The applicability of the local and international water quality guidelines to Al-Gassim Region of Central Saudi Arabia

The quality of 109 water samples, comprised of 70 drinking water and 39 irrigation water samples, in Al-Gassim Region of Saudi Arabia was investigated with respect to total dissolved salts (TDS), electric conductivity (EC), pH, total hardness and the major cations (Ca2+, Mg2+, Na+ and K+) and anions (Cl-, SO42-, NO3-, F- and HCO3-) beside coliform bacteria as an indicator of faecal contamination. The concentrations of TDS varied widely, from 109 to 6995 mg L-1, with a mean of 1427 mg L-1. Of the 109 water samples examined, 81 (74.3%) comply with the maximum permissible drinking water limits set by the local and international standards and guidelines and 28 (25.7%) were above the limits of these standards. The concentrations of the cations and anions (with the exception of NO3- and F-) follow, more or less, a trend similar to TDS. NO3- concentrations (range 0-30 mg L-1) comply with the limit of 50 mg L-1 NO3- as the highest tolerable NO3- content. The concentrations of F- in drinking water (range 0.2-1.5 mg L-1) are alarming since 88% of samples were below the lower permissible limit of 0.6 mg L-1 set by SASO (1984), the guideline of the WHO is 1.5 mg L-1 while the EEC maximum concentration lies within the range 0.7-1.5 mg L-1. Microbiological analyses showed negative coliform tests, which confirms that they are devoid of any faecal contamination.