Wetlands boosted by sewage
Parish first in nation to trade carbon credits with program
The parish began discharging secondarily treated sewage from the Luling Oxidation Pond into the adjacent wetlands in 2006. The wetlands in the vicinity of the pond are composed of freshwater forested wetlands. Because these wetlands are isolated from the Mississippi River, there was inadequate freshwater, sediment and nutrient input.
The project is similar to using manure in a garden because it provides nutrients that help revive plant life. The fresh water from the treated effluent has also improved cypress tree growth in the area.
The parish began the wetland discharge program to not only introduce nutrients and fresh water intended to enhance vegetative growth, but also to meet more stringent water quality standards that were introduced by the Department of Environmental Quality. The sewage is treated and disinfected prior to discharge to eliminate harmful microorganisms.
Wetland ecologist Dr. Rachael Hunter said that the program is a win-win for both the parish and the Luling wetlands.
"The Luling site is working great and it’s a very healthy wetland," she said. "Those wetlands are starved for fresh water and nutrients, and this process gives those wetlands what they need to be more productive."
Studies of the Luling wetlands have shown that vegetation productivity has increased significantly since the program began. In fact, productivity was reported to be twice as high in the discharge area as it is in a similar wetland that is not receiving the discharge.
Dr. John Day, a retired professor of oceanography and coastal sciences at LSU who serves as a project advisor, said that the treated effluent has increased the growth of the cypress forest in the area while reducing the levels of nitrogen, phosphorus and other components of the effluent to background levels.
When the project began, the parish did not have the funding available to compensate Rathborne for the use of their land, so both parties agreed that the parish would pursue carbon credits to compensate Rathborne. Dr. Sarah Mack, president and CEO of Tierra Resources, said that now that her company’s methodology has been certified, other companies can invest in the Luling wetland project.
As for trading carbon credits, Mack said it is similar to a diet.
"If you want to lose weight you have to either eat less or exercise. Just as a calorie is your standard unit, a carbon credit is the standard unit that represents one ton of carbon dioxide," she said. "If an industry wants to reduce their greenhouse gas emissions they either need to retrofit their facility or invest in a project that removes greenhouse gasses from the air.
"Previously an industry that wanted to reduce their emissions could invest in forest or agriculture projects, but there was no certified methodology to transact wetland carbon credits."
Extensive monitoring will be performed to calculate the amount of carbon dioxide the Luling wetlands naturally remove during photosynthesis. Mack said the project benefits both the parish and Rathborne.
"The project reduces the costs to the parish to provide hurricane resilient wastewater infrastructure that restores wetlands vital to the sustainability of the parish," Mack said. "The carbon credits will allow the parish to compensate the landowner without additional cost to parish residents."
In a few years, Rathborne will be able to sell those credits to other companies.
While waste is going into the wetlands, it is treated to remove contaminants.
"We have to monitor the site continuously in order to keep the Louisiana Pollutant Discharge Elimination System permit that allows us to discharge the treated effluent," Hunter said.
The site is so intensely monitored that scientists collect fallen leaves monthly and water samples quarterly to really gauge the effect the process is having on the wetlands.
Prior to discharge, the municipal effluent is analyzed for volatile compounds, metals and hazardous substances. Hunter said that the Luling effluent was below the EPA minimum required concentrations. That means that the pollutant would not be a problem in the receiving water body.
"All sewage treatment plants are required to test for priority pollutants prior to discharging into any water body," Hunter said.
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