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Coarse & Fine Screen Units in Municipal WWTPs
Core Pretreatment Components
Configuration varies based on screen type (e.g., chain, rake, drum) to match hydraulic and waste characteristics.
Coarse & Fine Screen Units in Municipal WWTPs
Core Pretreatment Components
Configuration varies based on screen type (e.g., chain, rake, drum) to match hydraulic and waste characteristics.
Ⅰ. Screen Host Unit (Primary Variant)
① Coarse Screens (Aperture ≥20mm)
|
Type |
Application |
Key Features |
|
Chain Screen |
Deep channels (>5m) |
Heavy-duty rakes for large debris (branches, plastics) |
|
Rake Screen |
Medium-shallow channels (2-5m) |
Adjustable gaps (20-50mm), requires high-pressure wash |
|
High-Chain Screen |
High-flow plants |
Impact-resistant for combined sewer systems |
② Fine Screens (Aperture 1-10mm)
|
Type |
Application |
Key Features |
|
Step Screen |
Fiber-rich wastewater |
Gradual lifting (1-6mm gaps), handles hair/textiles |
|
Internal Drum Screen |
Space-limited plants |
Center-feed design (3-10mm), precision backwash needed |
|
Rotary Drum Screen |
Compact layouts |
Integrated screening + screw press (0.5-6mm) |
Ⅱ. Hydraulic Auxiliary Units (Channel/Tank Systems)
|
Component |
Function |
Compatible Screen Types |
|
Inlet Channel |
Velocity control (0.6-1.0 m/s), anti-sedimentation; isolation gates |
All types |
|
Overflow Bypass |
Protects screens during peak flows (>Qdesign) |
High-chain/Rake (storm events) |
|
Post-screen Zone |
Stabilization (length ≥5×width), laminar flow |
Internal Drum/Rotary Drum |
|
Washwater Tank |
High-pressure system (0.3-0.5 MPa), inline filters |
Rake/Step (wash-dependent) |
Ⅲ. Screenings Handling Unit
① Conveyance Systems
• Belt Conveyor: For chain/high-chain coarse screens; ≤30° incline, corrosion-resistant
• Screw Conveyor: Step/Rotary drum fine screens; pre-dewatering (↓15% moisture)
• Shaftless Spiral: Tangle-proof design for fibrous waste
② Dewatering & Compaction
• Hydraulic Baler: Coarse debris (bottles/wood); compression ratio ≥3:1
• Screw Press: Fine organic sludge (80%→60% moisture); volume reduction
• Centrifuge: High-organics sludge (e.g., food processing); solids ↑40%
③ Sanitation & Containment
• UV Disinfection: Pathogen control (30-40 mJ/cm² dose for Vibrio)
• Negative Pressure Hood: H₂S removal >90% via biofilter linkage
Ⅳ. Control & Safety Systems
① Smart Automation
• Level differential (Δh≥0.3m) → Screen speed boost + intensified washing
• Torque overload (≥120% rated) → Auto-reverse anti-jamming
② Intrinsic Safety
• Rotating part enclosures (ISO 13857 compliant)
• Emergency stop + CO/O₂ monitoring in screen wells
Appendix: Configuration Comparison
|
Screen Type |
Gap (mm) |
Core Modules |
Maintenance Challenges |
|
Chain Coarse Screen |
20-100 |
Rake + Belt conveyor + Baler |
Chain wear (2-year replacement) |
|
Step Fine Screen |
1-6 |
Step panels + Shaftless spiral + Press |
Shaft clogging (daily washing) |
|
Rotary Drum Screen |
0.5-3 |
Drum mesh + Integrated press + UV |
High washwater use (3m³/t waste) |
Integration Principle
Design must consider influent impurities (e.g., grit chambers for sandy combined sewers), space constraints (drum screens use 60% less area than step screens), and automation needs (smart wash algorithms reduce energy by 20%) to avoid operational bottlenecks from over-emphasis on host units.
Ⅰ. Screen Host Unit (Primary Variant)
① Coarse Screens (Aperture ≥20mm)
|
Type |
Application |
Key Features |
|
Chain Screen |
Deep channels (>5m) |
Heavy-duty rakes for large debris (branches, plastics) |
|
Rake Screen |
Medium-shallow channels (2-5m) |
Adjustable gaps (20-50mm), requires high-pressure wash |
|
High-Chain Screen |
High-flow plants |
Impact-resistant for combined sewer systems |
② Fine Screens (Aperture 1-10mm)
|
Type |
Application |
Key Features |
|
Step Screen |
Fiber-rich wastewater |
Gradual lifting (1-6mm gaps), handles hair/textiles |
|
Internal Drum Screen |
Space-limited plants |
Center-feed design (3-10mm), precision backwash needed |
|
Rotary Drum Screen |
Compact layouts |
Integrated screening + screw press (0.5-6mm) |
Ⅱ. Hydraulic Auxiliary Units (Channel/Tank Systems)
|
Component |
Function |
Compatible Screen Types |
|
Inlet Channel |
Velocity control (0.6-1.0 m/s), anti-sedimentation; isolation gates |
All types |
|
Overflow Bypass |
Protects screens during peak flows (>Qdesign) |
High-chain/Rake (storm events) |
|
Post-screen Zone |
Stabilization (length ≥5×width), laminar flow |
Internal Drum/Rotary Drum |
|
Washwater Tank |
High-pressure system (0.3-0.5 MPa), inline filters |
Rake/Step (wash-dependent) |
Ⅲ. Screenings Handling Unit
① Conveyance Systems
• Belt Conveyor: For chain/high-chain coarse screens; ≤30° incline, corrosion-resistant
• Screw Conveyor: Step/Rotary drum fine screens; pre-dewatering (↓15% moisture)
• Shaftless Spiral: Tangle-proof design for fibrous waste
② Dewatering & Compaction
• Hydraulic Baler: Coarse debris (bottles/wood); compression ratio ≥3:1
• Screw Press: Fine organic sludge (80%→60% moisture); volume reduction
• Centrifuge: High-organics sludge (e.g., food processing); solids ↑40%
③ Sanitation & Containment
• UV Disinfection: Pathogen control (30-40 mJ/cm² dose for Vibrio)
• Negative Pressure Hood: H₂S removal >90% via biofilter linkage
Ⅳ. Control & Safety Systems
① Smart Automation
• Level differential (Δh≥0.3m) → Screen speed boost + intensified washing
• Torque overload (≥120% rated) → Auto-reverse anti-jamming
② Intrinsic Safety
• Rotating part enclosures (ISO 13857 compliant)
• Emergency stop + CO/O₂ monitoring in screen wells
Appendix: Configuration Comparison
|
Screen Type |
Gap (mm) |
Core Modules |
Maintenance Challenges |
|
Chain Coarse Screen |
20-100 |
Rake + Belt conveyor + Baler |
Chain wear (2-year replacement) |
|
Step Fine Screen |
1-6 |
Step panels + Shaftless spiral + Press |
Shaft clogging (daily washing) |
|
Rotary Drum Screen |
0.5-3 |
Drum mesh + Integrated press + UV |
High washwater use (3m³/t waste) |
Integration Principle
Design must consider influent impurities (e.g., grit chambers for sandy combined sewers), space constraints (drum screens use 60% less area than step screens), and automation needs (smart wash algorithms reduce energy by 20%) to avoid operational bottlenecks from over-emphasis on host units.