Evaluation of Treatment Systems for the Removal of Arsenic from Groundwater

High concentrations of iron and arsenic are common in Saskatchewan groundwater. Their cost effective removal from groundwater is a challenge for small communities. Four small treatment systems were tested for iron and arsenic removal with and without ozone pretreatment using groundwater high in iron (6.4–8.4mg∕L) and arsenic (14.5–27.2μg∕L). The systems tested were (1) coagulation, (2) biological activated carbon (BAC) filter, (3) slow sand filter, and (4) rapid sand filter. Coagulation removed 70% of arsenic and 85% of iron. With ozone pretreatment, the removal increased to 95% for arsenic and 93% for iron. The BAC system was highly effective in the removal of both arsenic and iron. On average, it removed 97% of arsenic and 99.8% of iron. With the ozone pretreatment, the average removal increased to 99% for arsenic and 99.9% for iron. The increase in iron removal with ozone was not statistically significant at P=0.1. The slow sand filter system was also highly effective in the removal of both arsenic and iron. On average, it removed 96% of arsenic and 99.8% of iron. The ozone pretreatment did not significantly change removal rates. The rapid sand treatment system removed an average of 50% of arsenic and 99% of iron. With the addition of ozone, the average arsenic removal increased to about 65%; however, the average iron removal was only 50%. The removal of arsenic by the rapid sand filter was extremely variable and this was possibly related to media saturation and some surge in the system as the ozone off gas valve was opened and closed.