Top OEMs for Clarification Equipment

1. INTRODUCTION

Clarification is the fundamental unit operation in water and wastewater treatment, serving as the primary method for gravity separation of suspended solids from liquid. In municipal and industrial applications, clarification equipment—often referred to as sedimentation tanks, settling basins, or clarifiers—operates on the principles of density difference and Stokes’ Law to settle particulate matter or float lighter substances such as oils and scum.

The scope of clarification equipment spans the entire treatment train. In potable water treatment, clarifiers typically follow flocculation basins to remove chemically coagulated flocs, reducing the turbidity load on downstream filtration units. In wastewater treatment, primary clarifiers reduce biochemical oxygen demand (BOD) and total suspended solids (TSS) entering biological processes, while secondary clarifiers separate activated sludge biomass from treated effluent, a critical step for process stability and regulatory compliance.

For consulting engineers and plant operators, the selection of clarification Original Equipment Manufacturers (OEMs) is not merely a procurement decision but a long-term engineering commitment. Clarifiers are massive, civil-intensive structures with mechanical service lives expected to exceed 20 to 30 years. The failure of a clarifier mechanism involves significant capital expenditure, operational downtime, and potential permit violations.

Operating conditions vary drastically between applications. Primary treatment involves heavy, inorganic loads and grit accumulation that demand high-torque drives and robust rake arms. Secondary treatment requires sensitive hydraulic management to prevent sludge blanket washout during peak wet weather flows, necessitating advanced energy dissipation and suction removal mechanisms. Furthermore, industrial applications often introduce corrosive environments, high temperatures, or thixotropic sludges that defy standard municipal design parameters.

Regulatory drivers, including stringent nutrient limits (Nitrogen and Phosphorus), have placed increased scrutiny on clarifier performance. The efficiency of a secondary clarifier directly impacts the feasibility of achieving low-level phosphorus limits, as particulate phosphorus escaping the weir contributes to effluent violations. Consequently, modern clarification equipment must be evaluated not just on mechanical durability, but on hydraulic sophistication—incorporating features like flocculating feedwells, density current baffles, and optimized sludge withdrawal systems.

2. HOW TO SELECT THIS PROCESS EQUIPMENT

Selecting clarification equipment requires a multi-dimensional engineering analysis that balances process hydraulics, mechanical integrity, and long-term maintainability. Engineers must move beyond simple catalog selection and engage in detailed specification of torque requirements, surface loading rates, and material compatibility.

Process Function and Performance Requirements

The design basis for any clarifier begins with the settling characteristics of the solids.
Type I Settling (Discrete): Used in grit chambers or pre-sedimentation, where particles settle individually without interaction.
Type II Settling (Flocculant): Common in primary clarification and chemically enhanced primary treatment (CEPT), where particles coalesce as they settle, increasing mass and settling velocity.
Type III (Zone) and Type IV (Compression) Settling: Critical in secondary activated sludge clarifiers, where particle concentration is high enough that solids settle as a blanket.

Equipment selection must match these regimes. For example, secondary clarifiers typically require rapid sludge removal mechanisms (suction headers or pipes) to prevent denitrification and rising sludge, whereas primary clarifiers can utilize simpler plow or scraper mechanisms due to the biological inactivity of the raw sludge.

Hydraulic and Process Loading Considerations

Surface Overflow Rate (SOR): Defined as flow rate divided by surface area (gpd/ft²), SOR determines the removal efficiency of discrete particles. Exceeding design SOR leads to solids carryover.
Solids Loading Rate (SLR): Critical for secondary clarifiers, defined as the mass of solids applied per unit area per day (lb/ft²/day). High SLR can overwhelm the thickening zone, causing blanket failure.
Weir Loading Rate (WLR): The flow per linear foot of weir. High WLR induces local velocities that can scour the sludge blanket.
Engineers must evaluate OEMs based on their ability to model these parameters (CFD modeling) and provide feedwell designs that dissipate energy and prevent short-circuiting.

Materials of Construction

The longevity of clarification equipment is dictated by material selection.
Submerged Steel: typically ASTM A36 or A992 carbon steel, requires high-performance coating systems (e.g., three-coat epoxy).
Stainless Steel: 304L or 316L is preferred for weirs, baffles, and hardware to resist corrosion, particularly in wastewater with high hydrogen sulfide potential.
Aluminum: Often used for launder covers and bridges to reduce weight and maintenance, though galvanic corrosion must be managed at connection points.
Concrete: The tank structure itself is civil work, but the grout layer on the floor is critical for scraper mechanisms to function without binding.

Integration with Upstream and Downstream Processes

A clarifier does not operate in isolation.
Upstream: Inaccurate flow splitting to multiple clarifiers is a common failure mode. The OEM equipment should be compatible with hydraulic splitting structures. For chemical precipitation applications, the integration of rapid mix and flocculation zones (either external or within a flocculating center well) is essential.
Downstream: The consistency of underflow concentration affects sludge handling (pumps, thickeners, dewatering). The clarity of the effluent affects UV transmittance for disinfection or solids loading on tertiary filters.

Drive Unit: The Heart of the System

The clarifier drive is the single most critical mechanical component. Engineers must specify:
Torque Rating: Continuous running torque, alarm torque, and cutoff torque. Specifications should require calculation based on the specific sludge density and scraper arm geometry, not just “standard” values.
Gear Design: Worm gear vs. spur gear. Precision main bearings (ball race vs. strip liner) significantly impact life expectancy. Strip liners are cheaper but require replacement; precision ball races are designed for the life of the unit.

Operations and Maintenance Impacts

Access: Bridges must provide safe, code-compliant access to the center drive for maintenance.
Lubrication: Automatic lubricators or accessible grease lines are preferred over manual zerks that require confined space entry or reaching over weirs.
Skum Removal: Scum beaches and skimmer mechanisms are high-maintenance items. OEMs offering flushing mechanisms or simplified beach designs reduce operator burden.

Lifecycle Cost Considerations

Initial capital cost is often dwarfed by lifecycle costs.
Painting: Repainting a steel mechanism requires draining the tank and typically sandblasting, a massive expense. Hot-dip galvanized or stainless steel mechanisms have higher CAPEX but lower OPEX.
Drive Replacement: A drive unit failure can cost tens of thousands in emergency procurement and installation. Drives with 20+ year design lives are standard specifications for municipal applications.

3. COMPARISON TABLE

The following table outlines the six locked OEMs for clarification equipment. Engineers should use this matrix to align project specificities—such as footprint constraints, retrofit needs, or specific sludge characteristics—with the inherent strengths of each manufacturer. Note that “limitations” often refer to application focus rather than quality deficiencies.

OEM Name	Typical Applications	Engineering Strengths	Limitations	Best-Fit Scenarios	Maintenance Considerations
WesTech Engineering	Municipal Water/WW, Industrial, Flocculating Clarifiers	Heavy-duty custom engineering; Precision bearing drives; Retrofit capabilities (drop-in drives).	Premium engineered solutions may carry higher initial CAPEX than commodity options.	Heavy industrial loads; Plants requiring custom retrofit of existing basins; High-torque applications.	Drive units are robust but require strict oil analysis programs to maximize 20+ year life.
Evoqua (Envirex/Tow-Bro)	Secondary Clarification, Rectangular Tanks, Biological Nutrient Removal	Tow-Bro hydraulic suction for rapid sludge removal; Extensive install base of Chain & Flight systems.	Complex hydraulic suction mechanisms require precise tuning; Chain & Flight has more moving parts submerged.	Biological Nutrient Removal (BNR) plants needing rapid sludge return; Rectangular tank footprints.	Chain & Flight systems require regular tensioning and wear strip monitoring. Tow-Bro requires orifice cleaning.
Ovivo	Municipal/Industrial, Eimco & Dorr-Oliver Heritage	Massive archive of legacy designs for exact replacements; Spiraflo (peripheral feed) technology.	Navigating the extensive legacy portfolio can be complex; long lead times for legacy castings.	Replacing 50-year-old Eimco/Dorr-Oliver mechanisms; Peripheral feed applications for hydraulic stability.	Standard gearbox maintenance; Skimmer mechanisms on peripheral feed units require specific adjustment.
NEFCO Systems	Effluent Quality Optimization, Algae Control, Hydraulic Control	Market leader in Launder Covers and Density Current Baffles (Stamford Baffles).	Does not manufacture the primary scraper mechanism/drive; focused on clarifier accessories/optimization.	Clarifiers failing TSS limits due to density currents; Algae issues in launders; Retrofits to improve capacity.	Very low maintenance; FRP materials require no painting. Periodic cleaning of covers may be required.
ClearStream Environmental	General Municipal and Industrial Clarification	Cost-effective standard designs; Strong retrofit engineering for circular clarifiers.	Less emphasis on highly specialized or exotic industrial processes compared to others.	Standard municipal circular clarifiers; Projects with tight budgets requiring reliable, standard engineering.	Standard drive maintenance; emphasis on using commercially available components where possible.
Parkson	Space-Constrained Plants, High-Rate Clarification	Lamella® Inclined Plate Settlers; EcoFlow Baffles; Compact footprint solutions.	Lamella plates prone to clogging with certain sticky sludges/grease; not for high-scum loads.	Plant expansions with zero available land; Indoor installations; Industrial pretreatment.	Plate packs require periodic cleaning/hosing to prevent bridging; Flash mix/floc tanks need mixer maintenance.

4. TOP OEM MANUFACTURERS

The following section provides a detailed technical analysis of the six designated OEMs for clarification equipment. The descriptions focus on engineering features, proprietary technologies, and mechanical configurations relevant to specification and design.

WesTech Engineering

WesTech Engineering is widely recognized in the municipal and industrial sectors for its focus on the central drive mechanism and custom steel fabrication. Unlike manufacturers that rely heavily on standardized catalogs, WesTech’s engineering model accommodates significant customization, making them a primary choice for complex retrofits where existing concrete structures dictate geometry.

Technical Highlights:
The core of WesTech’s offering is the COP Clarifier (Clarifier Optimization Package) and their proprietary drive units. WesTech manufactures its own drives, typically utilizing a precision ball-race main bearing. Unlike strip liner bearings, which rely on plastic strips that wear down and require replacement (often necessitating crane usage to lift the drive), the ball-race bearing is designed to last the life of the clarifier, calculating L10 life in excess of 100,000 hours.

For sludge removal, WesTech provides both spiral blade and suction header designs. The spiral blade scrapers are engineered to transport sludge to the center hopper in a single revolution, reducing sludge residence time—a critical factor in preventing septicity in primary clarifiers. In secondary applications, their suction header designs utilize varying orifice sizes to ensure uniform withdrawal rates across the tank floor, balancing the mass loading.

Evoqua (an Xylem brand)

Evoqua Water Technologies holds one of the most significant portfolios in the history of wastewater treatment, incorporating legacy brands like Envirex, Rex, and Link-Belt. Their clarification technologies are divided primarily between circular and rectangular tank solutions.

Technical Highlights:
For circular secondary clarifiers, the Tow-Bro® hydraulic sludge removal system is the industry standard for rapid sludge removal. Unlike scraper systems that push sludge to a hopper, the Tow-Bro utilizes a suction header that removes sludge directly from the floor where it settles. This is critical for Biological Nutrient Removal (BNR) processes where minimizing anoxic time in the clarifier prevents the release of phosphorus or nitrogen gas formation.

For rectangular tanks, Evoqua is the leader in Chain and Flight systems (Envirex). While historically utilizing metallic chains, modern specifications favor non-metallic, heavy-duty composite chains and fiberglass flights. These systems maximize the footprint efficiency of rectangular tanks. Evoqua also offers the Rim-Flo® peripheral feed clarifier, which introduces flow at the periphery and takes effluent from the center, a hydraulic reversal that can offer superior stability in specific loading conditions.

Ovivo

Ovivo represents the consolidation of major historical clarification names, most notably Eimco and Dorr-Oliver. This lineage gives Ovivo access to original drawings for thousands of installations dating back nearly a century, providing them a unique advantage in “like-for-like” replacement of aging infrastructure.

Technical Highlights:
Ovivo is heavily invested in drive unit technology, offering both worm gear and spur gear arrangements depending on torque requirements. Their drives are typically rated for continuous 24/7 duty in harsh environments.

A flagship technology for Ovivo is the Spiraflo Clarifier. This is a peripheral feed design where the influent enters a race around the skirt of the clarifier, traveling down beneath the skirt before entering the main settling zone. This configuration utilizes the tank periphery for flocculation and energy dissipation, creating a very stable hydraulic environment that resists density current short-circuiting. It is particularly effective in preventing “wall creep” of solids over the weir. Ovivo also specializes in Solids Contact Clarifiers, which combine mixing, flocculation, and sedimentation in a single basin, widely used in potable water softening and industrial precipitation.

NEFCO Systems

NEFCO Systems occupies a unique and critical niche in the clarification market. While they do not manufacture the rake arms or drive units, they are the premier OEM for Clarification Optimization Equipment. Specifically, they engineer and manufacture Density Current Baffles (often called Stamford Baffles) and Launder Covers.

Technical Highlights:
In secondary clarifiers, density currents caused by the difference in specific gravity between the influent mixed liquor and the clear supernatant can cause solids to dive to the floor, travel along the bottom, and ride the wall up over the effluent weir. NEFCO’s Stamford Baffles are engineered fiberglass panels installed on the tank wall, angled downward to intercept this current and redirect it back toward the center of the tank. This simple hydraulic modification can reduce effluent TSS by 30–50% without mechanical changes.

Additionally, NEFCO’s Launder Covers are essential for preventing algae growth in effluent weirs. By blocking sunlight, they eliminate the labor-intensive need for operators to scrub weirs, while also preventing algae solids from contributing to effluent violations. For engineers, specifying NEFCO components is often the most cost-effective method to upgrade the capacity rating of an existing clarifier.

ClearStream Environmental

ClearStream Environmental has established itself as a reliable OEM focusing on high-quality, standard, and custom circular clarification equipment. They position themselves as a nimble alternative to the massive conglomerates, often providing competitive lead times and hands-on engineering support.

Technical Highlights:
ClearStream provides a full range of mechanism types: bridge-supported (for smaller tanks) and pier-supported (for larger tanks). Their designs often feature large rigid cage structures and robust truss arms. A key engineering strength is their retrofit capability; they are adept at designing replacement mechanisms that interface with existing concrete geometries that may be out of tolerance or non-standard.

They employ advanced Finite Element Analysis (FEA) to ensure structural integrity of the underwater rake arms and feedwells. Their flocculating clarifiers utilize low-shear turbine mixers within an enlarged center well to promote floc growth immediately prior to the settling zone, optimizing performance for chemical plants and tertiary treatment.

Parkson

Parkson is distinct from the other OEMs on this list due to their specialization in Lamella® High-Rate Clarification (Inclined Plate Settlers). While they offer other technologies, their name is synonymous with plate settling.

Technical Highlights:
The Lamella® Gravity Settler utilizes a series of inclined plates to vastly increase the effective settling area within a small footprint. According to the “projected area” theory, the settling capacity is a function of the horizontal projected area of the plates. A Parkson Lamella unit can provide the same settling capacity as a conventional circular clarifier in 10% of the footprint.

This technology is ideal for industrial applications, potable water treatment, and municipal applications where land is unavailable. Parkson also offers the EcoFlow baffle system, similar in function to NEFCO’s offerings, designed to optimize hydraulic usage of existing basins. For engineers, Parkson is the “go-to” when the hydraulic loading rate is high and the available real estate is non-existent.

5. APPLICATION FIT GUIDANCE

Understanding the strengths of these OEMs allows engineers to match the right vendor to the specific project constraints.

Municipal Wastewater (Secondary Treatment)

For standard activated sludge plants, WesTech and Ovivo are strong contenders for circular scraper or suction header mechanisms. If the process requires rapid sludge removal (e.g., preventing phosphorus release), Evoqua’s Tow-Bro is the specific technical solution often mandated. If the plant utilizes rectangular tanks (common in older cities with tight land), Evoqua’s Envirex chain and flight systems are the dominant choice.

Municipal Water (Potable)

Water treatment often requires “Solids Contact Clarifiers” where chemical mixing and settling occur in one unit. WesTech and Ovivo excel here with robust turbine reactor clarifiers. For plants needing to expand capacity without new civil structures, adding Parkson Lamella plates or upgrading weirs with NEFCO baffles are common strategies.

Industrial Wastewater

Industrial streams (food and bev, mining, pulp and paper) often have variable loads and heavy solids. Parkson is heavily favored here for compact, indoor, packaged units. WesTech is frequently selected for heavy-duty industrial thickeners and clarifiers where torque loads exceed municipal standards.

Retrofit vs. Greenfield

Greenfield: Any of the circular OEMs (WesTech, Ovivo, ClearStream, Evoqua) are suitable, and selection often comes down to competitive bidding on lifecycle cost and technical features.
Retrofit: ClearStream and WesTech have strong engineering departments dedicated to fitting new mechanisms into old, out-of-square concrete. NEFCO is the primary choice for “performance retrofits” where the mechanism is fine, but the process results (TSS) are failing.

6. ENGINEER & OPERATOR CONSIDERATIONS

Successful implementation of clarification equipment goes beyond OEM selection. The following factors must be integrated into the design and operational planning.

Installation and Commissioning

Grout Design: The performance of a scraper clarifier is dependent on the floor grout. If the grout is not swept to the precise profile of the rake arm, the blades will either bind (high torque) or leave a layer of septic sludge. Specifications must require the OEM to provide a sweeping template and onsite supervision during grouting.
Weir Leveling: Weirs must be leveled to within 1/16th to 1/8th of an inch. Uneven weirs cause flow maldistribution, pulling solids over the low points.

Maintenance Access

Engineers should specify wide bridges with non-slip grating. For center drives, the oil fill and drain ports must be accessible without requiring the operator to lean dangerously over the tank. Automated condensate drains on gearboxes help prevent water intrusion into the oil, a common cause of bearing failure.

Operational Lessons Learned

Torque Overload: Operators often experience torque alarms during wet weather events when sludge blankets rise and thicken. Systems should be designed with “lifting devices” (if applicable to the design) or variable frequency drives (VFDs) that allow for temporary torque management, though increasing speed is rarely the solution for a heavy blanket.
Skimmer Jams: The scum ramp is a frequent failure point. Hinged skimmer blades that can deflect if they hit an obstruction are preferred over rigid assemblies that can bend the skimmer arm.

Long-Term Reliability Risks

The primary risk is the main gear drive. Proprietary gearboxes from OEMs (like WesTech or Ovivo) are highly reliable but have long lead times for replacement. Engineers should discuss spare parts strategy: does the utility buy a spare drive to keep on the shelf (capital intensive), or rely on the OEM’s refurbished drive exchange program?

7. CONCLUSION

Clarification equipment serves as the gatekeeper for water quality in both potable and wastewater systems. While the fundamental physics of sedimentation remains constant, the mechanical execution varies significantly among OEMs.

WesTech and Ovivo offer robust, heavy-duty mechanisms suited for long-term municipal reliability and custom industrial needs. Evoqua provides specialized hydraulic solutions like the Tow-Bro for nutrient removal and dominates the rectangular tank market. ClearStream offers a competitive, standard engineering approach ideal for municipal retrofits. Parkson solves the problem of footprint through inclined plate technology. Finally, NEFCO provides the critical optimization accessories that ensure these mechanisms meet stringent effluent permits.

For the consulting engineer and utility decision-maker, the goal is to match the specific hydraulic challenges and sludge characteristics of the facility with the mechanical philosophy of the OEM. A successful selection prioritizes lifecycle value—measured in decades of reliable torque and consistent effluent quality—over the lowest initial bid price.

source https://www.waterandwastewater.com/top-oems-for-clarification-equipment/