Dual Scales Cause Frequent Cleans and Membrane Replacement
Membrane scaling triggered an on site visit by Avista. Review of operations indicated that membrane cleaning occurred every 2 weeks. An updated water analysis revealed that the well water quality had changed with a marked increase in sulfate.
BACKGROUND
Rapid reverse osmosis (RO) membrane scaling from silica and sulfate. Well feedwater was high in silica, sulfate, and calcium.
SYSTEM DESCRIPTION
System Information: Array 3:2:1
Pretreatment: 5 micron cartridge filters
Feedwater: Well water
Application: Resort
ACTION/APPROACH
Membrane scaling triggered an on site visit by Avista. Elements were removed for visual inspection, and heavy scaling was observed. Review of operations indicated that membrane cleaning occurred every 2 weeks. An updated water analysis revealed that the well water quality had changed with a marked increase in sulfate. A membrane autopsy identified dual scales, silica and calcium sulfate (see CEI).
To temporarily control the high silica and sulfate in the water, two antiscalants were injected at two dose rates; one to inhibit silica and one to inhibit sulfate scale. Concurrently, the lab developed Vitec 7400, a single inhibitor to effectively control both silica and sulfate scale with one dosage rate (see Avista™ Advisor™Ci projection).
Vitec 7400 has provided consistent performance for over one year. Cleaning frequency decreased from twice monthly to only one annual maintenance clean.
Avista trained on-site personnel to collect membrane performance data and monitor the system performance during the Vitec 7400 run period. Ongoing data collection and twice-yearly site visits by Avista ensure the RO continues to run at optimal levels.
