Study of the quality of some Algerian thermal waters

F. Bahri and A. Addou

Laboratoire STEVA, Facult? des sciences, Universit? de Mostaganem (Alg?rie)

ABSTRACT: The study of thermal water quality is an essential parameter for the good health of people treated at a spa. Physico-chemical parameters (conductivity, pH, Cl-, HCO3-, PO43-, SO42-, NO3-, NO2-, F-, TH, Ca2+, K+, Mg2+, Na+ and DS) were measured on forty-one samples taken from fourteen different areas in Algeria. The temperature of the thermal waters samples at collection vary from 26°C to 86°C. pH values vary from 6.5 to 8.5, slightly neutral to moderately alkaline. 90.24% of the samples exhibit a relatively high salinity (DS = 550 – 5500mg.l-1). The total hardness (TH) shows that these waters are moderately hard. Nitrite concentration analysis shows that the waters studied have very low content of this substance by W.H.O standards (0.1mgl-1). The Schoeller-Berkaloff diagram revealed the importance of chloride-calcic waters, representing 46.4 % of the samples analysed. 19.5 % of the samples are bicarbonate-sodic and 14.6 % are chloride-sodic. Bicarbonate-calcic waters represent 9.7 % whereas other types: sulphate-calcic and chloride-bicarbonate are present in 4.9 % of the cases. The hydrogeochemical parameters (Mg2+ / Ca2+, Na+ / Ca2+, Na+ / Mg2+, Na+ / K+, (Na+ + K+) / Cl-, (Na+ + K+) / (Ca2+ + Mg2+), Cl- / SO42-, Cl- / HCO3-, (Cl -+ SO42-) / HCO3-, CEV ) were considered. The cationic exchange value (CEV) calculated for all the samples is positive for 58.5 %, negative for 31.7 % and close to zero for 9.8% of the samples analysed. The ratios Na+ / Ca2+, Na+ / Mg2+ and (Na+ + K+) / (Ca2+ + Mg2+) are high in 90.24 % of the samples. This shows the ions exchange process is important. The Mg2+ / Ca2+ ratio values show that 61,5% of the samples have had a sufficient contact true with the rock. The Cl- / SO42- ratio values are high in 85.36% of the thermal waters samples. This shows that the most of the Algerian thermal waters have developed for a long time in depth and reacting with the rock. The statistical analysis of the physico-chemical data gives positive correlation values enabling a good interpretation of the results and a suggestion for the form of ions present in waters as well as some information about the thermal waters origin. The therapeutic properties associated with thermal waters encourage people taking the waters at a spa to drink it. To that effect, the drink ability of the thermal waters was investigated. W.H.O standards were used to evaluate the thermal waters quality for drinking. According to total dissolved salt content (DS). Nineteen samples, (i.e. 46.34%) are fresh waters and twenty two (i.e. 53.66%) are brackish waters. With respect to hardness, the samples are classified as moderately hard (58.54% of the samples), very hard (36.58% of the samples) and soft (4.88% of the samples). Based on Cl-, SO42-, HCO3- concentrations, the samples were classified as follows : nineteen samples (i.e.46.34%) are lower in chlorine than W.H.O standards, (<15 meq.l-1) and twenty two (i.e. 53.66%) are higher; twenty nine samples (i.e.70.73%) are lower than W.H.O in sulphates (<6 meq.l-1) and twelve (i.e. 29.27%) are higher; twenty height (i.e. 68.29%) are lower than W.H.O in bicarbonates (<7 meq.l-1) and thirteen (i.e. 31.71%) are higher. Sixteen samples (i.e. 39%) of the investigated waters are drinkable. They may be consumed without special precaution. On the other hand, twenty-five samples (i.e. 61%) are contra-indicated for consumption and should be pointed out to people taking waters at spas.

KEYWORDS: Thermal water; hydrogeochemistry; drinkability

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