Sandia National Laboratories (SNL) is conducting a study on the use of nanofiltration (NF) treatment options to enable use of non-traditional water sources as an alternative to freshwater make-up for thermoelectric power plants.

The project includes a technical and economic evaluation of NF for two types of water that contain moderate to high levels of total dissolved solids (TDS): (1) cooling tower recirculating water and (2) produced waters from oil & gas extraction operations. Reverse osmosis (RO) is the most mature and commonly considered option for high TDS water treatment. However, RO is generally considered to be too expensive to make treatment of produced waters for power plant use a feasible application. Therefore, SNL is investigating the use of NF, which could be a more cost effective treatment option than RO. Similar to RO, NF is a membrane-based process. Although NF is not as effective as RO for the removal of TDS (typical salt rejection is ~85 percent, compared to >95 percent for RO), its performance should be sufficient for typical power plant applications. In addition to its lower capital cost, an NF system should have lower operating costs because it requires less pressure to achieve an equivalent flux of product water.