Groundwater in Moldova contains different pollutants. Iron, manganese and strontium
ions, hydrogen sulfide and ammonia are the most frequently encountered depending on the
geography of the given locality. The need to remove these pollutants from groundwater is
obvious, since they have a negative impact on human health. For example, strontium ions present
in water at concentrations above the maximum allowable limit stop the growth in height of
children, and replace calcium ions from bones, causing various diseases. Divalent iron ions are
accumulatet in the liver and affect it. Hydrogen sulfide is a highly toxic substance. In some wells
the strontium ion content can be as high as 48 mg/L - value that exceeds the maximum
permissible limit adopted in European countries (7mg/L, ГОСТ 2874-82).
In the present work the removal process of strontium ions, divalent iron, hydrogen
sulfide, and the process of reducing the water hardness from the wells in the Costesti village of
the Ialoveni district have been studied. The pH of the considered water was 7.5. Strontium ion
concentration was 9.66 mg/L, of iron ions - 2.77 mg/L, of hydrogen sulfide - 1.3 mg/L, water
hardness -14.6 mg-eq/L, the calcium ion content was 105.6 mg/L (5.27 mg-eq/L) and
magnesium ion 111.1 mg/L (9.13 mg-eq/L).
At pH 9.5, the ions of iron, strontium, calcium and magnesium form the water-
Indeed, after treating the water with sodium hydroxide, stirring and filtering through the sand
filter, the concentration of strontium ions became equal to 2.07mg/L, of iron ions - l .14 mg/L,
water hardness - 9.86 mg-eq/L. The content of calcium ions became 44.4 mg/L (2.22 mg-eq/L),
of magnesium ions 93.0 mg/L (7.64 mg-eq/L). Hydrogen sulfide was removed from the system
by oxidation with hydrogen peroxide. Oxidation yielded sulfates and not colloid sulfur, which
would cause additional problems in its removal from the treated water. A major problem, likely
to occur when large volumes of water are required to be treated, is that formed hydroxides will
interact with carbon dioxide also present in the system, with the formation of carbonates, which
can be deposited on the walls of the reactor and the pump. In any case, following semi - pilot
tests this phenomenon was present after the first treatment cycle.