Water is an  inorganic, transparent, tasteless, odorless and nearly colorless chemical substance, which is the main constituent of Earth’s hydrosphere and the fluids of all known living organism . It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds.

Water covers 71% of the Earth’s surface, mostly in seas and oceans. Small portions of water occur as groundwater (1.7%), in the glaciers and the ice caps of Antarctica and Greenland(1.7%), and in the air as vapor, clouds (consisting of ice and liquid water suspended in air), and precipitation(0.001%). 

The Safe Drinking Water Act defines the term “contaminant” as meaning any physical, chemical, biological, or radiological substance or matter in water. Therefore, the law defines “contaminant” very broadly as being anything other than water molecules. Drinking water may reasonably be expected to contain at least small amounts of some contaminants. Some drinking water contaminants may be harmful if consumed at certain levels in drinking water while others may be harmless. The presence of contaminants does not necessarily indicate that the water poses a health risk.

The following are general categories of organic drinking water contaminants and examples of each:

  • Physical contaminants primarily impact the physical appearance or other physical properties of water. Examples of physical contaminants are sediment or organic material suspended in the water of lakes, rivers, and streams from soil erosion.
  • Chemical contaminants are elements or compounds. These contaminants may be naturally occurring or man-made. Examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal drugs.
  • Biological contaminants are organisms in the water. They are also referred to as microbes or microbiological contaminants. Examples of biological or microbial contaminants include bacteria, viruses, protozoan, and parasites.
  • Radiological contaminants are chemical elements with an unbalanced number of protons and neutrons resulting in unstable atoms that can emit ionizing radiation. Examples of radiological contaminants include cesium, plutonium, and uranium.

Water can be contaminated in several ways. It can contain micro-organisms like bacteria and parasites that get in the water from human or animal fecal matter. It can contain chemicals from industrial waste or from spraying crops. Nitrates used in fertilizers can enter the water with runoff from the land. Various minerals such as lead or mercury can enter the water supply, sometimes from natural deposits underground, or more often from improper disposal of pollutants. Lead can leach into drinking water through old lead pipes.

Drinking Contaminated water causes these effects. The immediate effects can include contraction of cholera, typhoid fever and dysentery while the long-term effects include serious damage to the kidney, liver, bone and brain.

Contaminated water can be classified into 2 categories according to what is causing the contamination: microbes and chemicals. Microbes (bacteria and parasites) often cause immediate effects to humans. On the other hand, chemicals (especially heavy metals such as arsenic, lead and mercury) can build up in our internal organs over time.

How microbes from drinking water harm humans?

Let’s start with microbes. Bacteria, protozoa and viruses can enter the body via consumption of contaminated water. Many of these are pathogens (disease-causing), which can send someone to a hospital within a few hours of ingestion.

Some of the harmful microbes present in contaminated water are:

  • Crypstosporidium
  • Ecoli
  • Legionella
  • Giardia
  • Salmonella

How microbes enter your water supply?

As mentioned above, pipe leaks and water runoffs may introduce microbes and parasites into our water system. Sewage leaks (wastewater spilling) or agricultural runoffs (wastes from infected animals get carried away) can be the catalyst for contaminated water. Water flowing from inland might also carry organic pathogens and other microbial contaminants if animals graze or water nearby.

Furthermore, microbes and parasites can enter our water supply or glass of water through the following:

  • Microorganisms in our water pipes.
  • Leaking pipes before or after our water metre.
  • Lack of water disinfection or other treatment.

Chlorine is often used for water disinfection. Chlorine’s effective mechanism might be due to its disruption of the microbes’ cell membranes. The cell’s contents will then spill out and eventually lead to the death of the cell.

Dangers of arsenic, lead, mercury and other heavy metals

We’ve discussed above the dangers of microbes and how they harm human health. In this section we’ll now focus on heavy metals and other substances.

Let’s start with arsenic. It’s a metallic element which can be naturally found in soil and rocks. As a result, rain and water runoffs may carry the arsenic into our water supply. It may already be present in groundwater. Some of the known health effects of arsenic are:

  • Inorganic arsenic is carcinogenic to humans.
  • Arsenic may increase the risk of cancer in the liver, bladder, and lungs.
  • Long-term exposure may cause lowering IQ scores (especially to kids).
  • Arsenic may cause fetal malformations.
  • Arsenic may find its way into the breastmilk.

Runoffs and leaks may also introduce arsenic into our drinking water supply. After all, arsenic is naturally found in the ground. Agricultural and industrial processes may result in arsenic being present in our drinking water.

Sources of lead and how it enters our water supply

Older homes (built during the 1980s or earlier) may have lead in the old pipes, fittings and other plumbing fixtures. The problem gets worse if the water has low pH levels (acidic) because it catalyses corrosion. Some of the lead particles might dissolve and get introduced into the water.

Other factors that might affect how much lead gets into the water are the following:

  • Other minerals present in the water (lead may react with those minerals).
  • Water temperature (higher temperatures may catalyse further dissolution).
  • Presence and amount of coating present inside pipes and other plumbing fixtures.
  • Eventual degradation of the pipes due to wear and tear.

Lead may cause the following problems:

  • Lower IQ.
  • Slower physical development.
  • Anaemia.
  • Premature birth and reduced fetal growth.
  • Reproductive problems in both men and women.

Other heavy metals that also pose health risks are the following:

  • Mercury.
  • Cadmium.
  • Chromium.
  • Copper.
  • Antimony.
  • Nickel.
  • Thallium.

These should all be removed to avoid gaining long-term negative health effects

Water Treatment:

Treatment fort contaminated water is as follows:

  • Coagulation and Flocculation:

Coagulation and flocculation are often the first steps in water treatment. Chemicals with a positive charge are added to the water. The positive charge of these chemicals neutralizes the negative charge of dirt and other dissolved particles in the water. When this occurs, the particles bind with the chemicals and form larger particles, called floc.

  • Sedimentation:

During sedimentation, floc settles to the bottom of the water supply, due to its weight. This settling process is called sedimentation.

  • Filtration:

Once the floc has settled to the bottom of the water supply, the clear water on top will pass through filters of varying compositions (sand, gravel, and charcoal) and pore sizes, in order to remove dissolved particles, such as dust, parasites, bacteria, viruses, and chemicals.

  • Disinfection:

After the water has been filtered, a disinfectant (for example, chlorine, chloramine) may be added in order to kill any remaining parasites, bacteria, and viruses, and to protect the water from germs when it is piped to homes and businesses.


Written by: SAKSHI KADAM

INSTAGRAM ID: _zero_six_


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