Bengaluru

Floating islands cleaning Puttenahalli lake

Karnataka : Bengaluru , 28/11/2016. Floating Island installed at Puttenahalli lake in Bengaluru . Photo : Bhagya Prakash K

Karnataka : Bengaluru , 28/11/2016. Floating Island installed at Puttenahalli lake in Bengaluru . Photo : Bhagya Prakash K   | Photo Credit: Bhagya Prakash K

They have plants that grow by absorbing pollutants in the water

Puttenahalli lake has taken a low-cost, low-tech approach to filter out sewage remnants that have made its way into the water body. Artificial Floating Islands were ‘launched’ in the lake - the first of its kind in Bengaluru - in June.

These islands were manufactured using the common polyvinyl chloride (PVC) pipes and discarded 1 litre PET bottles.

Floating gently on the serene lake, which is fed through rainwater as well as treated water from a neighbouring apartment complex, are seven such Islands. Three species of nutrient-absorbing plants — vetiver, canna and colocasia — have been planted on the islands. They grow by absorbing pollutants in the water.

Encouraging results

So far, the results have been encouraging.

Volunteers, in association with BMS College of Engineering, tested the water. The result revealed an improvement in major parameters that determine the health of the lake.

Biochemical Oxygen Demand (BOD) — amount of dissolved oxygen needed by aerobic biological organisms to break down organic material — has come down by two-thirds while dissolved oxygen — amount of oxygen present in the lake — had gone up by a third between June and October.

“BOD needs to come down further, but these are encouraging results. This is just the beginning. We will launch more islands and more plants,” said Usha Rajagopalan, trustee of the citizen-driven Puttenahalli Neighbourhood Lake Improvement Trust (PNLIT), which conceived the project.

After experimenting with multiple varieties, including bamboo and eucalyptus bundles, and stainless steel nets, volunteers of the Trust settled on the current design involving PVC pipes, fishing nets and plants.

The floating islands have already been accepted by the fragile ecology of the lake. A Common Coot has made a nest on one of the islands while a sandpiper uses them to gauge the surface of the lake for its next meal. The lake has two silt islands, which are over-run by weeds.

The new system, says PNLIT, complements existing wetlands but can be controlled to ensure that the floating plants do not grow out of control.

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Printable version | Feb 23, 2020 3:53:21 PM | https://www.thehindu.com/news/cities/bangalore/Floating-islands-cleaning-Puttenahalli-lake/article16734931.ece

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