The prospects of water removal by hyperfiltration using thin film composite membranes

Abstract

A new thin film composite membrane named HR introduced by DDS is described. The properties of the membrane regarding pure water flux and salt rejection, capability of rejecting low molecular weight organic compounds, temperature and pH stability, and stability against different chemicals are described. For all the mentioned properties, the HR membrane has proved to be superior to CA membranes. The membrane is developed for water desalination, but the greatly improved properties increase the possibility of using hyperfiltration for water removal within a large number of fields. In order to benefit from the better properties of the HR membrane compared to CA membranes, which are normally used hyperfiltration membranes, the DDS plate-and-frame system has been improved. Experiments with hyperfiltration using the HR membranes at a temperature as high as 80°C have been carried out on thin juice from the beet sugar industry. A pilot plant working at 30 bar and 80°C for one month has shown promising results in spite of the, with regard to hyperfiltration, quite extreme operating conditions. Also, promising results have been obtained with the HR membranes working at 60 bar and 60°C on fermentation broth from yeast production. For these applications, the possibilities of using strong acid and strong alkaline cleaning agents have proved to be useful. Preliminary experiments on hyperfiltration of orange juice have indicated that the HR membranes have a greatly improved rejection of aroma carrying compounds, thus improving the possibilities to use hyperfiltration for orange juice concentration.