Evaluation and optimization of reverse osmosis pretreatment technology using the modified intermediate blocking model

Membrane fouling is the unavoidable obstruction that occurs during reverse osmosis (RO), the use of pretreatment technology is highly effective for mitigating membrane fouling. In this study, the modified intermediate blocking model was applied to fit the data from literature about RO pretreatment, getting good fitting performance, over 86% of the determination coefficient (R2) exceeding 0.90. The working law of RO pretreatment on model parameters (final permeate flux (Jpss) and fouling velocity (k)) was systematically studied. The result showed that pretreatment works by three pathways: enhancing Jpss and reducing k, reducing both k and Jpss, and increasing both k and Jpss; it exerts more of an effect by improving k rather than Jpss. Furthermore, ultrafiltration exhibits a 10% higher effect on Jpss compared to ozonation while its effect on k is about 20% better than that of ozonation. Additionally, ultrafiltration demonstrates greater stability than ozonation. We further analyzed and found that the improvement in Jpss or k does mitigate membrane fouling, however, it does not necessarily produce more volume of clean water than without pretreatment. With the aim of obtaining more volume of permeate water, a new model, the Normalized Total Permeate Water Volume (VN) model is proposed, which enables pretreatment efficiency comparable and has been applied to optimize the application of pretreatment, achieving great application results.