Top OEMs for Filtration Systems

1. Introduction

Filtration systems represent a critical unit process in both municipal water treatment and wastewater resource recovery facilities. As regulatory limits for turbidity, suspended solids, phosphorus, and pathogens tighten, the reliance on advanced filtration technologies has intensified. In the context of potable water, filtration serves as the primary barrier against protozoan cysts (Giardia and Cryptosporidium), bacteria, and particulate matter that can harbor viruses or interfere with downstream disinfection. In wastewater treatment, tertiary filtration is the gatekeeper for water reuse (Title 22 compliance and equivalent standards), ensuring that effluent meets the stringent clarity and pathogen reduction requirements necessary for irrigation, industrial reuse, or aquifer recharge.

The engineering landscape for filtration is diverse, encompassing traditional granular media gravity filters, continuous backwash sand filters, cloth media surface filtration, and low-pressure membrane systems (Microfiltration/Ultrafiltration). The selection of an Original Equipment Manufacturer (OEM) in this category is rarely a simple procurement decision; it is a complex engineering evaluation of hydraulic profiles, solids loading capacities, backwash efficiencies, and long-term mechanical reliability.

For consulting engineers and plant superintendents, the “black box” approach to filtration is insufficient. Understanding the internal mechanics of how an OEM designs their underdrains, backwash shoes, air scour systems, and control algorithms is essential. A poorly matched filtration system can lead to hydraulic bottlenecks during peak wet weather flows, excessive parasitic loads from frequent backwashing, or compliance violations due to media breakthrough. Furthermore, as facilities move toward total plant automation, the integration of filtration PLCs with plant-wide SCADA systems becomes a pivotal factor in operational success.

This article provides a technical, specification-focused analysis of the leading OEMs in the filtration sector. It avoids marketing rhetoric to focus on the engineering attributes, application suitability, and maintenance realities of the equipment provided by DuPont (Memcor), Aqua-Aerobic Systems, WesTech Engineering, Evoqua, and Parkson.

2. How to Select This Process Equipment

Selecting a filtration system requires a holistic review of the treatment train. Engineers must define the influent characteristics—specifically particle size distribution and compressibility of solids—and the required effluent quality. The following technical criteria are paramount when evaluating systems.

Process Function and Hydraulic Loading

The fundamental sizing parameter for any filter is the hydraulic loading rate (HLR) or flux, typically expressed in gallons per minute per square foot (gpm/ft²) or gallons per square foot per day (gfd) for membranes. However, HLR must be balanced against Solids Loading Rate (SLR). A system designed for high hydraulic throughput may fail catastrophically if the influent solids load exceeds the media’s holding capacity, leading to rapid headloss accumulation and short run times.

Engineers must specify peaking factors carefully. Granular media filters typically operate between 2 and 6 gpm/ft², but deep-bed monomedia filters may push higher. Cloth media filters can often sustain higher peak loading rates (up to 6–9 gpm/ft²) due to their distinct surface filtration mechanism. Membrane systems are strictly flux-limited; exceeding the critical flux leads to irreversible fouling.

Materials of Construction and Media Life

The longevity of a filtration system is dictated by its materials.

• Granular Media: Specification of media effective size (ES) and uniformity coefficient (UC) is critical. For multimedia filters, the intermixing of anthracite and sand must be managed through proper backwash fluidization rates.
• Cloth Media: The pile cloth material (typically Nylon or Polyester) must be resistant to biological degradation and chemical attack (e.g., from chlorine or coagulants). The mechanical support structure—often 304 or 316 stainless steel—must withstand the submerged, corrosive environment.
• Membranes: Polyvinylidene fluoride (PVDF) is the industry standard for polymeric membranes due to its chlorine tolerance and mechanical strength. Engineers must evaluate the potting material and module housing durability.

Backwash Efficiency and Parasitic Load

A critical operational metric is the backwash waste volume, expressed as a percentage of forward flow. High-efficiency systems (like cloth media or air-scour equipped gravity filters) may achieve waste volumes of <3-5%. Older or poorly optimized designs can exceed 10%, representing a significant parasitic load that must be treated again at the headworks. The method of backwashing—whether continuous (e.g., moving sand bed), intermittent pulsing, or full operational stop—impacts hydraulic profiles and equalization requirements upstream.

Integration with Upstream Processes

Filters do not operate in a vacuum. Their performance is inextricably linked to upstream clarification and chemical conditioning.

• Floc Strength: Some filters (like continuous backwash sand) can tolerate fragile flocs, while others (pressurized media) may shear weak flocs, causing turbidity breakthrough.
• Chemical Compatibility: If upstream processes use polymers, engineers must ensure the filter media is not susceptible to blinding. Unreacted polymer is a leading cause of irreversible fouling in membrane and cloth systems.

Lifecycle Cost and Maintenance

The Total Cost of Ownership (TCO) analysis must include:

• Energy: Pumping head requirements (static lift + headloss through clean/dirty media).
• Consumables: Frequency of media replacement (every 5–10 years for cloth/membranes vs. 15+ for sand).
• Chemicals: Clean-in-Place (CIP) chemicals for membranes (Citric Acid, Hypochlorite).
• Labor: Man-hours required for mechanical maintenance (valves, actuators, backwash pumps).

3. Comparison Table

The following table contrasts the five specified OEMs based on their primary filtration technologies. Engineers should use this to align project constraints (e.g., footprint, solids loading, nutrient limits) with the specific engineering strengths of each manufacturer.

OEM Name	Typical Applications	Engineering Strengths	Limitations	Maintenance Considerations
DuPont (Memcor)	Potable Water, Water Reuse (Title 22), RO Pretreatment, Industrial Process Water	High-performance PVDF membranes; Submerged and pressurized configurations; Absolute barrier to pathogens (Log removal credits); High packing density.	Higher capital cost than granular media; Sensitive to sharp objects and unreacted polymer; Requires strict integrity testing protocols.	Regular CIP (Clean-in-Place) required; Module repair/pinning for broken fibers; Valve maintenance on pneumatic systems.
Aqua-Aerobic Systems	Tertiary Wastewater, CSO/SSO Treatment, Phosphorus Removal, Water Reuse	Cloth media filtration (AquaDisk/AquaDiamond); Very low backwash waste volume; Small footprint; continuous filtration during backwash (unit level); Low headloss.	Not an absolute barrier for viruses without disinfection; Cloth replacement required every 5-7 years; Limited to surface filtration (no depth storage).	Cloth replacement is a manual process; Mechanical maintenance of drive motors and backwash shoes; Vacuum pump maintenance.
WesTech Engineering	Municipal Potable Water, Iron/Manganese Removal, Tertiary Wastewater, Industrial	Robust conventional gravity filtration; Excellent custom vessel fabrication; diverse underdrain systems; Deep bed applications; Integration with flocculation.	Large civil footprint for gravity basins; Higher backwash water volume compared to cloth media; Batch operation (unless multiple cells used).	Media top-off or replacement; Underdrain inspection requiring confined space entry; Actuated valve maintenance.
Evoqua	Potable Water, Wastewater Reuse, Industrial Intake, Aquatic Systems	Extensive portfolio including V-Block underdrains, packaged gravity systems, and sand filtration; Strong retrofit capabilities for existing basins.	Portfolio breadth can complicate selection; Specific product lines (e.g., legacy systems) may have different support chains.	Depends heavily on specific technology selected (media vs. membrane); General valve and instrumentation calibration.
Parkson	Tertiary Wastewater, Nutrient Removal, Industrial Process Water, Potable Water	Continuous backwash sand filtration (DynaSand); No moving parts within the media bed; Continuous steady-state operation; simultaneous biological denitrification capability.	Requires deep tanks/vertical clearance; Airlift pump tuning required; Constant reject stream (though low volume) requires management.	Airlift maintenance; Sand washer inspection; Feed tube cleaning; Minimal mechanical parts reduce overall complexity.

4. Top OEM Manufacturers

This section details the specific technical offerings of the locked OEM list. The focus is on the engineering principles behind their flagship filtration technologies.

DuPont (Memcor)

DuPont, through its acquisition of the Memcor heritage, is a dominant force in the low-pressure membrane filtration market (Microfiltration and Ultrafiltration). Their systems are engineered primarily around PVDF (Polyvinylidene Fluoride) hollow fiber chemistry, known for high oxidant tolerance and mechanical durability.

Technology Focus: DuPont’s portfolio is split between pressurized systems (typically for potable water or industrial applications requiring closed-loop pressure maintenance) and submerged systems (typically for wastewater membrane bioreactors or tertiary reuse).
A key engineering feature of the Memcor line is the air scour mechanism. During the backwash sequence, air is introduced to shake the fibers, dislodging the cake layer formed on the membrane surface. This allows for flux recovery without aggressive chemical cleaning in the short term. The fibers are typically potted in a way that allows for some movement, reducing stress at the potting interface—a common failure point in early membrane designs.
Engineering Considerations: When specifying DuPont systems, engineers must calculate the flux rate carefully based on temperature (viscosity correction) and fouling potential. The systems utilize a distinct “pressure decay test” (PDT) or “integrity test” protocol, which uses compressed air to detect breached fibers. This automated integrity verification is crucial for regulatory compliance in potable water and reuse applications where log-removal credits for pathogens are claimed.

Aqua-Aerobic Systems

Aqua-Aerobic Systems is synonymous with cloth media filtration in the municipal wastewater sector. They revolutionized tertiary filtration by moving away from granular media toward pile cloth surface filtration, primarily through their AquaDisk® and AquaDiamond® configurations.

Technology Focus: The core technology utilizes a pile cloth media (similar in concept to shag carpet loops) mounted on rotating disks or drums. Flow enters the tank and passes through the cloth by gravity (outside-in). Solids form a mat on the exterior of the cloth.
The distinct engineering advantage is the backwash mechanism. Unlike sand filters that require fluidizing an entire bed, Aqua-Aerobic systems use a suction shoe that touches the cloth surface. As the disk rotates, the shoe vacuums off the solids using a small pump. This results in continuous filtration (the submerged portion of the disk continues to filter while the shoe cleans a strip) and extremely low backwash waste volumes.
Engineering Considerations: The AquaDiamond fits into the profile of existing traveling bridge sand filters, making it a prime candidate for retrofits where civil work must be minimized. Engineers should note that this is surface filtration, not depth filtration. Therefore, it handles spikes in hydraulic loading well but has a finite solids loading capacity per square foot before the backwash frequency becomes continuous.

WesTech Engineering

WesTech Engineering is a traditional powerhouse in physical-chemical treatment, offering heavy-duty, customized filtration solutions. While they offer various technologies, they are particularly renowned for optimizing conventional gravity media filtration and pressure filtration systems.

Technology Focus: WesTech’s strength lies in the optimization of the filter underdrain and backwash troughs. They utilize various nozzle and plenum designs to ensure uniform distribution of backwash water and air scour. Uneven backwashing is the primary cause of “mud-balling” and media channeling in gravity filters; WesTech’s hydraulic designs focus on preventing these localized failures.
They also specialize in iron and manganese removal systems (oxidation filtration) for potable water, utilizing manganese greensand or proprietary media. Their horizontal and vertical pressure filters are staples in industrial applications and smaller municipal footprints.
Engineering Considerations: WesTech excels in “engineered-to-order” scenarios. If a plant has unique hydraulic profiles, corrosive water chemistry requiring exotic metallurgies (Duplex stainless, rubber-lined carbon steel), or specific seismic constraints, WesTech’s engineering team typically accommodates these custom fabrication needs. Their systems often integrate seamlessly with their upstream flocculation and clarification equipment (e.g., Solids Contact Clarifiers), providing a single-source responsibility for the entire liquid stream.

Evoqua

Evoqua (now part of Xylem) holds one of the most extensive installed bases in North America, incorporating legacies of several historic brands. Their filtration portfolio spans from sand and multimedia to advanced membranes.

Technology Focus: A cornerstone of Evoqua’s gravity filtration line is the V-Block Underdrain system. This dual-lateral underdrain is designed to improve backwash distribution and air scour efficiency. It features a snap-lock design and laser-cut orifices to manage headloss and prevent media migration. The “multicycle” operation allows for simultaneous air/water backwash, which is aggressive enough to clean media thoroughly without flushing it out of the basin.
Evoqua also offers the Forty-X Disc Filter, a woven media filter that competes in the tertiary microscreening space. This provides an alternative to their granular media solutions for projects requiring small footprints and high hydraulic throughputs.
Engineering Considerations: Because Evoqua offers both granular media and microscreening/membrane technologies, they can provide a relatively agnostic evaluation of which technology fits a specific application. Engineers should pay close attention to the specific media retention caps and air scour nozzles specified with the V-Block system to ensure compatibility with the selected media effective size.

Parkson

Parkson is best known for championing the continuous backwash sand filter technology, specifically the DynaSand® filter. This technology differs fundamentally from the static bed filters offered by WesTech or Evoqua (in their conventional lines).

Technology Focus: The DynaSand filter operates on an upflow, deep-bed, granular media principle with continuous regeneration. Influent enters near the bottom and flows upward. Simultaneously, the sand bed moves slowly downward to the center. An airlift pump at the center of the unit lifts the dirty sand from the bottom to a washbox at the top. In the washbox, the sand falls through a labyrinth where a small portion of filtrate flows counter-current to wash the sand. Clean sand falls back onto the top of the bed.
Engineering Considerations: The primary advantage is the elimination of backwash pumps, valves, and complex control sequences required to take a filter offline for cleaning. The filter is always online. Furthermore, because the sand is deep and moves slowly, these units can be configured as DynaSand EcoWash® or biological filters (for denitrification) by adding a carbon source. The biomass grows on the sand grains, converting nitrates to nitrogen gas. Engineers must design for the constant reject stream and ensure sufficient plant air is available for the airlift pumps.

5. Application Fit Guidance

Different water quality objectives dictate different OEM selections. The following guide assists engineers in matching the application to the most appropriate manufacturer technology.

Municipal Potable Water

For surface water treatment requiring turbidity removal and pathogen barriers:

• Primary Choices: WesTech and Evoqua are standard for conventional gravity filtration (Anthracite/Sand) in large water treatment plants (WTPs). Their underdrain technologies ensure reliable long-term performance.
• Membrane Option: DuPont (Memcor) is preferred when Log Removal Value (LRV) credits are needed for Giardia/Cryptosporidium without relying solely on chemical disinfection.

Municipal Wastewater (Tertiary/Reuse)

For Title 22 reuse or low phosphorus limits:

• Primary Choices: Aqua-Aerobic Systems and Parkson (cloth media options) dominate this sector due to small footprints and the ability to handle secondary effluent variability.
• Nutrient Removal: Parkson’s DynaSand is uniquely suited for tertiary denitrification, serving a dual purpose of filtration and biological treatment.

Industrial Wastewater

For high solids loading or process water recycling:

• Primary Choices: WesTech provides robust pressure filters capable of withstanding industrial pressure classes. Parkson’s continuous sand filter is favored in steel and metal finishing for its ability to handle high oil/grease and solids without blinding, as the sand is constantly scrubbed.

Retrofits vs. Greenfield

• Retrofits: Aqua-Aerobic (AquaDiamond) and Evoqua are highly effective at retrofitting existing concrete traveling bridge filter basins. They allow plants to increase hydraulic capacity (3x to 4x) without pouring new concrete.
• Greenfield: For new plants, the choice is open. However, DuPont membrane systems are often selected for greenfield Membrane Bioreactors (MBR) or advanced water purification facilities (AWPF).

6. Engineer & Operator Considerations

Beyond the catalog specifications, the reality of installing and operating these systems involves practical challenges that must be addressed in the design and commissioning phases.

Installation and Commissioning

Levelness and Hydraulics: For cloth media filters (Aqua-Aerobic) and continuous sand filters (Parkson), hydraulic leveling is critical. If weirs or airlift assemblies are not perfectly level, flow distribution will be uneven, leading to localized loading and breakthrough.
Media Installation: For WesTech and Evoqua gravity filters, the installation of the underdrain and support gravel (if used) is the most critical step. Walking on underdrains or improper gravel placement can lead to immediate failure upon first backwash.

Maintenance Access

Submerged Components: Engineers must design for the retrieval of submerged components.

• For DuPont submerged membranes, overhead cranes or monorails are mandatory for lifting cassettes for inspection.
• For Aqua-Aerobic disk filters, operators need clear access to change cloth socks. While the tank doesn’t always need to be drained, safe access platforms are essential.
• For Parkson, the central airlift assembly may need to be pulled if clogged by large debris; overhead clearance is required.

Spare Parts and Supply Chain

Proprietary Dependencies:

• Membranes (DuPont) and Cloth Media (Aqua-Aerobic) are proprietary consumables. Utilities should negotiate long-term pricing for replacement modules/cloths at the time of capital purchase. Unlike sand, which is a commodity, these parts have single-source supply chains.
• Valve Actuators: Regardless of the OEM, the most common failure point in filtration galleries is the pneumatic or electric valve actuator. Standardization of actuators across the plant is recommended to reduce spare part inventory.

Operational Lessons Learned

Algae and Biofouling: In open basins (typical for tertiary filters), algae growth on weirs and launders is inevitable. Design should include covers or chlorination points upstream to mitigate bio-growth on the filter decks.
Cold Weather: For outdoor installations, continuous backwash filters (Parkson) and exposed piping on pressure filters (WesTech) require heat tracing. The small diameter reject lines are prone to freezing if flow stops even briefly.

7. Conclusion

The selection of a filtration OEM is a pivotal decision that dictates the hydraulic stability and compliance reliability of a treatment plant. There is no single “best” manufacturer; rather, there are optimal engineering fits for specific process constraints.

DuPont (Memcor) is the engineer’s choice for absolute barrier requirements and potable reuse applications where membrane integrity is non-negotiable. Aqua-Aerobic Systems sets the standard for tertiary wastewater polishing where low backwash rates and small footprints are required. WesTech Engineering remains the go-to for robust, custom-fabricated conventional gravity and pressure filtration in heavy municipal and industrial settings. Evoqua provides a massive portfolio with strong retrofit capabilities and advanced underdrain technologies. Parkson offers the unique advantage of continuous, steady-state operation ideal for denitrification and applications where taking filters offline is operationally difficult.

Engineers are advised to look past the capital cost and rigorously evaluate the lifecycle implications of media replacement, backwash waste management, and mechanical complexity. By aligning the specific influent chemistry and hydraulic profile with the inherent strengths of these Top OEMs, utilities can ensure long-term operational success.

source https://www.waterandwastewater.com/top-oems-for-filtration-systems/