Economic reformation and industrial liberalization by Indian government have attracted varied national and multinational companies to invest on major industries like power plant, petroleum refineries, fertilizers and petro-chemicals and metal industries. Most of these industries are located very close to the sea due to a variety of reasons like convenience in transporting raw materials, availability of seawater for desalination, cooling tower and disposal of trade effluents. Both central and state pollution control boards have set standards for checking and controlling the quality of effluents discharged into marine/fresh water bodies so that the adverse impact on the marine and other ecosystem is minimal. But it is seen that many of these companies do not strictly adhere to these standards. This is because the effluents are discharged directly into the water body without any pre-treatment thereby seriously affecting the marine ecosystem. In many cases the discharge of effluents directly into sea at locations very near to the coast has resulted in high acidic nature thereby killing all the marine organisms in the locality. The Travancore Titanium Products Limited (TTPL) located near the famous Shankumukham beach of Trivandrum is a classic example of this.
1.2 A critical analysis of the industrial wastes from Travancore Titanium Products Limited (TTPL)
Titanium dioxide factory in Thiruvananthapuram dumps hazardous waste into the sea in spite of court orders. The canal carrying untreated effluents from the Travancore Titanium Products Ltd. (TTPL) plant at Veli in Thiruvananthapuram (Fig.1) runs right up to the sea. This profit making titanium dioxide plant in Kerala, which has been dumping concentrated sulphuric acid and other pollutants into the Arabian Sea for decades, coerces the authorities to grant it more time to comply with environmental laws. The 50-year-old TTPL, one of the few profit-making public sector units in Kerala, uses the conventional sulphate route technology to recover titanium dioxide from illmenite ore, which is abundant on the south Kerala-Tamil Nadu coast. iIlmenite and rutile are the main sources of titanium in the world, although the metal occurs in numerous other minerals too. While ilmenite contains compound oxides of titanium and iron, rutile is an impure form of titanium dioxide. Approximately 95 per cent of the titanium consumed in the world is in the form of titanium dioxide, a strikingly white pigment used in the manufacture of paints, plastics, paper, ink, rubber and other products. Titanium dioxide is produced in two grades, anatase and rutile. The TTPL is the largest producer of anatase grade titanium dioxide in India, claiming a market share of nearly 70 per cent. The public sector Kerala Minerals and Metals Ltd. (KMML) in Kollam holds the largest market share for (synthetic) rutile grade titanium dioxide. In fact, the TTPL enjoyed a monopoly in the market until the KMML was set up in 1985. The rutile grade pigment produced by the KMML from ilmenite through the less-polluting chloride route technology is more expensive and preferred in exterior paints and for various other uses. The TTPL's "softer" anatase grade pigment is considered ideal for interior paints, tyres, printed fabrics, electronic components, footwear and leather goods, and flooring materials like linoleum and white mosaic and for "delustering" artificial fibre in the textile industry. The sulphate process was the first commercial-scale technology used to convert ilmenite (a mixture of titanium, ferrous iron and ferric iron) to titanium dioxide. The TTPL extracts titanium in ilmenite using sulphuric acid. At present, it generates around 120 tonnes of concentrated sulphuric acid every day, along with lesser quantities of ferrous sulphate, titanyl sulphate and manganese sulphate as waste products. These are discharged into the Arabian Sea without treatment and they continue to be discharged even after the Water and Air Acts came into force in the mid-1970s. According to the PCB, the company discharged 2,073,577,400 kg of hazardous liquid effluent into the sea during 2003-04. In this, free sulphuric acid was present at a concentration of 5,47,246 mg/kg of dry matter, well above the 50,000 mg/kg limit prescribed in the Hazardous Wastes Rules. The company has no material recovery or waste water (effluent) treatment facilities and it dumps huge quantities of toxic and polluting matter on the coast in violation of the Water Act and a 1995 order of the Water Appellate Authority that "treated" effluents should be discharged to the sea through a 750-metre submarine pipeline. The pollution control board (PCB) norms state that the pH value (which indicates the acidity or alkalinity level) of the wastewater should be in the range of 5.5 to 9.0. The pH of the effluent from the TTPL is "always" around 1 (taken from COMAPS data), indicating very high acidity. The company has also been flouting the PCB's direction to dispose of its untreated ilmenite (containing traces of heavy metals) at a secure landfill. Over the years, several studies tried to raise the alarm, but the TTPL countered them successfully by claiming that the sea, an alkaline medium, was traditionally used to discharge the acidic effluent from titanium dioxide plants and that the waste was neutralised within minutes of entering the sea and did no harm to the environment. However, fish and other marine species have deserted the area, and fisher folk have lived on this coast for decades enduring the acidic discharge and pungent smell and the deep yellow-brown crust of sea(fig.1). An earlier study, conducted by the National Institute of Oceanography, had indicated biomass depletion in a 100 sq km area of the sea surrounding the point of discharge. Even though the company claims that the impact of its effluent is limited to less than 100 metres of the discharge point, after which the acidity is neutralised by the alkaline sea. Neutralisation is not the only problem; it is one of toxicity, too. The carbon dioxide absorption capacity of seawater is increased many times because of the continuous stream of pollutants entering it. As per the old reports of PCB the effluent discharged from the company has certainly a negative impact on the marine environment. According to Pollution Control Board (PCB) because of untreated effluent discharge from the TTPL plant the marine environment is forced to act as a carbon dioxide sink thereby making its marine dump yard one of the most toxic spots in coastal India. However, for nearly 11 years from the late 1980s, Travancore Sulphates Ltd. (TSL), a joint-venture company working literally next door, used a part of the effluent load from the TTPL to produce byproducts that could be used in neutralising effluents from other industries or in treating domestic sewage. That has been the only `pollution-abatement' measure tried by the TTPL to reduce the environmental impact of its acidic effluent. But the TSL, in which the TTPL and the Kerala State Industrial Development Corporation (KSIDC) had a 46 per cent joint stake, closed down in 1991 in controversial circumstances. It is said that, there are theoretically three possibilities of dealing with effluents from sulphate plants.
The simplest solution is to neutralize the acidic effluent using an alkaline medium, such as hydrated lime. But such a process would generate mountains of sludge - about 500 tonnes a day in a plant like the TTPL - the storage and disposal of which would become unmanageable. The second option, called the acid recovery process, is to crystallise the ferrous sulphate (known as copperas) from the effluent, re-concentrate the remaining acid and re-use it in the production process. But this requires a lot of energy to evaporate water while re-concentrating the acid, and the acid so recovered would be about three and a half times more expensive than the virgin acid that the TTPL produces now by burning imported sulphur. This process, too, would produce large quantities of solid wastes. The third alternative is to convert the effluent into some other non-toxic form that could be of use in other industrial applications, similar to what the TSL had done for years before it closed down. The TSL process converted the effluent into a range of inorganic sulphates that were used in the purification of other industrial effluents and domestic sewage.
1.3 Effluent disposal from TTPL -COMAPS study
A programme on Coastal Ocean Monitoring and Prediction Systems (COMAPS) is being operated since 1991 by the Department of Ocean Development (MoES) in close co-operation with the Ministry of Environment and Forests for systematic monitoring of levels of pollutants along the selected regions of India’s coastline. The main objective of the programme is to constantly assess the health of India marine environment and indicate areas that need immediate and long term remedial action. Data on nearly 25 environmental parameters are being collected at 77 locations with the help of 11 R&D institutions in the 0 -25 km sector of the coastline of the country. Parameters and locations of monitoring marine pollution were selected on the basis of (a) location of industries (b) ecologically sensitive areas and © location of urban establishments and d) based on earlier base line survey.
Traditionally coastal areas of ocean have been used for the disposal of domestic and industrial effluents from times immemorial. As the quantity of effluents being discharged into the sea is increasing day by day, its impacts on the marine environment been considered as a hot topic for research and development. A good number of research work has been done in this field.A summary of available literatures related to this present study are mentioned below
Richard C. Baldwet al in 1970 conducted a mathematical model for dispersion of a heated effluent from an ocean outfall near Huntington Beach, California . Input parameters include atmospheric and oceanic conditions and discharge characteristics. The model solves the steady-state, two-dimensional differential equation for non-conservative diffusion of heat in a moving fluidThe solution is calibrated and verified using data from surveys conducted at the Southern California Edison Company power plant at Huntington Beach, California. Temperature fields predicted by the model are compared with the actual fields for seven different surveys. These comparisons indicate that the model can be used to predict the large scale influence of the outfall on the local oceanic environment.
Steven F. Railsback et al in April 1991 had conducted a numerical modelling study by comparing mixing characteristics of the existing surface wastewater discharge and a proposed submerged wastewater outfall at McMurdo Station, Antarctica . The wastewater is a combination of sanitary sewage and brine from a desalination plant. Dispersion from a proposed submerged (15 m-deep) outfall was simulated using the CORMIX1 computer model. The mixing characteristics of the surface discharge were estimated from visual observations and a conceptual analysis. The wastewater was found to be less dense than ambient seawater. From the submerged outfall, the effluent is predicted to be diluted by ratios ranging from 80:1 to 450:1 between the point of discharge and the point where the effluent plume begins to spread out underneath the sea ice. The variation in dilution depends mostly on tidal current speed, and dilution of the wastewater with desalinator brine is predicted to provide only minor reductions in concentrations of the effluent. The heat content of the discharge plume from a submerged outfall is expected to cause at least partial melting of the sea ice from underneath. A surface discharge provides much less mixing with ambient water before the effluent spreads along tidal cracks and underneath the sea ice. The submerged discharge is expected to confine settleable wastewater solids to a benthic area near the outfall, but a surface discharge allows solids to settle over a wider area.
Jayakumar et al.(1991) used MIKE21 AD, a 2D hydrodynamic model to study the fate of discharged ballast water in the marine environment. The fate of discharged Ballast water plume at different locations in the study region has been modeled using the advection-diffusion processes. The model results showed that the ballast water discharged near the shore tends to move alongshore and that discharged in the mid-gulf traverses back and forth in the channel eventually spreading towards the northern shore. The model was validated with the help of measured data of March 1994.
Thomann et al. (1991) constructed a model to describe the physico-chemical fate and transport of chemicals in water-sediment systems. They used a one-dimensional advection model with rapid sorption-desorption kinetics between water and bed sediments by assuming an interfacial exchange rate, and solved the resulting systems of equations for the total concentration of the contaminant (dissolved plus particulate). They modeled sediments as one well mixed layer. This model was used to predict the fate and transport of PCBs in the Hudson River, and to simulate the fate of cadmium in Foundry Cove superfund site.
P. Vethamony et al ( 1994) carried out thermal plume simulation using 2D model to understand the nature of spreading and rate of cooling of water discharge, from a proposed out fall in near shore coast off Vishakhapatnam. It was observed that the plume showed northward spreading during the months of March and July and southward during December. During October the spreading was mostly around the outfall with a weak southward component.
Ebtessam E.E. Mohamed et al during ( December 1996 ) conducted a case study of dilution of effluent such that 27 sampling stations were explored along the coastal zone in front of Alexandria situated between Agamy beach in the West and Abu-Qir headland in the East. Also, current measurements have been obtained by using current meter and Drougs. The dispersion coefficient Kx and Ky of water during the time of measurements in front of Alexandria were calculated. A predictive model based on the equations described by Bonazountas (1987) was applied to estimate initial dilution and waste water field in front of Alexandria coastal zone and estimated the waste effluent discharge outfall locations for different seasons.
Shrestha (1996) used a two-dimensional (2-D) vertically averaged model to predict the spatial and temporal distribution of cohesive sediments and associated toxic heavy metals in estuaries. He used an experimental relation obtained by fitting Krone’s experimental data (1962) to describe the bulk deposition and aggregation of the particles, and solved the model using the finite elements method. For adsorption, he assumed instant equilibrium using a linear reversible sorption isotherm. This model was used later to simulate heavy metal transport in South San Francisco Bay (Shrestha and Orlob, 1996).
Mandal et al. (1996) conducted a study on the discharge of industrial effluents near Mangalore coast. Based on the results of dye patch test indicated by dilution of dye, it was estimated that the longitudinal dispersion co-efficient was 7 and flow rate 0.3m2/sec and the corresponding lateral dispersion co-efficient and flow rates were 1 and 0.03m2/sec respectively. The dilution, dispersion and diffusion design was simulated by SEAMIX model developed by NIO Goa
Chandramohan et al. (1997) using SEAMIX model diffuser estimated that effluent discharge at 200m3/hr for 9.5hr per day undergoes initial dilution to the order of 50 at water depth of 5.3m.
Suryanarayana et al. (1998) developed a 2D model for pollution dispersion at Paradip using Navier Stoke equation and it was found that outfall must be kept 993m away from sea wall.
Young Do Kim et al (2000) conducted modelling study using a 3-D particle tracking model with normalized characteristic equations which has been has been developed to predict the variation of near-field mixing characteristics and the far-field transport of the effluent plumes discharged from sea outfalls. The model was applied to the case study on the Masan sea outfall plumes discharged through a submerged multiport-diffuser. Numerical simulations of the effluent transport for 15 days which cover neap and spring tidal cycles in Masan Bay were conducted using fall velocities of the solid wastes and the initial plume characteristics obtained from normalized near-field characteristic equations. The results showed that time variations in near-field minimum dilutions with tidal ambient flow conditions are about 45~49hrs. Most of the heavy particles in the effluent plumes were settled and deposited in the vicinity of the outfalls immediately, and the finer particles were transported eastwards 3 km away from the outfalls for 15 days. A similar depositional trend of contaminated sediment was also found during a recent field survey.
Kobayashi et al. in December 2001 developed a 3D model to predict the ocean dispersion of radionuclides released in off Shimkotta region of Japan. For predicting ocean currents, Princeton Ocean Model (POM) was used. They concluded that the sea surface wind and Tsugaru current entering in to the Tsugaru strait, significantly affected the current field of that region and POM was able to simulate the seasonal variation of Tsugaru wave current successfully.
Ozcan and Gokce (2002) carried out a case study for outfall design in Turkey using MIKE21 advection-dispersion (AD) model, coupled with CORMIX. The initial dilution and near field temperature gradient was first calculated by CORMIX and the results were transferred to MIKE21 AD for far-field modelling. The results indicated that numerical models can be used as tools for obtaining information on the oceanographic conditions of the design area even when the field data is limited.
Robert et al (Dec 2003) conducted field surveys near the Boston (U.S.A) sewage outfall plume to test and certify the outfall's initial dilution in the near field and to investigate its dispersion in the far field. Rhodamine WT dye was added to the effluent at the treatment plant at a constant concentration over a 6-h period and tracked offshore over three days. During the near-field surveys, the current was flowing closely parallel to the diffuser, resulting in the wastefield spreading laterally as a dynamic density current at a rate that was closely predicted by theoretical equations. The plume was submerged by the oceanic density stratification, with a minimum initial dilution of about 102 within a few tens of meters from the diffuser. The initial dilution and the other near-field characteristics were in good agreement with predictions of mathematical models and with the physical model study on which the diffuser design was based.It was found that after a travel time of 24 h, the dye patch was still intact and oceanographic mixing and dispersion had increased dilution by a factor of about two to more than 200:1 and after 48 h, the plume had broken into large patches, and most dilutions considerably exceeded 400 with an average dilution of order 1000 and after 52 h that the dye patch was followed in the far field, mixing was due to lateral diffusion; vertical mixing was negligible. This slow vertical mixing is due to the stable density stratification in the water column. The outfall was performing as designed. The field surveys provided a strong confirmation of the ability of small-scale laboratory model studies to replicate and predict the near-field characteristics of ocean wastewater outfalls. They also increase the confidence that mathematical models can be used to reliably estimate initial dilution under other effluent flows, oceanographic conditions, and stratification regimes.
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