Abstract:
Coagulation/flocculation pre-treatment of feeds can successfully mitigate the
drawbacks ofmembranemicro- and ultra filtration processes: fouling and limited ability to
remove organic pollutants.Laboratory experiments conducted with a syntheticwastewater
(representing biologically treated secondary effluent) using 0.1 mm pore size hollow fiber
membrane showed that simple in-line flocculation pre-treatment with inorganic coagulants
dramatically reduced membrane fouling rates. The hybrid system also ensured
over 70% organic matter removal in terms of dissolved organic carbon (DOC). In the
experiments in in-line flocculation outperformed clarification pre-treatment at optimum
coagulant dosages. Differences in floc characteristics and elevated suspended solids concentrations
in the membrane tank may explain this finding, but the exact causes were not
investigated in this study. The beneficial effects of in-line flocculation pre-treatment to
MF/UF separation were also confirmed in the treatment of septic tank effluent in a
membrane bioreactor (MBR). The fouling rate of the 0.4 mm pore size (flat-sheet)
membrane was substantially reduced with 10–100 mg L21 ferric chloride coagulant
doses, and total dissolved chemical oxygen demand (DCOD) removal also increased
from 66% up to 93%. These findings are consistent with the results of other experimental
studies and show that pre-treatment controls submersed MF/UF filtration performance.
