Magnetite Ballasted System – BioMag & CoMaG


Evoqua BioMag – Ballasted biological process to allow WWTP to handle 3x flow and solids loadings, and to operate at longer sludge ages to achieve enhanced nutrient removal, without physically adding tankage to the plant.

Magnetite is a dense, non-abrasive, iron oxide mined locally in Missouri  that can be recovered magnetically from the waste activated sludge and reused in the process to maintain an extremely dense, fast settling biomass. Results in a plant with small footprint, low capital, and low operational costs.

Easy to incorporate in any type of activated sludge treatment where biological process remains unchanged and BioMag equipment is located in the sidestream location (WAS stream) without impacting main liquid stream in the WWTP.  Ability to with multi-stage treatment processes, to meet TN to ≤ 3.0 mg/L and TP to ≤ 0.2 mg/L without tertiary filters

The enhanced settling capabilities of the BioMag System has been proven at municipal and industrial facilities to deliver the following results:

  • BOD5 < 5.0 mg/L
  • TSS < 10 mg/L
  • NH3-N < 0.2 mg/L
  • TP < 0.2 mg/L without filters
  • TN < 3.0 mg/L without filters
  • SVI < 70 mL/gram
  • Clarifier SLR up to 100 lb/day-ft2
  • Clarifier SOR up to 2,500 gpd/ft2
  • MLSS up to 10,000 mg/L
  • MLVSS up to 8,000 mg/




  • Simplicity and reliability – Ballasting biological floc with magnetite dramatically increases secondary settling rates eliminating bottlenecks to process greater loads, flows or both.
  • Up to triple the capacity – Rapid and reliable settling enables a 2 – 3x increase in MLSS concentrations without the risk of upset, and an equivalent increase in treatment capacity — all within existing bioreactors and clarifiers.
  • Low-cost ENR – Increased capacity and superior solids removal enable existing activated sludge systems to free up reactor capacity for multi-stage treatment processes, thereby enabling the removal of TN to ≤ 3.0 mg/L and TP to ≤ 0.2 mg/L without tertiary filters.
  • Lower life-cycle costs – The BioMag™ System continuously recovers and reuses up to 95% of the injected magnetite offering a cost-effective, sustainable process.
  • Dedication and experience—Evoqua has 40 years of experience in biological processes, offering a holistic view when upgrading a plant, and maximizing synergies between BioMag and secondary treatment equipment.



A high rate clarification process utilizing internal recycling of settled solids and small amount of Magnetite (non-abrasive, high specific gravity) for floc formation to allow for less chemical use and  footprints up to 20x smaller than conventional clarification. The CoMag System easily integrates with planned or existing facilities to allow the use of existing clarifiers of any size or type. Applications included treating wet weather flows, phosphorus removal and water re-use.

  • Enhances traditional floc by adding Magnetite ballast for reliable and rapid settling
  • Allows for increased treatment capacity
  • Allows for enhanced clarification
  • Meet tighter regulations in smaller footprint
  • Superior solids removal
  • Magnetite is readily available and has SG of 5.1 to increase density of flocs
    • Inexpensive and easy to recover
  • Applications
    • Enhanced tertiary
    • Enhanced primary treatment
    • Lagoon effluent to remove algae

The CoMag System competes effectively with all forms of media and membrane filtration and conventional clarification, and is proven effective for:

Municipal applications:

  • Primary treatment (chemically enhanced primary treatment)
  • Tertiary treatment for polishing secondary effluent
  • Stormwater/CSO (combined sewer overflow)
  • SSO (sanitary sewer overflow)
  • Wet weather control
  • Recycle-reuse applications
  • Reverse osmosis pretreatment
  • Drinking water
  • Heavy metals removal
  • Lagoon/reservoir for high solids, algae, and phosphorus
  • Fixed film application (right after fixed-film bioreactor)
  • Temporary treatment during or before plant upgrade projects

Video: Underwater Clarifier Footage of Magnetite-Ballasted Clarification


  • Easy to incorporate into any type of coagulation/flocculation process
  • Can use with any type of clarifier (circular, rectangular, squircle, inclined plate/tube settlers)
  • Only ballasting technology with an internal recycle from clarifier underflow to process tanks that reduces chemical consumption
  • Recycling promotes sludge densification and solids contact for better flocculation and sweeping effect in clarifiers to enhance capture of colloidal particles.
  • Magnetite is dense (2X more dense than silica sand), readily available (iron ore commodity), fully inert (NSF certified for DW applications), not abrasive (particle size is 40-50 microns) and magnetically retrievable (high recovery rates.)
  • Package plug and play offering for up to 300,000 gpd
  • Easy to pilot—Evoqua has two pilot units available and has conducted 35-40 pilots.
  • Rapid startup and quick process optimization for operation with frequent shut-down and re-starts
  • Fully automated


The enhanced settling capabilities of the CoMag System has been proven at municipal and industrial facilities to deliver the following results:

SOR up to 15 gpm/ft2 with conventional
SOR up to 50 gpm/ft2 with plate settlers
Turbidity < 1 NTU
TP < 0.05 mg/L
TSS < 2.0 mg/L
Color 2 Pt-Co Units
Fecal Coliform < 200 Col/100 mL
Copper < 8 μg/L
Aluminum < 80 μg/L
Arsenic < 5 μg/L
UV Transmittance > 75%
Oil and Grease Removal



  • Superior contaminant removal – Efficiently reduces total suspended solids (TSS), total phosphorus (TP), turbidity, color, pathogens, and metals far below conventional treatment, without the need for filters
  • Low costs – High-rate, ballasted clarification allows for smaller reaction and solids separation tanks, minimal power consumption and moderate chemical use
  • Easy incorporation – CoMag is easy to incorporate into existing tankage
  • Lower OPEX – Continuously recovers and reuses up to 99+% of the injected magnetite, offering a sustainable process for lower OPEX
  • Process stability – Stability under shock loads – does not choke or plug; rapid startup and quick process optimization
  • Ultraviolet enabling – The high transmissivity of the CoMag System effluent reduces energy and operating costs of final purification
  • User friendly – Fully automated, requires minimum operator attention, easy to operate, core equipment has been used by industry for decades
  • Plug and play – Package plug and play offering for up to 300,000 gpd

Product Assistance

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