Pressure Sand Filter & Activated Carbon Filter Vessel & Media Calculation for Water & Wastewater Treatment Plant

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Description

1. Working Principles

Pressure Sand Filter

  • Uses a bed of graded sand/gravel media in a pressurized vessel
  • Water flows downward through media layers under pressure
  • Removes suspended solids, turbidity, and particulate matter
  • Typical media arrangement (top to bottom):
    • Fine sand (0.5-1.0 mm)
    • Coarse sand (1-2 mm)
    • Fine gravel (2-4 mm)
    • Coarse gravel (4-8 mm)

Activated Carbon Filter

  • Uses activated carbon media in a pressurized vessel
  • Removes organic compounds, chlorine, odor, and taste
  • Works through adsorption process
  • Types of carbon:
    • Granular Activated Carbon (GAC)
    • Powdered Activated Carbon (PAC)

2. Key Design Parameters & Calculations

A. Vessel Size Calculations

  1. Filter Area (A) calculation:

A = Q / DFV

Where:

A = Filter area (m²)

Q = Flow rate (m³/hr)

DFV = Design Filtration Velocity (m/hr)

  1. Vessel Diameter (D) calculation:

D = √(4A/π)

Where:

D = Diameter (m)

A = Filter area (m²)

  1. Media Bed Height:
  • PSF: Typically 0.9-1.2m
  • ACF: Typically 1.0-1.5m

B. Backwash System Design

  1. Backwash Flow Rate:

Qbw = A × Vbw

Where:

Qbw = Backwash flow rate (m³/hr)

A = Filter area (m²)

Vbw = Backwash velocity (m/hr)

  1. Air Scour Rate:

Qair = A × Vair

Where:

Qair = Air flow rate (m³/hr)

A = Filter area (m²)

Vair = Air velocity (m/hr)

C. Operating Parameters

  1. Service Flow Rate:

SFR = Q / A

Where:

SFR = Service Flow Rate (m³/m²/hr)

Q = Flow rate (m³/hr)

A = Filter area (m²)

  1. Daily Treatment Capacity:

DTC = Q × Operating Hours

Where:

DTC = Daily Treatment Capacity (m³/day)

Q = Flow rate (m³/hr)

3. Design Considerations

Typical Design Values

  • Design Filtration Velocity (DFV): 10-15 m/hr for PSF, 8-12 m/hr for ACF
  • Backwash Velocity: 30-45 m/hr for PSF, 25-35 m/hr for ACF
  • Air Scour Velocity: 50-60 m/hr
  • Operating Hours: Usually 16-24 hrs/day
  • Service Flow Rate: Should not exceed maximum recommended by media manufacturer

Safety Factors

  1. Vessel Height:
  • Add 40-50% to media height for expansion during backwash
  • Additional 20% freeboard for water distribution
  1. Pressure Rating:
  • Design pressure: typically 3-6 bar
  • Test pressure: 1.5 × design pressure

Important Notes

  1. Media Specifications:
  • Use proper gradation for even flow distribution
  • Ensure media meets AWWA standards
  • Consider local water quality for media selection
  1. Maintenance Requirements:
  • Regular backwashing schedule based on pressure drop
  • Media replacement every 3-5 years for PSF
  • GAC replacement based on breakthrough (typically 1-3 years)

Calculation Preview

Gowtham V (gowthamv112)
20 Nov 2024
File Size: 58
Downloads: 3
File Version: 1.0
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Comments: 1
johndoyle-admin 9 days ago
A useful debut calculation! Thanks for sharing! I have awarded a three month XLC Pro subscription by way of thanks.
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