Chapter 1 Introduction
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CHAPTER 1 INTRODUCTION 1.1 GENERAL As we plunge into a new century and a new millennium, the environment is being called on to supply the growing needs of an expanding human population in the developing countries and increasing affluence in the developed countries. In many areas we are already taking more from the earth’s systems than they can provide in a sustainable fashion. Environmental pollution means the presence in the environment of any environmental pollutant. Environmental pollutant means any solid, liquid or gaseous substance present in such concentration as may be, or tend to be, injurious to environment. Water is a major constituent of all living organisms. Over 70% of the Earth’s surface is covered by water. Without water, life on Earth would be impossible. It is essential for everything on our planet to grow and prosper. Although we as humans recognize this fact, we disregard it by polluting our rivers, lakes, and oceans. Subsequently, we are slowly but surely harming our planet to the point where organisms are dying at a very alarming rate. As per the Water (Prevention and Control of Pollution) Act, 1974, pollution means such concentration of water or such alteration of the physical, chemical and biological properties of water or such discharge of any sewage or trade effluent or any other liquid, gaseous or solid substance into water (whether directly or indirectly) as may, or likely to, create or nuisance or render such water harmful or injurious to public health safety or to domestic, commercial, industrial, agricultural or other legitimate uses, or to the life and health of animals or plants or of aquatic organisms. 1.2 WATER POLLUTION Water typically referred to as polluted when it is impaired by anthropogenic contaminants and either support a human use or undergoes a marked shift in its ability to 1 support its constituent biotic communities. It is being polluted due to over population in terms of sewage and garbage, agricultural development in terms of pesticide and fertilizer application and rapid industrialization in terms of effluent and hazardous waste. In India, the main culprits for the degradation of water bodies are sewage and garbage generated especially in the urban areas. Absence of sewage treatment plant and garbage treatment leads to discharge of untreated sewage and garbage into water bodies. In Kerala, water bodies are polluted due to sewage and garbage. Wastes generated within households are often disposed of in nearby drains. Rubbish like plastic, glass is dumped into canals and rivers. Industries discharge wastes directly into water bodies leading to death of aquatic organisms due to the decrease in oxygen in water and due to reduction in pH. Some stretch of rivers and lakes namely Periyar are affected due to industrial effluent. Sewage, manure and chemical fertilizers contain nutrients such as nitrate and phosphate and when it enters water body in excess levels, nutrients over stimulate the growth of aquatic plants and algae. Excessive growth of these organisms clogs our water ways and blocks light to deeper waters. When the organisms die, they use up dissolved oxygen as they decompose causing depletion of oxygen in water. Sewage contains pathogens which cause diseases such as cholera, diarrhoea, typhoid and skin diseases. Pathogens include such organisms as bacteria, virus and protozoan. Stagnated water bodies are breeding grounds for mosquitoes causing dreadful diseases like chikunguinea, malaria. Polluted water kills fish, vegetation and other aquatic organisms. Weeds make waterways impassable. When a lot of soil is washed into rivers and drains, this causes aquatic life to perish and floods especially with heavy rainfall. 1.3 LAKE POLLUTION The lakes are vital ecosystems deserving utmost care. Increasing population pressure and the resultant socio-economic development around this water bodies result in the deterioration of water quality. The problems faced by the lake systems can be generalized as 1) eutrophication 2) siltation 3) shrinkage in water spread 4) reclamation 5) encroachments 6) pollution resulting from natural as well as anthropogenic activities 7) excessive tourism load 8) over fishing[8]. Eutrophication means excessive plant growth 2 in lakes, estuaries and slow moving streams due to excess nutrients mainly from sewage and agricultural runoff. Excessive weed growth leads to high rate of siltation and results in shoaling of the lake. The shrinkage in lake water spread is mainly due to reclamation and rooted weed growth. When sediments enter water bodies, fish respiration becomes impaired, plant productivity and water depth become reduced and aquatic organisms and their environment become suffocated [8]. 1.4 WATER QUALITY INDEX Water quality monitoring data consists of routine measurements of physical, chemical and biological variables that are intended to give insight into the aquatic environment. The WQI serves as a tool, to examine the trends, to highlight specific water quality conditions, and help governmental organizations to evaluate the effectiveness or regulatory programs. In essence, WQI has following important purposes. 1. Trend Analysis: Index may be applied to water quality data at different points in time to determine the changes in water quality (degradation or improvement) which have occurred over the period. 2. Public Information: Index may be used to inform the public about environmental conditions. 3. Ranking and Rationalization of locations: Index may be applied to assist in comparing environmental conditions at different locations of geographic areas. 4. Scientific Research: Index may be applied as a means of reducing a large quantity of data to form that give insights to the researcher conducting a study of some water quality processes. 1.5 EUTROPHICATION Eutrophication is a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants weeds). This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die. Nutrients can come 3 from many sources, such as discharge of untreated sewage, fertilizers applied to agricultural fields, golf courses and suburban lawns; deposition of nitrogen from the atmosphere and erosion of soil containing nutrients. Water with a low concentration of dissolved oxygen is called hypoxic. Eutrophication is caused by the increase of an ecosystem with chemical nutrients, typically compounds containing nitrogen or phosphorus. It may occur on land or in the water[16]. Eutrophication is frequently a result of nutrient pollution such as the release of sewage effluent into natural waters (rivers or coasts) although it may occur naturally in situations where nutrients accumulate (e.g. depositional environments) or where they flow into systems on an ephemeral basis (e.g. intermittent upwelling in coastal systems). Estuaries tend to be naturally Eutrophic because land-derived nutrients are concentrated where run-off enters the marine environment in a confined channel and mixing of relatively high nutrient fresh water with low nutrient marine water occurs. The names of the four trophic states, from the lowest level of biological productivity to the highest, are listed below (Source: http://lakewatch.ifas.ufl.edu) 1. Oligotrophic 2. Mesotrophic 3. Eutrophic 4. Hypereutrophic The root word ’trophic’ means “of or relating to nutrition.” 1. Oligotrophic Oligotrophic water bodies have the lowest level of biological productivity. Oligo means “scant or lacking.” Criteria: Total chlorophyll is less than 3 μg/L Total phosphorus is less than 15μ g/L 4 Total nitrogen is less than 400μ g/L Water clarity is greater than 13 feet 2. Mesotrophic Mesotrophic water bodies have a moderate level of biological productivity. Meso means “mid-range.” Criteria: Total chlorophyll is between 3 and 7 μ g/L Total phosphorus is between 15 and 25 μ g/L Total nitrogen is between 400 and 600 μ g/L Water clarity is between 8 and 13 feet 3. Eutrophic Eutrophic water bodies have a high level of biological productivity. Eu means “good or sufficient.” Criteria: Total chlorophyll is between 7 and 40 μ g/L Total phosphorus is between 25 and 100 μ g/L Total nitrogen is between 600 and 1500 μ g/L Water clarity is between 3 and 8 feet 4. Hypereutrophic Hypereutrophic water bodies have the highest level of biological productivity. Hyper means “over abundant.” 5 Criteria: Total chlorophyll is greater than 40 μ g/L Total phosphorus is greater than 100 μ g/L Total nitrogen is greater than 1500 μ g/L Water clarity is less than 3 feet Water hyacinth [Eichhornia crassipes], a native of Amazon river basin in South America is a troublesome aquatic weed all over the world. It was introduced into India in 1896 as an ornamental pond plant. Now this weed is seen infesting more than 200,000 ha of water surface, causing concern in 98 out of 246 districts in India. This fast multiplying weed can produce 3000 offspring in 50 days and can double its biomass in 10–12 days. The disadvantages of this weed outweigh its merits. It interferes with production of hydroelectricity, blocks water flow in irrigation and drainage canals, channels and streams leading to flooding and seepage into adjoining areas, hinders anti-mosquito operations and forms a breeding ground for obnoxious insects like mosquitoes which transmit infectious diseases such as malaria and encephalomyelitis. It also affects the aquatic fauna through elimination of habitat and depletion of oxygen level caused by respiration and decomposition of vegetative parts. The excessive weed population is strong enough to stop boats or slow down navigation. It also makes recreational water activity difficult and unsafe in lakes. Algae play an important role in the limnology and ecology. Algae are the predominant photo synthesizers of fresh water and all aquatic environments. The density and distribution of phytoplanktons are determined by the variability and distribution of nutrients in an aquatic system.