physical separation
Industrial Wastewater Oil Removal | Beta Pramesti Asia
Industrial wastewater oil removal for free and emulsified oil, selecting gravity separation, DAF, chemistry, polishing, and measurable sludge handling.
Short Answer
Industrial wastewater oil removal must distinguish free oil, dispersed or emulsified oil, oil attached to solids, and dissolved organic compounds. Gravity separation suits a layer or droplets that can rise; emulsions commonly need emulsion breaking and DAF; while the dissolved fraction requires treatability testing for further polishing.
PT Beta Pramesti Asia, through beta.co.id, designs oily-wastewater treatment programmes in Indonesia combining equalisation, gravity separation, coagulation-flocculation, dissolved air flotation (DAF), filtration or polishing, and sludge handling. Select the train from sample tests and a mass-load balance, not from one oil-and-grease result.
The U.S. EPA Industrial Wastewater Treatment Technology Database distinguishes oil/water separation for gross oil and solids from DAF, which floats solids and oil/grease with air bubbles. This distinction matters because one unit does not automatically treat every form of oil.
Which method matches the form of oil?
| Sample finding | First checks | Process path to test | Acceptance evidence |
|---|---|---|---|
| Oil layer or large droplets rise quickly | Settling test, density, temperature, peak flow, TSS, and emulsion stability | Skimming, gravity separator, or coalescing | Oil is collected and removed without carryover when flow changes |
| Stable cloudy water without clear separation | Emulsion test, surfactants/detergents, pH, temperature, oil and grease, and available zeta potential | Equalisation, emulsion breaking, coagulant, flocculant, then DAF | Supernatant and sludge meet targets across a dose range, not in one beaker only |
| Oil is attached to solids | TSS, particle size, sludge character, and process source | Screening/equalisation, coagulation-flocculation, DAF or sedimentation | TSS and oil/grease fall, the sludge blanket is stable, and sludge remains manageable |
| Organics remain high after physical separation | Dissolved/total COD, oil and grease, relevant TOC, biodegradability, and compound analysis | Source control plus biological, adsorption, oxidation, or membrane polishing tests | Results meet the target without transferring the load to unmanaged residue |
A practical oily-wastewater evaluation sequence
- Separate the sources. Record process drains, first flush, leaks, coolant, washing, and surfactant-bearing batches. Reducing contamination at source is usually more stable than enlarging downstream equipment.
- Collect representative samples. Compare normal, peak-load, and upset conditions. Record temperature because viscosity and oil separation can change.
- Calculate the mass load. Use concentration and flow to calculate kg/day; a unit selected from average concentration alone may fail during a hydraulic peak.
- Test separation in stages. Begin with gravity/coalescing for free oil, then jar testing and DAF for dispersed or emulsified fractions. Measure the sludge produced as well.
- Select polishing from the result. Do not place membranes or a biological process downstream until free oil, solids, and disruptive emulsions are controlled.
Data needed before requesting an oil-removal concept
Prepare the source and drainage diagram, average/peak flow, batch pattern, temperature, pH, TSS, oil and grease, available total and dissolved COD, oil/coolant/surfactant type, settling or jar-test results, effluent/reuse target, space constraints, and the route for recovered oil and sludge. For downstream handling, review grease traps and sludge treatment.
When the programme uses chemical dosing, select pump type, wetted materials, tank, dilution, interlocks, and calibration from the chemical and flow. See Watermart dosing pumps for injection hardware, then send the process data through the Beta Pramesti Asia contact page.
Frequently Asked Questions
Can a gravity separator remove emulsified oil?
A gravity separator is usually most effective for free oil that can rise because of density difference. Stable emulsions have small droplets or surfactants that inhibit separation, so emulsion breaking, coagulation-flocculation, or DAF should be tested.
When is DAF used for oily wastewater?
DAF is considered when oil or fine solids do not separate quickly enough by gravity and can be carried to the surface by microbubbles. Recycle ratio, pressure, chemistry, solids loading, skimming, and sludge handling should be tested as one system.
Does lower COD prove that oil has been removed?
No. COD covers many oxidisable materials and does not identify the physical form of oil. Use oil and grease, TSS, dissolved/total COD, inspection, and a residue balance to assess the treatment path.