Multi-stage filtration and softening module and reduced scaling operation

• Main Authors: Husain, Hidayat, Behmann, Henry, Côté, Pierre, Pottinger, Ian, Murphy, Ella
• Format: Patent
• Language: English
• Published: 09.03.2004

This invention relates to a multi-stage nanofiltration or reverse osmosis membrane module, to processes for using such a module to filter water or to remove hardness, to processes for cleaning or maintaining the permeability of such a module, and to a small-scale system particularly for use in private homes and small commercial buildings. A filtration module has at least one nanofiltration or reverse osmosis membrane. The module is used to filter water and, when optionally fitted with at least one membrane adapted to selectively reject hardness causing salts, is used to remove hardness. Methods of cleaning using acidic solutions or gaseous carbon dioxide are discussed. Cleaning methods include the steps of periodically stopping permeation, injecting an acidic solution or gaseous carbon dioxide into the feed/retentate side of the module, holding the acidic solution or gaseous carbon dioxide in the module for a selected time, and flushing the acidic solution or gaseous carbon dioxide from the feed/retentate side of the module after expiration of the selected time.