Efficacy of selected phosphorous sorbing materials (PSMs) to enhance the orthophosphate sorption capacity of filter socks

Agricultural phosphate (PO43‐) is a major cause of water quality compliance failures. Filter socks (FS) are a sediment‐control method proven to be effective at removing sediment and sediment bound‐P. Within the water and wastewater treatment industries phosphorous sorbing materials (PSMs) are widely used to remove reactive PO43‐. Combining PSMs with FS provides an opportunity to concomitantly remove sediment, sediment bound‐P and PO43‐ from agricultural runoff.

A column experiment was undertaken to evaluate the efficacy of selected PSMs to remove PO43‐ across a range of PO43‐ concentrations (0.08, 0.26 and 1.3 mg/l) and contrasting FS fill media (PAS 100 Compost and Woodchip). The results indicate that Ca‐enriched ferrihydrite removed up to 99% of PO43‐, and was the only PSM to reduce PO43‐ to below the target value of <0.05 mg/l. An initial cost benefit analysis indicates that PSM‐enhanced FS are a viable option to remove PO43‐ from agricultural runoff.