Classification of Treatment Wetlands

Question 1

Three types of wetlands used to

treat water

Answer 1

1. Natural wetlands
2. Surface flow wetlands (constructed wetlands)
3. Subsurface flow wetlands (constructed wetlands)

Question 2

Surface flow wetlands (Free Water Surface)

Answer 2

• Mimic natural wetlands
• Standing water through most (sometimes all) of the year

•Pros:
–Ancillary benefits: attract a wide variety of wildlife

•Cons:
–Potential for human exposure to pathogens
–Does not work well in cold climates

• Rarely used for secondary treatment
• Used for the advanced treatment after secondary or tertiary treatment

Question 3

Surface flow wetlands (Free Water Surface) part 2

Answer 3

• Typically used for the treatment of:
– Urban, agricultural, and industrial
stormwaters
– Mine waters
– Groundwater remediation
– Leachate treatment

• Can deal with pulse flows and changing water levels

Question 4

Subsurface Flow Wetlands

Answer 4

• Water flows horizontally or vertically through a porous medium (sand
or gravel)

• Rarely standing water
• Developed and most common in Europe

Question 5

Subsurface Flow Wetlands Part 2

Answer 5

• Pros:
– Less risk of human or wildlife exposure the pathogenic organisms
– Can operate under colder conditions (top insolated)

• Cons:
– More expensive than surface flow wetlands
– Few ancillary benefits
• Used for smaller flow rates:
– Secondary treatment of single family homes

Question 6

Subsurface flow wetlands sketch

Answer 6

see slide 16

Question 7

Types of subsurface flow wetlands

Answer 7

• horizontal subsurface flow

* vertical subsurface flow

Question 8

horizontal VS vertical subsurface flow

Description

Answer 8

• Horizontal Subsurface Flow
Large gravel and sand-filled basin planted with wetland vegetation
WL: 5 - 15 cm below the surface

• Vertical Subsurface Flow
Wastewater is intermittently applied (4-12 doses per day) and drains down toward the bottom

Question 9

horizontal VS vertical subsurface flow

How it treats waste water

Answer 9

• Horizontal Subsurface Flow
Filter material filters particles Microorganisms (facultative and anaerobic ) degrade organic waste

• Vertical Subsurface Flow
The batch loading leads to high aerobic degradation

Question 10

horizontal VS vertical subsurface flow

Type of wastewater treated

Answer 10

• Horizontal Subsurface Flow
2nd treatment of single-family homes or a group of homes

• Vertical Subsurface Flow
Wastewater with high ammonia levels (landfill leachate and food processing)

Question 11

horizontal VS vertical subsurface flow

Area required

Answer 11

• Horizontal Subsurface Flow
5-10 m2 per person equivalent

• Vertical Subsurface Flow
1-3 m2 per person equivalent