By Lucy Gibson
Neknampur Lake, in Hyderabad, was previously a rubbish dump. Spread over 108 acres, this 450-year old water body had often made the headlines for its continued pollution. A weed-choked mixture of chemical pollutants and domestic sewage from the increasing numbers of housing that cropped up around the lake’s edge.
Now, although it may be mistaken that water hyacinth has consumed Neknampur Lake, this could not be further from the truth.
A closer look reveals that floating gently on the water’s surface there are a number of artificial ‘structures’ each covered in a meticulous selection of plants and joined together to form an island.
The island is, in fact, a “floating treatment wetland” that was released into Neknampur Lake in 2016 by Madhulika Choudhary and the NGO Dhruvansh who incorporated phytoremediation techniques into their restoration plans. This was achieved with supervision and support from the State Irrigation Department, Rangareddy District Collector, Hyderabad Metropolitan Development Authority, Telangana State Pollution Control Board, Telangana Fisheries Department and the Telangana State Biodiversity Board.
The island structure is simple, but effective. With thermocol on all four sides with plastic bottles attached to ensure that they remain afloat, a plastic mesh, a gunny bag placed on the top, and followed by a layer of gravel in which aquatic plants known to absorb pollutants are planted. For example, vetivers, canna, bulrush, lemon grass, fountain grass, lillies, khus, and other flowering plants. Mosquito repelling plants, such as citronella were also planted. Once floating, the plants grow and their roots reach into the water absorbing pollutants like phosphate and nitrates, cleaning the lake. Such hydroponics systems allow plants to grow only in sunlight and water.
Each 10ftx10ft raft, of which there are 27, are joined together to form an island which spreads across over 2,500ft2 of the lake. In total, the island is covered by approximately 3,500 saplings which break down and consume harmful nutrients and organic matter in the water through microbial decomposition.
An additional problem has also been that cement debris and rubbish were commonly found to be dumped alongside the water’s edge, threatening the homes of pythons and monitor lizards. In response, Dhruvansh, along with the Irrigation Department, established a barricade on the bund. Fencing, walking tails and cycle tracks have also been proposed, to transform the lake into a public recreation site.
Far cheaper than sewage treatment plants, these floating islands demonstrate that sometimes restoration efforts don’t need a big budget to be effective. In fact, recent analysis of water samples collected from the lake show that, thanks to the floating island, water quality has improved significantly. According to the latest data collected by the Telangana State Pollution Control Board, the Biological Oxygen Demand (BOD) at the outlet of the lake had decreased from 27mg/L to 3.8mg/L in only 5 months.
Biodiversity is also on the rise. Conservationists have found bird nests and eggs belonging to Whistling ducks, herons, and geese, as well as new turtles. Moreover, when the floating island was brought to shore for maintenance a young python was spotted on the island! The lake is now home to 132 species of flora, 178 species of birds, 12 species of mammals, 21 species of reptiles, and 20,000 fish.
Projects such as this highlight the potentials of such a replicable model of bio-remediation. That nature, when allowed, can take care of itself.