Overview of Constructed Wetlands

1
Overview of Constructed Wetlands

• Bruce Lesikar
• Associate Professor
• Texas Cooperative Extension

2
On-Site Sewage Facilities Regulations

• Prior 1989- regulation enforced by local
  government and/or Texas Dept. of Health
• September 1989 - statewide regulation of OSSF
  systems
• May 1993 TNRCC responsible for
• permitting
• inspection
• compliant investigations
• enforcement action

3
Overview and Basic Treatment

• A constructed wetland treats wastewater through
  the naturally occurring processes
• Chemical
• Physical
• Biological
• A constructed wetland is an alternative treatment
  method for additional effluent treatment.

4
Overview and Basic Treatment

• Often referred to Microbial Rock Filters
• Microbial Rock Plant Filters
• Gravel Bed Filters
• Two types of wetlands
• Free Water Surface (FWS)
• Subsurface Flow (SF)
• Due to health risks Subsurface flow filters are
  used for residential systems.

5
Overview and Basic Treatment

• SF constructed wetlands consist of an earthen
  basin lined with
• Compact native clay
• Bentonite Clay
• Concrete
• PVC
• Hypalon
• PondGard ethylene propylene diene terpolymer
  rubber

6
Overview and Basic Treatment

• Within the basis a bed of graded stone media a
  header is used to evenly distribute the effluent
  into the stones.
• An additional header is used at the outlet end to
  collect the effluent for final dispersal.
• Vegetation placed into the stone media is often
  used for additional nutrient removal.

7
Overview and Basic Treatment

• Microbes attach themselves to the stone media.
• The microbes digest organic matter measured in
  TSS and BOD.
• Either soft tissue or hard tissue plants can be
  used in wetlands.
• Hard tissue plants provide a better path for
  oxygen to get into the media, while soft tissue
  plants provide different floral options.

8
Plant Selection

• Once a constructed wetland is constructed plants
  need to be selected to best fit the climate of
  the system.

9
Plant Selection
10
Wetland Plant Options
11
Wetland Plant Options
12
Wetland Plant Options
13
Operation and Maintenance

• Maintain the septic tank pump out frequency.
• Check the effluent filter if applicable.
• Maintain the water level in the wetland cell.
• Maintain a cover over the sides of the liner to
  prevent UV degradation.

14
Operation and Maintenance

• Repair any earthen berms as soon as possible.
• Routine maintenance on the vegetation
• Pulling weeds
• Replacing dead plants
• Removing mature plants in the fall.
• Replanting during the spring.