Pilot test dissolved air flotation with written pass-fail numbers, worst-day samples and sludge checks, and keep the vendor out of the room while you set the criteria. A rented skid or small pilot unit costs far less than a tank that fails on the hardest day. Decide what passing means before the unit arrives.

Write Pass-Fail Numbers Before the Pilot Arrives

Set the targets first: effluent turbidity or suspended solids, oil and grease, COD or phosphorus, and the float solids you can dispose of. Write them in a one-page test plan that the vendor and your operators both sign. A pilot without pass-fail numbers becomes a sales demo.

I’d also write down the fail case, such as bubbles in the effluent, so everyone knows when the test has found a limit rather than a flaw.

Test the Worst Day, Not the Average

A guide on DAF design says operators often set recycle ratio and saturator pressure by vendor specification, and it advises tuning them to measured solids and floc size with jar tests and short pilots. A pilot on a calm Tuesday tunes nothing. Include a cleaning shift, a changeover and the heaviest production day.

Pilots at Newport News and Fairfield pushed hydraulic loadings from 17 to 44 meters per hour, according to the research summary, which shows how a good pilot hunts for the failure point.

Hire a Skid Unit for Short Trials

MSE hires skid-mounted DAF units with capacity up to 30 m³/h for short or long periods, with a containerized dosing unit that handles flow-proportional pH, coagulant and polymer. A 30 m³/h unit sits in the same size class as the RDAF-030 model on Wuxi Yosun’s DAF table.

Hire costs and delivery logistics belong in the plan. Ask any vendor, including Yosun, whether a trial unit is available for your flow range.

Vary One Lever at a Time

A water-treatment reference lists solids loading, hydraulic loading, recycle ratio, air-to-solids ratio and polymer type and dose as the parameters a pilot should test. Change one, hold the others, and record at least a full residence time before reading the result.

I’d order the tests by cost of change, starting with polymer dose and ending with pressure.

Pilot Dissolved Air Flotation With Bubble Checks

A design article suggests including bubble imaging or simple rise-time tests during commissioning, alongside jar tests. Those checks tell you whether poor results come from the air or from the floc.

A study of oily wastewater built a pilot to treat 1.0 m³/h and compared synthetic emulsions with real wastewater, which is a useful template, since synthetic wastewater alone flatters the tank.

Keep the Sludge

A tertiary phosphorus trial at a UK works reported an average sludge concentration of 4.1 percent dry solids from its flotation pilot, alongside the effluent results. Collect float samples from every run, measure solids and moisture, and run a dewatering test on at least one.

I’d refuse a pilot report that lists effluent quality and says nothing about the sludge.

Sign the Test Plan, Then Order

Send the signed plan to two vendors, including Wuxi Yosun, whose models run from 2 to 200 m³/h, and compare their pilot results against the same pass-fail sheet. Choose the dissolved air flotation supplier whose numbers survive your worst day.

Frequently Asked Questions

Q: How long should a DAF pilot run?
A: Long enough to cover your worst day and a full chemistry cycle, with at least a full residence time between changes. Skimp on that and the data will mislead.

Q: Can I rent a DAF unit?
A: Yes. MSE hires skid units up to 30 m³/h with containerized dosing, and a water-treatment reference says most manufacturers rent pilot units.

Q: What should I test besides effluent quality?
A: Float solids and moisture, since disposal costs depend on them. A UK trial reported 4.1 percent dry solids.

Q: What counts as a failed pilot?
A: A miss against your signed pass-fail numbers, or bubbles leaving with the effluent at the design rate. Define both before the test starts.