Boron contamination in groundwater at a sewage waste disposal facility near Jeddah, Saudi Arabia

Shallow aquifers underlying sewage disposal facilities contain salts much higher than non-contaminated shallow aquifers of surrounding areas. This study focuses on the spatial distribution of boron in an alluvial aquifer subjected to sewage waste contamination. Nineteen groundwater samples were collected from the water wells present in the Wadi Bani Malik area known to have a history of sewage waste disposal. The sampling locations were carefully selected to cover an area upstream and downstream to the dam axis, within the boundary as well as around the lake perimeter. Prior to sampling, in situ field parameters such as top of the casing, depth to water table, temperature, salinity, electrical conductivity (EC) and the pH were measured. A total of 10 trace elements most commonly found in the groundwater contamination context were selected for the analysis which are: Li, Al, Cr, Mn, Fe, Ni, Ba, Hg, Pb and B. The results of this study indicate that concentrations of all the trace elements except boron are largely less than 1.0 mg/L. The concentration of boron varies between 3.70 and 44.98 mg/L with an average of 13.24 mg/L. The highest boron concentration is found in the cluster of wells located adjacent to a point source. The lowest concentration of boron is upgradient to this location. When compared with the EC data, the pattern of highs and lows of boron corresponds well with the EC. This pattern is consistent with the description of other plumes in sand and gravel of somewhat similar grain-size distributions. Also, the correlation coefficient analysis performed on the dataset indicates a strong correlation coefficient (r = 0.8) between the boron and EC. This suggests the possibility of using boron as an indicator for plumes originating from sewage waste disposal facilities.