Aquatic Pollution and Coastal Management

Unit 11 : Monitoring and control of pollution

11.3.4.Karnataka Coast
The coast line is well defined and almost straight, but broken at numerous points by rivers, rivulets, creeks and bays. The river outfalls in the coast are formed by rivers namely Gurupur, Nethravathi, Mulki-pavanje, Udyavar, Sita, Kalinadi, Bedti, Sharavathi and Swarna.

The development of all weather port during 1974 intiated the industrial activity in the district. The Mangalore Chemicals and Fertilizers Ltd. (MCF), the first mega industry was established in 1976. The industry produces urea, ammonium bicarbonate and diammonium phosphate. For these products the raw materials such as naphtha, ammonia and phosphoric acid etc. are used. The industry uses about 15,400 m3/day of Nethravathi river water and lets out 13,800 m3 treated effluent per day into the coastal waters.

The high levels of ammonia (NH₃) which is present in the effluent quickly gets converted into ammonium (NH₄) due to high buffering action of the seawater. Nevertheless, over a longer period, it was observed that the total nitrogenous content of the water has increased and as a result the normal N:P ratio in the coastal water (16:1) was also increased. This leading to increased total phytoplankton crop, but with reduced species diversity index. The reduction in the species diversity of benthic organisms was also observed near the vicinity of the effluent fallout. The unprecedented blooming of Trichodesmium, (blue green algae) might also be due to the activity of the industry.

The Kudremukh Iron Ore Company Ltd. is the second mega industry established in 1980. This industry produces approximately 4.5 million tonnes of iron ore concentrations per year and 3 million tonnes of iron oxide pellets annually. The ore extracted from Kudremukh was transported to Mangalore in the form of slurry for which 40,000 m³ of Badra river used. The slurry is treated and above products are produced, in the process 18,000 m³ of effluent are discharged into the sea per day.

Treated effluent mainly consists of high COD and trace concentrations of unrecovered metals. The discharge of treated effluent into the coastal waters has resulted in increased concentration of dissolved and particulate iron along with other metals associated with the ore. The reduced phytoplankton species diversity near the vicinity of the effluent fallout has been observed. In addition, decreased macrobenthic species diversity near the effluent fallout was also documented.

Mangalore Refinery and Petrochemicals Ltd. was the third mega industry established in 1996. The industry uses 834 m³ of Nethravathi river water per hour. The treated effluent is discharged into the coastal waters at 4 m depth. The effluent mainly contains higher levels of BOD, suspended solids, hydrocarbons and various heavy metals in low concentrations. The effluent discharge has resulted in following changes.

• Increased concentrations of total hydrocarbons in the surface waters.
• Reduced species diversity index of phytoplankton and zooplankton.
• Increased concentrations of organic carbon in the sediment.
• Frequent changes in the texture of the sediment.
• Reduced species diversity index of macrobenthic organisms.

The BASF, the 4th mega industry of the coast was established in 1996 and it produces dyes and dispersions. For manufacturing the products, 29 to 35 various chemicals are used. Nearly 273 m³ of water is used per day. The treated effluent mainly consists of high BOD, COD, suspended solids and residues of various organic chemicals. In addition, the effluent contains traces of cyanide, chromium, copper and zinc. The treated effluent is let into the sea at 7.5 m depth. The discharge of treated effluent has brought the following adverse effects.

• Frequent and unpredictable changes in textural characteristics of the sediment.
• Increase in organic carbon in the sediment from 0.3 to 1.6%.
• Reduced species diversity of macrobenthic organisms near the vicinity of effluent fallout.

Caustic soda factory in Karwar discharges its treated effluent, which has resulted in following changes.

• Frequent mass morality of marine organisms.
• Reduction in bivalve bed.
• Mercury contamination in fin and shellfishes.

Tungabadra is a major tributary of river Krishna and flows through several districts of Karnataka., It is a major river irrigating several thousand hectares of land and supporting great fishery wealth. M/s Grasim industry basically has two units. In the first unit, the industry manufactures rayon grade pulp using mainly soft wood as raw material. The second unit manufactures polyfibres by making use of the pulp manufactured in the first unit. The first unit was established in 1972 and the second unit in 1977. The industry uses nearly 49800 m3 of water per day for manufacturing pulp and polyfibres. Partially treated effluent is discharged into the river. The effluent is dark brown in colour with the typical wood burning odour. The effluent contains very high load of BOD, total sulphates, sulphides including hydrogen sulfide. In addition, the effluent also contains high levels of zinc and other heavy metals. The impact of the effluent on the riverine ecosystem is severe during summer season, when quantity of drainage substantially gets reduced. The impact of effluent is so high that, on many occasions especially in 1984, 1986, 1992 and 1994 mass morality of fish in the Tungabhadra River was reported along Davanagere and Chitradurga districts. In addition, elevated levels of heavy metals in the fish caught in the river were documented. The reduced diversity of benthic forms was found to be mainly due to the higher levels of sulphides. Pathological symptoms in mussels, cyprinids and gobies were evident.

In Karnataka, untreated domestic sewage is often discharged into bigger tanks and other water bodies. Sankey tank, Ulsoor tank, Belandur tank and Hebbal tank situated around Bangalore city receives substantial quantity of untreated sewage. In addition, the effluents from pharmaceutical industry, soap industry, and cosmetic industry are let into these tanks. This has resulted in greater eutrophication, reduced biodiversity and in extreme condition, mass mortality of fish. The intensive growth of aquatic weeds and siltation not only rendered these water bodies unfit for fisheries, but also deteriorated the aesthetic value.