Saalem Adera
Evaluation of a filter for nps phosphorus removal in the Lake Champlain watershed.
Excess phosphorus inputs to Lake Champlain are causing unwanted algal growth resulting in decreased lake water transparency, odor, and reduced dissolved oxygen levels, while the presence of pathogen-‐indicating bacteria in the lake cause occasional beach closings. This has implications for both recreational and drinking water uses of the lake. It has been determined that non-‐point sources of phosphorus, mostly from surface runoff, are responsible for 80% of the phosphorus inputs to Lake Champlain, mostly from agricultural runoff. Pathogenic bacteria are also associated with agricultural runoff – particularly from livestock operations. Simple, low-‐cost technologies for phosphorus and pathogen removal from stormwater and agricultural wastewater are needed. One such technology is an on-‐site, combined constructed wetland-‐EAF steel slag filter system. This experiment had two levels. In the first level, aerated horizontal flow, aerated vertical flow, and unaerated vertical flow constructed wetlands were evaluated for their pollutant removal efficiencies. In the second level, constructed wetlands in series were compared to constructed wetlands paired with EAF steel slag filters for their E. coli removal efficiencies. In the first level of treatment, aeration significantly increased removal of DRP, E. coli, NH3, and BOD. Furthermore, horizontal flow cells removed significantly more TSS than vertical flow cells. In the second level of treatment, wetland-‐slag systems removed significantly more DRP and E. coli than wetland-‐wetland systems.