This comprehensive guide helps engineers, plant owners, and decision-makers navigate the complexities of DAF selection, ensuring they invest in a high-performing, durable, and cost-effective solution tailored to their specific needs. The Ultimate DAF System Buyer's Guide Critical Considerations For Choosing A High-Performing DAF System This comprehensive guide helps engineers, plant owners, and decision-makers navigate the complexities of DAF selection, ensuring they invest in a high-performing, durable, and cost-effective solution tailored to their specific needs. Key Takeaways: Critical design considerations for selecting the best DAF system Insights on aeration, dissolved air distribution, and sludge handling Material selection for durability and long-term performance Automation and control features to enhance efficiency Application-specific engineering for optimal wastewater treatment Make an informed decision and ensure your wastewater treatment system operates at peak performance. To download the guide, please provide the following: First name* Last name* Email* Company name* Download the Guide

FRC Systems provides wastewater treatment solutions, including Dissolved Air Flotation DAF, Sludge Dewatering, Chemical Dosing and Biological wastewater treatment systems. Sludge Dewatering Technology for Smarter Water Management Multi-Disk Volute Press Check it out Featured Products PCL & PCCS Series High-Rate DAF The PCL & PCCS Series high-rate Dissolved Air Flotation (DAF) design provides an efficient and cost-effective solution for removing pollutants from your wastewater. Learn More Sludge Dewatering Multi-Disk Volute Press Managing sludge can be challenging, but not with the Multi-Disk Volute Press from FRC Systems. Learn More Rentals & Pilots FRC rental systems and stand-alone equipment are installed in a “plug-and-play” configuration for ease of installation and start-up. Learn More See All Products The FRC Difference With nearly 50 years of industry experience and thousands of Dissolved Air Flotation (DAF) installations across the globe, FRC Systems is dedicated to leveraging our extensive application expertise in industrial wastewater treatment solutions to benefit you. We’re committed to offering ongoing support and innovative wastewater solutions for the future. About FRC Systems Meet Our Team Almost 50 Years of Industrial Wastewater Treatment Solutions Thousands of Worldwide Installations Application Experience and Endless Knowledge Client Focused. Solutions Based. Results Guaranteed. FRC Systems transformed our wastewater treatment process. Their expertise and innovative solutions have significantly improved our plant’s efficiency. We’re grateful for their ongoing support and highly recommend their services. Chief Product Officer Food & Beverage Company The installation of FRC Systems’ wastewater treatment solution was seamless and professional. Their team’s knowledge and dedication have made a noticeable difference in our operations. We couldn’t be happier with the results. Facilities Design Manager Health & Beauty Company Choosing FRC Systems for our wastewater treatment needs was a game-changer. Their system is reliable, and their customer service is exceptional. We’ve seen a marked improvement in our environmental compliance and operational costs. Plant Operations Director Oil & Gas Company Why Choose FRC Systems? Application Experience & Know-How Our design and engineering teams are led by highly regarded specialists in the industrial wastewater treatment field with an average of 25+ years of experience in the industry. Client Focused All of our systems are engineered for the specific challenge at hand. We focus on client objectives from the beginning of the design process through installation and start-up. Our goal is not just to make a system that works, but one that works for you. Personal Attention Each wastewater project receives one-on-one attention throughout the entire process from a dedicated project manager and a team of our experienced engineers. Quality You Can Trust The FRC design process includes professional submittals with detailed 3D drawings for approval before manufacturing. Our wastewater treatment products are constructed using laser-cut, stainless-steel manufacturing and assembly to ensure quality control. FAQ What industries does FRC Systems serve? FRC Systems provides wastewater treatment solutions across multiple industries, including: Oil & Gas – Handling produced water, frac flowback, and oily wastewater. Poultry Processing – Managing high-fat and protein-laden wastewater. Meat & Seafood Processing – Treating organic-rich effluents with high BOD and TSS. Municipal Water Treatment – Supporting wastewater clarification and sludge removal. General Manufacturing – Custom solutions for diverse industrial wastewater challenges. What technologies does FRC Systems offer? Our solutions include: Dissolved Air Flotation (DAF) Systems – For efficient solids and oil removal. Chemical Treatment Systems – Coagulation, flocculation, and pH adjustment. Sludge Dewatering Solutions – Reducing waste volume and disposal costs. Filtration & Screening – For pre-treatment and solid separation. What is Dissolved Air Flotation (DAF)? Dissolved Air Flotation (DAF) is a wastewater treatment process that is highly effective in the removal of suspended solids (TSS), fats/oils & grease (FOG), biological oxygen demand (BOD) and other contaminants from water. It is particularly effective in situations where conventional sedimentation methods are less efficient. Here’s a breakdown of what DAF is and its primary uses: Air Dissolution: In DAF, air is dissolved into water under pressure in a specialized tank, saturation tube or pump. Pressure Release: When this pressurized water is injected into the flotation vessel, the pressure drops which releases the dissolved air as tiny microbubbles. Flotation Mechanism: These microbubbles attach to suspended particles and contaminants, causing them to rise to the surface. Skimming: The accumulated material (sludge or float) at the surface is skimmed off, while the clarified water is collected from below. What Are Some Uses of DAF? Dissolved Air Flotation, or DAF, is used in a variety of applications, including: Industrial Water Treatment: In industries such as food and beverage, oil and gas, and pulp and paper, to treat process water and wastewater. Municipal Wastewater Treatment: To remove solids, algae, phosphorus and other contaminants before further treatment or discharge. Sludge Thickening: DAF is used thicken biological sludge, reducing the overall sludge volume reducing transportation, handling and disposal costs. Drinking Water Purification: To remove algae, particulates, and other contaminants from source water. Pre-treatment: As a pre-treatment step for more advanced treatment processes, enhancing overall efficiency. Stormwater Management: To treat runoff and reduce pollutants before discharge. Does FRC Provide Rentals or Pilots? With the largest Dissolved Air Flotation (DAF) rental fleet in the US and equipment ranging from 10–3,000 gpm, we can tailor a solution to your needs. All FRC rental equipment is available for short-term and long-term rental agreements as well as pilot testing and long-term lease agreements. FRC rental systems and stand-alone equipment are installed in a “plug-and-play” configuration for ease of installation and start-up. Once in place on-site, the unit can be operational within a matter of hours. What is a Flocculator? A Flocculator from FRC Systems is designed to provide the necessary mixing action and retention time to chemically treat wastewater. Here’s how it works: Coagulation: Coagulants are added to the wastewater to break emulsions and form micro-flocs. Flocculation: Flocculants are then added to agglomerate these micro-flocs into larger, more robust macro-flocs. Mixing: Mixing: The flocculator ensures proper mixing energy required by the chemicals and maintains the integrity of the flocs, which is crucial for effective separation in the subsequent Dissolved Air Flotation (DAF) process. FRC Systems offers both Plug-Flow Reactors (PFR) and Continuous-Stirred Tank Reactors (CSTR) as flocculators, each designed to optimize the chemical treatment process. What is the difference between the PCL, PCCS and PWL? The main differences between PWL, PCL, and PCCS Dissolved Air Flotation (DAF) systems from FRC Systems lie in their design and application: PWL (Open-Tank DAF System): Design: Open tank, low-built separators with side walls typically 8 to 10.5 feet tall. Application: Better suited for high solids loading rates. The skimmer assembly rotates against the hydraulic flow, shortening sludge skimming distance and eliminating solids carry-over. PCL (High-Rate DAF System): Design: Features corrugated plate packs that increase the effective separation area, allowing for a smaller footprint. Application: Ideal for high hydraulic loads with lower solids loading rates. The plate packs help maintain laminar flow and increase effective separation area which increases overall system performance. PCCS (High-Rate DAF System): Design: Similar to PCL, the PCCS features a high-rate design and corrugated plate packs. However, the PCCS is specifically designed to fit within a shipping container, making it easily transportable. Ideal for temporary or mobile wastewater treatment needs, such as remote locations or construction sites. Application: Efficient for removing Total Suspended Solids (TSS), Fats, Oils, and Grease (FOG), and other pollutants from wastewater. Each system is tailored to specific wastewater treatment needs, with PWL being more suitable for higher solids content and PCL/PCCS for higher hydraulic loads. If you have a specific application in mind, I can help you determine which system might be the best fit! Is FRC a part of Sulzer? In 2018, FRC Systems joined the Chemtech division of Sulzer, where our clients receive our expert team’s dedicated attention backed by Sulzer’s global resources.

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If you haven’t already, be sure to check out Part 1 & 2 before continuing here. 5. Dissolved Air Distribution: Why Methodology Matters The way whitewater is generated and distributed into the incoming wastewater stream has an impact on floc formation and flotation within the DAF vessel. Let’s compare two common approaches. Vertical Saturation Tank Configuration Some DAF manufacturers utilize a vertical saturation tank paired with a specialty whitewater pump and a diaphragm valve assembly to generate and inject whitewater. While this method can be effective, it has notable drawbacks: Excess Air Issues : The vertical saturation tank is designed to vent undissolved air from the top. However, some undissolved air escapes through the side-mounted discharge line, entering the flotation cell. This can cause large bubbles to enter the flotation cell, disrupting the sludge and immersing solids back into the water. Limited Coverage : Often these systems rely on a single dissolved air injection port into the wastewater stream immediately before it enters the DAF.  This single injection point can distribute whitewater unevenly, resulting in inconsistent bubble coverage.  Additionally, the large stream of white water injected at one single location can cause shear forces on the newly formed floc, breaking them apart typically requiring additional polymer. Slow Saturation : Start-up procedures often require time for whitewater to disperse across the DAF Cell. Manuals often recommend waiting 5-10 minutes before initiating treatment, delaying operational workflows. Angled Saturation Tube and Whitewater Manifold Configuration In contrast, systems using an angled air saturation tube and a whitewater distribution manifold offer several advantages: Complete Air Removal : Excess air escapes from the elevated end of the angled tube, ensuring only dissolved air enters the flotation cell. This eliminates large bubbles, maintaining stable sludge flotation. Even Distribution : Whitewater manifolds feature multiple injection ports strategically placed across the width and height of the DAF tank.  Additionally, some white water can be injected at the time of floc formation when the DAF is paired with a Pipe Flocculator Reactor. This design ensures uniform microbubble distribution throughout the wastewater, enhancing separation efficiency and preventing overloading in specific areas. Rapid Saturation : With multiple injection points, these systems saturate the tank in under 60 seconds, significantly reducing start-up times and improving overall productivity. Reduced Footprint and Complexity :  When properly configured the Angled Saturation Tube has an incredibly high air to water contact area relative to the size of the Saturation Tube.  This results in extremely high saturation efficiency in a small footprint.  Additionally, with no need for level sensors, automatic relief valves, proprietary aeration valves or other moving parts, complexity is kept to a minimum. Key Takeaway: Design Details Matter When evaluating DAF systems, take a close look at the dissolved air distribution design. Ask the manufacturer: How does the system manage excess air? What measures ensure even whitewater distribution? How long does it take to saturate the tank and begin treatment? Does the system rely on complex components? These details can make the difference between a smooth operation and one plagued by inefficiencies. 6. Application-Specific Design: A Tailored Approach Materials Selection Consider the example of a cattle processing plant, where wastewater is laden with abrasive, gritty solids. A typical DAF system with a cast iron recycle pump might initially seem cost-effective but would fail prematurely due to abrasive wear. A better choice would be a pump with a CD4MCu casing, offering higher hardness and resistance to abrasion. Thoughtful materials selection prevents costly downtime and replacement expenses.  Understanding the application and tailoring the equipment to that application leads to a reliable, trouble free system. Process Engineering The application also dictates critical engineering parameters, such as: Hydraulic Surface Loading Rate : The rate at which wastewater flows through the DAF system’s effective separation area. Solids Loading Rate : The rate at which the DAFs free separation area is loaded with solids. Air-to-Solids Ratio : The ratio of dissolved air relative the solids being removed by mass. For instance, primary poultry solids separate more easily than biomass solids from an activated sludge system. Using the same design parameters for both would result in an oversized poultry DAF and an undersized biomass separator—wasting resources in one case and failing to meet performance requirements in the other. Questions to Ask When selecting a DAF system, don’t hesitate to ask: Why was this configuration chosen for my application? What material upgrades are available to address specific challenges? Explain the calculations behind system sizing and performance metrics? A manufacturer’s ability to provide clear, application-specific justifications reflects their expertise and ensures you receive a system optimized for your needs.

During the project development process, you will eventually narrow down a list of potential dissolved air flotation (DAF) system manufacturers. At this stage, the critical task is to determine which manufacturer and system best meet your specific needs. How Should You Choose? Whether you are an engineer specifying equipment for a client, a plant owner addressing wastewater treatment challenges, or someone seeking a deeper understanding of wastewater process equipment, this guide aims to provide a comprehensive understanding of key DAF system design considerations. By exploring mechanical and process design elements in this series, you will gain valuable insights to evaluate DAF systems effectively. This knowledge will enable you to identify superior designs and, most importantly, make an informed purchasing decision. Given the significant investment, selecting the right DAF system is essential. 1. Aeration System: The heart of the DAF unit. The aeration systems are the central component of a DAF, representing one of the largest capital and maintenance expenses. Therefore, understanding its design and functionality is crucial. Below is a breakdown of common pump types used in DAF aeration systems and their respective advantages and limitations. Multistage Impeller Pumps These pumps are often referred to as "whitewater pumps".  They draw atmospheric air (or compressed air) into the pump, where impellers mix/shear the air with water to create micron-sized bubbles that dissolve into the solution. While effective in generating whitewater, multistage impeller pumps pose several challenges in wastewater environments: Low Solids Tolerance : These pumps are prone to failures when handling oily, stringy, or gritty materials, which are common in wastewater applications. Cavitation/Airlock : In general, these pumps are not designed to handle entrained air.  Air can collect at the eye of the impellers which can cause loss of flow (airlock) and binding.  Air being introduced to the pump for “white water” generation can cause cavitation leading to increased energy usage, increased noise/vibration, and in more extreme instances cause damage to seals, bearings and impellers. Dependency on Manufacturer-Specific Components : These pumps tend to be “special order” or made in low quantities. Typically, these pumps must be sourced directly from the manufacturer which can lead to high replacement cost and extended downtime due to limited availability or long lead times. Multistage impeller pumps can generate quality “white water”; however, they lack the robustness in a wastewater environment where solids, grit and oily materials are prevalent.  With the high associated maintenance costs and lower reliability, most DAF manufacturers have moved away from the Multistage Impeller Pump.   Regenerative Turbine Pumps Regenerative turbine pumps are another type of pump often marketed as "whitewater pumps". These pumps are often characterized as providing high discharge pressures associated with positive displacement pumps with the versatility of a centrifugal pump.  They utilize a turbine-like impeller with radially oriented blades/vanes to draw in atmospheric or compressed air and mix with water to create microbubbles.  When choosing a Regenerative Turbine pump for a DAF application it is important to consider: High Pressure Capability : These pumps can generate high pressures and low flows in a compact design.  They can operate at discharge pressures of 90-120 psi in DAF applications while being resistant to cavitation and other ill effects of air entrained fluids. Clean Liquid Requirement : Due to tight internal clearances, these pumps typically require liquids with minimal abrasives or solid content, limiting their suitability for wastewater treatment. Limited Parts Availability : Popular models, such as those manufactured by Nikuni, often have very small supplier networks, leading to limited options in accessing quick replacement parts. Several manufactures utilize regenerative turbine pumps for “whitewater generation” on their DAF units, and their compact footprint make them a popular choice for upgrades of older Multistage technology.   Tight tolerances and poor solids handling make them less suitable for certain wastewater environments and care should be taken to ensure proper application. End-Suction Centrifugal Pumps End-Suction Centrifugal pump are produced by many pump manufacturers and are available in a variety of materials and configurations that can be adapted to a wide variety of applications.  Due to the large variety in available pumps, there is a high degree of versatility across various industries, including food processing, oil refining, and chemical manufacturing.  As with any pump selection, application is important.  Here are some important considerations when evaluating a system using an end suction centrifugal pump. Simplified Whitewater Generation : In most DAFs that use an end-suction centrifugal pump for “whitewater” generation, the pump is utilized only for the pressurization of the recycle stream.  The air and water are mixed in a separate vessel or saturation tube, meaning the pump is only doing what it was design for (pumping).  This ensures that the pump can be selected for high efficiency and reliability.  In some designs, manufacturers will use the pump in a similar manner to the Multistage pump where atmospheric air (or compressed air) is injected at the pump suction and the pump is used to dissolve the air.  When the pump is utilized in this manner, it is prone to the same Cavitation/Airlock issues as the Multistage Pump. Adaptability : These pumps can be selected based on the application to handle a wide variety of liquids (with or without solids) and can be fitted with various materials and alloys for corrosive environments. Manufacturer Choice : Unlike specialized whitewater pumps, the end-suction centrifugal pump is typically not mixing the air in water.  This allows more choice in manufacture and style of pump.  Some DAF providers can work with the end user to select a pump that aligns with their preferred manufacturer/plant standard providing improved access to parts and service.    By assigning the task of whitewater generation to a static tube or vessel, end-suction centrifugal pumps focus solely on pressurization, enhancing reliability and efficiency. When evaluating DAF systems, the aeration system reflects the manufacturer's design philosophy. Prospective buyers should inquire about the reasoning behind the selected pump type and its suitability for their specific wastewater treatment needs. 2. Controls and Automation: Enhancing Operational Simplicity The operational efficiency of a DAF system often hinges on its control and automation features. A well-designed system should be intuitive and user-friendly, akin to the seamless functionality of modern smartphones. Unfortunately, some DAF systems rely on overly complex operational procedures and have limited automation to reduce costs.  This typically leads to increased labor, frustration, and hidden expenses. Often these systems require frequent operator intervention and manual procedures which take more time and require more knowledge from the operator: Start/Stopping the system based on incoming flow. Make regular adjustments to the DAF aeration system to achieve “whitewater” generation. Manually adjust chemical dosing rates based on changing flows and/or pH. Check the system for faults and evaluate performance based on visual inspection. In contrast, a well-automated system streamlines operations significantly by: Automatically starting and stopping the treatment system as determined by incoming flow and tank levels. Automating the aeration features such as low-pressure detection, system warm-up and off-cycle air purging. Automatically adjust chemical dosing rates based on flow rate to the system and pH. Report and alarm system faults and provide warnings for reduced system performance. Trend and store data for system flows, tank levels, pH turbidity, chemical consumption, and alarms. When considering a DAF system, request details its operating procedure and automation. This will provide insights into its usability and the time/labor necessary to operate it.  A system with intuitive controls not only saves time but also reduces operational errors and long-term costs.

If you’re relying on coagulants to adjust pH, it’s time to rethink your approach. Coagulants are specifically designed to aid in solids coagulation, not to serve as pH adjusters. The distinction is critical, yet many wastewater treatment facilities inadvertently misuse coagulants in this way. The question is simple: why use iron or aluminum salts for pH adjustment when acids (like sulfuric acid) or bases (such as sodium hydroxide) are specifically designed for this purpose? By understanding the role of coagulants and their proper application, facilities can avoid unnecessary costs, inefficiencies, and complications. The True Purpose of Coagulants The primary function of coagulants is to coagulate solids in wastewater, not to adjust pH levels. This fundamental concept is sometimes overlooked by wastewater operators and environmental engineers. Coagulants, such as aluminum- and ferric-based compounds, generally work by neutralizing the electrical charges to destabilize emulsions enabling them to form together into a floc. These flocs can then be separated from the water more easily. While many coagulants do have an acidic nature and can reduce pH as a secondary effect, relying on them for pH adjustment is inefficient and problematic. Misuse of Coagulants This issue arises when facilities attempt to lower pH levels using coagulants instead of acids. For example: pH Neutralization Before Treatment : Aluminum- and ferric-based coagulants operate most effectively within a specific pH range (alum: 5.5–7.5; ferric: 5.0–8.5). When wastewater has a higher pH, the correct approach is to use acids like sulfuric or hydrochloric acid to bring the pH into the optimal range. However, some operators incorrectly add coagulants in large quantities to achieve this adjustment, which leads to several unintended consequences. Negative Impacts of Misusing Coagulants Under/Overdosing When pH is used to determine the amount of coagulant being dosed rather than rates that have been determined through jar testing there is the obvious potential to underdose or overdose.  The effects of underdosing are self-evident in that adding too little may not achieve destabilization of the emulsion and result in poor performance.   Overdosing, however, can also be a problem as it can cause a reversal in charge (overcharge) which can return the colloidal particles back to an emulsified state. High Costs Coagulants are significantly more expensive than acids or bases. Using coagulants for pH adjustment results in unnecessary chemical expenses, as large volumes are required to achieve the same effect that a smaller quantity of sulfuric acid could accomplish. Increased Sludge Volume Coagulants are metal-based, which means they contribute to the volume of sludge generated during wastewater treatment. Excessive use of coagulants leads to higher sludge production, increasing the costs and labor associated with its storage, dewatering, and disposal. Elevated COD Levels When coagulants are added in excess and there are insufficient solids for them to bind with, the unreacted metals dissolve into the water. This can increase chemical oxygen demand (COD), potentially disrupting downstream biological treatment processes. Best Practices for pH Adjustment The proper way to adjust pH in wastewater is to use the appropriate chemical reagent: Use acid (such as sulfuric acid) to lower pH. Use base (such as sodium hydroxide) to raise pH. Once pH is within the desired range, apply coagulants to achieve the necessary water clarity. Coagulant dosing should always be determined based on the clarity of the treated water, not to manipulate pH. Pro Tip: Perform a jar test  to determine the optimal coagulant dosage. When the treated water appears clear and solids are clumped into stable flocs, the coagulant dosage is correctly calibrated. A Smarter Approach By minimizing coagulant usage and applying it solely for its intended purpose, facilities can significantly reduce costs, lower sludge production, and maintain a more stable wastewater treatment process. If your facility struggles with pH adjustment and coagulant misuse, FRC offers systems that automate pH balancing with the correct chemicals, ensuring an efficient and cost-effective treatment process. Contact us to learn more about designing a solution tailored to your needs.