Our thanks to Robin Knox of the UH Botany Department and Pam Daoust for providing the following:
There are two aspects of use of wetlands for wastewater management to discuss.
1) Constructed wetlands as treatment
2) Wetland assimilation projects – Due to higher assimilative capacity ( especially for nitrogen), wetlands get less stringent water quality-based discharge limitations than some other waterbody types. The discharges in these projects are actually being used to restore wetland functions where wetlands have been hydrologically separated from their sources of water, nutrients, and sediments by anthropogenic activity (roads, drainage, water diversion, etc.)
1. CONSTRUCTED WETLANDS
City of Crowley has a rock reed filter (constructed wetland) I think there are about 50 of these constructed wetlands permitted in LA now. The EPA link is for a 1993 design document that reviewed some of these systems.
www.epa.gov/wetlands/pdf/sub.pdf
www.crowley-la.com/GOVERNMENT/DEPTwater.html
2. WETLAND ASSIMILATION PROJECTS
The LDEQ site has links to numerous projects that are online or proposed in Louisiana and explains the regulatory approach under CWA
www.deq.state.la.us/portal/DIVISIONS/WaterPermits/WetlandAssimilationProjects.aspx
The City of Thibodaux LA was the first to use a wetland assimilation project. A couple of links to the City of Thibodeaux, LA which has both constructed wetlands (biological rock filter) and a natural wetland discharge –
www.comiteresources.com/wa_thibodaux.asp
www.ci.thibodaux.la.us/departments/pw/sewage/index.asp – caution – some of the wording on this site is not consistent with the regulatory strategy that was outlined with the agency (ie the wetlands are not tertiary treatment – discharge to a wetland of a secondary effluent was allowed in lieu of constructing tertiary treatment for discharge to a drainage canal that did not flow unless it rained and it was pumped.) This project was funded by a construction grant and required the approval of a total of six clean water regulatory branches at state and federal levels (permitting, water quality standards, and construction grants approvals).
For those interested in more information about the use of wetlands, here is the info, including an explanation of the many different types. Wetlands are essentially another way (reportedly much less expensive and often far more effective than many other methods) of recycling wastewater, replenishing freshwater aquifers and preventing nitrogen, etc. from entering nearby bodies of water:
www.dep.state.fl.us/water/wastewater/dom/wetsites.htm
This link provides a complete listing of Florida’s domestic wastewater wetlands. Of particular note are the three general types being used: Natural Receiving Wetlands, Natural Treatment Wetlands and Man-made (Constructed Wetlands.) Each listing shows size of wetland and volume of water in the wetland, with constructed wetlands showing the highest volume of water to lowest required acreage, e.g. 5.0 mgd to approximately 125 acres at Green Cay, 3.0 mgd to approximately 70 acres at Orange County, 2.0 MGD to 50 acres at Palm Beach County Southern Region.
Below is a good description of the Green Cay Wetlands that has become a recreational area. This one is considered “state of the art.” (They don’t all have to be this elaborate!)
Palm Beach County Green Cay Wetlands: Description of project:
www.pbcgov.com/waterutilities/waterfacts/green_cay.htm
Here is some info on a a small-size but EPA award-winning storm and wastewater recycling project here in Hawaii. It saves on land space needed for a wetland by using a cool new technology known as The Restorer:
http://rothecologicaldesign.com/technology.php
Here’s another California coastal project utilizing a town’s wastewater for a wetland system that filters harmful nutrients and prevents them from getting into the nearby ocean. This is a great article from Audubon Magazine that addresses both point and non-point pollution sources, dealing with how a community handled both at the same time. Well worth your time to read. (Also references The Restorer technology and explains it.)
http://audubonmagazine.org/solutions/solutions0703.html
Below is a May 2010 article containing good general information on wetland use for smaller applications and rural communities. Today’s technology for constructed wetlands has been much improved over time. Issues such as “mosquitoes” and other insects, etc. should not be a problem in a properly constructed and maintained wetland.
http://wrdc.usu.edu/files/uploads/Newsletter/RC_May10/ConstructedWetlands.pdf
