Assimilation wetlands are natural wetlands into which secondarily treated and disinfected effluent from a wastewater treatment plant is discharged to improve water quality and wetland sustainability. Nutrients in the municipal effluent increases wetland plant growth, and organic matter deposition on the wetland surface, which increases elevation and offsets subsidence and produces a positive feedback loop of increased ecosystem vigor and resiliency. Freshwater in the effluent provides a buffer against saltwater intrusion events, especially during drought. Thus, the introduction of treated municipal effluent into disturbed and isolated wetlands is a positive step towards their ecological restoration. This practice also benefits dischargers by reducing capital, operations, and maintenance costs compared to conventional wastewater treatment.

Conceptual model of the effects of effluent application to wetlands

The concept of using municipal effluent for restoration of wetlands in coastal Louisiana originated with Breaux and Day (1994), who proposed that adding nutrient-rich effluent to hydrologically isolated and subsiding wetlands could promote vertical accretion through increased organic matter production and deposition. Their work, and other studies, has shown that treated municipal effluent does stimulate productivity and accretion in wetlands (Hesse et al. 1998; Hunter et al. 2009a; Shaffer et al. 2015; Hunter et al. 2018). In addition, removal of nutrients and sediments from municipal effluent by assimilation wetlands has been well documented at the cities of Amelia (Day et al. 2006), Breaux Bridge (Blahnik & Day 2000; Hunter et al. 2009a,b; Hunter et al. 2018), Broussard (Hunter et al. 2018), Hammond (Shaffer et al. 2015; Hunter et al. 2018), Luling (Hunter et al. 2009b; Hunter et al. 2018), Mandeville (Brantley et al. 2008; Hunter et al. 2018), St. Bernard (Day et al. 1997), and Thibodaux (Zhang et al. 2000; Izdepski et al. 2009).

Design and construction of an assimilation wetland typically requires a Louisiana Department of Natural Resources (LDNR) Coastal Use Permit (CUP), Louisiana Department of Environmental Quality (LDEQ) Louisiana Pollutant Discharge Elimination System (LPDES) permit, and US Army Corps of Engineers (USACE) 404 permit and Water Quality Standards certification, along with potential levee board permits, all of which Comite Resources has obtained for numerous projects.

Comite Resources works with municipalities to assess wastewater treatment needs and to identify potential wetland areas that would benefit from effluent discharge. Comite Resources collaborates with project engineers to design the effluent distribution pipeline and with LDEQ, LDNR, and USACE to secure  permits. Comite Resources monitors assimilation wetlands serving the cities of Breaux Bridge, St. Martinville, Luling, Hammond and Mandeville and visits each wetland monthly to collect ecological data.

The reference site at the Breaux Bridge assimilation wetlands 
The reference site at the Breaux Bridge assimilation wetlands 
Site 3M at the St. Martinville assimilation wetlands
Site 3M at the St. Martinville assimilation wetlands
The treatment boardwalk at the Luling assimilation wetlands
The treatment boardwalk at the Luling assimilation wetlands
Photo  (top)  of  a  fenced  2  x  2  m  exclosure  at  the  Hammond  assimilation  wetlands  that  prevented  nutria  entry  established  in  2008  after  intense  grazing  over  the  fall  and  winter  of  2007-2008,  and  another  exclosure  (bottom)  during  the  Summer  of  2011  after  substantial  recovery  of  marsh  growth.  The  discharge  pipe  is  located  near  the  tree  line  in  the  background  in  the  upper  left  of  both  photos.
Photo (top) of a fenced 2 x 2 m exclosure at the Hammond assimilation wetlands that prevented nutria entry established in 2008 after intense grazing over the fall and winter of 2007-2008, and another exclosure (bottom) during the Summer of 2011 after substantial recovery of marsh growth. The discharge pipe is located near the tree line in the background in the upper left of both photos.
The out site at the Hammond assimilation wetlands 
The out site at the Hammond assimilation wetlands