ClearStream Clarification – Clarifiers, Thickeners, Solids Contact, Drives, Clearflow Jet/SBR


ClearStream offers a complete line of sedimentation equipment for most water, wastewater, and industrial applications. ClearStream utilizes cutting edge analysis and design technologies to custom design each piece of process equipment to meet each individual customer’s needs. Capabilities include advanced computational fluid dynamic (CFD), finite element analysis (FEA) and civil / structural software codes, to ensure process performance and structural integrity. All mechanisms are fully designed in a 3-D CAD environment to produce the highest quality, and customer friendly designs possible.

ClearStream offers a complete line of process equipment for most water and industrial applications.


Segmented Rake, Plow Style


Raking blades turned at an approximately 45 degree angle are supported from two structural support arms.  The settled sludge is plowed inward from one blade to another until it is deposited into a sludge pit.


1.    Simple design.
2.    Nothing to “plug up” under water.
3.    Regardless of solids loading settled sludge will be transported to the sludge pit.


1.    Sludge transport from the outside may take many hours, especially on large (>100’ diameter) units, leading to the potential of septicity.
2.    Under high flows and/or high solids loading conditions, the raking mechanism may not be able to transport solids as quickly as they are settling, causing a buildup of solids in the basin.  The deeper sludge blanket can lead to scouring and short circuiting.


1.    Change to the angle of the blade to the radius.
2.    Increase the depth of all the blades.
3.    Increase the depth of each blade as it gets nearer to the center and settle sludge sump.
4.    Add two more half radius arms to aid in solids transport for clarifiers larger than 100’.


Spiral Blade Design


The spiral scraper blade has a constant attack angle of 30 to 35 degrees and generally increases in depth towards the center of the clarifier.


1.    Nothing to “plug up” under water.
2.    Regardless of solids loading settled sludge will be transported to the settled sludge pit, and/or rotating sludge manifold.
3.    The settled sludge transport time is significantly decreased over the segmented blade design. Many consider the spiral blade clarifier to be a rapid solids removal clarifier.


1.    Increased capital costs.
2.    Increased installation costs.
3.    Larger clarifiers (>120’) will require multiple spiral blades.


1.    Change the attack angle of the blade to the radius.
2.    Add two half radius arms to aid in solids transport near the clarifier center.
3.    Dual slope bottom (steeper near the center) to decrease the solids inventory in the bottom of the clarifier.


Suction Header Clarifier


One or two round or square tapered headers stretch from a manifold radially across the bottom of the clarifier.  Varying size and spaced orifices located in the leading edge of the suction header are designed to draw settled sludge at an even removal rate across the entire basin floor.  Through pumping, or head differential, settled solids are drawn through the header into the manifold and out of the clarifier.


1.    Rapid removal of solids across the whole clarifier floor.


1.    Potential plugging of the suction header holes at low RAS removal rates.
2.    If the actual RAS flow rate is different than designed for, the header may draw solids at an uneven rate across the basin floor.
3.    Because the header draws equal to the area it rotates through, a sludge blanket must be maintained over the entire clarifier deeper than the suction header.
4.    A seal must be maintained between the rotating manifold, the clarifier center column, and the tank floor.  High head differentials for the suction header may cause the seals to collapse or “suck in” rendering them useless.
5.    The seas must be replaced approximately every 5 – 7 years.


1.    Install a segmented rake as one arm opposite the suction header to aid in redistribution of the sludge on the bottom.


Suction Pipe Clarifier


Suction or draw-off pipes are equally spaced along the rake arm to draw off settled sludge across the clarifier.  Blades on the rake arm are arranged in a “V” pattern to direct the collected sludge towards the Suction Pipe.  A RAS valve, located in the RAS Box, on each individual suction pipe allows the flow from each pipe to be adjusted to optimize the solids removal from the clarifier leading to potential higher RAS concentrations.


1.    Rapid removal of settled solids across the entire basin floor.

2.    Optimization of the flow removal across the clarifier bottom as process conditions change.


1.    Potential plugging of the suction pipes and, in particular, the valves.
2.    A seal must be maintained between the rotating RAS box the clarifier center column.
3.    Highest capital cost of all clarifier designs.
4.    The required RAS valve box makes adding an Influent Dispersion Well (sometimes referred to as a Energy Dissipation Well or EDI) difficult.
5.    Many times the Suction Header Clarifier is not utilized to its full potential due to the higher sophistication of operation.


Gravity Sludge Thickener Center Column Mounted


Thickeners are used in water and wastewater applications to take solids from other liquid solids separation processes and thicken the solids prior to further dewatering and/or digestion. The drive is mounted on a stationary center pier. The rotating portion of the drive turns a structural torque cage, which in turn rotates the sludge removal mechanism. The drive also supports the walkway and center platform.


1.    Can handle extreme torque conditions.
2.    Bridge has shorter unsupported span and is less expensive in units over 50 feet in diameter.
3.    Center column doubles as a walkway support and influent pipe.
4.    Lifting device option allows for heavy sludge loadings.


1.    The influent pipe must be buried beneath the thickener basin.
2.    Tanks are generally concrete to adequately support the center column.
3.    Center column and cage are more expensive than shaft driven rakes in smaller diameter tanks.


Gravity Sludge Thickener Bridge Mounted


Thickeners are used in water and wastewater applications to take solids from other liquid solids separation processes and thicken the solids prior to further dewatering and/or digestion. The drive is mounted on the walkway or bridge. The rotating portion of the drive turns a structural torque tube or shaft, which in turn rotates the solids removal mechanism.


1.    Can develop high torque in compact units.

2.    Torque tube is generally more economical than a torque cage in smaller units.
3.     Can be installed in concrete or steel tank configurations. Generally most economical in tanks less than 50’ in diameter.
4.    Generally the most economical way to provide lifting of rake arms under severe torque loads.
5.    Lifting device option allows for heavy sludge loading.


1.    Walkway or bridge must span the tank and support the weight and torque of the mechanism, the bridge will be more expensive


Solids Contact Clarifers


Solids contact clarifiers combine the process of mixing, flocculation and sedimentation in a single tank. Recirculation of solids and mixing is accomplished by a radial or axial turbine. Flocculation occurs within the reaction well. Sedimentation occurs in the clarification zone. The clarifier is comprised of a mixing zone, flocculation (reaction) zone, sludge blanket zone, and a clarification zone. A turbine draws concentrated settled solids from the bottom, and mixes them with the lower solids concentration influent and disperses it into the reaction well. Solids Contact Clarifiers are typically used in water softening and color and turbidity removal clarifiers in water treatment plants, and polishing or tertiary clarifiers in waste water treatment plants. Solids Contact Clarifiers are particularly advantageous in lime softening of groundwater since the precipitated solids help speed the flow, growing larger crystals of precipitate to provide a thicker waste sludge. Solids Contact Clarifiers have also been applied in the chemical treatment of industrial wastes such as metals removal, and used successfully for cooling tower make up water.

Columbus, Kansas

ClearStream manufactured Solids Contact Units in Columbus, Kansas. Walters Morgan constructed the water treatment plant in 2014.



Column Mount Cage Drive


Bridge Mount Shaft Drive with Lift


Bridge Mount Shaft Drive


Column Mount Cage Drive with Lift



ClearFlo SBR systems are optimized for a wide variety of applications; from small packaged single train systems, to large Constant Level SBR systems. State of the art SBR designs are available to meet the Nation’s toughest BNR standards. Our proprietary operating strategy enables ClearFlo SBR systems to treat flows from zero to 350% of design flow without bypassing, or permit violations.





ClearFlo CLR systems are optimized for a wide variety of applications; from small packaged “bullseye” systems with an oxidation channel wrapped around a ClearStream clarifier for carbonaceous and ammonia removal, to large multi-channel systems for reliable and cost effective BNR processes.

Deeper space saving basins increase overall efficiency, and reduce heat loss during winter operation. Clean operating subsurface jet aeration eliminates mist and spray, Low maintenance, (no shafts or disks to break, or expensive gear drives to service), and long life make ClearFlo CLR Systems the clear choice.




Tightening effluent standards and rising energy costs have left many facilities in an untenable situation. Process systems designed and installed in the 1970s and 80s are incapable of meeting current effluent standards, and the power costs continue to rise. Let ClearStream process engineers evaluate your current system and develop a plan to increase capacity, meet current standards, and reduce energy consumption.



By combining facultative/anaerobic and aerobic digestion chambers, ClearFlo process engineers can reduce solids sent to disposal by up 80% compared to conventional solids digestion systems. Using proven principles of enhanced facultative cell lysis, coupled with state of the art ORP control, a ClearFlo Hybrid digestion system can reduce solids handling costs to a fraction of that of current aerobic systems.



ClearFlo jet aeration systems offer state of the art aeration and mixing for a wide variety municipal and industrial wastewater and process applications.

Independent control of oxygen transfer and mixing, low installation costs, long life, high clean water transfer efficiency, high “dirty water” transfer efficiency, low maintenance, thermal conservation, and clean operation (eliminates airborn volatiles) make jets the ideal choice for new facilities, as well as upgrades, and process optimization projects.

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