I don't know much about waste treatment but a few years ago, Hammond, La.- close to where I live, was preparing to purchase about 60 acres of land and convert it to a swamp to pump the treated effluent from the city's waste treatment plant. This effluent is supposedly clean. I have a smaller scale system at home and when installing, the contractor said you could drink the water that comes out. I asked him to show me and he declined. Anyway, a biologist from LSU made a presentation to the city by pointing out one of the largest natural swamps in the state is just 5 miles south of the city and literally starving for fresh water. The swamp grasses and other plants were/ are dieing due to salt water intrusion. The effluent is pumped down to the edge of the swamp in a 36" pipe and then a massive manifold distributes the water through over 120 valves across about a two mile stretch. The swamp is much 'healthier' in this area and the city saved some money. Some theories are that the Ms River Gulf Outlet ( MRGO -a navigational shortcut from New Orleans to the GOM) allowed more flow from the GOM into L. Pontchartrain, and its subsequent closing after being blamed for a significant portion of the flooding during Hurricane Katrina, could signal a rejeuvination for some of the eroding wetlands around the lake.
Many years ago, N.O. and other municipalities around the lake basically pumped treated sewage directly into the lake. It was closed to swimming in the 1980's and eventually cleaned up. It still gets runoff but not the sewege and is very healthy ecosystem in general.That is, until the Ms River was diverted due to high water. Now it is entirely full of fresh river water.