Flow rate testing was performed on MS19 and MS12 elements (217 and 219 elements, 26 mil-spacer) to establish a temperature correction curve for current HR(PA) membranes. The results obtained were evaluated against the existing Osmonics® correction curve and other manufacturers’ information. Salt passage characteristics and the effect of elevated temperature on membrane performance were also noted during the study.
1.- Good correlation with the theoretical temperature correction curve (see Discussion sections 5.1.1 and 5.1.2) in all ranges of temperature was observed, as well as with the current Osmo® curve in the high temperature range, and with FilmTec and Desal™ curves in the low temperature range (see Discussion section 5.1.3).
2.- The temperature correction curves for MS19 and MS12 elements are functionally identical (see Discussion section 5.4.3).
3.- Salt passage of the membrane elements is a function of temperature, correlated to research studies. In the low range of temperature, passage is constant. At higher temperature, it decreases as temperature increases (see Discussion section 5.3)
4.- Elevated temperature has a significant negative effect on the permeate flow rate (see Discussion section 5.2)
1.- The new temperature correction factors (Table #1) should be used to compensate for HR(PA) element and system performance changes with temperature. This table will be part-numbered and placed under document control through ECO 3022, which is currently routing; a general distribution of the new factors will be done once the ECO has passed.
2.- The old Osmonics temperature correction chart should continue to be used for CA and UF products.
3.- A study of CA membrane element performance under varying temperatures should be considered to confirm that the existing factors (old chart) apply accurately.
RO water was filtered by a UF element and adjusted with NaCl to 3800µS. The applied pressure was 225 psi. pH of the solution was kept within 6.5-7.5. Elements were held to 10% recovery. All elements had been flushed for more than 24 hours prior to test. Temperature of the solution was varied from 5°C (41°F) to 47°C (116°F). Performance was measured by conductivity and volumetric flow.
Temperature of the solution was controlled by adjusting the cooling water flow rate through a heat exchanger. Cooling water for low temperature testing was a mixture of about 15% of NaCl and ice.
Testing began at 24°C (75°F) and proceeded to 5°C (41°F). Temperature then was raised to 47°C (116°F) and finally returned to 25°C (77°F). Data were collected at every -17° to -12°C (2 to10°F) once the operating parameters had been stabilized.