Innovation: Floating islands clean polluted lakes in Bengaluru

There is good news for those who are concerned about the deterioration of water quality of the lakes in their respective neighborhoods. Local residents’ brain stormed and came up with the idea of floating islands. Y. Maheswara Reddy finds out more about this simple solution to the complex problems plaguing our water bodies.

There are many reasons for the deterioration in water quality in the lakes of Bengaluru. The causes vary from Lake to Lake. Sewage, Industrial effluents and overgrown weeds are some to the causes.

The good news is that Puttenahalli Neighbourhood Lake Improvement Trust (PNLIT) has come out with a unique and economical concept to improve the quality of water in the lakes.

It all began when Karnataka State Pollution Control Board (KSPCB) permitted a residential apartment complex to pump treated water into the Puttenahalli Lake which was bone dry due to lack of water supply from storm water drains.

“The lake was dry due to the failure of monsoon. South City Apartments has a sewage treatment plant (STP). The treated water was used for flushing and gardening. Yet, there was excess water. The residents wanted to pump the excess water into Puttenahalli Lake. After availing permission from the KSPCB, the treated water was pumped into the lake beginning May 2015. Around 6 lakh liters of treated water is being pumped into the lake daily,’’ PNLIT chairperson Usha Rajagopalan said.

The residents were happy to see Puttenahalli Lake brimming with water but the quality of the water made them to introspect. Brain storming led them to the concept of floating islands.

“I had been to Kolkata in December 2015. I came to know about vetiver through someone. In February, 2016, a team from Indore visited the Puttenahalli Lake. They told me about how they were using floating islands at one of the lakes in Indore,’’ recalls Usha Rajagopalan.

The members of PNLIT decided to emulate the Indore model to ensure quality water in Puttenahalli Lake.

“We came to know that maintaining plants such as vetiver, canna and colocasia would be a tough task if those were planted on the wet land. We cannot ask the gardener to enter the wetland either to trim the plants or focus the maintenance of these plants. So, we designed the floating island. Each of the floating islands (5 ft 5ft) cost Rs 4,000. As of now, there are more than 60 floating islands in the Puttenahalli Lake,’’ Usha Rajagopalan narrates.

The floating island was a pilot project for the volunteers of Puttenahalli Lake. They wanted to test the quality of the treated water pumped into the lake. So, they joined hands with BMS College of Engineering. “The concept is ours. We approached BMS College of Engineering to test the quality of water. The results were encouraging. The quality of water was found to be good,’’ she said.

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 2016.

What is a floating island?

It is a low-cost, low-tech approach to filter out sewage remnants that have made its way into the water body.

These islands are made using the common polyvinyl chloride (PVC) pipes and discarded 1 litre plastic bottles and 5-ft-long nets above and below.

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, according to Usha Rajagopalan, complements existing wetlands but can be controlled to ensure that the floating plants do not grow out of control. It is said the initiative has increased the number of bird species in the area as many perch on these islands as well. The floating islands have not only benefited the water body but also the wetlands.

Other lakes

Now, the Karnataka Lake Conservation and Development Authority (KLCDA) authorities want to emulate Puttenahalli Lake model to improve water quality in other lakes in the city.

“It all happened during my visit to Puttenahalli Lake. I found the floating island concept very interesting and viable. I enquired with the residents about it. Impressed by the concept, we want to introduce floating islands at Madiwala Lake. The low-cost, low-maintenance concept will also be introduced at Agara lake on the Outer Ring Road and Vengaiah lake near KR Puram in the near future,’’ KLCDA Chief Executive Officer Seema Garg said.

For any guidance and information on floating islands, contact Usha Rajagopalan 72597 22996.

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