Mechanism of acid-base control

Abstract

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.