(613f) Results and Insight from a Seven-Month RO Membrane Study: Autopsy and Fouling Assessment

Reverse Osmosis (RO) technology has become a crucial purification technique, producing pure water via high-pressure membrane filtration. While RO technology is generally dependable, it encounters the issue of membrane fouling, where impurities deposit permanently on the membrane surface, leading to decreased purification effectiveness and a shortened membrane lifespan. To investigate RO membrane fouling and the effectiveness of anti-fouling agents such as antiscalants, a comprehensive seven-month pilot study was undertaken. Four RO pilot skids, each operating at a 20x scale, were utilized, including two commercial variants of anti-scale forming agents, an in-house ‘green’ carboxymethyl cellulose-based antiscalant, and a skid operating without any antifoulants.

From the pilot study, we observed a seasonal variation in terms of recovery performance. We report the seasonal variations in water chemistry and operational impacts, particularly evident during warmer months. Findings from the study revealed varied fouling behaviors induced by anti-scaling agents, with phosphate-assisted biofouling demonstrating synergistic effects. Moreover, fouling variations were also reported from the head to tail sections of the membrane module. A membrane autopsy was conducted, where the four used membranes were dissected to collect membrane samples and foulants. Various analytical techniques such as SEM-EDS, FTIR, and sessile drop tests were employed to analyze membrane surface changes, while foulants were analyzed using XRD, ICP-MS, HPC and TGA, revealing variations in deposition based on the type of antiscalants used. Additionally, foulants were analyzed for bioactivity using peddle growth tests, and gram-stain identification was performed to identify the class of growth. The autopsy was complemented with a cleaning study using three different cleaning solutions, providing guidance for future cleaning operations for similar fouling.

This comprehensive study provides insights into fouling patterns under different classes of antiscalants and offers operational recommendations for RO filtration processes in freshwater purification. It underscores the effectiveness of antiscalants in mitigating inorganic scales; however, synergistic biofoulant deposition is also reported.