Scientific dispute over using sewage to restore Louisiana's wetlands turns political

Yahoo

13-04-2025

On right, the City of Hammond's assimilation wetland on the northern coast of Pass Manchac. The wastewater effluent flows to the right of the pipeline, labeled for clarity in the image. (Photo: Wes Muller/Louisiana Illuminator)
Opposing views among environmental groups and coastal scientists in Louisiana have spurred intense debates over the use of treated sewage to restore Louisiana's wetlands. The conflicts could jeopardize some decades-long efforts to restore the state's disappearing coast.
Wetlands are sometimes referred to as the kidneys of the earth — and for good reason. They keep water clean by filtering out pollutants and managing the amount of nutrients, such as nitrogen and phosphorus, that can lead to the harmful algae blooms that create 'dead zones' without the oxygen needed to support aquatic life.
Wetlands can even be created to treat wastewater processed from sewage treatment plants. The practice can avoid polluting rivers and streams while providing valuable habitat.
But in Louisiana, the use of natural wetlands for wastewater treatment is a topic rife with controversy.
Originally pitched as a method of coastal restoration, a natural assimilation wetland is typically an area of degraded forested swamp or marshland where disinfected treated sewage water is pumped in an effort to push away saltwater, provide nutrients for the growth of plants and trees, and reverse the sinking and eroding of the land. Louisiana's 3 million acres of wetlands, which include coastal marshes and swamps, are lost at the rate of roughly 75 square kilometers annually and are on pace to disappear entirely within 200 years, according to the U.S. Geological Survey.
Both federal and state regulators permit local wastewater utilities to use natural wetlands for assimilation. One of the sites, located in Breaux Bridge, began in the 1940s as the city's solution to discharging its treated wastewater. But it wasn't until around the 1980s when LSU scientists began using and studying assimilation wetlands as a way to rebuild Louisiana's coast. There are now 15 such assimilation sites across the state.
Local utilities and scientists, led by wetlands ecologist John Day, believe assimilation sites have been largely successful in restoring wetlands. Day is one of the LSU researchers who spearheaded their use for coastal restoration. He founded Comite Resources, a company of environmental scientists who work on coastal restoration projects and currently monitor a few of the assimilation wetland sites.
On the other side of the debate is Eugene Turner, emeritus professor of coastal sciences at LSU, who says assimilation is killing rather than restoring wetlands. Turner has a vocal public following, including organizations such as the Ponchartrain Conservancy and Louisiana Wildlife Federation, that has rallied around his argument: Feeding treated wastewater to Louisiana's wetlands hurts rather than helps.
Such disagreements are a normal and even necessary part of science, but Day and his colleagues say Turner's side is venturing outside the scientific process and lobbying state lawmakers to halt the projects in an 'undemocratic' manner.
On March 18, Turner gave a presentation to the Louisiana House Committee on Natural Resources and Environment, claiming assimilation is a failure. He urged lawmakers to defund work on the South Slough Wetland project, just south of Ponchatoula. Much of the money for it comes from federal grants.
Six out of the nine assimilation areas LDEQ monitors passed their long-term health assessments, according to the agency's 2024 report. Wetland health is determined in the report solely by the amount of vegetation growth at the site, called net primary productivity, evaluated over a period of five years. The South Slough Wetland is one of the six sites that passed its evaluation.
Turner's claims received no pushback at the time because, according to Day, no other coastal scientists were invited to the hearing or even aware that the wetlands projects were up for discussion.
Turner did the same thing at a legislative hearing last year, catching the scientific community by surprise with misleading testimony that no one got a chance to refute, Day said in an interview.
'It's happened twice, and it's undemocratic,' he said. 'They never alert the larger scientific community that's interested in this.'
Turner disputed the idea he's doing anything underhanded and accused Day of trying to protect his funding source. Comite Resources provides the monitoring services for the site, though Day said he hasn't received a paycheck from the company in nearly 20 years.
'What is undemocratic? Testifying at a legislative session? Speaking up with facts?' Turner said in an interview. 'Is publishing in open access scientific journals undemocratic? Democracy includes public discourse in this country.'
Representatives from the Ponchartrain Conservancy and Louisiana Wildlife Federation also attended the March 18 meeting and gave testimony supporting Turner's position to pull money back from wetland assimilation projects. While the organizations supported the idea in the past, they have since changed their stance.
Ponchartrain Conservancy executive director Kristi Trail said she thinks Louisiana should stop issuing permits for new assimilation projects.
Both organizations cite many of Turner's arguments and are calling for treatment plants associated with assimilation projects to improve the quality level of the water they discharge into manufactured wetland areas. They also argue that the water may need to be mixed between assimilation wetlands and an open water body in an effort to protect wetlands against long periods of exposure to extra nutrients.
Ponchatoula state Rep. Kim Coates asked Louisiana Department of Equality Secretary Aurelia Giacometto, who was also at the March hearing, to respond to Turner's claims. Giacometto told Coates the agency could get back to her later if she submits her questions in writing.
Coates expressed some frustration with Giacometto's lack of response during the hearing. She reiterated that in a phone interview several days later, saying she was 'disappointed' LDEQ came to the hearing unprepared to discuss the work it has been doing.
Giacometto was at the hearing to discuss the agency's waste tire program. No one from the committee had asked LDEQ to prepare for a discussion on wastewater wetlands, the agency's communications division said in an email. Coates had not yet sent questions to the agency as of April 13, according to LDEQ.
Coastal researchers say one of Louisiana's greatest environmental threats is coastal erosion. The state has experienced significant deterioration of wetlands along its coast, eroding barrier islands that provide natural hurricane protection, threatening vital habitat for fish and wildlife and losing an ecosystem that absorbs greenhouse gases and is one of the earth's greatest carbon sinks.
Researchers have found geological evidence that the Mississippi River went through natural cycles of flooding and course meandering prior to the construction of levees. Like the tail of a snake, the river would frequently whip back and forth, changing its position and forming new deltas across the coast roughly every millennium.
These natural cycles created the wetlands along Louisiana's coast. The building of levees locked the Mississippi River in place, preventing it from depositing its nutrient-rich freshwater and sediments across the region's natural coastal plain, according to studies by LSU coastal scientists Harry Roberts and Irv Mendelssohn.
Through their research, Day and Turner have made significant contributions to science's general consensus on Louisiana's land loss, which points to climate change, sea-level rise, hurricanes and various human activities such as oil drilling, canal dredging and perhaps most significantly, the building of levees.
However, Turner agrees with only part of this theory and has spent much of his research arguing that canal dredging, above all else, is the primary cause of land loss. He points to more than 35,000 canals that have lacerated Louisiana's coastal wetlands, with massive amounts of soil dredged away for oil and gas operations and shipping lanes.
Turner has positioned himself against the consensus' view of how to solve Louisiana's coastal crisis, criticizing river diversion and wetland assimilation projects as costly and ignorant. He has published papers pointing out the large amounts of taxpayer money spent on such work and arguing that backfilling dredged canals is an easier and more cost-effective solution to restore the coast.
Day agrees that canal dredging has had a detrimental effect on the coast, but he said Turner has taken an extreme position by dismissing all the other causes of wetland loss.
Part of the controversy surrounding Louisiana's wetland assimilation projects lies in the difference between natural wetlands and artificial ones constructed for sewage assimilation.
Constructed wetlands are usually contained within a perimeter of concrete walls, making it easier for people to control the exact amount of water and nutrients that enters and exits a system. These engineered areas are used much more commonly around the world to treat wastewater.
Louisiana is one of few places that sends wastewater effluent to natural wetlands. Florida has a similar program intended to reuse wastewater and, in some capacity, restore wetland health. Both constructed and natural wetlands are used to treat the wastewater, but natural wetlands have stricter monitoring rules and allow smaller amounts of nutrients to be discharged.
Assimilation wetlands are similar to river diversions but on a smaller and less expensive scale, proponents say. In theory, both methods rebuild wetlands by introducing freshwater, nutrients and sediment into a degrading marsh, encouraging more plants to take root and allowing soil to accumulate over time.
Day and other supporters of natural assimilation wetlands argue resources shouldn't be spent on expensive artificial wetland systems when those resources can be used to save the state's natural wetlands.
With the Mississippi River delta sinking and the sea level rising, Louisiana's wetlands need to rise at at least the same rate to stop from disappearing, Day said.
Dr. Rachel Hunter, a wetlands ecologist with Comite Resources, said the method provides nutrients and freshwater to a hydrologically isolated wetland.
'So normally, where that water may be stagnant, you're getting water flowing through the area, and those nutrients and that fresh water will stimulate primary productivity,' Hunter said.
If regulators were to require sewage treatment plants to provide cleaner water for assimilation wastewater, proponents say it could cause the projects to fail. Increasing treatment reduces the amount of sediment pumped into a site to rebuild the land.
One of the most controversial assimilation sites is the South Slough Wetland just north of Pass Manchac, in Coates' district. Owned by the city of Hammond, it opened in 2006 and almost immediately generated public suspicion because marsh deterioration occurred at the site the following year, leaving mostly standing water in the area.
The initial deterioration at the Hammond site was attributed to nutria eating the vegetation, but the site rebounded after the project managers killed more than 2,000 nutria there, Day said.
Turner, a natural assimilation wetlands critic, argues wastewater overloaded with nutrients inundates the marsh. That weakens its soil strength and speeds up the rate of plant decomposition, causing wetlands to break apart, he said.
He dismissed claims that nutria are responsible for destroying new wetlands and doubled down on the unpredictability of a natural wetland making it hard to manage nutrient overload.
'It's very undefined,' Turner said, adding that without restraints on how effluent enters and leaves the marsh, wastewater nutrients have overloaded the system.
In his presentation to lawmakers on March 18, he displayed a photo of the site that showed what he said were dying trees and vegetation. Healthier looking vegetation was growing in the adjacent area north of the discharge pipe that does not receive any effluent.
The picture was taken in 2009, however, and Day accused Turner of using an outdated photograph and said he hasn't cited any data to show that effluent or nutrients are being affected by a lack of artificial containment structures.
The Illuminator visited the South Slough Wetland on March 20 and 25 and took drone photographs that show what appears to be thriving vegetation in the assimilation site, in contrast to mostly brown vegetation in the area north of the pipeline that does not receive wastewater. Proponents say this is a sign of the project's success.
Those on either side of the issue can present convincing arguments, but often lost in the debate is what might happen if the projects are shuttered.
Charles Borchers IV, Hammond's director of administration, said the opponents of the assimilation site never talk about alternatives for disposing the city's treated wastewater.
'A lot of people don't understand where wastewater goes after they flush their toilet … It has to go somewhere,' Borchers said. 'It's not like it just sits at the wastewater treatment plant and just goes away.'
If not for the assimilation wetland, the city would be discharging its wastewater into a river, lake or some other body of water, he said.
Borchers was also upset when he learned lawmakers had a hearing in which Hammond's project was criticized and no one was there to defend it. Like Day and Hunter, city officials only learned about the hearing when they received calls from the Illuminator.
'The city's position is that the science is on our side,' Borchers said.
He considers the site healthy and growing and said the city has its own scientist who monitors the water quality and reports the data to LDEQ on a regular basis.
'You can go to Google Earth and look at that area evolve over time,' Borchers said. 'It's got more vegetation, and it's more green now than it was in 2005.'
Turner, the Louisiana Wildlife Federation and Ponchartrain Conservancy called for a full review of the natural wetland assimilation program at the legislative meeting in March, urging LDEQ to discontinue permits for natural wetlands assimilation projects. Day supported the idea of a review, saying the science supports the projects.
'I'm all in favor of it, but let's have full involvement of everybody in there,' Day said.
SUPPORT: YOU MAKE OUR WORK POSSIBLE