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WASTEWATER GRIT EFFECTS, MANAGEMENT, AND REMOVAL PRESENTED BY MARK - - PowerPoint PPT Presentation
WASTEWATER GRIT EFFECTS, MANAGEMENT, AND REMOVAL PRESENTED BY MARK - - PowerPoint PPT Presentation
WASTEWATER GRIT EFFECTS, MANAGEMENT, AND REMOVAL PRESENTED BY MARK MANN, P.E. WHAT IS GRIT? Inert material, both organic and inorganic, that is not benefitted by secondary treatment or sludge processing. WHAT IS GRIT? Majority of particles
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WHAT IS GRIT?
Majority of particles fall in 75-150 micron range.
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HOW SMALL IS THAT?
- Grit Particles:
Majority 75-150 micron
- Typical Raindrop:
2000 microns
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HOW SMALL IS THAT?
- Grit Particles:
Majority 75-150 micron
- Human Hair:
70-100 microns
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EXAMPLES OF GRIT
Inorganic Sand Gravel Cinders Asphalt Concrete
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EXAMPLES OF GRIT
Inorganic Sand Gravel Cinders Asphalt Concrete Organic Eggshells Seeds Bone Chips Coffee Grounds
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CHARACTERISTICS OF GRIT
- Higher specific gravity
than treatable organic solids.
- Particle shape can be
spherical, flat, or angular.
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WHERE DOES GRIT COME FROM?
The Collection System
- Materials that are
flushed by homeowners
- Infiltration/Inflow
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WHERE DOES GRIT COME FROM?
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WHERE DOES GRIT COME FROM?
Within the Plant
- Fixed film predators
- Wind blown sand and
dust
- Damaged piping
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HOW DOES GRIT AFFECT MY PLANT?
Disrupts biological processes and reduces effluent quality
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- Wear and tear on mechanical
equipment Disrupts biological processes and reduces effluent quality
HOW DOES GRIT AFFECT MY PLANT?
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- Increase in energy demand
Disrupts biological processes and reduces effluent quality
HOW DOES GRIT AFFECT MY PLANT?
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- Reduction of treatment
capacity Disrupts biological processes and reduces effluent quality
HOW DOES GRIT AFFECT MY PLANT?
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Removal
HOW CAN GRIT BE MANAGED?
, Mitigation , or Both
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Option 1: Head of Plant
- Better protection of process equipment
- Larger unit required to handle full flows
- Additional protection or removal may be
needed after fixed film treatment processes
GRI GRIT REM REMOVAL
WHERE SHOULD GRIT BE REMOVED?
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Option 2: Sludge Stream
- Located prior to thickener or digester
- Solids concentration should not exceed 2% TS
- Protection of upstream process equipment and
tanks may be required
GRI GRIT REM REMOVAL
WHERE SHOULD GRIT BE REMOVED?
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Option 3: Multiple Locations
- Protects upstream process equipment and basins
- Removes grit generated within the plant prior to
sludge digestion
- Cost may be prohibitive
GRI GRIT REM REMOVAL
WHERE SHOULD GRIT BE REMOVED?
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No matter which
- ption is selected,
bar screening is required.
GRI GRIT REM REMOVAL
WHERE SHOULD GRIT BE REMOVED?
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- Range of Flow
- Type of Treatment
Process
- Location of Grit
Removal
- Allowable Headloss
- Grit Testing Results
- Other Benefits to
Treatment
PLANT FACTORS
GRI GRIT REM REMOVAL
SELECTING GRIT REMOVAL OPTIONS
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REMOVAL SYSTEM FACTORS
- Particle Size Range
- Equipment and Energy Requirements
- Maintenance Requirements
GRI GRIT REM REMOVAL
SELECTING GRIT REMOVAL OPTIONS
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OTHER FACTORS
GRIT
- Source of Grit
- Size of Particles
OPERATIONAL
- Maintenance Requirements
- Construction Cost
- Age and Maintenance of
System
GRI GRIT REM REMOVAL
SELECTING GRIT REMOVAL OPTIONS
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GRI GRIT REM REMOVAL
- Detridus Tank/Channel
- Aerated Chamber
- Hydraulic Vortex/Stacked Tray
- Mechanical Vortex
OVERVIEW OF REMOVAL OPTIONS
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GRI GRIT REM REMOVAL
OVERVIEW OF SYSTEM ELEMENTS
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GRI GRIT REM REMOVAL
OVERVIEW OF SYSTEM ELEMENTS
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GRI GRIT REM REMOVAL
OVERVIEW OF SYSTEM ELEMENTS
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GRI GRIT REM REMOVAL
OVERVIEW OF SYSTEM ELEMENTS
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GRI GRIT REM REMOVAL
DETRITUS/ SEDIMENTATION TANK OR CHANNEL
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GRI GRIT REM REMOVAL
AERATED GRIT CHAMBER
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GRI GRIT REM REMOVAL
HYDRAULIC VORTEX
Stacked Tray
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GRI GRIT REM REMOVAL
MECHANICAL VORTEX
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There are several ways to mitigate the effects of grit in the wastewater stream.
GRIT M MITIGATION
WHAT IF REMOVAL ISN’T AN OPTION?
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Hardening of Exposed Equipment
- Pump Impellers
- Clarifier Scrapers
GRIT M MITIGATION
WHAT IF REMOVAL ISN’T AN OPTION?
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Frequent Basin Cleaning
- Manual Removal/Liquidization
GRIT M MITIGATION
- Combination Trucks
WHAT IF REMOVAL ISN’T AN OPTION?
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Aeration: Fine Bubble vs Coarse Bubble
- Grit migration into
diffuser heads
GRIT M MITIGATION
WHAT IF REMOVAL ISN’T AN OPTION?
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Predator Control for Trickling Filter/Fixed Film Treatment
- Toxic chemicals (short term)
- r adverse environmental
conditions
GRIT M MITIGATION
WHAT IF REMOVAL ISN’T AN OPTION?
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MARK MANN, P.E. mmann@spi-eng.com 409-866-0341 A BIG THANK YOU TO THE FOLLOWING CONTRIBUTORS: City of Orange City of Beaumont Smith & Loveless Hydro International
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