Prof disputes column that declared dumping sewage in wetlands a big ‘green’ mistake

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The recent column by Ed Bodker is generally misleading and filled with statements that are factually incorrect.

Sewage is not being dumped into wetlands, not legally at least.  Sewage is what goes into a treatment plant and what comes out is treated municipal effluent.  The degree of treatment depends on the method of treatment and the condition of the receiving waterbody.  Bodker understands this but he continually misleads readers by claiming sewage is being discharged into wetlands.

Bodker says that partially treated sewage is being dumped into wetlands.  All sewage is partially treated unless it is treated to the level of drinking water.  The level of treatment depends on the limits set by the Louisiana Department of Environmental Quality in the discharge permit and by the condition of the receiving waterbody.  For example, treated effluent that is discharged to the Mississippi River has less stringent limits than that discharged to a water quality-limited stream or lake.

The decision to approve wetlands assimilation, or any treatment system, is not based on cost but on the permitted treatment level in balance with surrounding natural systems.  The New Orleans Sewerage & Water Board (S&WB) project referred to by Bodker is a small-scale project that will discharge effluent from the East Bank treatment plant into the Central Wetlands.  The great majority of the plant’s effluent will continue to be pumped to the river.

Bodker compares constructed wetlands to assimilation wetlands (which he wrongly terms wastewater assimilation).  Although the biogeochemical processes are the same in both systems, constructed wetlands are more heavily loaded than assimilation wetlands and are midway between conventional treatment and assimilation wetlands.  Constructed wetlands are more intensive and assimilation wetlands are more extensive.

Bodker mentions treated and partially treated sewage, but it is the level of treatment that is the issue; all effluent that is discharged from a wastewater treatment plant is partially treated.  He also mentions a higher degree of control, but both conventional treatment and constructed wetlands are strongly impacted by heavy rainfall where flows can go up by a factor of five or six or more.

Bodker states that once in the wetland, control over the discharge is lost and becomes loosely regulated.  This is not true and Bodker offers no data to back up this statement (or most of the other claims in his column).

Before a wetland assimilation project can be approved, there must be a detailed ecological baseline study covering hydrology, biogeochemistry, and vegetation dynamics of the wetland.  One aspect that is carefully considered is the potential for short-circuiting of water flow.  After a project is initiated, regular monitoring is required.  This monitoring has proved valuable in understanding the response of the wetland ecosystem, and to counter statements that discharge is short-circuiting or that trees are being killed, for example.

Bodker and others in the community of non-governmental organizations have suggested that consultants have adjusted their statements about assimilation wetlands because they are receiving funding from municipalities to carry out monitoring at the assimilation sites.  This is definitely not the case and no evidence has ever been presented to substantiate this suggestion.  Funding from municipalities is for ecological baseline studies and for routine monitoring.  It is not an exorbitant amount, and the contract is usually awarded to the lowest bidder.  Several entities are currently carrying out monitoring of assimilation wetlands including Comite Resources, Providence Engineering, and Nicholls State University.

One attribute that has characterized wetland assimilation is the abundance of intensive studies that have been carried out and published in the scientific literature.  This is in addition to the required monitoring.  Studies of assimilation wetlands have provided a focus for undergraduate and graduate education and research efforts.  Sixteen students have received graduate degrees from LSU, Southeast Louisiana University, Nicholls State University and Tulane University for work on topics related to assimilation wetlands.

More than 40 papers, authored by 76 scientists, have been published in peer-reviewed scientific literature related directly to assimilation wetlands in Louisiana, and many additional papers have been published about the ecology and biogeochemistry of nutrients and wetlands. Issues addressed by these studies have included hydrology, above- and below-ground wetland plant productivity and decomposition, tree ring analysis, nutrient dynamics, wetland biogeochemistry and stoichiometry, carbon sequestration, uptake of pharmaceuticals and personal care products, dynamics of animal populations, stable isotope analysis, policy considerations, and cost analyses. For lists of publications, students and scientists, click here.

Thus, rather than tailoring their comments to support assimilation wetlands, scientists involved in these projects have carried out extensive and detailed studies to better understand the functioning of these systems.  The suggestion that scientists are tailoring their discussion of wetland assimilation for financial reasons is reminiscent of the climate conspiracy that thousands of climate scientists worldwide are interpreting their publications on climate change to get more funding.  Suggestions by some in the NGO community that scientists are basing their conclusions on wetland assimilation for financial reasons is unsupported and patently ridiculous.

Bodker states that tertiary treatment (i.e., nutrient removal) does not occur.  This is correct in strict comparison to what occurs at a treatment plant.  But for all cases of wetland assimilation in Louisiana, nutrient concentrations are reduced to background levels, even after decades of operation.  Bodker’s suggestion that nutrient reduction by assimilation wetlands is largely due to dilution is simply not correct.  Denitrificaton, plant uptake, and burial are the primary pathways for nutrient reduction, as has been shown by studies of assimilation wetlands, as well as many studies of a broad range of wetlands.

Bodker discusses pathogens such as antibiotic-resistant bacteria that may grow in wetlands due to  the combination of low oxygen, high levels of organic matter and nutrients, but, like most of his claims, he offers no data to support such statements. Recent studies indicate that antibiotic-resistant bacteria can actually be removed by treatment wetlands.

Studies in Louisiana have shown that antibiotic resistant bacteria are widespread in the environment including Bayou Lafourche, which is a source of drinking water, and coastal waters that are used for fishing, boating, and swimming.  This pattern also holds globally. But this is unrelated to assimilation wetlands.

Organic contaminants, such as pharmaceuticals and personal care products, which include antibiotics, anti-inflammatory drugs, cosmetics, pesticides, and compounds used in making plastics, and related compounds, are widespread in the environment and are not eliminated by conventional treatment but are substantially reduced by treatment wetlands.

Home septic systems, of which there are thousands in the watershed of Lakes Maurepas and Pontchartrain, have little effect on these compounds.  And many of these compounds are not associated with conventional sewage treatment but come from upland runoff (urban and agricultural), landfill leachates, and storm-water pumps.  In the Central Wetlands, for example, storm water pumps discharge more than 30 times the amount of water flowing to the Riverbend pond. Surface runoff has a variety of pollutants including oil and grease from streets, animal feces, and fertilizers and biocides sprayed on the landscape.  Advanced treatment would be extremely expensive and would fail to address many of these problems.

Bodker states that discharge to wetlands usually produces more liabilities than benefits but, once again, offers no support for this statement.  Nor does he offer any support for his contention that  cost savings are “illusory” or a matter of “smoke and mirrors.” He states that what takes place in an assimilation wetland is what takes place in a treatment facility, ignoring the fact that, for example, chemicals are often added in a treatment plant to cause precipitation.  At any wastewater treatment facility, solids and organic matter are reduced and the effluent is disinfected.

Studies at several assimilation wetlands have shown that vertical elevation gain is higher than in adjacent reference areas, and that nutrients are reduced to background levels. Neither of these processes occur in treatment plants.

With regard to the proposed S&WB project, the idea is to expand the project area to create more wetlands.  Water exchange in the area is currently very low, and the area would benefit from increased hydrological flow.  The amount of water and nutrients will be carefully balanced with the receiving area.  Because the triangle area is located so far from the Central Wetlands, water exchange with waterbodies outside the Central Wetlands is minimal.

Since the partial closure of the Mississippi River Gulf Outlet (MRGO), salinity has been reduced significantly.  Recent studies have shown that salinities are approaching pre-MRGO levels, and the triangle area will soon become fresh if it is not already so.  Near the Gore pumping station, which also receives effluent from the Riverbend pond, is one of only two small areas of cypress left in the Central Wetlands. Its vitality has been maintained by discharge from the pumping station. The proposed S&WB project will build on that success.

John Day

Using spoil material to create a wetland in the triangle will mostly eliminate the potential for algal blooms. And the suggestion that the small amount of proposed discharge in the triangle poses a threat to oysters in Lake Borgne is without merit.

John W. Day is professor emeritus with the Department of Oceanography and Coastal Sciences at Louisiana State University. He founded Comite Resources, which carries out environmental monitoring for several of Louisiana’s assimilation wetlands projects.

The opinion section is a community forum. Views expressed are not necessarily those of The Lens or its staff. To propose an idea for a column, contact Lens founder Karen Gadbois.


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