Don't Forget About Nitrogen

Lake Marion is an “impaired water” due to excess phosphorus and nitrogen. The inclusion of both nutrients as a source of lake pollution is significant because the Columbia Wetlands issue to date has been framed by comparing constructed wetlands to conventional treatment for the removal of phosphorus (only) from wastewater. This is not the whole picture. We provided a link in an earlier post showing that conventional removal of nitrogen and phosphorous is much more complicated and expensive than removing phosphorous alone.
Wetlands, on the other hand, treat both phosphorus and nitrogen more cost effectively than conventional treatment.
The EPA reports that over a twenty year period the cost (in present value terms) of constructed treatment wetlands is a mere 14% of the cost of conventional wastewater treatment. A WERF report also indicates conventional costs to remove nitrogen are 50% greater than the conventional costs to remove phosphorus.
It would be nice if the debate were only about phosphorous. But it’s not.