Research on refurbishing of the used RO membrane through chemical cleaning and repairing with a new system

• System design of improved off-line chemical cleaning and repairing RO membranes
• The used RO membranes were polluted by groundwater contained SiO2 and some minerals.
• The system will consume fewer chemical reagents and produce less waste water.
• The membrane can be pre-cleaned with only water through back-flushing channel.
• Membrane's parameters can reflect cleaning effects and direct the next cleaning step.

A new system of chemical cleaning and repairing of the used reverse osmosis membranes (CCR-ROM) has been designed and used for researching. The results indicate that the average salt rejection of the cleaned membranes was increased from 67.5% (32.3%, 80.0%, 71.9%, 85.8%) to 90.6% (88.2%, 93.0%, 86.9%, 94.3%), the average water recovery of the cleaned membranes was decreased from 18.8% (12.6%, 32.4%, 11.4%, 18.6%) to 14.6% (13.8%, 15.8%, 13.8%, 15.0%), and the average difference pressure was decreased from 0.30 MPa (0.60 MPa, 0.17 MPa, 0.17 MPa, 0.25 MPa) to 0.15 MPa (0.12 MPa, 0.17 MPa, 0.13 MPa, 0.17 MPa). Furthermore, the treated RO membranes were tested in an industrial-line producing water system for three months with positive results. Compared with the traditional on-line chemical cleaning, the CCR-ROM method could prolong the period of water production of the RO membranes for about four times. In this new method, a single RO membrane consumes only 22.5 L of cleaning solution, only 37.5% of that used in the traditional on-line chemical cleaning. The advantages of the new system include re-utilization of the discarded RO membranes and significant reduction of dosage and waste of the cleaning solutions.