Influence of Ca and CO3
In order to prove that the improved removal using lime-
stone was a chemical phenomenon, each metal solution
was prepared either with the addition of 15 mg/L of cal-
cium chloride or 15 mg/L of calcium carbonate solutions
(pre-experiments have shown that at these concentrations,
Ca and microparticle of CaCO3 has reached super-satura-
tion after 2 h shaking period). Then solutions were shaken
separately with gravel as the solid media. The objective of
the experiment with the addition of calcium chloride solu-
tion was to establish the effect of soluble calcium on each
metal removal. The experiment with calcium carbonate
solution was to establish the effects of soluble carbonate
on metals removal for samples with gravel plus metal
solutions.