Determination of natural radioactivity in public drinking water quality assessment

The determination of ⁹⁰Sr and the gross α-particle activity originating from radium isotopes was performed on water samples at various stages of treatment taken from water treatment plants before distribution to the consumers. Four stages of analyses were involved in the radiostrontium determination, namely scavenging-precipitation as a pre-purification step, separation of ⁹⁰Sr and Ca from the matrix constituents, separation of ⁹⁰Sr from calcium and finally the purification of ⁹⁰Sr. Both the detection and chemical efficiencies were performed using standard ²²⁶Ra solution in the gross α-particle activity determination. The ⁹⁰Sr and gross α-particle activities were measured using a Canberra Alpha/Beta System Model 2400 low α/β counter. The average activity reported for ⁹⁰Sr for the drinking water samples was 0.52±0.07 Bq/l, which is lower than the maximum permissable level (MCL) of 1.11 Bq/l allowed by WHO. The average reading recorded from 12 water samples from different treatment plants for gross α-particle activity was 0.396±0.039 Bq/l and this is much lower than the maximum contaminant level (MCL) suggested by the USEPA which is 0.555 Bq/l. However the specific activity for ²²⁶Ra for clean water was 0.268±0.035 Bq/l, higher than the MCL of 0.185 Bq/l. Generally the treatment process has effectively reduced the natural radioactivity concentrations in all water samples taken at various stages of the process. The results obtained from this study were also discussed in the context of the source of raw water and its environment.