A. Vengosh et I. Pankratov, CHLORIDE BROMIDE AND CHLORIDE/FLUORIDE RATIOS OF DOMESTIC SEWAGE EFFLUENTS AND ASSOCIATED CONTAMINATED GROUND-WATER/, Ground water, 36(5), 1998, pp. 815-824
To establish geochemical tools for tracing the origin of ground water
contamination, we examined the variations of Cl/Br and Cl/F (weight) r
atios in (1) domestic waste water from the Dan Region Sewage Reclamati
on Project and from reservoirs in the central coast of Israel; (2) ass
ociated contaminated ground water; and (3) pristine ground water from
the Mediterranean coastal aquifer of Israel. Our data show that supply
water, anthropogenic NaCl and fluoridation control the Cl/Br (410 to
873) and Cl/F (468 to 1070) ratios of domestic waste water, and conven
tional sewage treatment does not affect the anthropogenic inorganic si
gnals, The Cl/Br ratios of ground water contaminated with sewage efflu
ent reflect conservative mixing proportions of sewage and regional gro
und water components. Sensitivity tests demonstrate that it is possibl
e to detect and distinguish sewage contamination from marine ratios af
ter a sewage contribution of 5 to 15% is mixed with regional ground wa
ter. Mixing,vith Br-enriched fresh water (e.g., Sea of Galilee; Cl/Br=
145), however, would reduce this sensitivity, Since the high Cl/Br sig
nal of sewage effluents is distinguishable from other anthropogenic so
urces with low Cl/Br ratios (e.g., street runoff, agriculture return f
lows) and from natural contamination sources (e.g., salt water intrusi
on; Cl/Br=293), Cl/Br ratios can therefore be a useful inorganic trace
r for identification of the origin of contaminated ground water. The C
l/F ratios of sewage-contaminated ground water (284 to 5186) were high
er than those in the original sewage effluent, which suggests retentio
n of fluoride into the aquifer solid phase.