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The Florida Water Quality Conundrum

Updated: Jul 11, 2022

co·nun·drum /kəˈnəndrəm/ noun: a confusing and difficult problem or question: "one of the most difficult conundrums for the experts.”

How did we get here? The entire state of Florida is stuck on the water quality question. The Department of Environmental Protection (FDEP), the Department of Agriculture (FDOA), and the five massive water management districts do not appear to be able to resolve the water quality issues that are so vital to the future welfare of the residents of Florida. Billions of dollars are being spent, yet many manatees are paying the price for our inability to correct this massive and vexing problem.

Let’s take a look at Marco Island. Examining the Marco Waterbody Oxygen Samples from the FDEP Water Information Network (WIN) for 2021, we see that 5% of the Marco Dissolved Oxygen Saturation Percent % (DOSAT) samples were impaired, and 10% of the Dissolved Oxygen (DO) samples were Hypoxic. If we used the old FDEP standard for oxygen impairment (2013) of DO less than five mg/L, an astounding 70% of the water samples taken in Marco Island over the year 2021 would have been considered impaired! Good thing FDEP lowered our standards.

In 2013, the FDEP changed the impairment standard for oxygen in the state waters, taking numerous water bodies away from the risk of being declared “impaired.” The oxygen impairment standard was switched from Dissolved Oxygen (DO) to Dissolved Oxygen Saturation % (DOSAT). DOSAT is the % of the oxygen the water contains compared to the amount of oxygen it could have, which varies based on the temperature of the water. Colder water can hold more oxygen. This explains the abundance of sea life in the North and South Poles. The amount of oxygen the water can have varies from winter to summer but is roughly constant in an average year-to-year comparison.

The old DO standard (pre-2013) was a minimum of 5 mg/L to stay out of impaired status for a waterbody: roughly equivalent to 60% DOSAT. The new standard of 42% DOSAT to keep out of impairment for oxygen; is approximately equal to DO of 3 mg/L. FDEP relaxed the impairment standard, which allowed many more polluters to escape the FDEP system of control. A lower standard reduces the number of potential violators. The oxygen limit for impairment was dropped from 5 mg/L to an equivalent of three mg/L - a 40% drop. This reduced the size of the problem immediately. Or so they thought.

The root cause of the depleted oxygen in the Marco Island waterways is the phosphorus in the reuse water distributed to the condominiums and hotels along Collier Boulevard and the golf courses for irrigation. I love that green grass!

The connection was discovered from a 5-year statistical correlation of the depleted oxygen in the Marco waterways against the nutrients that come with the reuse water distributed by the Wastewater Treatment Plant (WWTP) here. The database covered the period from 2017 to 2021. This database was compiled from Marco Island's monthly water quality samples. Nineteen chemical “analytes” in the waterways, including oxygen taken monthly from 14 locations on Marco Island. Increasing the sampling frequency from 4 times per year to 12 times per year was one of the best decisions ever made by the Marco Island City Councilors. When you have a problem, get more data!

The strongest correlation with the reduced oxygen in the waterways was the phosphorus in the reuse water. The second strongest correlation was with the nitrogen in the reuse water. Fertilizers on the island showed up as the third-largest contributor. However, the fertilizer bans during the summer periods showed a positive effect. Perhaps we should consider a moratorium on fertilizer use on Marco Island and see the results after a year. The stormwater runoff benefits the Island with oxygen carried in the rain. That was a surprise.

If you are not current with statistics, don’t worry; look at the “smoking gun” chart. This provides a visual link between the reduced waterbody oxygen levels and the increased reuse water phosphorus levels that occurred over a 5-month period between October 2019 and February 2020. The phosphorus in the reuse water on Marco dropped to abnormally low levels for an unknown reason. Did a batch of good wine hit the island? Immediately the oxygen levels in the waterways spiked to healthy levels above 6 mg/L. In March 2020, the phosphorus in the reuse water returned to normal levels, and the oxygen in the waterways dropped again. If not for this event, we would still be guessing what was happening.

According to many scientific articles, the phosphorus, as well as the nitrogen in the reuse water (called nutrients), are a food source for algae which results in Harmful Algal Blooms (HAB) that then block sunlight going into the water body and kill the seagrass which is the primary food source of the Manatee. The Manatee either go somewhere else for food, as they do in Marco Island, or they die of starvation, as they do in the Indian River Lagoon. As algal blooms die off, the waterbody oxygen is consumed, which drives away the fish and other aquatic life. This is nothing new. We have known about this for literally 50 years or more.

Ironically, after the death of the algae, decomposition produces more nutrients to feed further HAB, which accelerates the process. Marco Island is undergoing this acceleration. (2017-2021 Trends Chart). In 2017 the number of oxygen “excursions” or samples with deficient oxygen levels was 4%. By 2021 the number of oxygen excursions increased to 64%. The Swallow sampling location near the Cape Marco condos is often “Hypoxic” or dead water.

The City of Marco Island likes to sell reuse water. After all, they have $120,000,000 in bond debt left over from the purchase of the water utility. The customers of reuse water like to buy it. Reuse water is cheap for irrigation as compared to potable water. We have a dilemma right away in the form of financial incentives that form a potent barrier to change.

Why is the Marco WWTP allowed to pollute the waterways? The FDEP imposes NO LIMITS to the amounts of nutrients that our WWTP introduces to the Marco waterbody. The Marco WWTP is just required to “report” the levels of nutrients in the reuse water. According to the permits we have examined, many WWTP in Collier County is not even required to report the pollution that they send to the waterbodies in the form of reuse irrigation water. Phosphorus is banned in fertilizer on Marco Island; why is phosphorus allowed in the reuse water here?

The Florida reuse water program was introduced years ago because of a drought in Florida. Reuse water was meant to preserve the water tables so that the county wells would not run dry. This was achieved. However, the unintended consequences of the nutrient loads from the reuse water were perhaps not understood. Well, now we know the impacts.

By the way, the WWTP is not really at fault. They are operating according to the permit FDEP has given them. The plant cannot physically remove phosphorus. The WWTP is doing its best with what they have been given. The FDEP allows the WWTP to continue its operations with no end. The Marco WWTP must be upgraded to add a phosphorus removal step called electrochemical precipitation. The cost is low compared to the other spending programs on the Island. Is this not a priority?

When we try to get attention brought to resolving this problem, we get blank stares. “The waterbody is not impaired.” “The WWTP is operating according to their permit.” This is all true. The City of Marco likes the revenue. The condos and golf courses like the cheap irrigation water. Why change? We could ask the Manatee about this if we could find one.

The Marco waterbody is slipping into what is called “eutrophication,” or the death of the waterbody. Marco Island is not in crisis. It is just that our waterbody is slowly dying. We can see this in periodic “flashes” of algal blooms, the “slicks” you see in the water. These blooms will eventually become permanent as the waterbody slips into advanced stages of eutrophication. The fish, turtles, and manatees no longer come to Smokehouse Bay. It might be too late when we eventually trigger the lowered oxygen impairment limits. We can do something about this now. It is time to be proactive.


Nanette Rivera

Candidate for City Council

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