Influence of pH, multivalent counter ions, and membrane fouling on phosphate retention during ceramic nanofiltration

Ceramic nanofiltration is an emerging technology for the recovery of water and nutrients (including phosphate) from municipal sewage which becomes more imperative worldwide. In order to use ceramic nanofiltration for phosphate recovery from municipal sewage, more knowledge is needed. This is the first paper reporting the phosphate retention of ceramic nanofiltration membranes. Furthermore, the influence of pH, multivalent counter ions, and membrane fouling on phosphate retention is reported in this paper. Various experiments were executed to analyse the phosphate retention and zeta potential under varying conditions. During filtration of a salt solution including phosphate, the phosphate retention increased, from 76% to 99%, with a change in pH from 5 to 9. Furthermore, magnesium ions and organic fouling had a large influence on the phosphate retention: at pH 7 the phosphate retention dropped from 92% to 42-43% due to the presence of either magnesium ions or organic fouling.