Metal content of drinking water supplied to the city of Maracaibo, Venezuela

Total dissolved aluminum, calcium, iron, potassium, magnesium and sodium were evaluated in the drinking water supplied to the city of Maracaibo, Venezuela, to ascertain the water quality for human consumption. Mean concentrations (+/- S.D.) of 533 +/- 313 micrograms/l Al, 32 +/- 4 mg/l Ca, 167 +/- 104 micrograms/l Fe, 2 +/- 1 mg/l K, 5 +/- 2 +/- 1 mg/l K, 5 +/- 1 mg/l Mg and 16 +/- 4 mg/l Na were obtained during a 4-month sampling period that included dry (January-February 1991) and wet (March-April 1991) seasons. Significant seasonal variations (P < 0.002) for aluminium, potassium and magnesium were as follows: 641 +/- 275 and 445 +/- 340 micrograms/l aluminium, 3 +/- 0.5 and 2 +/- 0.5 mg/l potassium and 4 +/- 0.2 and 6 +/- 2 mg/l magnesium for the wet and dry seasons, respectively. The concentration of aluminum was consistently higher than the levels accepted by most international water quality criteria (approximate acceptable value < 300 micrograms/l aluminum), probably because of the inadequate flocculation treatment given to the raw water at the water plant. The rest of the metals under consideration complied with international guidelines of quality criteria for drinking water. The presence of an elevated concentration of humic material (22 +/- 2 mg/l of total organic carbon) in the drinking water should be a matter of public concern.