Industrial Waste

Table of contents

Introduction to Industrial Waste

Though industries are playing very significant role in our modern life, these have harmful impact on the environment also. The wastes arising from commercial industries or trade activities or from laboratories which contains substances that are potentially harmful and affect human life as well as nature in various ways. Industrial waste affects the quality of air, water and soil which are discussed below in detail.

Effects of Industrial Waste in Polluting Air

The increasing number of industries are causing greater and greater pollution problems. Many of the environmental problems are directly or indirectly related to the activities of the chemical industry. To protect ourselves from the pollution these industries have to be monitored and controlled to avoid damaging effects on the environment. Some of the common categories which contribute to various forms of pollution are discussed below:

Sources of Energy

The main sources of energy for the industries are the combustion of oil and natural gas and to some extent coal. Combustion of these fuels produce carbon dioxide, sulphur dioxide, nitrogen oxides, unreacted hydrocarbons, etc., which cause air pollution.

Large amount of smoke is released from Thermal Power PlantsFig- Large amount of smoke is released from Thermal Power Plants

Isolation of Raw Materials

Isolation of raw materials from their sources such as mining cause damage to the environment. It releases large quantities of undesirable and harmful gases like CO2, SO2, CH4. Oil drilling on land or beneath the sea is also causing harm to the environment. Large scale oil spills during transportation such as that which occurred in Alaska in 1989 are of major concern.

Chemical Processes

Many chemical industries are constantly adding harmful pollutants to the atmosphere during their different processes. For example, the industries release harmful gases, soot, dust, metallic particles, unburnt hydrocarbons, etc. in the atmosphere and therefore, causing environmental problems.

Industrial accidents can also play havoc for the environment. For Example an industrial accident occurred in the Union Carbide factory on December 3, 1984 in Bhopal. It released a large scale of poisonous MIC (methyl isocyanides) and caused excessive damage to all forms of life.

Disposal of Solid Waste

Most industries produce one or more unwanted by-products which must be discarded. The problem of solid waste disposal is one of the most serious problems facing our society. The industrial wastes may also be classified as biodegradable and non-biodegradable. Biodegradable wastes are generated by food processing units, cotton mills, paper mills and textile factories. Non-biodegradable wastes are generated by many industrial processes such as:

(i) thermal plants produce fly ash

(ii) iron and steel plants produce blast furnace slag and steel melting slag.

(iii) industries manufacturing aluminum, zinc, copper, etc. produce mud and tailings.

(iv) fertilizer industries produce gypsum.

(v) industries dealing with metals, chemicals, drugs, pharmaceuticals, dyes, rubber, goods, etc. produce hazardous wastes such as inflammables, composite explosives or highly reactive species.

Industries are largely responsible for polluting the airFig- Industries are largely responsible for polluting the air

The disposal of non-biodegradable industrial solid waste, is very essential. If it is not done by a proper and suitable method it may cause serious threat to the environment. New innovative methods have been designed to make use of waste materials. Great care has to be taken for the disposal of toxic wastes. For Example, nowadays, fly ash and slag from the steel industry are used in the cement industry. Large amounts of toxic and hazardous wastes are destroyed by controlled incineration whereas small quantities are burnt along with factory garbage in open bins.

Effect of Industrial Wastes on Water

Industrial wastes are also the major source of water pollution. The industrial wastes polluting water are mainly from industries such as coal or ore mines, textile industries, paper industries, food processing industries, dairies, chemical industries, pharmaceuticals, sugar and distilleries, oil refineries, tanneries, vegetable oil and soap industries etc. These wastes may contain inorganic and organic suspended particles and inorganic and organic soluble matter.

Industries dumping their waste in RiversFig- Industries dumping their waste in Rivers

Some common types of industrial wastes polluting water are:

Heavy Metals

These are metals such as cadmium, lead and mercury which are present in industrial or mining wastes. These metals are poisonous and can be dangerous to humans. For Example, cadmium and mercury can cause kidney damage whereas lead poisoning can cause damage to the kidneys, liver, intestines, brain and central nervous system. Mercury poisoning causes a disease called Minamata in human beings which weakens the muscles and results in weakness in hearing and vision power, mental retardation and paralysis. All of these metals enter the food-chain by various sources and as the human body is unable to excrete them and their concentration increases in the human body.

Detergents and Fertilizers

Various detergents contain phosphates as additives in them. It may be noted that these do not pose any threat to the aquatic life but serve as nutrients for plants leading to their excessive growth in ponds, lakes and rivers. Dissolved oxygen concentration of water gets reduced because of formation of algae which are encouraged by these detergents and fertilizers. This process of over nutrition is known as eutrophication. This impedes the development of higher life forms such as fish.

Petroleum Products

Petroleum products also pollute many sources of water. For Example, major oil spills in ocean. This is because of wreckage of oil tankers in open sea or accidents of ships carrying oil in the sea. The spreading of oil into sea is called oil spill and the thick layer of oil on the surface of sea water is called Oil Slick. In India, an oil spill occurred in Bombay on March 17, 1993 due to rupture of pipeline which damaged the ecosystem and marine life.

Oil Spill in Atlantic OceanFig- Oil Spill in Atlantic Ocean

Acid Polluted Water

If the pH of water is less than 3, then the water is said to be acid polluted water and is considered harmful to aquatic life. The water coming out of the mines or the water which is used for mining process contaminates the ground water because of microbial oxidation of discarded waste materials at the mine site. Sulphuric acid forms a main component of the acid mine water which is produced because of oxidation of iron pyrites (FeS2). Industrial wastes and acid rain also contribute to the acidic nature of natural water. Natural water becomes acidic by industrial wastes and acid rain

As water is a good solvent it dissolves various water soluble inorganic chemicals which include heavy metals such as cadmium, mercury, nickel, etc. These metals cannot be digested by the human body and there are considered dangerous. By the time these cross the tolerance limit, these metals can cause harm to central nervous system kidneys, liver, etc. The raw salt (sodium and calcium chloride) used to melt snow and ice in colder climates also causes water soluble chemical pollution.

Polychlorinated biphenyls (PCBs)

Polychlorinated biphenyls have very high stabilities and therefore, are finding many applications these days. For example, fluids inside transformers and capacitors is made up of PCB’s. They are used as cleansing solvents, in detergents and fertilizers. PCBs are resistant to oxidation and their release into the environment has become a serious pollutant. These are carcinogenic and cause skin disorders in humans. Nowadays most of the detergents available are biodegradable. But using them create other problems. The bacteria responsible for their degradation feed on degradable detergent and grow very rapidly. During their growth, the bacteria may take all the oxygen dissolved in water. As a result, other forms of aquatic life such as fish and plants may die because of dearth of oxygen in water. Fertilizers, as we know contain phosphates as additives. The addition of phosphorus in water promotes algae growth. Such a large growth of algae may cover the water surface. This algae growth often release toxins in water. This bloom which occurs in water affects the living organisms in the water body by inhibiting their growth. The process of nutrient enrichment of water bodies, which results in loss of biodiversity is called Eutrophication.

Structure of PCB’sFig. No. 6 Structure of PCB’s

Until recently, it was a common practice to dump the industrial wastes into nearby stream. These days, this practice has been stopped to prevent stream pollution and to recover some expensive chemicals from these wastes. However, it may be noted that the treatment of industrial wastes is very tedious problem because of the large variety of chemicals present in black liquor coming from the industries. The treatment of industrial wastes depend upon the nature of the pollutants present.

Effects of Industrial Wastes on Soil

Soil is the thin layer of organic and inorganic materials that covers the earth surface. Untreated effluents when discharged directly in water bodies disrupt the physicochemical properties of soil. The waste water discharged by many industries is not treated before and thus the waste water contains toxic compounds, chemicals and salts, radioactive material, disease causing agents which goes in the soil .Buildup of these substances in soil have adverse effect on plant growth and human health.

pH of the soil changes because of discharge of waste water effluents. Elements such as Ca and Mg needed for plant growth can accumulate in soils thereby improving the pH especially of acidic soils. Safe utilization of waste water for irrigation to crops requires several precautionary measures viz. adequate dilution, selection of crop etc. Soil physical properties needs to be reviewed periodically for long-term sustainability of the system. Long-term use of waste water for irrigation to crops results in significant increase in soil organic content than the soils irrigated with ground water.

Thus, long term use of waste water may have the following effects on soil

  • Yield loss and decline in soil microbial activity.
  • Soil and groundwater contamination.
  • Reduction in soil fertility.
  • Contamination of the human feed chain.

Change in Physical Properties

Industrial effluents when released in the open or on agricultural land contaminate the soil with heavy metals and organic pollutants. The total Pb, Ni, Cd and Cr were higher in soils irrigated with lead battery and distillery industries effluent compared to soils irrigated either with canal or tube well water. In case of distillery effluent irrigated soil, about 14 times increase in organic C was observed. It may be because of presence of higher C amounts in distillery effluent samples.

Excessive use of Fertilizers affects the quality of soil.Fig- Excessive use of Fertilizers affects the quality of soil.

Lead content was almost 11.5 times more in lead battery effluent irrigated soils as compared to canal or tube well irrigated soils. Organic C and toxic metal content (Pb, Ni and Cd) in soil is increased due to irrigation with cycle industrial effluent as compared to tube well irrigated soils. Excessive use of cycle industry effluent had converted the productive land to unproductive land and soil became rust colored and fluffy. In this soil, very high amounts of toxic metals were accumulated.

Effect on Plants

Crops grown on this soil indicated the high accumulation of toxic metal. The health hazard problems due to Ni absorption by crops grown on metal polluted soil was more in carrot followed by spinach, fenugreek and wheat. The accumulation of high amounts of heavy metal in plants may influence the consumer’s health. The high intake of metals by human affects the body system and may deteriorate the health.

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