Sewage-treatment plants clean up polluted Hyderabad lake

Mahesh Bacham/101Reporters

Hyderabad: A radical new solution to cleanse India’s polluted water bodies has transformed Neknampur Lake on the outskirts of the city. The floating treatment wetland (or FTW) is an artificial island planted with 3,500 saplings that cleans the lake, improves the habitat for the creatures that depend on it and beautifies it at the same time.

Inaugurated on 2nd February 2018 on World Wetlands Day, the Neknampur FTW has been recognised as the largest of its kind in the country by The India Book of Records. It’s the creation of Dhruvansh, an NGO, that along with the Hyderabad Metropolitan Development Authority (HMDA) and district authorities, has been working to revive the lake since 2016. 

Ibrahim Bagh ‘river’ is a 100-acre water body situated in Neknampur village in Rangareddy district of Telangana. It consists of two distinct water bodies, chinna cheruvu (small river) also called Neknampur Lake covering 25 acres, and pedda cheruvu (big river) of around 75 acres.  While chinna cheruvu has been transformed into a beautiful lake, pedda cheruvu is still used as a garbage dump and is choked with hyacinth.

Untreated sewage from the nearby Alkapur township apartments flows into the lake and residents from the surrounding houses used to dump garbage in the lake. “When we approached government authorities to clear the garbage, they had to employ 10 trucks to do the job in 15 days. We also found dead bodies of animals and human beings in the lake,” says Madhulika Chowdary, founder of Dhruvansh. 

“Diverting sewage is not a solution as you will end up polluting another water body,” she explains. “A sewage treatment plant (STP) is costly to build and maintain and it does not remove pathogens and metallic content. So, we chose this biological STP based on a hydroponics technique that cleans the lake by absorbing nutrients dissolved in the water and supports living species inside the lake.” 

The FTW is an ingenious bamboo raft with sides made of thermocol blocks and plastic bottles, that enable it to float without reacting with the water. A layer of gunny sacking stretches across the raft’s bottom to create a tray that holds two centimere layer of gravel. Saplings have been planted in the soil with their roots reaching into the water.

This 3,000 sq. ft. raft supports around 3,500 saplings of different varieties. These include wetland plants, mosquito repellents and ornamental plants including cattails, bulrush, citronella, canna, hibiscus, fountain grass, flowering herbs, tulsi and ashvagandha. The FTW costs a fraction of what a conventional sewage-treatment plant would.

The plants absorb the high levels of phosphorous and nitrogen in the sewage water entering the lake. These wetlands plants also compete with the water hyacinth in absorbing nitrates and phosphorus. The first FTW, with 140 saplings, was introduced in May 2017 in a small area of the lake and it showed remarkable results. The team then increased its size to hold 3,500 saplings.

Another unique feature of the restoration process is the way they have used water hyacinth to clean the lake. Water hyacinth is usually seen as a problem because it chokes water bodies and destroys other aquatic life. “If we can use hyacinth in a creative way, it plays a major role in cleaning the lake by absorbing the pollutants in the sewage. We have cleared 80% of the hyacinth in the lake and grow it in the remaining 20%. We are using the cleared weed as an organic manure by mixing it with cow dung to grow plants,” says Madhulika.

Besides the FTW, Dhruvansh is also using aerators to oxygenate the water and have planted more than 5,000 shrubs around the lake. The combination of all these measures has had a significant impact on the lake. The biological oxygen demand (BOD) in the water has fallen from 28 to 3.2, nitrates from 27 to 8, phosphates from 7 to 0.5 while dissolved oxygen levels have increased from 0 to 4.5 according to the pollution control board. “The lake has so much biodiversity, with 178 species of birds, 41 species of reptiles, pythons, mongoose, mammals and it is increasing day by day,” exults Madhulika.

The lake has not only contributed to the biodiversity and beautification but also to helping some earn a living. “This lake was clean long back and has gradually deteriorated due to sewage and other pollutants,” says Suresh, who fishes in the lake. “We had released small fish in the lake in the past but they all died. Now as the lake is clean, I am planning to grow fish in the lake again.”

This initiative has gained attention from many volunteers and college students who are now working with the organisation in cleaning the lake and maintain the plantation. “When I first visited the lake one and half year ago, the lake was full of sewage, hyacinth and I have seen the lake gradually turning into a beautiful one,” says Vamsi M, a volunteer.

“This has become a tourist place as I have seen many people visiting the place. We have many volunteers who work with us every Saturday and Sunday in plantation and cleaning the lake. We have also conducted many programmes for school children to create awareness about our responsibility towards the ecosystem,” she adds.

“Being a commerce student, I didn’t know anything about the lake and pollutants,” says Vishal, a student from IIMC college in Hyderabad. “After joining the team, I have learnt that sewage water is just a combination of nitrates and phosphates and with the help of FTW that contains wetland plants, those chemicals can be eliminated.”

The initiative has also gained recognition from the government, which contributed Rs. 5 lakhs towards the FTW and Rs. 1.8 lakhs for cleaning the lake. “We welcome NGOs like Dhruvansh to adopt lakes and work for their restoration,” says T Chiranjeevulu, HMDA commissioner. “We have sanctioned around Rs. 12 lakhs for the work and we are very happy with their innovative techniques at minimum cost. We are also planning to start the restoration of 10 other lakes in Hyderabad this year.”