An industry generates wastewater that contains both Ag+ and Hg2+ and is consider
ID: 1026557 • Letter: A
Question
An industry generates wastewater that contains both Ag+ and Hg2+ and is considering two options for discharge of the water after treatment. One option is to discharge the water through an ocean outfall, in which case the initial dilution is predicted to yield concentrations of 0.04 mg/L TOTHg and 2.5 mg/L TOTAg. The alternative is to discharge to a large river, in which the dilution would be faster and more extensive. Both Ag+ and Hg2+ are thought to be considerably more toxic as free ions than as complexes. The major complexing ligands in the two potential receiving waters are Cl(19,400 mg/L in the ocean, 35 mg/L in the river) and SO4 2- (2710 mg/L in the ocean, 12 mg/L in the river). Which disposal option would you recommend?
Explanation / Answer
Due to greater availability of binding ligand concentration in ocean water, I would recommend to dispose in ocean water than the river. Despite of the faster and more extensive dilution in river water, the stability of the complexes formed in ocean will be more than that of river due to greater concentration of cation binding ligands which will help in stabilization of the formed complexes. So free metal ions will be less in ocean compared to the river.