled by PLC, it enables fully automated continuous operation with cleaning frequency adjusted based on time or liquid level differential signals.
- Main technical parameters
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Parameter item
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Description / Customizable range example
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Equipment diameter (drum)
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Common specifications: Φ1.2m, Φ1.5m, Φ1.8m, Φ2.0m, etc.
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gutter gap
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Common spacing: 1mm, 2mm, 3mm, 5mm, 6mm
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handling capacity
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The capacity is related to diameter, grid spacing, and water depth, with a typical range of hundreds to thousands of cubic meters per hour for a single unit.
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rotating drum speed
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Slow, typically 1-5 rpm (adjustable)
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backwash pressure
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The standard requirement is ≥ 0.5 MPa.
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driving power
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Smaller, commonly ranging from 1.1kW to 3.0kW
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Main material (liquid-contacting part)
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Stainless steel (304/316) is the primary option
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control method
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Automatic control (time/liquid level difference), equipped with overload protection
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- Typical Application Fields
This equipment is designed for the following pretreatment scenarios requiring precise solid-liquid separation:
- Municipal sewage treatment plant: Functioning as a fine screen, it is installed either after the aeration grit chamber or before the biological tank.
- Industrial wastewater treatment: pretreatment of wastewater containing high levels of fiber or fine impurities from industries such as papermaking, textiles, food processing, and slaughter.
- Pre-treatment protection for membrane processes: Serving as a precision pretreatment unit for membrane systems including MBR (Membrane Bioreactor) and ultrafiltration.
- Waterworks: interception of fine impurities at the raw water intake.
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