What is a DAF for oily water treatment?
The Oil Water and Produced Water Dissolved air flotation (DAF) is a water treatment process that clarifies wastewater by removing oils and suspended solids simultaneously. The removal is achieved by introducing ambient air and dissolving it in the recycled wastewater stream by shear pumps and then releasing the air at atmospheric pressure in a flotation tank while creating nano and micro bubbles.
The released air forms nano and micro bubbles which adhere to the oil and suspended matter causing the it to float to the surface of the water where it is then removed by a chain skimming device. Chemicals can be added to the feed water to improve oil and solids removal. Heavy solids are collected in the sludge hoppers and removed frequently by pumps or manual draining.
The unit contains two stages for oil removal.
Stage one and contains parallel plates lamella packing that multiply the surface area for the settling of solids and floating of oils. It works by minimizing the height required for the solids to drop and oils to raise and attach to other drops of oils.
The floating of oil is assisted by micro bubbles rising through the water.
The water then passes to the second oil removal stage through parallel perforated collector pipes. The collector pipe assists in balancing water flow through the lamella plates.
The collected water then passes through two stages of coalescing packing that helps capture escaped oil droplets and make it collide with each other and grow in size so it can be collected to the surface and skimmed by second stage chain skimmer.
The treated water then passes through baffle and collected by weirs. The weir help maintaining stable water level inside the DAF.
The DAF has the following advantages:
Small footprint and more rapid implementation
Mobilized package
Higher sludge solids content (4%TS vs. 1%TS) resulting in a much lower sludge volume
Ability to handle bulking solids that tend to float
More reliable effluent quality down to 10 ppm from 2% oil content.