Radium removal using sorption to filter sand

This study evaluated the use of a novel sand filtration process that exploits the natural capacity of filter sand to sorb radium through the use of a periodic dilute acid rinse to maintain its sorptive capacity. Batch studies were conducted to determine distribution coefficients so that performance estimates could be made. Laboratory pilot studies using a partially softened ground water showed the process capable of reducing 226Ra concentrations by 80 to 90% in the presence of iron flocs when daily rinsing was practiced using pH 1 (0.36 percent) or pH 2 (0.04 percent) HCl. Similar removals could be achieved in field studies using water containing 9-11 pCi 226R a/L obtained from the existing sand filters in a city whose supply is treated for iron removal. Removals in the field were less when simultaneous iron and radium removal was attempted. In addition, estimates of the total sorptive capacity of the sand obtained in continuous-flow experiments were generally significantly greater than those predicted based on batch results