What are man-made Wetlands? Know the process, benefits here

Why in News?

A man-made wetland is being made at South Delhi Biodiversity Park developed by Delhi Development Authority, DDA.

About Delhi Development Authority South Biodiversity Park:

1. It is being built on 200 hectares of land behind Kalindi Colony. 
2. The wetland system would use boulders and a variety of plants to naturally treat sewage from 25 drains which would carry waters from Okhla to Kalindi Colony, Delhi. 
3. One of the 11 constructed wetlands began to function on December 18, 2020, treating about 15 MLD of waste from Kilokari drain. 

What are man-made wetlands?

Man-made wetlands are treatment systems that use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.

Usually, the constructed wetland has three primary components: 

• One impermeable layer (generally clay)
• One gravel layer that provides a substrate (which is supposed to be an area that provides nutrients and support) for the root
• An above-surface vegetation zone

Materials used for the construction of wetland and function

1. The gravel layer and root zone takes in all the water flows where the process of bio remediation and denitrification take place. 
2. The above-ground vegetative layer is present which contains the plant material. 
3. Both aerobic and anaerobic systems exist in the wetland, divided into separate cells. 
4. Groundwater is either pumped or can naturally flow through the wetland. 
5. The anaerobic cell uses plants with natural microbes to degrade all contaminants.
6. The aerobic cells improve water quality by regular exposure to the plants along with the movement of water between cell compartments. 
7. Straw, manure or compost is used, with little or no soil, in wetlands constructed primarily for the removal of metals. 

What is Phyto-remediation:

For wetlands constructed to treat explosives-contaminated water, certain plant species are used to support degradation. The process of using plants to break down contaminants is also referred to as phyto-remediation.

Steps in Wetland building: 

Step 1: 

The drain opens into an oxidation pond. The solid material in the waste is removed from a wire mesh and atmospheric oxygen dissolves in the water. 

Step 2:

The water travels and passes through channels and small ridges made from boulders, that creates turbulence and causes aeration.

Step 3:

Higher turbulence ensures better oxygen saturation and enhanced quality of water. The treatment process passes through 25 species of plants 

Concerns about the process:

1. Wetland ageing contributes to a decrease in contaminant removal rates in years of plantation.
2. Constructed wetlands are limited by the ability of the biota to withstand exposure to their environment. 
3. Large wetlands are required as high contaminant concentrations with low permissible effluent concentrations require long retention times
4. Constructed wetlands don’t destroy metals as they restrict their mobility through the sorption process

Constructed wetlands have most commonly been used in wastewater treatment to control organic matter, nitrogen, and phosphorus. The wetland process is also used for controlling trace metals and other toxic materials in groundwater.

Know all Ramsar Wetland Sites in India by taking this quiz

Credits: cpeo.org, epa.gov.in