Top OEMs for Packaged Treatment Plants

1. Introduction to Packaged Treatment Plants in Municipal and Industrial Applications

Packaged Treatment Plants (PTPs) represent a critical segment of the wastewater infrastructure market, serving as the backbone for decentralized wastewater management. Unlike large-scale, custom-designed civil works facilities that treat tens or hundreds of millions of gallons per day (MGD), packaged plants are pre-engineered, prefabricated, and often skid-mounted or modular systems designed for smaller flow rates—typically ranging from 5,000 gallons per day (GPD) up to 2 or 3 MGD. These systems are essential for municipalities, remote industrial sites, housing developments, and satellite water reclamation facilities where connecting to a centralized sewer system is either cost-prohibitive or geographically impossible.

From an engineering perspective, the definition of a “packaged plant” has evolved. Historically viewed as temporary solutions or “band-aids” until main sewer lines could be extended, modern PTPs are now specified as permanent, high-performance assets. They are subject to the same rigorous National Pollutant Discharge Elimination System (NPDES) permit requirements as major municipal plants, including strict limits on Biological Oxygen Demand (BOD), Total Suspended Solids (TSS), Ammonia, Total Nitrogen, and Phosphorus. Consequently, the engineering behind these units has advanced from simple extended aeration flow-through systems to complex biological nutrient removal (BNR) reactors and Membrane Bioreactors (MBR).

The selection of an Original Equipment Manufacturer (OEM) in this category is uniquely challenging. Unlike buying a pump or a blower—where the component is inserted into a larger system—buying a packaged plant is effectively purchasing the entire process train. The OEM is often responsible for the hydraulic profile, biological process sizing, aeration efficiency, clarification kinetics, and sludge management strategy. A mismatch in OEM selection does not merely result in equipment failure; it results in process failure, permit violations, and potential regulatory fines. Therefore, the evaluation must move beyond capital cost and focus heavily on process resilience, fabrication quality (corrosion resistance), and ease of operation.

This article provides a technical analysis of the leading OEMs in the Packaged Treatment Plant category. It is designed for consulting engineers and utility decision-makers who require an unbiased, specification-level breakdown of the available technologies, fabrication standards, and operational realities associated with these vendors.

2. How to Select Packaged Treatment Plants: Engineering Criteria

Selecting a packaged treatment plant requires a multi-disciplinary approach involving process engineering, structural evaluation, and operations planning. Consulting engineers must develop performance-based specifications that prevent “low-bid” procurement of under-sized or structurally deficient units. The following criteria are paramount.

Process Function and Biological Loading

The core of any PTP is the biological process. Engineers must first define the influent characteristics—not just average flows, but peaking factors, diurnal load variations, and specific pollutant concentrations. Packaged plants are notoriously sensitive to hydraulic and organic shock loads due to their smaller total volume.
Extended Aeration vs. SBR vs. MBR: The most common legacy design is extended aeration, which is stable but energy-intensive and requires large footprints. Sequencing Batch Reactors (SBR) offer batch-mode treatment that handles variable flows well and allows for denitrification (anoxic cycles) in a single tank. Membrane Bioreactors (MBR) provide the highest effluent quality and smallest footprint but require rigorous screening and chemical cleaning regimes. The choice of OEM often dictates the process technology available.

Hydraulic Considerations and Peak Flow Management

Small systems frequently experience peak hourly flows that are 3 to 4 times the average daily flow. If the OEM design relies on gravity clarification, hydraulic surges can wash out the mixed liquor suspended solids (MLSS), leading to permit violations. Engineers must scrutinize the clarifier surface overflow rate (SOR) at peak flow.
Many OEMs utilize flow equalization (EQ) tanks upstream of the biological reactor to buffer these surges. The integration of EQ into the package design—and the logic controls governing the feed pumps—is a critical differentiator. Systems that rely on batch processing (like SBRs) inherently manage hydraulics differently than flow-through systems, often eliminating the risk of clarifier washout.

Materials of Construction and Corrosion Protection

Read more4D-Printed Smart Materials For Water Treatment

This is the most common failure mode for packaged plants. PTPs are typically constructed of carbon steel, though concrete and stainless steel options exist.
Coating Systems: For carbon steel plants, the coating specification is vital. A standard “commercial blast” is insufficient for submerged wastewater environments. Engineers should specify a near-white metal blast (SSPC-SP10) followed by high-build epoxy, often requiring 12-16 mils DFT (Dry Film Thickness).
Field-Erected vs. Factory-Built: Smaller units are factory-welded and shipped in one piece. Larger units (0.1 MGD+) often require field erection. Field welding introduces quality control risks regarding weld porosity and coating continuity. Field-erected circular steel plants (a specialty of certain OEMs) offer distinct structural advantages over rectangular tanks due to hoop stress distribution, allowing for thinner wall sections without compromising integrity.

Integration with Upstream and Downstream Processes

A packaged plant does not operate in a vacuum. It requires effective headworks (screening and grit removal) to protect aeration diffusers and pumps. MBRs, for example, require fine screening (2mm or less) to prevent membrane clogging. Some OEMs include integrated headworks, while others assume the engineer will spec a separate unit. Similarly, waste activated sludge (WAS) must be stabilized (digested) and dewatered or hauled. The volume of the aerobic digester included in the package determines the sludge hauling frequency—a major O&M cost driver.

Energy Efficiency and Aeration Control

Energy consumption in PTPs is historically high per gallon treated because equipment sizes are small and turndown is limited. However, modern designs incorporate Dissolved Oxygen (DO) probes and Variable Frequency Drives (VFDs) on blowers. Engineers should evaluate the minimum turndown capability of the aeration system. Positive Displacement (PD) blowers are standard, but hybrid or screw blowers may be specified for larger package plants to reduce lifecycle energy costs.

Lifecycle Cost and Obsolescence

The initial capital cost of a PTP is often only 20-30% of its 20-year lifecycle cost. Energy, sludge hauling, and component replacement dominate the equation. Proprietary components—such as specialized decanters, proprietary membrane modules, or locked-down PLC code—can create “vendor capture,” making future maintenance expensive. Engineers should prioritize designs that utilize standard industrial components (NEMA motors, standard instrumentation) where possible.

3. Comparison Table: Leading Packaged Plant OEMs

The following table compares the five primary OEMs identified for this category. It is designed to help engineers match the specific constraints of a project (e.g., tight footprint, high nutrient limits, remote location) with the vendor best suited to meet those challenges.

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

4. Top OEM Manufacturers: Deep Dive Analysis

This section provides a detailed engineering analysis of the five locked OEMs. The focus is on their specific technological differentiators, fabrication philosophies, and suitability for various wastewater treatment scenarios.

Aqua-Aerobic Systems

Aqua-Aerobic Systems is widely recognized as the market leader in Sequencing Batch Reactor (SBR) technology in the United States. Unlike traditional flow-through package plants that rely on spatial separation (a dedicated aeration tank followed by a dedicated clarifier), Aqua-Aerobic’s flagship AquaSBR® utilizes time-based separation. All treatment steps—fill, react, settle, decant, and idle—occur in the same reactor volume.

Engineering & Process Analysis:
The primary advantage of the Aqua-Aerobic approach for package applications is the elimination of the secondary clarifier and return activated sludge (RAS) pumping systems. Clarifiers are notoriously difficult to design for small package plants due to hydraulic scaling issues; by settling in the quiescent reactor, Aqua-Aerobic achieves superior solids separation. This method also facilitates biological nutrient removal (BNR). By simply adjusting the aeration blower run-times during the “react” phase, operators can create anoxic or anaerobic conditions to promote denitrification and biological phosphorus removal without needing separate internal recycle pumps.

Equipment & Fabrication:
While Aqua-Aerobic provides equipment for concrete basins, they also offer packaged steel tank solutions. A critical component in their system is the decanter. Unlike fixed weirs, the Aqua-Aerobic decanter is a floating or mechanical device that lowers into the water column to withdraw clear effluent after the settling phase. Engineers must evaluate the maintenance access to this mechanism, although the company’s wire-rope and floating decanter designs have proven reliable over decades.

Control Philosophy:
Aqua-Aerobic differentiates itself with the IntelliPro® process monitoring and control system. For engineers specifying package plants, the control system is often the weak link. Aqua-Aerobic provides a robust, industrial-grade SCADA interface that actively optimizes energy by adjusting cycle times based on influent loading, rather than fixed timers. This is particularly valuable in decentralized applications where full-time operator attention is rare.

Aero-Mod

Aero-Mod approaches the packaged plant market with a philosophy centered on “Operator Simplicity.” Their designs are heavily favored by municipal public works departments that manage mid-sized facilities (0.5 to 5 MGD), particularly in the Midwest and West. Their core differentiation lies in the ClarAtor technology.

Engineering & Process Analysis:
The ClarAtor is a final clarifier design that eliminates the need for mechanical scraper bridges, suction headers, or submerged moving parts. Instead of mechanical collection, it uses hydraulic differential and an array of rapid-sludge-uptake pipes to remove settled solids. For a consulting engineer, this removes a significant maintenance headache: the failure of submerged bearings or chain-and-flight mechanisms in small tanks.

Equipment & Fabrication:
Aero-Mod systems are typically associated with the SEQUOX process, which combines sequencing batch concepts with continuous flow. This allows for excellent nutrient removal capabilities. While Aero-Mod is often associated with cast-in-place concrete installations, they apply their process equipment into packaged configurations as well. Their aeration systems utilize a monorail-mounted diffuser assembly that can be retrieved for cleaning without draining the tank—a critical feature for plants with only one or two process trains.

Maintenance Considerations:
The absence of submerged moving parts is the primary “spec-lock” feature for Aero-Mod. Engineers specifying for municipalities with limited maintenance staff often weigh this heavily against slightly higher civil costs. The system relies on air-lift pumps and gravity, reducing the number of centrifugal pumps required for RAS/WAS.

Smith & Loveless

Smith & Loveless (S&L) is a titan in the factory-built water infrastructure market. They are synonymous with “packaged” in the literal sense—pre-fabricated, steel-constructed units shipped ready to install. S&L is particularly dominant in the lift station market, but their treatment plant division is equally robust, offering the TITAN MBR and the FAST® (Fixed Activated Sludge Treatment) systems.

Engineering & Process Analysis:
The FAST® system is an Integrated Fixed-Film Activated Sludge (IFAS) process. It utilizes submerged media to grow biomass, providing a robust process that is highly resistant to hydraulic washout. This is ideal for applications with extreme peaking factors, such as schools, RV parks, or resort communities. Because the biomass is attached to the media, the system maintains a high solids retention time (SRT) even during high flow events.

Equipment & Fabrication:
S&L builds primarily in carbon steel. Their factory fabrication quality is high, employing rigorous surface preparation and proprietary coating systems (Versapox®) designed to extend the life of the steel. However, engineers must account for shipping limitations. S&L plants are modular; large capacity plants are shipped in sections and bolted/welded together on site. The TITAN MBR integrates their process knowledge with flat-plate or hollow-fiber membranes, providing a Title 22 compliant effluent in a compact steel skid.

Application Fit:
S&L is often the “fastest” solution. For emergency replacements or developments needing immediate capacity, the factory-built nature of S&L allows for concurrent site work and plant fabrication. Their Model R wastewater treatment plants are concentric circular steel units that have been an industry standard for decades in rural applications.

Evoqua (now Xylem, but listed as Evoqua)

Evoqua Water Technologies (whose relevant legacy brands include Davco, Envirex, and Jet Tech) brings a massive portfolio to the packaged plant sector. The Davco product line is the most significant for this discussion. Davco is unique in its delivery method: they are essentially a field-erection construction company that manufactures the equipment. They specialize in large-diameter, field-erected circular steel treatment plants.

Engineering & Process Analysis:
The classic Davco design is a concentric circle plant. The inner ring typically serves as the clarifier, while the outer ring serves as the aeration basin (or vice versa depending on the model). This geometry is structurally efficient, handling hoop stresses better than rectangular tanks, which allows for larger volumes above ground. Evoqua incorporates various biological processes into these vessels, including the Orbal oxidation ditch technology and vertical loop reactors (VLR) for larger applications.

Equipment & Fabrication:
Evoqua’s field crews erect these plants on a concrete slab. This approach bridges the gap between a small factory-built skid and a large concrete civil works project. They can treat flows from 0.1 MGD up to 2.0 MGD or more in steel vessels. This is a significant advantage for projects with medium flow rates where concrete construction is too slow or expensive, but factory-skids are too small.

Lifecycle factors:
The crucial engineering consideration for Evoqua/Davco plants is the long-term maintenance of the steel. While initial coatings are excellent, re-coating a large field-erected tank 15-20 years later is a major capital expense that requires taking the plant offline. Engineers must design redundancy (dual trains) to allow for this inevitable maintenance.

Ovivo

Ovivo (inheriting the legacy of Eimco and other major brands) focuses heavily on high-technology process solutions. In the packaged plant market, they are a primary driver of Membrane Bioreactor (MBR) adoption. Their Ovivo MBR systems, often utilizing Kubota flat-plate membranes, are engineered for high-performance applications.

Engineering & Process Analysis:
Ovivo’s strength lies in the integration of the membrane system with the biological process. MBRs operate at much higher Mixed Liquor Suspended Solids (MLSS) concentrations (8,000 – 12,000 mg/L) compared to conventional plants (2,000 – 4,000 mg/L). This allows Ovivo to deliver the same treatment capacity in a tank volume that is 50-70% smaller. The flat-plate membrane design favored by Ovivo is generally considered more robust and easier to clean in place (CIP) than hollow fiber alternatives, though it may have a lower packing density.

Equipment & Fabrication:
Ovivo offers the microBLOX MBR system, a decentralized standalone solution. These are plug-and-play units designed for rapid deployment. Beyond MBRs, Ovivo creates packaged versions of the Carrousel® oxidation ditch, a highly efficient BNR process. The engineering behind the Carrousel involves surface aerators that impart propulsion to the mixed liquor, creating long channel velocities that allow for simultaneous nitrification and denitrification within the same loop.

Best-Fit Scenarios:
Ovivo is the engineer’s choice when effluent requirements are stringent (e.g., water reuse for irrigation, discharge into sensitive waterways) or when space is at an absolute premium. The trade-off is higher energy consumption (due to scouring air requirements for membranes) and a higher level of operator sophistication required to manage transmembrane pressure and chemical cleaning cycles.

5. Application Fit Guidance

Choosing the right OEM depends heavily on the specific application vertical. Engineers should categorize their project needs to narrow the field.

Small Municipal & Housing Developments (Flows < 0.1 MGD)

For these applications, the priority is often “install and forget” (though this is never truly possible) and low visual impact.
Recommendation: Smith & Loveless and Aqua-Aerobic Systems excel here. Smith & Loveless’ FAST system is particularly good for unmanned stations due to its self-regulating nature. Aqua-Aerobic’s batch systems work well where flow is highly variable, such as in bedroom communities.

Mid-Sized Municipal (0.1 – 2.0 MGD)

This is the “danger zone” where package plants compete with custom concrete plants.
Recommendation: Evoqua (Davco) and Aero-Mod are strong contenders. Evoqua’s field-erected steel is cost-competitive against concrete and faster to build. Aero-Mod’s concrete process equipment packages offer the longevity of civil works with the pre-engineered benefits of a package plant.

Water Reuse & Strict Nutrient Limits

If the permit requires “Title 22” quality water (turbidity < 0.2 NTU) or very low Total Phosphorus.
Recommendation: Ovivo and Aqua-Aerobic Systems. Ovivo’s MBR expertise guarantees the effluent quality required for reuse. Aqua-Aerobic’s cloth media filters (AquaDisk®) can be integrated into their package plants to achieve tertiary quality effluent without membranes.

Industrial Retrofits

Industrial wastewater often varies in temperature, pH, and nutrient balance.
Recommendation: Smith & Loveless and Ovivo. S&L’s industrial division has deep experience in customizing steel tanks for specific industrial footprints. Ovivo’s process engineering depth helps in calculating the complex kinetics required for non-sewage waste streams.

6. Engineer & Operator Considerations

Beyond the catalog specifications, the long-term success of a packaged treatment plant relies on practical design considerations.

Installation and Commissioning

Engineers must clearly define the scope of installation. “FOB Factory” means the contractor is responsible for offloading and setting. For large steel tanks, crane logistics are non-trivial. Field-erected options (like Evoqua) shift this risk to the OEM. Commissioning periods for biological systems can take weeks to establish a healthy biomass; the specification must require OEM process support during this seeding phase, not just mechanical startup.

Maintenance Access and Safety

Package plants are notoriously cramped. Engineers must review 3D models to ensure there is clearance to pull pumps, access blowers, and clean diffusers.
• Walkways: Specifying galvanized or stainless steel grating with proper handrails is mandatory.
• Blower Noise: Package plants often place blowers on the same skid. Sound attenuation enclosures are critical if the plant is near residential areas.
• Spare Parts: Proprietary parts (like specific membrane cassettes or decanter actuators) can lead to long lead times. Verify the OEM’s domestic inventory of critical spares.

Long-Term Reliability Risks

The biggest risk to a steel package plant is corrosion. An interior coating failure after 7 years is a catastrophic financial event for a small utility. Engineers should consider specifying:
• Cathodic protection (sacrificial anodes) for steel tanks.
• Stainless steel for wetted parts prone to corrosion (weirs, air piping).
• 3rd party holiday testing (spark testing) of coatings before the tank is filled.

7. Conclusion

The selection of a Packaged Treatment Plant OEM is a fundamental decision that dictates the operational viability of a decentralized wastewater system for 20 to 30 years. The market is divided between factory-built steel modularity (Smith & Loveless), advanced batch technology (Aqua-Aerobic Systems), large-scale field erection (Evoqua), operator-centric process design (Aero-Mod), and high-tech membrane integration (Ovivo).

Engineers must look beyond the initial bid price and evaluate the Cost of Compliance. A cheaper plant that cannot reliably meet nutrient limits or requires excessive operator overtime will cost the municipality significantly more over its lifecycle. By matching the hydraulic and biological constraints of the specific site with the unique engineering strengths of these top OEMs, engineers can deliver sustainable, compliant, and robust treatment infrastructure.