The land is purchased, the pipeline is installed and later this month, the city of Mandeville will begin pumping up to 2 million gallons of biologically treated effluent daily into 1,700 acres of marshland.

The city has been treating its sewerage waste biologically at its state-of-the-art plant located behind Mandeville High School since 1989.

Through the wetlands assimilation process, sewage is brought into the treatment plant through the headworks, where non-biological solids, such as paper and plastics, are separated out. The wastewater is then filtered through a series of three gravity-fed ponds of increasing aeration, where aerobic and anaerobic bacteria treat it biologically and ammonia is transformed into nitrates and nitrites.

Public Works Director David deGeneres shows a water collection device located at the end of one of the observation platforms along the pipeline. (Staff Photo by Suzanne Le Breton)

The wastewater is then released into a man-made wetland, where plants use the nitrogen as fertilizer. The wastewater is then refiltered and sprayed over a rock bed before being circulated through the constructed wetlands.

Prior to be disbursed into the wetlands surrounding the facility, the effluent is sterilized through a UV system. The system was modified and improved in 2000.

Currently the treated effluent is dispelled directly behind the plant into the Bayou Chinchuba marsh.

The effects of the effluent on the marsh are monitored closely by testing water samples, collecting leaves and measure trunk sizes.

Public Works Director David DeGeneres said since the city has started dispelling the effluent in the marsh, the area has flourished.

“The marsh has grown dramatically,” he said. “The trees have grown three times faster.”

Not only does the treated wastewater carry nutrients into the marsh, it also pushes back the brackish lake water that inundates the wetlands when the Lake Pontchartrain rises.

This water causes salt-water intrusion, which stunts plant growth.

Using federal grant money, the city recently installed a little more than 3,300 feet of 18-inch pipe carrying the treated effluent further into the wetlands.

A three-mile long underground pipe runs down Mandeville High Boulevard and behind Beau Rivage subdivision. From that point the pipeline rises above ground and travels down the CLECO right-of-way. The pipeline travels through the East Tchefuncte wetlands and a piece of property commonly referred to as the Dendinger Tract, which the city purchased in 2001and leads all the way to the lake and the Tchefuncte River.

Along this pipeline there are 25 discharge points, where the wastewater will be released into the wetlands.

Before the wastewater can be pumped down the pipeline, the city must first upgrade to a larger pump to be able to push the effluent down the line.

DeGeneres said as soon as that pump comes in and is installed the city can started using the pipeline.

For maintenance reasons an elevated boardwalk was constructed along the length of the line as well as two observation platforms extending out into the marsh. These platforms will be used to monitor the effects on the wetlands, through leaf collection and water sampling.

DeGeneres expects the wetlands to flourish much like the Bayou Chinchuba marsh did.

He said by stopping the saltwater intrusion and building the marsh back up, erosion will also be decreased. Therefore the wetlands will offer a better buffer for the city against storms.

DeGeneres said in addition to helping the wetlands, treating wastewater biologically also uses less energy then other means of treatment.

The next phase is to upgrade the headworks and the effluent pumps, which will double the facility’s capacity and allow the city to start accepting wastewater from outside of city limits.

The parish will be responsible for getting the wastewater from homes and businesses location inside the city’s growth management areas to the plant but from there it will be treated and released along with that coming from homes and businesses inside the city limits.

DeGeneres said the city’s long-range plans include installing more pipelines coming off the main pipeline in order for the effluent to reach more area.

He said studies will be done to determine how much effluent should be released at what point and how far out that the effects of that effluent will reach.

“We know the concept works,” he said. “We now have to determine how to make it work the most efficiently.”�