Strip free oil with a primary separator before vortex air flotation handles the rest. Induced flotation is a polishing step for oily water, with published inlet limits near 200 mg/L of free oil and under 100 mg/L of solids, and it works best on droplets that are not emulsified. Check your oil state before you check the price.
Reject Vortex Air Flotation Quotes That Skip Oil Concentration
A quote for oily wastewater that does not state the inlet oil concentration is a quote for a different stream. Veolia’s AutoFlot, an induced gas flotation separator, lists a maximum inlet of 200 mg/L free oil and under 100 mg/L total suspended solids, with 90 to 95 percent reduction of both, according to a trade-press product listing.
Those limits come from oilfield practice, not from Wuxi Yosun’s equipment. They show the order of magnitude that induced flotation designers expect, and I’d ask any vendor, including Yosun, for the equivalent numbers on its own units.
Put a Primary Separator Ahead
Veolia’s product page says induced gas flotation separators are typically installed after a primary step such as a corrugated plate interceptor that reduces free oil to 200 to 300 ppm. The same page says AutoFlot can reach oil and suspended solids under 10 ppm, depending on feed water conditions.
The pattern is clear. A primary separator takes the bulk of free oil, and flotation polishes what remains. A plant that sends raw oily sewage straight to a flotation tank asks it to do both jobs.
Expect Polishing and Not a Miracle
CECO’s Peerless impeller-type flotation units list removal of free oil-in-water to less than 15 ppm as a headline result. Both figures, 10 and 15 ppm, come from vendors working on free oil under good conditions. Neither promises the same result for emulsified oil.
I’d read those numbers as the best case for free oil with decent pretreatment, and I’d write acceptance limits for my own wastewater based on a pilot instead.
Break Emulsions Before the Aerator
CECO says that when oil is a very fine dispersed emulsion, dissolved air flotation with adequate chemical conditioning is the process that provides the solution, while induced flotation suits non-emulsified oil. Wuxi Yosun’s page says wastewater is dosed with PAC and PAM before the aeration zone.
That order fits the physics. Coagulant must break the emulsion and build floc before the air arrives, so the dose and mixing in the reaction tank carry the load that the impeller cannot.
Sort the Oil State First
A study of oily wastewater treatment by flotation separates oil into free oil, unstable emulsion and highly stable emulsion. It says free oil responds to gravity separators, unstable emulsions can be broken mechanically or chemically, and stable emulsions need sophisticated methods to meet legal limits.
Test your wastewater before you pick a machine. A sample left to stand for an hour or two will show how much oil separates on its own, and a jar test with coagulant shows how much more chemistry recovers.
Remove Free Oil Early to Save Chemistry
Ecologix, a flotation supplier, advises removing free-floating fats, oils and grease at the start of treatment, because it cuts coagulant and flocculant cost at the flotation stage. Coagulant that does not have to chase free droplets stays available for emulsified oil and solids.
For a vortex air flotation unit, that means the upstream oil trap is part of the process design, not an optional extra.
Read the Application Pages Critically
Wuxi Yosun lists petrochemical oily sewage first among its uses for the unit, and its oil and emulsion page and petroleum page discuss the applications. Ask for inlet and outlet oil data from a plant like yours, with the pretreatment train described.
A case study that reports only outlet oil proves little, because a low outlet number after a good oil trap says more about the trap than about the flotation unit.
Sort, Strip, Dose, Float
Take three samples across shifts, test the oil state and plan the line in order: primary oil separation, coagulation and flocculation, then vortex air flotation. Write the inlet limit into the specification so that nobody sends raw oily sewage to the tank, and ask for a pilot on your water before you order.
Frequently Asked Questions
Q: How much oil can an induced flotation unit take?
A: One induced-flotation product listing states a maximum inlet of 200 mg/L free oil and under 100 mg/L solids. Check the limits for any unit you buy.
Q: Do I need a separator before vortex air flotation?
A: Usually yes. Induced flotation units are typically installed after a primary step that brings free oil down to 200 to 300 ppm.
Q: Can induced flotation remove emulsified oil?
A: Poorly without chemistry. CECO says finely dispersed emulsions suit dissolved air flotation with chemical conditioning.
Q: What effluent oil can I expect?
A: Vendors cite under 10 to 15 ppm on free oil, but that is a best case. Pilot your wastewater.
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