NAMS 2002 Workshop - ICOM 2008

Drinking and Wastewater Applications II – 4
Tuesday July 15, 4:00 PM-4:30 PM, Maui
Effects of Organic Fouling on the Removal of Trace Chemicals in
Nanofiltration Membrane Processes
S. Foo, University of New South Wales, Sydney, Australia
J. Mcdonald, University of New South Wales, Sydney, Australia
J. Drewes, Colorado School of Mines, Colorado, USA
L. Nghiem, University of Wollongong, Wollongong, Australia
S. Khan, University of New South Wales, Sydney, Australia
P. Le-Clech (Speaker), University of New South Wales, Sydney, Australia - p.leclech@unsw.edu.au
Trace chemicals, like endocrine disrupting compounds (EDCs), pharmaceutically
active compounds (PhACs) and personal care products (PCPs), present in
wastewater effluents are known to potentially cause detrimental effects to human
health and to the biotic environment if not removed during the treatment process.
High-pressure membrane processes such as nanofiltration (NF) can be used
efficiently in applications where a high water quality is required. Previous
research indicated that the fouling layer formed on the membrane surface during
filtration could significantly affect the rejection of trace chemicals and could either
improve or jeopardize the quality of the treated water. Conflicting results on the
exact effect of fouling on rejection have indeed been reported and the
mechanisms and physicochemical interactions occurring during the rejection of
the trace chemicals by fouled NF membrane are, so far, limited.
Accelerated organic fouling was achieved on a NF270 membrane (from DOW) by
using a variety of natural organic matter (NOM) fractions ranging from humic
acids, extracted from river water and from soil, surface water, protein (bovine
serum albumin) solution, and wastewater effluent from a tertiary treatment
process (membrane bioreactor). Different concentrations of NOM and operating
modes (such as constant flux and constant pressure operation) were considered.
A mixture of 18 trace chemicals representing a wide range of different
physicochemical properties was added at the nanogram per liter (ng/L) range to
the different feed water qualities and their level of rejection was assessed by a
gas chromatography-mass spectrometry (GC-MS). According to their
characteristics, the trace chemicals were grouped into three categories: (1)
hydrophilic non-ionic, (2) hydrophilic ionic, and (3) hydrophobic non-ionic.
Variations in hydraulic resistance, membrane surface charge, roughness and
relative hydrophobicity were measured for each experiment. Preliminary results
indicated that the feed matrices and operational modes were the major factors
governing the trace chemicals rejection. Under constant flux operation, it was
found that the rejection of contaminants increased after fouling, as compared to
those obtained under constant transmembrane pressure. Changes of the