Fractionation of a secondary effluent with membrane separation

The purpose of this study is to investigate, through fractionation experiments, the efficiency with which secondary effluents can be treated using UF and MF membranes alone or coupled with coagulation and/or adsorption. The results obtained prove that there are two mains fractions in a secondary effluent: colloids and infra-colloids retained by an MF membrane (0.1 micron pore size) and solutes (which cross a membrane of 10 000 Dalton cut-off). Adsorption is mainly efficient for removing the solutes, whereas coagulation allows MF membranes to be as efficient as UF membranes while providing a higher and better controlled permeate flux.

Fig. 3 shows the variation of the permeate flux (at given trans-membrane pressure) for the different Industrial reuse of secondary treated wastewater will be made easier by membrane filtration. Perm eate flux (l/h m 2 ) UF F eCl3 +UF PAC+UF FeCl3+PAC+UF By fractionation of the water it is possible to make a choice of the MWCO depending on the quality required. However these fractionation tests must include the addition of coagulants and or adsorbents. Very good efficiency of residual COD removal and improvement in permeate flux may be obtained by coupling flocculation and MF. This hybrid membrane process might become the best solution for direct reuse of waste water or as a pre-treatment before a second step of RO.