The use of continuous low-level alum injection to reduce soluble reactive phosphorus concentrations in the Lake Apopka Marsh Flow-way: final report

摘要

The St. Johns Water Management District (SJRWMD) is utilizing several approaches to remove phosphorus (P) from Lake Apopka waters in an effort to improve the trophic status of the lake. One approach involves operation of a “recycle treatment wetland”, in which lake water is fed through a large constructed wetland for treatment, and then discharged back into the lake. The wetland, designated the Apopka Marsh Flow-Way, serves as a filter and settling basin for the particulate-laden lake waters. In 2005, the SJRWMD commissioned DB Environmental, Inc. to design and construct the infrastructure for dosing alum at two locations within the Apopka Marsh Flow-Way. The overall goal of this project was two-fold: first, to assess the utility of an inflow or midregion low-dose alum application for enhancing total P and/or SRP removal by the Marsh Flow-Way; and second, to evaluate the effectiveness of the wetland in attenuating export of the dosed aluminum. This report describes the findings from these two injection trials. (93pp.)