Septic tanks suspected as origin of Stuart algae bloom


For the generations who grew up seeing green slime dumped on people to great comedic effect, it’s a kind of melancholy nostalgia to now see slime coating the water and killing vital marine plant life. Call it, “You Can’t Do That On Waterways,” but it’s happening on the Sailfish Flats near Stuart, threatening seagrass meadows Floridians took so much time and money to save.  

“In the past, the long past, a lot of times folks were somewhat reasonably pointing fingers that some of the problem was Lake Okeechobee discharges,” said Brandon Shuler, Executive Director of the American Water Security Project. “Other folks were pointing fingers that it is sewage issues and septic tank issues. It’s definitely got cyanobacteria and algae bloom issues going on over there, but … Lake O has not had a discharge and there have been very few basin runoffs from rain events, because we’re in extreme drought, for the last three and a half years.

“So, that takes one of the biggest voices that was blaming everything on Lake Okeechobee discharges being the issue and really kind of points back to, there are other issues here that need to be explained more deeply.”

With Lake Okeechobee excused from the lineup of usual suspects, that leaves two likely culprits — either septic tanks or legacy pollution.

It comes at the same time Jacqui Thurlow-Lippisch, a Board member for the South Florida Water Management District, posted aerial photos celebrating the return of seagrass to the area.

“Today’s photos highlight the area’s returning seagrass meadows after their disappearance primarily because of years of damaging cyanobacteria laden Lake Okeechobee discharges, especially in 2013, 2016, & 2018,” she wrote in late August.

As a result, the appearance of this toxic algae bloom — coating the water and wrapping around angler’s fishing lines — lends a sense of urgency to the need for action so as not to lose the rewards of all the work that went into restoring the seagrass so far.

One issue is an elevated level of nitrogen and phosphorus in the local basin waters compared to water that comes in from Lake Okeechobee.

“It’s really easy on the St. Lucie River to fall into the trap of thinking that all of our problems come from Lake Okeechobee, and if we could just stop the discharges, then we would have a healthy, pristine estuary,” said Nyla Pipes of the One Florida Foundation.

Whenever there is a time of less rain or drought, she said, and the water looks as it did in the photos posted by Thurlow-Lippisch, people feel ready to call it mission accomplished when it’s not necessarily the case.

“You have tons of septic tanks — Florida is, I think, No. 3 in the nation for the number of septic tanks that still service homes,” Shuler said. “Just knowing how septic tanks work, it’s designed to fail.”

Liquid wastewater exits the septic tank and goes into what’s called a drainfield, into which the wastewater filters through the soil before discharging into the groundwater.

“We know that we have to work on septic-to-sewer conversion,” Pipes said.

“The argument people say is, ‘When we don’t have releases, we don’t have any algae.’ I would say that this situation with that filamentous algae that’s covering the seagrass right now, shows that to be untrue. We just have a different kind.”

Another of the next steps, Shuler said, is to work with municipalities to do third-level wastewater treatment, taking nitrogen and phosphorus out of the sewage and returning nutrient-lowered water to the wider world without it having such a detrimental impact on local waterways. 

“The other part of that step that goes hand-in-hand is taking an inventory of septic tanks and really getting serious about upgrading our wastewater facilities to third-level treatment that takes most of the nutrient waste out,” he said, “and centralizing septic tanks and getting them connected back up to a centralized sewage treatment plant that actually is treated to levels that are outlined in (federal and state law).”  


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