Fluorescent whitening agents (FWAs) are contained in most modern laund
ry detergents and are thus discharged in substantial quantities with h
ousehold wastewater. To determine the mass flows and fate of the predo
minant detergent FWAs, a field study was conducted at a full-scale mec
hanical-biological sewage treatment plant at Zurich-Glatt, Switzerland
. Samples of wastewater (raw sewage, and primary and secondary effluen
t) and sludge (raw, activated, and anaerobically-digested sludge) were
collected during a 10-day period. The concentration of FWAs in water
samples was determined using solid-phase extraction with C-18 disks an
d high-performance liquid chromatography (HPLC). The concentration of
FWAs in sludge was determined by supercritical fluid extraction and HP
LC. The removal of FWAs from wastewater during sewage treatment varied
significantly (53-98%) between different FWAs. Removal was due to ads
orption to primary and activated sludge and the observed extent of rem
oval was consistent with the individual sorption behavior of FWAs. No
evidence for biodegradation of FWAs was found during the aerobic biolo
gical treatment of municipal wastewater with activated sludge and duri
ng anaerobic-mesophilic digestion of sewage sludge. Average annual dis
charge of FWAs to Swiss surface water is approximately 20 t (22% of th
e consumed FWAs) while FWA disposal to farmland associated with sewage
sludge is 11 t/y (12%), estimated based on the extent of removal from
sewage and on a previously reported survey of FWA concentrations in s
ewage sludge. The discharge of FWAs to surface water leads to a projec
ted average FWA concentration in surface waters of 0.5 mu g/l, which i
s well below toxic levels for these compounds. (C) 1998 Elsevier Scien
ce Ltd. All rights reserved.