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Marine Lab testing filter to improve pond’s water quality

By Staff | Aug 12, 2020

SCCF Filter at Heron's Landing

The Sanibel-Captiva Conservation Foundation Marine Lab, in cooperation with the Sanibel Natural Resources Department, is investigating the use of a nutrient filter for removing pollution from an impaired pond downstream of a neighborhood wastewater plant that was closed in the early 2000s.

As one of the island’s poorest water quality ponds, it has constant algae blooms and low to no dissolved oxygen, the SCCF reported. The pond has such poor water quality that current efforts to reduce fertilizer runoff would not lead to improving conditions in it.

The city has repurposed one of the Marine Lab’s fish aquaculture tanks at the former Bayous wastewater treatment plant site. At the corner of Sanibel Bayous Road and Sanibel-Captive Road, the site previously had a wastewater treatment plant that served the Bayous development.

The treatment plant had two large ponds that held treated wastewater. Even though the city has now purchased the property, properly closed the treatment facility and filled in the ponds in an effort to solve the problems caused by wastewater there, residual nutrients remain in the groundwater and soil, the SCCF reported.

The repurposed aquaculture tank has been filled with four types of filter media which can physically and biologically remove nitrogen and phosphorus from polluted water. The treatment tank supplements two small lakes that were dug on the site and planted with vegetation, which acts as a natural filter to remove nutrients. In the tank, a small pump now keeps water flowing from one lake, then through the new nutrient filter and into the second lake.

The SCCF monitors the removal of nutrients through the filter. The filter was put online in May and initial sampling has shown the filter does remove nitrogen and phosphorus. It will take several more months for the filter media to grow bacteria. The effectiveness of the filter is expected to increase over time. These are bacteria naturally found in the environment and pose no danger to humans.