Top OEMs for Grit Removal Systems

1. Introduction

In the hierarchy of wastewater treatment unit processes, grit removal serves as the critical line of defense for downstream mechanical equipment and biological processes. Located at the headworks of a facility—typically immediately following coarse screening and raw sewage pumping—grit removal systems are tasked with the physical separation of inorganic solids from the waste stream. These solids, collectively termed “grit,” include sand, gravel, cinders, eggshells, bone chips, coffee grounds, and other non-putrescible materials that possess a specific gravity significantly higher than organic solids (typically > 2.65).

The engineering imperative for efficient grit removal is threefold: abrasion protection, capacity preservation, and process efficiency. Uncaptured grit is highly abrasive. When it passes through the headworks, it accelerates wear on downstream pump impellers, pipe linings, valves, and sludge dewatering equipment. In biological treatment basins and anaerobic digesters, grit accumulates in dead zones, reducing the effective volume of the tanks and necessitating expensive, hazardous, and disruptive cleaning operations. From a regulatory and operational standpoint, the failure to remove grit results in increased lifecycle costs and energy consumption due to the transport of inert mass through the treatment train.

OEM selection in this category is complex because “grit” is not a uniform constituent. Its characteristics vary based on the collection system (combined vs. separate sewers), geography, soil conditions, and seasonal weather patterns. Furthermore, the hydraulic conditions at a treatment plant headworks are highly variable, with systems required to perform across a wide range of flows, from minimum nighttime flows to peak wet weather events. The selected equipment must maintain separation efficiency under these dynamic conditions while minimizing the capture of organic material, which can lead to odors and increased disposal costs.

This article provides a detailed engineering analysis of the primary Original Equipment Manufacturers (OEMs) specializing in grit removal technologies. The focus is strictly on technical capabilities, system architecture, and operational considerations, aiding consulting engineers and utility decision-makers in specifying the correct technology for their unique hydraulic and process constraints.

2. How to Select This Process Equipment

Selecting a grit removal system requires a balance between hydraulic engineering, particle physics, and mechanical reliability. Engineers must move beyond simple flow capacity ratings and evaluate systems based on removal efficiency across the full particle size distribution (PSD) spectrum.

Process Function and Performance Requirements

The core function of a grit removal system is differential sedimentation. The system must create hydraulic conditions where heavy inorganic particles settle out while lighter organic particles remain in suspension. Historically, specifications called for the removal of 95% of grit particles larger than 65 mesh (210 microns). However, modern specifications often demand removal of particles as fine as 100 mesh (150 microns) or even 140 mesh (106 microns), particularly in plants using membrane bioreactors (MBR) or fine-pore aeration, where fine grit can cause significant clogging and damage.

Engineers must specify performance based on:

• Cut Point: The particle size at which the system achieves a specific removal efficiency (e.g., 95% removal of 150-micron sand with a Specific Gravity of 2.65).
• Organics Capture: The system should minimize the quantity of putrescible organics settled with the grit. High organic content leads to odors and refusal by landfills. A target of less than 20% volatile solids in the washed grit is a common standard.

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Hydraulic and Process Loading Considerations

Headworks experience the most extreme flow variations in a treatment plant.

• Turndown Ratio: The equipment must operate effectively at Average Dry Weather Flow (ADWF) while handling Peak Wet Weather Flow (PWWF). Vortex systems typically handle wide turndowns better than horizontal flow aerated chambers, which rely on specific velocity profiles.
• Headloss: Consulting engineers must account for the hydraulic profile. Some advanced vortex systems or stacked-tray systems require significant head (elevation difference) to drive the separation process. If the hydraulic grade line is constrained, this may dictate the selection of mechanically induced vortex systems or aerated chambers over gravity-induced designs.
• Short-Circuiting: The design must prevent flow short-circuiting during peak events. Baffles, inlet configurations, and tank geometry are critical design elements that OEMs approach differently.

Materials of Construction

Given the abrasive nature of grit, material selection determines the longevity of the asset.

• Tankage: Options include cast-in-place concrete (common for large aerated chambers and some forced vortex systems) or fabricated stainless steel (304 or 316) for smaller vortex units and packaged plants.
• Wear Components: Pumps, impellers, and piping handling grit slurry require hardened materials. Ni-Hard (nickel-chromium white cast iron), High-Chrome iron, or heat-treated stainless steel are standard. Ceramic linings or glass-lined piping are frequently specified for suction and discharge piping to prevent scour.
• Internals: Rotating assemblies, paddles, and propellers located in the grit chamber should be constructed of abrasion-resistant alloys or coated with robust protective systems.

Integration with Upstream and Downstream Processes

Grit removal is a multi-stage system comprising:

1. Separation: The tank or chamber where settling occurs.
2. Extraction: The mechanism to remove settled grit from the chamber (e.g., grit pumps, airlifts, or clamshell buckets).
3. Classification/Washing: The separation of organics from the grit and the dewatering of the final product (e.g., screw classifiers, hydrocyclones, grit snails).

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The selection of the extraction method heavily influences the choice of the washing equipment. For instance, airlift pumps introduce significant air into the slurry, which must be managed at the classifier. Recessed impeller torque-flow pumps are preferred for their ability to pass large solids without clogging.

Lifecycle Cost and Operations

Energy Efficiency: Forced vortex systems use electric motors to drive paddles, while aerated chambers require blowers. Gravity-forced vortex systems have no moving parts in the chamber but may incur costs related to pumping head.
Maintenance: Systems with submerged moving parts (chains, flights, submerged bearings) generally incur higher maintenance costs and confine space entry risks compared to systems where drive units are accessible from the deck.

3. Comparison Table

The following table outlines the five specified OEMs for grit removal systems. This comparison aids engineers in identifying the primary engineering focus, typical application range, and specific limitations of each manufacturer’s technology. It is intended to guide preliminary selection rather than serve as a final procurement tool.

4. Top OEM Manufacturers

This section provides a detailed technical analysis of the mandated OEM list. The descriptions focus on the specific engineering principles, proprietary technologies, and system configurations offered by each manufacturer.

Smith & Loveless

Smith & Loveless (S&L) is a prominent name in the North American grit removal market, largely defined by its PISTA® brand. The PISTA® system is a forced hydraulic vortex grit chamber. Unlike gravity settling tanks that rely solely on residence time, the PISTA® utilizes a rotating paddle assembly to maintain a constant velocity within the chamber, inducing a vortex that separates heavier grit particles from lighter organic solids.

Technology and Design:
The core of the S&L design is the flat-floor chamber with a central hopper. The flow enters tangentially, and the mechanical paddles enhance the natural vortex. This creates a secondary flow pattern—a “tea cup” effect—that sweeps grit along the floor toward the center hopper while lifting lighter organics up and out of the chamber. S&L has evolved this technology with the PISTA® V-FORCE Baffle, an internal component designed to prevent flow short-circuiting and improve capture rates during peak hydraulic events.

System Components:
S&L typically provides the complete train, including the grit chamber mechanisms, the Top-Mounted Turbo Grit Pump, and the grit concentrator/classifier. Their pumps are specifically engineered for grit service, featuring recessed impellers and Ni-Hard construction to withstand the scouring action of the slurry. The system allows for 270-degree or 360-degree hydraulic loops, providing flexibility in civil layout.

Engineering Considerations:
Engineers often specify S&L PISTA® units for their known hydraulic stability. Because the paddles are driven by a constant-speed motor, the velocity in the chamber remains relatively consistent regardless of influent flow rate (within design limits), ensuring consistent removal efficiency. This is a distinct advantage over non-mechanically induced systems where efficiency might drop during low-flow periods.

Hydro International

Hydro International specializes in advanced hydrodynamic separation and is widely recognized for high-performance, small-footprint technologies. Their approach often utilizes gravity and flow energy rather than mechanical paddles to achieve separation, leveraging the Coanda effect and complex internal geometries.

Technology and Design:
The flagship product for Hydro International in this category is the HeadCell®. This modular, stacked-tray grit separator effectively multiplies the available surface area for settling within a compact footprint. It operates on the principle of removing grit across multiple thin layers, which reduces the settling distance required for a particle to be captured. This allows the HeadCell® to remove extremely fine grit (down to 75 microns) at high hydraulic loadings.

System Components:
The HeadCell® is typically paired with the SlurryCup (a washing and classifying hydrocyclone) and the Grit Snail® (a dewatering escalator). The SlurryCup uses centrifugal force to separate volatile organics from the grit slurry before it is discharged to the Grit Snail® for final dewatering. This “Advanced Grit Management” train is designed to produce a clean, dry grit output with low volatile solids content.

Engineering Considerations:
The absence of moving parts within the HeadCell® unit is a significant maintenance advantage, eliminating the need for underwater bearings or drive chains. However, the system relies on the efficient operation of the external grit pumps to maintain the hydraulic balance. Engineers must also account for the headloss profile of the stacked tray system during hydraulic modeling. The modularity makes it an excellent candidate for retrofitting existing detritus tanks or aerated chambers to increase capacity without expanding the civil footprint.

Lakeside Equipment

Lakeside Equipment Corporation has a long-standing history in the water industry, offering robust, mechanical designs. Their reputation is built on reliability and the durability of their equipment in harsh headworks environments. While they offer screening and clarification equipment, their grit removal portfolio is anchored by the SpiraGrit and aerated grit chamber mechanisms.

Technology and Design:
The SpiraGrit Vortex Grit Removal System is a mechanically induced vortex system. It typically employs a rotating paddle within a circular tank to maintain the velocity required for separation. Lakeside designs focus on creating a consistent toroid flow path. In addition to vortex systems, Lakeside is a key provider of equipment for Aerated Grit Chambers. These rectangular tanks use diffused air to induce a spiral roll in the wastewater. The roll velocity is controlled to allow heavy grit to settle while keeping lighter organics in suspension.

System Components:
Lakeside provides the internal drive mechanisms, air lift pumps, or recessed impeller pumps for grit extraction. For aerated chambers, they supply the screw conveyors or chain-and-bucket collectors that transport settled grit to a hopper. Their Raptor® line, while primarily screening, includes integrated washing and compacting solutions that sometimes overlap with grit handling in smaller packaged headworks.

Engineering Considerations:
Lakeside’s equipment is often favored in municipal specifications requiring heavy-duty construction and ease of operation. The SpiraGrit system is noted for its ability to handle “ragging”—the accumulation of fibrous materials—without fouling the paddle mechanisms. For engineers designing aerated grit chambers, Lakeside provides detailed guidance on tank geometry and diffuser placement to optimize the spiral roll and prevent dead zones.

Evoqua (Water Technologies)

Evoqua (now part of Xylem, though legally and historically referenced as Evoqua in specifications) holds one of the largest installed bases of water treatment equipment in North America, largely due to its acquisition of legacy brands like Envirex, FMC, and Rex. Their grit removal portfolio is extensive, covering virtually every method of separation.

Technology and Design:
Evoqua’s offerings include the V-Force® Vortex Grit Removal System, which competes directly with other mechanically induced vortex technologies. However, Evoqua is also a primary source for Aerated Grit Chamber mechanisms, including screw and bucket collectors, and chain and scraper systems for rectangular tanks. They also support Detritus Tank designs, a simplified constant-velocity settling channel often used in older or smaller plants.

System Components:
The V-Force® system utilizes a unique paddle design and baffle arrangement to optimize hydraulic shear and particle settling. For aerated grit chambers, Evoqua offers non-metallic chain and flight systems which resist corrosion and reduce weight compared to traditional steel chains. Their grit washing and dewatering screws are standard industry specifications for removing organics from the captured slurry.

Engineering Considerations:
The strength of Evoqua lies in its versatility. A consulting engineer can work with Evoqua to evaluate whether a vortex system or an aerated chamber is better suited for a specific project. For example, in a plant with significant pre-aeration requirements, an aerated grit chamber might be preferred to freshen the raw sewage. Conversely, for a footprint-constrained site, the V-Force® would be the recommendation. Their deep archive of legacy drawings facilitates direct replacement of worn-out mechanisms in 30- or 40-year-old plants.

Egger

Egger differs from the other OEMs on this list as they are primarily a pump and valve manufacturer rather than a fabricator of civil separation tanks. However, their inclusion is mandatory in any discussion of high-performance grit systems because the Turo® Vortex Pump is frequently the “heart” of custom-engineered grit removal systems and is often specified as the upgrade solution for failing extraction pumps in competitor systems.

Technology and Design:
Egger’s core competency is the Turo® T/TA Vortex Pump. This pump features a fully recessed impeller, meaning the impeller is located outside the main flow path within the volute. This creates a hydraulic vortex that transmits energy to the fluid without the solid particles having to pass through impeller vanes. This design allows the pump to handle grit slurries with high solids concentrations and large particle sizes without clogging or suffering the rapid erosion seen in standard centrifugal pumps.

System Components:
Beyond the pumps, Egger manufactures the Iris® Diaphragm Control Valve, which is critical for flow regulation in grit lines. The precise aperture control of the Iris valve allows for accurate flow pacing without the risk of clogging or dewatering that occurs with butterfly or gate valves. Egger also produces the Tura reactor, a less common but specific technology for mass transfer, though their dominance remains in the pumping and transport of the abrasive grit slurry.

Engineering Considerations:
When designing a grit system, the failure point is rarely the concrete tank; it is almost always the extraction pump. Standard non-clog pumps fail rapidly in grit service due to the abrasive wear on wear rings and impeller vanes. Engineers specify Egger Turo® pumps to ensure lifecycle reliability. They are capable of running dry and handling significant air entrainment, which is common when pumping form a grit hopper. While Egger may not supply the separation tank, they are the OEM for the critical motive equipment that makes the system viable.

5. Application Fit Guidance

Matching the OEM and technology to the application is critical for system success. The following guidelines help differentiate where these systems are best applied.

Municipal Wastewater

Large Facilities (>20 MGD): Large municipal plants often favor Aerated Grit Chambers (Lakeside, Evoqua) due to the linear footprint fitting well with primary clarifier layouts, or large banks of Vortex units (Smith & Loveless, Hydro International). In these applications, redundancy is key. The mechanical robustness of chain-and-flight systems (Evoqua) or screw conveyors (Lakeside) in aerated chambers is a proven approach, provided maintenance access is planned.

Small to Medium Facilities (<10 MGD): Vortex systems are the standard here. Smith & Loveless PISTA® units are ubiquitous in this range due to their packaged nature and predictable performance. Hydro International’s HeadCell® is particularly strong here when the footprint is extremely tight or when the plant is enclosed in a building.

Combined Sewer Overflows (CSO) and Stormwater

Systems handling CSOs face massive hydraulic spikes and heavy inorganic loads. Hydro International is a leader in this specific niche with technologies adapted for high-rate treatment. The system must be able to come online instantly without a “warm-up” period. Gravity-based systems are often preferred here over aerated systems, which may take time to establish the correct spiral roll.

Retrofits vs. Greenfield

Retrofits: When upgrading an existing plant, the civil works (concrete) represent the largest cost. Technologies that can drop into existing channels or basins are preferred. Hydro International’s modular trays can often be installed inside existing failed detritus tanks. Smith & Loveless offers components to upgrade older PISTA® units to current V-Force standards.
Greenfield: In new construction, the engineer has the luxury of optimizing the hydraulic profile. This often favors the Forced Vortex design (Smith & Loveless, Lakeside SpiraGrit) where the civil engineer can design the approach channels to perfect specifications, maximizing removal efficiency.

6. Engineer & Operator Considerations

Beyond the primary selection, several practical factors influence the long-term success of the installation.

Installation and Commissioning

Grouting: For vortex systems, the grout slope in the bottom of the chamber is critical. If the concrete work is poor, grit will accumulate in banks rather than sliding into the collection hopper. Manufacturers like Smith & Loveless provide detailed grout templates; adherence to these during construction is mandatory.
Piping Layout: Suction piping for grit pumps should be as short and straight as possible. Engineers should specify long-radius elbows and avoid vertical lifts on the suction side to prevent priming issues.

Maintenance Access

Operators prefer systems where drive units are accessible without entering the tank.

• Top-Mounted Drives: S&L and Lakeside vortex units typically have motors and gearboxes located on the bridge, well above the water line. This facilitates easy oil changes and belt tensioning.
• Submerged Components: Aerated grit chambers with chain-and-flight collectors (Evoqua) have submerged bearings and chains. While reliable, when they fail, the tank must be drained and cleaned for access, representing a significant confined space entry hazard.

Wear and Spare Parts

Grit systems destroy themselves by design. Engineers must plan for the replacement of wear liners and impellers.

• Pump Wear: Using Egger pumps or equivalent high-hardness alloy pumps extends the interval between failures. Standard cast iron pumps are unacceptable in this service.
• Classifier Screws: The shoes on screw classifiers wear down. Specifying manageable, bolt-on wear shoes rather than welded hard-facing can simplify maintenance.

Operational Lessons Learned

A common operational failure is the “blinding” of the grit removal system by grease. If the upstream screening is poor, rags and grease balls can enter the grit chamber. In vortex systems, these can wrap around paddles. In tray systems (Hydro International), they can blind the flow paths. Therefore, grit removal should never be specified without adequate upstream screening (typically < 6mm openings).

7. Conclusion

The selection of a Grit Removal System is a foundational decision in the design of a water resource recovery facility. It dictates the protection level of every subsequent unit process. There is no single “best” OEM; rather, there are optimal fits for specific hydraulic and physical constraints.

Smith & Loveless provides a standard-setting forced vortex solution ideal for variable municipal flows. Hydro International offers unmatched surface area and fine particle removal in constrained footprints. Lakeside Equipment delivers robust, mechanically simple designs favored by operators for their durability. Evoqua offers the breadth of portfolio to address massive custom civil designs and legacy retrofits. Finally, Egger remains the critical partner for the hydraulic transport of the captured slurry, providing the pumping technology that keeps the other systems operational.

Engineers should approach this selection by first defining the target cut point (particle size) and characterizing the influent grit load. From there, the choice should balance capital cost against the 20-year lifecycle cost of maintenance, energy, and downstream equipment protection.