MAN MADE WETLANDS

MAN MADE WETLANDS

Subject: Environment

Context : A unique sustainable experiment is under way in Delhi, where a ‘constructed’ natural feature brings hope of reducing the need for expensive sewage treatment plants, with issues of capacity and utility.

Concept :

• At the South Delhi Biodiversity Park, being developed by the Delhi Development Authority (DDA) on about 200 hectares of land behind Kalindi Colony, Delhi University professor is making 11 constructed wetland systems.
• These constructed wetland systems will use boulders and a variety of plants to naturally treat sewage from 25 drains, stretching from Okhla to Kalindi Colony, before it enters the river

How treatment works

• The method involves a three-step process, which does not require electricity. At the mouth of the drain, a team of scientists led by Prof Babu have made a one-acre wide wetland from boulders and plants.
• The drain opens into an oxidation pond, which is the first step of the treatment process. Here the solid material in the waste is removed from a wire mesh and atmospheric oxygen dissolves in the water.
• The water then travels further and passes through channels and small ridges made from boulders, which creates turbulence and causes aeration.
• Aeration brings water and air in close contact, introducing small bubbles of air which rise through the water and remove dissolved gases in it.
• Higher turbulence means better oxygen saturation and better quality of water. Waterfalls have maximum oxygen saturation and, therefore, have very good water quality.
• The final step in the treatment process happens when water passes through 25 species of plants — including typha, phragmites, ipomoea and cyprus — which are effective in the treatment of heavy metals, including arsenic.