Jellyfish Bloom Clogs Nemmeli Desalination Plants, Disrupts South Chennai Water

An unusual jellyfish bloom off the Nemmeli coast in South Chennai clogged seawater intake pipelines and severely disrupted operations at two major desalination plants, cutting water supply to several southern neighborhoods across the city.

The Chennai Metropolitan Water Supply and Sewerage Board (Metro Water) reported that the marine life managed to enter and block intake pipes despite protective systems designed to keep ocean organisms out. The incident forced both the 150 MLD and 110 MLD desalination facilities to operate at drastically reduced capacities over the past two weeks.

During this period, the 150 MLD plant ran at roughly half its normal capacity, while the 110 MLD plant operated at around 60 percent. Production hit its lowest point on July 18, when the 150 MLD facility produced only 21 MLD and the 110 MLD facility managed 59 MLD. Officials noted that while Metro Water encounters jellyfish blooms every one or two years, last week's situation was exacerbated because the jellyfish were significantly larger than those seen in previous years, combined with concurrent power shutdowns and damaged distribution lines.

The drop in output led to direct supply deficits in several parts of South Chennai. In the Adyar zone, which typically receives an allocation of 93.5 MLD from the Nemmeli plants, daily supply fell to 84.8 MLD on July 23. This capped a cumulative shortfall of 24 MLD over two weeks, which reduced piped water supply to tail-end locations such as Velachery. Metro Water officials confirmed that alternate supply arrangements are being organized to compensate for the deficits.

Metro Water stated that the jellyfish blockage has now cleared and that the Nemmeli plants have returned to meeting local drinking water demand. To avoid future operational disruptions, the utility has engaged experts from the Indian Institute of Technology Madras (IIT-M) and the National Institute of Ocean Technology (NIOT) to study the ecological event.

Specialists from IIT-M and NIOT have gathered jellyfish samples from the ocean waters off Nemmeli. The joint research team is currently investigating what environmental or marine factors triggered the sudden biological surge near the plant intakes to help design better safeguards for future blooms.