Comparison of surface water treatment efficiency using integrated pressure-driven membrane processes and conventional treatment systems

Abstract

Pressure-driven membrane techniques are increasingly being applied to natural water treatment as an alternative to conventional physico-chemical processes. This makes it essential to compare the effectiveness of these two approaches, particularly under long-term operational conditions. In the preliminary phase of the study, short-term tests were conducted to select the most suitable membranes based on their separation and transport properties: two out of three microfiltration (MF) membranes, two out of three ultrafiltration (UF) membranes, and one out of two nanofiltration (NF) membranes were chosen for subsequent long-term tests. During these long-term evaluations, the efficiency of surface water treatment in integrated MF+NF and UF+NF systems was assessed and compared with the performance of a conventional treatment train comprising coagulation, sedimentation, filtration, and adsorption. The results indicate that integrated MF+NF and UF+NF systems achieve significantly higher treatment efficiency than conventional processes, with, for example, dissolved organic carbon (DOC) reduction of 93% in membrane systems compared with 50% using conventional methods. Membrane processes also enable highly effective removal of specific microorganisms, which is not achievable using traditional treatment methods. Additionally, integrated MF+NF and UF+NF systems reduce water salinity and achieve water softening, whereas conventional systems tend to increase salinity. An analysis of operational costs revealed that the UF+NF system is nearly 50% less expensive to operate than the MF+NF system. Nevertheless, both membrane-based systems remain several times more costly than conventional water treatment.