(a) Air Pollution
Chemical and allied industries are the major source of air pollution because these industries discharge tons of toxious gases. With the increasing standard of living and a growing need for a faster moving life, the numbers of automobiles on the Indian roads have been increasing and simultaneously so is the pollution from them.
The exhaust of automobiles and diesel driven heavy vehicles contain many harmful gases and the problem of air pollution is more significant at ground level. Air pollution caused by motor vehicles contaminates surroundings with Smoke, odour and irritating compounds are causes of nuisance, especial!}’ to a person standing next to a moving vehicle.
The cumulative effect of many vehicles, plying especially on busy roads during peak hours has highly deteriorated effects. Those residing in the vicinity of such roads are worst affected and they often suffer from chronic heart and lung diseases.
Automobiles emit large quantities of both organic compounds and oxides of nitrogen, and under certain favorable conditions of temperature and the Multi-Disciplinary Nature of Environmental Studies 23 sunlight. Certain photochemical reactions are highly toxic, irritate the eyes and the respiratory system, damage vegetation and impair visibility.
Today the number of planes, rails and vehicles which emit carbon monoxide along with smoke is much larger than earlier. According to one estimate the oxygen consumed by one automobile after covering a distance of 960 km. is enough for a man for one year.
Every policeman there is provided with an oxygen cylinder so that he may use it when the need arises. Tokyo is the most polluted town in the world. In Los Angeles people are advised not to undertake any exercise and inhale air in foggy environment.
The toxic vehicular exhausts are sources of considerable air pollution. The ever increasing vehicular traffic density poses continuous threat to the ambient air quality. It is estimated that in all the major cities of a countiy about 800-1000 tonnes of pollutants are being emitted into the air daily, of which 50% comes from automobiles exhausts alone. The sources of emission in automobiles are:
(i) Exhaust system: producing hydrocarbons COx, NOx and lead oxides.
(ii) Fuel tank and carburetor.
Broadly two types of air pollutants- primary and secondary air pollutants are emitted. Primary air pollutants are carbon monoxide / dioxide hydrocarbons, particulate matter, sulfur dioxide and nitrogen oxides. These five pollutants are released into the atmosphere in an unmodified as well as in sufficient quantities which pose hazards and risks to human health.
Environmental science teaches how to maintain AAQ (Ambient Air Quality) and keep air pollutants within the Environmental Studies permissible limits. Replacement of diesel driven heavy vehicles with CNG (Compressed Natural Gas) is one important attempt in this direction.
(b) Water pollution
Report reveals that 90% of pollution load in the river systems is on account of human wastes.
The different types of diarrhoea, which in themselves may not be killers, but could prove very dangerous when accompanied by malnutrition and about 3 million children die per minute. Water borne disease occurs primarily due to the lack of proper environmental sanitation. More than 100 different viruses are known to be found in human refuse. Viruses are quite common in sewage.
They can survive for months in water and soil. Recently a number of diseases have been linked to contaminate drinking water Malaria. Filaria and Kalazhar caused by contaminated water are increasing.
The contaminated water used for irrigation purposes has adverse effects on the fruits, vegetables that we consume in our day to day life. The extension of irrigation is creating excellent breeding grounds for disease carriers.
The poor sewage system of the cities and towns promote disease by leaps and bounds. Intensive agriculture based on chemicals as fertilizers, pesticides and herbicides have also become a major cause of water contamination.
The major causes or water pollution is sewage and other wastes, industrial effluents and agricultural discharges. Broadly biodegradable and non-biodegradable pollutants are responsible for water pollution.
Environmental engineers suggest the various ways of controlling water pollution as follow:
1. Stablization of the ecosystem:
It is the most scientific way of controlling pollution and is done by reducing waste input, harvesting, and removal of biomass, trapping of nutrients, fish management and aeration. This can be done by biological and physical methods to maintain ecological balance.
2. Re-utilization and recycling of waste:
Different types of wastes such as industrial effluents. Sewage and sullage of municipal and other systems and thermal pollutants can be recycled for beneficial use. Urban waste may be recycled to generate cheaper fuel gas and electricity.
Technology has been developed for management of radio-active wastes and chemical wastes. In Okhla, New Delhi a large treatment plant for sewage recycles is already in operation.
Waste water reclamation through aqua culture, utilization of domestic and industrial waste water in agriculture and detoxification of phenol is a suitable technique developed. One distillery in Gujarat is able to treat 4, 50,000 litres of waste daily and generate energy equal to that produced by 10 tonnes of coal.
3. Removal of pollution:
Various pollutants such as radioactive, chemical and biological present in water body can be removed by appropriate methods such as (i) Adsorption (ii) Electrolysis (Hi) Ion-exchange (iv) Reverse-osmosis etc. CSIR (Council of Scientific and Industrial Research), New Delhi have devised the following techniques for successful removal of different pollutants from water.
(a) Ammonia: This can be removed from waste water in industry by ion-exchange technique, (b) Mercury: This could be removed from Chloro- alkali effluent plants by using mercury selective ion-exchange resin.
(c) Phenols: This can be removed from waste water of pulp and paper mills, carbonisation plants, petroleum refineries, tanneries and resin plants by the use of polymeric absorbents.
(d) Decolorization of water: The waste water from printing and sari dying industries could be’ decolorised by an electrolyte decomposition technique.
(e) Sodium Salts: These could be removed by reverse osmosis method. Sodium sulphate from a rayon mill effluent can be easily removed. The water for reuse can be recovered by this method.