Treatment of waste water containing polysiloxanes using nanofiltration: Impact of the salt composition
Siloxanes are used in many industrial domains. In recent years, some countries have established aqueous discharge limits. In a perspective of sustainable development, industries are looking for new treatment processes. Nanofiltration seems to be promising option, given the expected separation capacity for molecules of the targeted size. This paper deals with a study of nanofiltration processes developed to treat waste water containing polysiloxanes. Filtrations were carried out with a synthetic effluent similar in composition to an industrial discharge, with a high salt concentration. Since some recent studies have pointed out that the presence of salt can change the performance of membrane separation processes, the present study paid particular attention to this factor. D4 (octamethyl-cyclotetrasiloxane) was chosen as the target compound in this study. The experimental results show indeed that the process efficiency changes according to the salinity and/or dilution. A decrease in total organic carbon (TOC) reduction and D4 retention is observed when diluting the effluent or increasing the salinity.