by Niraj Bhatt, Researcher - Environment and Climate Change
For coal-fired thermal power plants, water is one of the key requirements for power generation. Water is required for generating steam in the boiler, for cooling process in the condenser, disposal of ash, heat removal in auxiliary units and other consumption needs in the plant. Power plants located away from the shore (inland) meet their water requirement from nearby freshwater sources, whereas those located at the coast meet their water requirements primarily from the sea. For power plants located near urban areas, municipality treated wastewater is also used as a source of raw water. The total water requirement of a plant is governed by a number of factors such as quality of raw water, quality of coal, type and quality of condenser cooling system, ash utilization, type of ash disposal system and wastewater management practices. According to Central Electricity Authority (CEA), for older power plants with cooling towers, the consumptive water requirement with cooling tower is about 7 m3 /h per MW without ash water recirculation and 5 m3 /h per MW with ash water recirculation. Power plants commissioned in the recent past have been designed with consumptive water requirement in the range 3.5 - 4 m3 /h per MW. For a typical power plant, over 90% of its total water requirement is for the cooling tower and for ash disposal.
Thermal power plants have a detrimental effect on the aquatic and marine ecosystems via two main factors. First, power plants take in cool water from a river or sea and let out water which is anywhere between 5 to 10℃ higher than intake water, back into the waterbody. Second, residues in fly ash contain a cocktail of heavy metals (mercury, cadmium, arsenic, nickel, lead, etc.) and volatile organic compounds (VOCs) which contaminate our air, soil, and water. These heavy metals and VOCs leach into the water and tend to accumulate in fish in a process known as bioaccumulation. Liver, kidney, and gills are the primary fish organs where these heavy metals and VOCs are concentrated. In fish, this can cause endocrine disruption, loss of equilibrium, increased opercular movement, irregular vertical movements, and even lead to death. Mercury, cadmium, lead and arsenic cause gill damage as well as severe damage to the renal and nervous systems of fish. Some of the adverse effects of heavy metals on human health include chances of cancer, endocrine disruption, renal failure, cardiovascular disease, liver failure, and even death. This poses a grave health risk for people consuming the fish.
The Mundra Ultra Mega Power Plant, owned by Tata Power and located on the coast of the Gulf of Kutch, is a well-documented example of how this temperature difference has affected the marine ecosystem and erased an important economic avenue for the local community. The water released back into the sea from the power plant at the Gulf of Kutch was found to be 5 to 7℃ higher than the temperature of the inlet seawater temperature. According to the Central Pollution Control Board (CPCB) guidelines, the temperature of the discharge water or effluent shall not exceed 5℃ above the ambient water temperature. It is known that a temperature difference of even 1℃ tends to have a harmful impact on the various life forms of the marine ecosystem, by altering their reproductivity and inducing heat stress. Such a temperature difference has driven away fishes from the shore, forcing fishermen to tread deeper into the sea to catch fish. Local fishermen have also reported a drastic reduction in their catch size since the inception of the power plant. For the fishermen, it is a double whammy as they are not able to get good price for such contaminated fish. In addition, coal dust from the air settles down on the fish kept for drying, thus eroding their quality and consequently price. What was once a unique and fragile ecosystem of the Gulf of Kutch has now been rendered as a lifeless coast without fish, mangroves and other marine and coastal life forms, thanks to coal.
A fisherman at Kutadi Bandar prepares the net for an overnight fishing trip. Locals say the World Bank Group-backed power plant in the distance has depleted fish stock.Sami Siva / International Consortium of Investigative Journalists
Water pollution emanating from thermal power plants has also decimated the fragile ecosystem of the Ennore Creek in Tamil Nadu, and the communities dependent on the creek. To its north is the North Chennai Thermal Power Station (NCTPS) and its south, the Ennore Thermal Power Station. What was once a thriving rich ecosystem supporting a variety of fishes, prawns, crabs, and other marine life forms, and supporting local communities, has in the last three decades of rapid industrialization and resultant pollution turned into an ecological dead zone. According to a study, 90% of the fishermen surveyed have reported a reduction in their catch over the years. There is enough visual evidence at the site to suggest this could be due to the ash sludge coming from the power plant. There are leakages in the pipes carrying ash sludge from the plant to be dumped into the sea.
A pipe carrying sludge from North Chennai Thermal Power Plant leaks near Athipatti.
These two examples, one on our west coast in the Gulf of Kutch, and the other in the east coast in the Ennore Creek along the Coromandel coast of the Bay of Bengal give a clear representation of the detrimental effect of coal power plants on the local coastal and marine ecosystems. The mangrove ecosystems in these coasts sustain fish populations by providing a breeding ground for various fish species. Coal-fired thermal power plants reduce the fish populations by destroying these ecosystems and, the coal dust and fly ash harm fish. This has severely impacted the livelihoods of the fishermen depending on these ecosystems for years. It is high time that we create favorable conditions for the fish to return to these areas and the ecosystem, and for the local fishing communities to thrive again.
(This article is part 1 of our 2-part series on impact of coal-fired power plants on fisheries. Part 1 describes the problem and part 2 shall describe the mitigation measures)