Mitigating tile drainage phosphorus using phosphorus sorbing materials in a continuous flow through pilot system

Contributions of elevated dissolved phosphorus (DP) lost through the subsurface tile drain have become a major concern. In order to address this environmental issue, phosphorus sorbing materials (PSMs) have been studied utilizing pilot scale studies for treatment of DP lost via the tile drainage network. The objective of this investigation was to assess the feasibility of acid treated and soap and water treated PSMs: steel slag and iron turnings, to reduce DP in a continuous flow through pilot system tested under short contact times. The continuous flow through reactor trials were tested at alkaline pH, constant temperature. DP % removal with respect to contact times and PSM type was evaluated using the pilot system. Among the four treatment types, acid treated iron turnings demonstrated the highest capacity to reduce orthophosphate by up to 68 % in under 20 min, without showing an addition of DP back into the system. Soap and water treated steel slag showed the next highest capacity to reduce DP (9.54 % reduction) without the addition of DP to the system. Continuous flow through experiments demonstrated the effectiveness of acid treated iron turnings and soap and water treated steel slag for use as PSM in a tile drainage P removal structure.