Environmental Isuues Water

Water Pollution Causes, point & nonpoint sources

In this article, a comprehensive discussion is arranged about water pollution. Besides, Sources of Water Pollution (point and non-point sources of water pollution) is also discussed here in detail. We hope, you will be benefited and get all the information that you are searching for.

Water pollution is nothing but a phenomenon that is characterized by the deterioration of the quality of land water (rivers, lakes, marshes and groundwater) or seawater as a result of various human activities. In this article, we will first classify various humus activities that cause water pollution, discuss water pollution according to their characteristics, and then take a general view of water pollution which is currently in progress in our modern society. Human activities related to water pollution include various industries such as mining, agriculture, stock-breeding, fisheries, forestry, urban human activities, manufacturing industry, construction works and various tertiary industries. Then, in the last section of this article, we will classify wastewaters according to their physical and chemical properties.

What is water pollution:

Water pollution is nothing but any type of physical or chemical change in water that can adversely affect organisms. Nowadays water pollution is a global problem, affecting both industrialized and developing nations. The water pollution problems in the rich and the poor nations, however, arc quite different in many respects. Heat, toxic metals, acids, sediments, animal and human wastes, and synthetic organic compounds foul the waterways of developed nations. Human and animal wastes, sediment, and pathogenic organisms head the list in the non-industrialized nations. In developing countries, unsanitary water and malnutrition account for most of the illness and death.

The term ‘water pollution’ is referred to the addition of something with water of excess material (or heat) that is harmful to humans, animals, to desire able aquatic life or otherwise causes significant hazards in the normal activities of various living communities in or near bodies of water. The National Water Commission stated (1973) that ‘water will be polluted if it has been not of sufficiently high quality to be suitable for the highest use people wish to make of it at present on int future.”
In reality, the term water pollution refers to a type of aquatic contamination between two extremes:
1. A highly enriched place such as a river or, over-productive biotic community, such as a river or lake with nutrients from sewage, fertilizer (cultural eutrophication), or
2. A body of water poisoned by hazardous or toxic chemicals which eliminate living organism or even exclude all forms of life.

The term “water pollution” seems to be clear to all. Nevertheless, it is worth determining that its real meaning as this has changed over the course of time. Felfoldy’s (1982) precise definition is the following: “Water pollution refers to every impact which changes the quality of our surface and subsoil waters to such a degree that its suitability either for human consumption or for the support of man’s natural life processes with decrease or cease”

Unpolluted vs. Polluted Water:

Pollution is totally contrary to purity. When environmental pollution has been the topic, the term has come to mean a deviation from a normal, rather than from a pure state. This has been particularly true for water. This widely distributed substance or material has been such a good solvent that it has been never found naturally in completely pure state.

Even in the most unpolluted geographical regions, rainwaters is having dissolved CO2, O2, N2 and other gases and may also carry in suspension dust or other particulates picked up from the atmosphere. Surface and ground waters generally contain dissolved compounds of metals like Na, Mg, Ca, and Fe. The term hard water used to describe water that contains minimal amounts of such compounds. Even the water we drink is also not pure in a chemical sense. It may happen that suspended solids have been removed and harmful bacteria or pathogens destroyed, but many substances still remain in solution. Indeed, completely pure water would not be pleasurable to drink, because it has been being the impurities that impart water the characteristic “taste” by which it is recognized. It is desirable that water need some purities because these elements are required for health. So, the desirable limits of water impurity depend on the purpose of water use.

Normal uses of water:

Water is used for different purposes. The normal uses of water are given in the below list:

  • Recreation and aesthetics
  • Public water supply
  • Fish, other aquatic life, and wildlife
  • Agriculture
  • Industry

Water Quality Parameters and Standards:

There are various water quality parameters and standards that differ from country to country. A table is given below with parameters of water-quality characterization. The permissible limits, which have been prescribed by the United States Public Health Drinking Water Standards (USPH), Indian Standards Institution (ISI) and Bangladesh standards prescribed by DoE have been given for comparison. These refer to domestic water supplies for drinking water.

ParametersUSPH StandardISI StandardDoE Standard
Total dissolve solids 500-
Suspended Solid5.0-
Sulphide0.1 micro per liter(ppb)-
Specific Conductance300 micro ohom Cm-1-
Physical Characteristics
Nitrate+ Nitrite<10-
Inorganic Chemicals
DO (Dissolve Oxygen)4.0-6.0(ppm)3.0
Iron (filterable)<0.3-
Manganese (filterable)<0.05
Organic Compounds
Carbon CHCl30.15
Policyclic aromatic0.2 ppb
hydrocarbons (PAH)0.002 ppm
Gross beta1000 pc/L
Radium-2263 pc/L
Strontium-9010 pc/L
Bacteriological parameters
Coliform cells/100 ml100
Total bacteria count/100 ml1* 10^6<5000

Sources of Water Pollution:

There are various sources of water pollution. Water pollution can result from natural runoff; dissolved chemicals in water that percolates through the soil and human sources such as agriculture, mining, construction, industry, homes, and businesses. It is useful to classify pollution sources as either point sources or non-point sources.

Point Sources of Water Pollution:

Point sources involve discharge of wastes from identifiable points.

These type of sources water pollution includes

  1. Sewage treatment plants (which remove some but not all pollutants)
  2. Storm water runoff from combined storm and sanitary sewer lines in urban areas;
  3. Industrial plants  and
  4. Animal feedlots where large numbers (sometimes 10,000 or more) of animals are scientifically fed in tightly restricted quarters before slaughter.

Non-point Sources of Water Pollution:

Non-point sources involve the diffuse discharge of wastes from land runoff, atmospheric washout, and sources that are difficult to identify and control. They include:

  1. Runoff of sediment from natural and human caused forest fires, construction, logging, and farming;
  2. Runoff of chemical fertilizers, pesticides, and saline irrigation water from croplands;
  3. Urban storm water runoff;
  4. Drainage of acids, minerals, and sediments from active and abandoned mines; and
  5. Spills of oil and other hazardous materials. Non-point source pollution is not recognized as a major problem, since the sources are widely spread out, difficult to identify, and bard to control.

Causes of Water Pollution:

The causes of water pollution are a lot. These causes are descrived with example below.

Water Pollution by Agriculture:

Agriculture has been a victim of water pollution in many instances, but sometimes it is also responsible for polluting water. Water pollution caused by agriculture is mainly an outcome of fertilizers and agricultural chemicals such as insecticides and herbicides. Agricaluture can pollute water by following ways.

Fertilizers given to crops are not always fully consumed by crops and a portion of it remains in the soil by being absorbed by soil colloid. Then the fertilizer influence the quality of underground, river and sea waters when it is dissolved. Chemical fertilizers mainly consists of relatively simple compounds of nitrogen, phosphorus and potassium which are the nutritive elements of plants. Their runoff coefficients vary depending on the solubility of the fertilizer itself, the rate of absorption by plants, rate of absorption by the soil and rate of decomposition. It is generally believed that the runoff co-efficient of nitrogen is 5.30%, and that of phosphorus is 0.5-5%. Due to high runoff co-efficient tends of Nitrogen the eutrophication of lakes and enclosed sea areas is occured. Fertilizers as the sources of water pollution are called “nor -point sources”.The non-point sources are not only difficult to eliminate, but also hard to measure their quantity. Organic fertilizers such as compost, farmyard manure, human waste and fish meal produce nitrogen and phosphorus when they are decomposed and also become the sources of water pollution. These organic fertilizers do not contain any toxic substances in general.

Water Pollution by Agricultural Chemicals:

Agricultural chemicals are considered as a source of peculiar water pollution which cannot be ignored. Agricultural chemicals include a variety of chemicals such as insecticides, sterilizers and weed killers. These chemicals have played vital roles in the production process of modern agriculture, but they have also caused serious environmental pollution specially water pollution.

The characteristics of agricultural chemicals as sources of water pollution substances are includes:

  1. Almost all of the agricaltural water polluting substances special compounds these don’t produce in  nature by itself. The behaviors and final products are sometimes unknow when  they are discharged into the natural environment.
  2. Many of the agricaltural water polluting substances has  negative influences on the human body because of their inherent characteristics.
  3. When these chemicals consumed into the human body they tend to accumulate or concentrate in it
  4. These chemicals are various kinds and new products are developed constantly in environment
  5. Some of them are extremely stable that is called persistent polluting (POPs) agents as chemicals and remain in nature or in the human body for a long time thereby eventually afflicting the human body
  6. It is common to all these chemicals to contain additives besides the main constituents and the additives can contribute to affect the environment though they do not have a strong toxicity
  7. Some of these chemicals require a special method of analysis

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