Trace metals were assessed in the raw and product waters of 8 water treatment plants in Riyadh, Buraydah and Unayzah (Saudi Arabia). Samples were analyzed for 12 trace metals by inductively coupled plasma spectrophotometer (ICP). All the detected metals were within the permissible limits of WHO. Cd, Ni and Se were absent in all plant waters. It was found that concentrations of metals like As, Fe and Mn decreased after various treatment processes compared to their levels in raw water. Al increased in all product waters of the plants that use chemicals in the softening process. The increase in Al levels is observed to take place after the softening process where sodium aluminate is used. However, most of Al is removed by sand filtration. Zn and Cu levels in the product water have increased in many cases, which may be attributed to the pipings. The removal of trace metals by reverse osmosis was in the range of 78.8-100%. Assessment of trace metals in the water distribution network is recommended.
