MBBR Aeration Design
Mixing Energy
Minimum mixing for biofilm carrier
dispersion
Different material properties and shapes
require differing amounts of energy. SSI’s
MBBR is designed to use lowest energy
compared to competitor MBBRs
• Slot size should be < 70% of the smallest dimension of
the biofilm carrier
• Wedge wire –
• Larger % open area
• Reduces headloss and slot velocity (preventing media from
moving towards the screens and building up)
• Design based on peak flow
• Place above aeration grids to keep energy high energy
• Primary screen should be smaller to prevent solids
buildup
Media Retention Screen Design
Post-MBBR Clarifier Design
• Rapid clarification
• Solids are smaller (will be even smaller with coarse
bubble) and therefore take longer to settle
-> Reduce settling distance
• But if retention time is too high, system can start
to denitrify, creating gas and issues with settling
• Surface overflow rate (SOR) is typically between
1.0-2.5
Industrial
Considerations
Thinking holistically
Design Considerations
Slaughter-House
What is different? How does that impact
design?
• High levels of COD and iron
• High levels of: • Requires advanced Primary Treatment
• Proteins • Screening
• Coliforms • DAF
• Lard, oil and grease • Oil/Water Separators
• Primary Clarifiers
• Higher viscosity and density • pH adjustment for precipitation
• Stratification of liquids
• Septic conditions
• Hair, meat, and other organic material • Proper aeration design
• 1.2 to 1.4 kgs O2/kg BOD
• MBBR: SALR will be impacted by
mineral and inorganic fouling
• Typical BOD SALR: 7-10 g/m2-day
Design Considerations
Fisheries (processing or farming)
What is different? How does that impact
design?
• High FOG
• Performance is crucial
• Nitrates (salting/smoking process) • Careful pH control
• High proteins/amines • High pH -> Free Ammonia (Toxic)
• Alkalinity control • Alkalinity Addition
• Alkalinity required for Nitrification
• Temperature
• Oil/Water Separation
• Lagoon or pond treatment typical
• Usually have side-stream MBBR
• Threshold for toxicity
• Requires low ammonia effluent • Typically have higher HRTs and
reduced SALRs
• Typical BOD SALR <9 g/m2-day
• Typical TAN SALR <1 g/m2-day
Design Considerations
Food and Beverage
What is different? How does that impact
design?
• High BOD and COD
• Usually Biodegradable • Salinity and TDS
• Impact Oxygen saturation
• pH, Calcium, and inorganics (salts) • Impact transfer efficiency
can be challenging
• Micronutrients (Mg, Ca, Zn) • Higher biodegradability -> higher
SALR
• High TDS (color, sugars, salts) • Watch for potential Calcium
• Ca+ and PO4 issues Phosphate
• High Specific O2 Uptake Rate • Typical BOD SALR: 10-16 g/m2-day
• Nutrient deficiency
Design Considerations
Pulp and Paper
How does that impact
What is different? design?
• High levels of Organic matter, Calcium • MBBR normally used as pre-treatment
• Alkaline step
• 50-70% removal by design
• Glues and Chemical Bleaching • SALR 12-25 g BOD/m2-day
• High Temperature** • Calcium Phosphate and Struvite
(Magnesium Ammonium Phosphate)
Buildup
• Reduced SALR
• Carbonic Acid Build up
• Negatively impacts biological metabolism
and creates filamentous growth in
clarifier
CASE STUDY – TEXTILE (Denim Washing)
Let’s talk
industry.
Textile
chemistry
GWL Bangladesh- 2015
3840 m3/day SSI MBBR for Textile Effluent
Design Objectives
Project
requirements
• Biofilm Carrier Design
• Surface area
• 650 m2/m3 @ 87% open area
• Higher SA ≠ better treatment
• Specific gravity (Critical!)
• 0.95 (+/- 10%)
• Material (Critical!)
• Virgin HDPE w/ Carbon Black
• Media fill %
• 33%
• HRT
• 6 hours (900 m3 @ 150 m3/hour)
Screening + Grit
Aeration
• PTFE 12-inch Fine Bubble Aeration • 12-inch diameter – 2mm
• Specialized Fine Bubble Aeration
• 1,800 kg BOD design (500 ppm)
• PTFE Coating –
Polytetrafluoroethylene • 293m2 plan area @ 20 m3/hr-m2
• Preferred for textile • 0.2 kWhr/m3
Design Objectives
Project Requirements
CASE STUDY – DAIRY
Design Considerations
Dairy
Dairy Chemistry
• Whey, Urea, Lactose
• Lipids, Proteins, Salts
• Enzymes, Casein, and Calcium
What does that mean?
• Every Dairy is different
• High organic loading
• Nitrogen and Carbon
• Long chain amino acids
• Insoluble
• Fatty Acids
• Cellulose
Design Considerations
Dairy Facilities
What is different? How does that impact
design?
• Production Variation = Large variance in COD • EQ tank, instrumentation to sense and adjust
Loads aeration, nutrient dosing, and pH dosing
• Most of BOD is Soluble during peaks
• COD:BOD is normally 2:1 or 3:1
• High levels of Calcium, Salt, Struvite, and • Adjust MBBR SALR to account for potential
inorganic fouling
FOG…
• DAF operation typically preferred
Whey Processing…
• Use “calamity” tank is common
• Extreme COD & BOD
• COD > 10,000 ppm • MBBR SALR (as primary treatment)
• 8-12g BOD/m2
• MBBR SALR (as pre-treatment)
• 14-25 g BOD/m2-day
• Influent is basic -> Add H2PO4 acid
• Calcium Phosphate Buildup
OR
• Calcium Hydroxide Buildup
• DAFs work better with low PH
• Add acid before DAF
• If added after tank, precipitation will occur in biological tank
• INSERT image from Colun of Struvite builtup
THANK YOU!
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