ACTIFLO® Clarification
Microsand Enhanced Flocculation and Settling

Actiflo process at North Table Mtn., Colorado 
Water Treatment Facility

ACTIFLO® is an ultra high-rate clarification process which combines microsand enhanced flocculation and lamellar settling. The applications for this process are:
  • Potable Water
  • Clarified water turbidity is normally reduced to 0.5 NTU or less at rise rates between 20 and 30 gpm/ft.2
  • Wastewater / CSO

  • Reduction of 85-95% of TSS, 60-80% of TBOD and 85-95% of TP at rise rates of 40-60 gpm/ft.2 or 60,000-85,000 gpd/ft.2.

    Krüger's High Rate Clarification Process Combines Microsand Enhanced Flocculation with Lamellar Settling

    Microsand enhanced flocculation is a technique which consists of fixing the flocs, or suspended solids, onto micro-sand with the aid of a polymer. The result is a reduction in mixing time by a factor of five compared to classical flocculation, and increased rise rate by a factor of ten compared to conventional tube settling. Lamellar settling, in turn, provides a large clarifier surface in a small tank volume. In Krüger's ACTIFLO® process, microsand enhanced flocculation is combined with lamellar settling to provide an extremely high rate system with a very small footprint.

    The Process

    In the Actiflo process, water first enters a flash mixing zone for the destabilization of the colloids. Here, raw water is mixed with coagulant in a high mixing energy environment. Retention time is about one minute.

    Actiflo Flow Diagram
    ACTIFLO Flow Diagram for Drinking Water

    The water then enters the injection tank, where micro-sand and polymer are added in a high mixing energy environment, also at a retention time of about one minute.

    Following this, the water enters a maturation zone which subjects the water to a more gentle mixing energy and a longer retention time: about four minutes.

    The longer retention time and low energy mixing in the maturation zone allows the micro-sand ballasted flocs to grow bigger, so that they can trap random flocs and settle faster in the sedimentation tank. The polymer works like a glue to affix the flocs to the micro-sand.

    The water then enters the settling tank where the micro-sand ballasted flocs settle out immediately, and the water flows up through settling tubes to collection troughs at the surface and exits the process.

    The micro-sand ballasted sludge is pumped from the bottom of the settling tank to a hydrocyclone, where the micro-sand is cleaned from the sludge by the centrifugal force. The sludge is continuously removed for sludge treatment whereas the micro-sand is reinjected back into the Actiflo system and continuously recycled.

    Quick, Effective

    Due to Actiflo's short flocculation time and high rise rate, the process is very compact, making it highly suitable for retrofit and upgrade of existing plants with space restrictions. It can easily go from start-up to steady state in less than 30 minutes, and at nominal flows retention time is approximately ten minutes. Design rise rates are between 20 and 30gpm/ft2 in most applications and the effluent turbidity is approximately 0.50 NTU or less. High micro-sand loading stabilizes the process when flow rates, turbidity or temperature fluctuate rapidly, thereby allowing the operation to be completely automated.

    Also Effectively Treats Combined Storm & Sanitary Sewer Overflows

    Short retention time and compact size also makes Actiflo effective for the on-line treatment, or peak-shaving of Combined Sewer Overflows (CSOs).

    For handling CSOs, the process provides a fast overflow rate (up to 85,000 gpd/ft.2) and can reduce total suspended solids (TSS) by up to 95 percent, and total biological oxygen demand (TBOD) by 60-80 percent, and total phosphorous 80-95 percent.

    Proven Performance * Less Chemical Consumption * Compact Size

    Test Site
    Existing Conventional Plant
    Actiflo Mobile Demonstration Plant*
    10 - 15
    40 - 50
    1.5 - 2
    20 - 40
    0.3 - 0.6
    3 - 10
    6 -7
    1 -2
    5 -6
    0.4 - 0.5
    10 - 15
    55 -60
    0.5 - 1.2
    20 - 30
    0.3 - 0.4
    2 - 3
    3 - 4
    15 - 20
    0.3 - 0.6
    50 - 90
    Ferric Sulfate
    14 - 15
    3 - 5
    10 - 15
    0.6 - 0.7
    0.8 - 1.2
    10 - 12
    0.5 - 0.7
    6 - 8
    0.2 - 0.3
    *Applied Rise rates 15 - 35 gpm/sf

    Mobile ACTIFLO Pilot Plant Always On The Go

    Question: What's 39 feet-long, has travelled more than 7,000 miles in eight months, and treats up to 1.3 million gallons of water per day? That's easy. It's Krüger's Mobile ACTIFLO® Pilot Plant, the country's hardest- working, most effective water treatment plant on wheels.

    The mobile pilot plant was built last summer and became fully operational in October. This high-tech unit has been on the go virtually nonstop ever since, demonstrating to cities from coast-to-coast the high rise rate, compact size, effluent consistency and low chemical consumption of the Actiflo process for the removal of turbidity from surface water. The mobile pilot plant has a design capacity of 0.67 (or 2/3) million gallons per day (mgd) and can actually treat a maximum flow rate of up to l.3 mgd. "People are amazed when they witness this unit effectively treating 1.3 mgd," says Krüger Pilot Study Manager Michael Gutshall. "But they're truly impressed when they realize that almost half the trailer serves as our office, not the actual treatment process." Setup time for the unit is only one day, and it can be taken off-line and be back on the road in less than half a day. Pilot studies and demonstrations for cities typically last two to three weeks. "The entire mobile unit is operated through a SCADA system of our design," Gutshall says. "Its computer system logs data every five minutes and provides a real-time visual display, an animated schematic, which allows us to show and track the Actiflo process as it's happening." Interested in having an Actiflo pilot study at your water facility? Call Michael Gutshall, Pilot Study Manager (919) 677-8310.



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