Ultrafiltration (UF) is a filtration process where components of a liquid are separated based on the difference in their molecular sizes.
In the treatment of oily wastewater, UF membranes will retain oil and grease while allowing water to pass through. UF membranes are especially effective at separating emulsified oils not separable by settling, skimming, or coalescing from water. The UF membranes are in the shape of a tube, with the membrane itself being a thin film on the inside of the tube. The wastewater is pumped across the surface of the tube at a high rate of speed. The surface of the tube is scoured as the fluid passes, preventing the formation of a filter cake. Operating pressures are 20 to 70 psi. Typical operating temperature are 100 to 1300F.
The filter retains all of the oil and allows only water and other low molecular weight materials to pass through. A batch of water is processed by continually removing water from the oil/water mixture until the oil level is nearly 50% of the volume. The water passing through the ultrafiltration membrane is sent to sewer, to further processing, or to reuse, depending on the specific requirement. The materials retained by the UF membrane are concentrated to a pudding-like consistency, then further de-watered or reused, depending on the specific requirements.
When ultrafiltration membranes become too dirty to effectively process
any further wastewater, they are not thrown away and replaced like conventional
filters. Instead, the membranes are cleaned with a simple solution of
soap and water and returned into use. UF membranes last from six months
to six years, depending on the application, before requiring replacement.
UF membranes may be reused over and over again, providing a cost effective
means of waste treatment and/or material recycle.
Ultrafiltration Advantages
Consistent Permeate Quality
- Ultrafiltration is a closed system. No major hourly or daily variation in discharge of permeate. Variations in feed only result in productivity changes; no compromises in permeate quality.
Reproducible Performance
- Membrane systems are designed for long-term operation; predictable productivity every day. Long membrane life.
Low Maintenance/Low Cost
- Reduced manpower requirements. Competitive with chemical/physical treatment.
Ability to Recycle
- Reuse process water, mop water, coolants and cleaners
Ultrafiltration Benefits to Industry
- Greatly reduce waste disposal and hauling cost
- Automatic operation, requiring virtually no operator attention
- Low pressure operation for reduced energy costs
- System requires no chemicals; customer avoids storage and mixing of chemicals
- Minimal pretreatment required
- Long membrane life