Buy DAF equipment only after the supplier shows the sizing basis, chemical-treatment assumptions and acceptance test. Nominal flow alone does not describe peak loading, emulsion behavior, sludge volume or the treated-water quality the system must deliver.
Whether the quote calls it a DAF unit, a DAF plant, or a flotation system, the evaluation is the same — the questions below apply to any dissolved air flotation equipment sized for plastic washing-line effluent.
The five questions below turn wastewater data into a comparable RFQ. They also separate this buying guide from our DAF working-principle article and the commercial industrial DAF water treatment system page.
Updated: July 18, 2026
Quick DAF Buying Checklist
| Decision | Evidence to request | Warning sign |
|---|---|---|
| Influent design basis | Time-based flow and contaminant results | One grab sample or flow only |
| Treatment target | Numeric influent and effluent limits | “High removal” without conditions |
| Process chemistry | Jar or pilot test with dose range | Fixed chemical dose for every wastewater |
| Operating cost | Power, chemical and sludge assumptions | Purchase price presented as total cost |
| Supplier scope | Drawings, commissioning and acceptance plan | Unclear boundary between vendor and buyer |
1. What Wastewater Data Will the Design Use?
Start with a sampling plan that captures normal production, cleaning cycles and peak discharge. Averages can hide the hour that overloads the flotation cell. Record flow over time and pair the samples with the production event that created the wastewater.
- Hydraulics: average flow, peak flow, peak duration and daily operating hours.
- Water condition: pH, temperature and conductivity where it affects treatment.
- Target contaminants: TSS, free or emulsified oil and grease, and COD/BOD where required by the permit or reuse plan.
- Solids behavior: particle size, settling or floating tendency, density and expected sludge volume.
- Variability: product changes, detergent use, washdown events and shutdown/startup conditions.
The U.S. EPA treatment technology document identifies operating variables such as pressure, recycle ratio, detention time, air-to-solids ratio, loading rates and chemical aids. Your supplier should state which of these variables are fixed by design and which the operator can adjust.
2. What Treated-Water Result Must Be Guaranteed?
Translate “clean water” into numeric limits for each relevant parameter. State whether the water goes to sewer, direct discharge, biological treatment or plant reuse. A DAF may be one stage in a larger process; it should not be held responsible for dissolved contaminants that require another treatment method.
| Guarantee item | Write it into the RFQ |
|---|---|
| Influent envelope | Minimum and maximum flow, temperature, pH and contaminant load used for the guarantee |
| Effluent target | Concentration limit, not only removal percentage |
| Test conditions | Chemical products, dose range, recycle setting and steady-state period |
| Sampling | Location, frequency, composite or grab method, laboratory method and retest rule |
| Exceptions | Events outside the design envelope and the required operator response |
Ask for both concentration and removal. A high removal percentage can still miss a discharge limit when the incoming load rises.
3. How Was the DAF Sized?
A useful proposal shows the hydraulic and solids design loads, equalization assumption, recycle flow, air-dissolving arrangement and skimmer capacity. It should also show the duty point for pumps, not only motor nameplate power. If pretreatment includes screening, pH correction, coagulation or flocculation, place each item on the process flow and equipment list.
Questions for the sizing calculation
- Which peak flow and peak duration set the hydraulic design?
- What mass of solids, oil or floc reaches the flotation cell per hour?
- How much equalization volume is assumed, and what happens when it is full?
- Which recycle rate and pressure range are expected during normal operation?
- How are sludge blanket depth, skimmer speed and bottom solids controlled?
- What redundancy is included for pumps, dosing and critical instruments?
4. What Is the Total Installed and Operating Cost?
Compare quotations on the same boundary. One supplier may include chemical preparation, controls and commissioning while another prices only the flotation tank. Ask for a line-item scope and a one-year operating estimate based on your hours and tested dose.
| Cost group | Items to include |
|---|---|
| Installed equipment | DAF cell, pumps, saturator or air system, dosing, tanks, instruments, controls and access platforms |
| Site work | Foundations, piping, cabling, ventilation, drainage, lifting and tie-ins |
| Operation | Electricity, coagulant, flocculant, pH chemicals, wash water and operator time |
| Residuals | Sludge storage, dewatering, hauling and disposal |
| Lifecycle | Wear parts, preventive maintenance, calibration, remote support and critical spares |
5. What Will the Supplier Prove Before Handover?
Define the factory checks, site commissioning steps and performance test before issuing the purchase order. Training should cover startup, chemical preparation, normal control ranges, sludge removal, shutdown, cleaning and troubleshooting. Request a spare-parts list tied to lead times and a named support path.
Comparable DAF RFQ package
- Wastewater analysis and flow profile.
- Process flow diagram and vendor scope boundary.
- Equipment data sheets, materials of construction and utility list.
- Jar-test or pilot-test report with dose and result range.
- Layout, access, lifting and maintenance clearances.
- Control philosophy, alarms, interlocks and remote signals.
- Commissioning plan, operator training and acceptance criteria.
- Warranty, exclusions, response time and critical spare parts.
Related DAF Resources
Compare DAF with sedimentation and filtration, review the DAF equipment configuration, and use this checklist to request proposals against the same wastewater data.
Frequently Asked Questions
What data is required to size DAF equipment?
Provide average, peak and time-based flow; pH and temperature; TSS, oil and grease, COD or BOD where relevant; settleability; chemical test results; operating hours; and the required treated-water target.
Should a DAF unit be sized for average or peak flow?
The design must show how peak hydraulic flow and peak contaminant load are handled. Equalization may reduce short peaks, but the supplier should state the assumed equalization volume and operating controls.
Can a supplier guarantee a generic removal percentage?
A useful guarantee is tied to defined influent ranges, chemical conditions, flow, sampling methods and treated-water limits. A generic percentage without those conditions is difficult to verify.
What costs belong in a DAF comparison?
Include the unit, pumps, air system, chemical storage and dosing, controls, installation, commissioning, electricity, chemicals, sludge dewatering and disposal, labor, wear parts and planned maintenance.
When should wastewater be jar-tested or pilot-tested?
Test when water chemistry varies, emulsified oil or fine solids are difficult to separate, chemical demand is uncertain, or the performance guarantee depends on coagulation and flocculation.
