Optimized design of wastewater stream treatment processes by membrane technologies

Wastewater treatment by membrane technologies is gaining more and more importance and the relevant market is increasing. This trend is mainly justified by novel and high-performance membrane materials, a wider number of successful applications by membrane technologies and the progressive reduction of the investment and operating costs. The main drawback of membrane technology is membrane fouling, that reduces the membrane performances along the time and leads to a premature substitution of the membrane modules. In the last years, a better understanding of the fouling phenomena has sensibly increased the confidence in this technology. This is especially true for wastewater treatment processes based on membranes. In this case low operating costs are mandatory, thus the membrane modules should not be frequently replaced. This work briefly covers the theory and measurement procedures of the critical, threshold and boundary flux, with the aim of process optimization and control design. The goal is to operate membranes modules by avoiding irreversible fouling for a long period of time (several years). The importance of specific pretreatment processes, such as flocculation and photocatalysis, adopted to reduce fouling phenomena will be also discussed. Moreover, the design of advanced control systems for batch membrane and some examples of wastewater treatment (olive mill wastewater and the effluents from the tannery industry) will be reported.