Page 18 - Opportunities in the Treatment of Water and Other Wast Streams

membranes, by definition, have a very low salt transport rate, and will reject as much 99.5 percent of all dissolved ions. Both types of membrane act on charged ions or molecules. Uncharged molecules will pass through the membrane, depending on the size. Some molecules may be too large to pass through the membrane and are retained in the concentrate.
Benefits:
• Produces high quality water for reuse • Modular and mobile systems • Consistent constituent removal
Limitations:
• High energy demand • Susceptible to scaling and biofouling • Require chemicals for operation and cleaning
Both processes are harmed by particulates, biological material, and high concentrations of slightly soluable salts, so pretreatment is necessary to provide an acceptable feed water.
Forward Osmosis
Application:
Why: Reduce volume of produced water for injection or disposal. May be energetically 18