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Egret Marsh and the Use of Periphytic Algae to Remove Dissolved Nutrients

Matt Van Ert and Keith McCully with a Strand of Algae at the Egret Marsh Managed Aquatic Plant System

Matt Van Ert and Keith McCully with a Strand of Algae at the Egret Marsh Managed Aquatic Plant System

About a week ago, I was shown around Egret Marsh by Matt Van Ert, a Phd Biochemist and Keith McCully, the Indian River Stormwater Engineer.  The purpose of this algal turf scrubber plant is to remove the algae before it ever enters the Indian River Lagoon and harvest it for a usable product.  This reduces the nitrogen, phosphorus, and potassium levels that are being dumped into the lagoon.  Since 2010, this plant has cleaned 10 million gallons of water coming from a large canal that drains over 9,000 acres. The water going back into the lagoon has approximately double the oxygen coming in.  The large strand of algae that Matt and Keith are holding came through the pipe and then continue to grow on the 4.6 acre sloped floway.

Algae Scrubbers at Work

Algae Scrubbers at Work

The water that is pumped out of the canal and travels through this system flows in a thin sheet over the algae, which assimilates dissolved nutrients and traps sediment.  The algae provides the structure in the water for tiny crustaceans to live in that birds feed on.  The image below shows some of these creatures.

Tiny Crustaceans in the Algae

Tiny Crustaceans in the Algae

There are several types of periphytic algae growing on the floway.  Periphytic algae includes cyanobacteria, diatoms, and chlorophytes and actually forms the basis of the oceanic good chain. Algae supports life and is not problematic until it grows out of control and removes oxygen from the water, causing plants and animals to die and break down, and creating bacteria that is toxic to the entire ecosystem. The most recent disaster in the Indian River Lagoon occurred in March, when oxygen levels plummeted to near zero for several hours and millions of fish died.  All of this algae would enter the lagoon, if it were not for this water treatment plant.  

Algae on the Floway

Algae on the Floway

Keith McCully Standing Beside Two Weeks of Harvested Algae

Keith McCully Standing Beside Two Weeks of Harvested Algae

Algae is one of the most rapidly growing plants, which is why blooms are so problematic.  Yet, as a controlled, harvested crop that has not broken down lifeforms and created toxic bacteria, algae also absorbs carbon dioxide and releases oxygen.  Carbon dioxide is one of the main culprits of global warming, so more of these plants around the world might help slow down climate change as well.  Currently there are only two of these plants in the United States, this one and the one in Lake Okeechobee that has since been shut down.  The reason for the closure of this plant was the chemical toxicity of the water in Taylor Creek, which had more than just high nitrogen and phosphorus loads, another reason why the water in Lake Okeechobee is so damaging to the Indian River Lagoon and the Caloosahatchee River.

Keith McCully Overseeing Where the Water is Released

Keith McCully Overseeing Where the Water is Released

The water then flows through a 15 acre polishing pond system before being released into the lagoon.  

Birds Fishing in the Pond Where the Water is Initially Released

Birds Fishing in the Pond Where the Water is Initially Released

Some of the water that is not fit to be recycled is released into a smaller canal that feeds into a marsh area and this muck is frequently cleaned out.  Muck is another huge issue in the Indian River Lagoon.

Algae Bloom that Would Have Entered the Lagoon

Algae Bloom that Would Have Entered the Lagoon

This image below shows a mountain of the algae and pond scum that has been removed.  The other, usable algae is taken off site to compost.

Mountain of Algae and Pond Scum

Mountain of Algae and Pond Scum