AWWA JAW60863

The continuous use of chlorine and chloramines can adversely affect reverse osmosis or nanofiltration membranes used in water treatment processes. However, no models were available to predict change in membrane performance over time. This work introduces a mass loading model to predict membrane water quality over time of operation. The model correlates solute mass transfer coefficients (MTCs) to initial solute MTCs, solute charge, feedwater temperature, monochloramine loading, and organic loading. In a 2,000-hour pilot study, the model was tested using a highly organic and brackish surface water. Four different thin-film-composite low-pressure reverse osmosis membranes were tested, and separate models were developed for all membranes. Results indicated that given reasonable assumptions of parameters, the models provided accurate predictions of membrane performance and replacement. This solute mass transfer model can be used to predict permeate water quality and sensitivity of permeate water quality to variations in temperature and organic and monocloramine mass loading. It should prove a valuable tool for water utilities by offering a systematic method of predicting performance that is applicable to all surface waters. Includes 26 references, tables, figures.