• Written By Saif_Ansari
  • Last Modified 01-03-2024

Wastewater Story for Class 7 Science Chapter 18: Notes


Wastewater Story: We all know that water is the elixir of life and that access to clean water is one of our fundamental human rights, but did you realise that this right is routinely violated in India, with around \(63\) million people lacking access to safe drinking water? There is a water crisis in every corner of India, from rural villages to teeming megacities.

The water crisis is not only engrossing India; it is also enthralling superpower countries. People all across the world are battling to get the water they need for drinking, cooking, bathing, handwashing, and growing food both in quantity and quality. Let us take a close look at this situation and ways to address it.

Wastewater Story

Water is our lifeline because all living organisms use it on Earth to perform their life processes. It is the fundamental component that bathes us and feeds us. It is essential for all dimensions of life. With two-thirds of the earth’s surface covered by water and comprising \(75\) per cent of the human body, it is clear that water is one of the prime elements responsible for life on Earth. Without water, life on Earth would not evolve.

Agriculture is the primary food source for us, and water is the prime requirement for raising food crops. The existence of fishes which make up a large chunk of our food, depends on water. Forests that keep our ecological balance intact and provide us with numerous things also need water. It is a renewable, pollution-source of energy and the cheapest resource for generating hydroelectricity.

However, this ultimate resource of the earth has become an indispensable site for the disposal of urban Sewage and dirt. It is necessary not only to conserve water but also to purify used water before dumping it into seas or other bodies of water. As a result, the United Nations designated the years \(2005\) to \(2015\) as the International Decade for Action on ‘Water for Life.’

What is Wastewater?

Wastewater is the used or polluted water generated from rainwater runoff and human activities. It is full of impurities and cannot be reused. It is also called Sewage, typically categorized by how it is generated—specifically, as domestic Sewage, industrial Sewage, or storm sewage (stormwater).

Water Pollution

Water pollution is defined as the contamination or the addition of pollutants to the water present on the earth in the oceans, seas, rivers, lakes, and ponds. These pollutants may be toxic chemicals and biological agents that exceed what is naturally found in the water and pose a severe threat to humans and the environment.

The contamination of water results in a change in water’s physical, biological, and chemical properties, making it unsafe for drinking or domestic purposes. The substances or biological agents that cause water pollution are called Water Pollutants. The pollution of water has severe effects on health, the ecosystem of a region, and aquatic life.

Some of the major Water pollutants are:

  1. Sewage: Sewage is a type of wastewater produced by a community of people. It contains wastewater from households and industries. When dumped in water bodies such as rivers and seas, it pollutes it and makes it unfit for any kind of consumption. It mainly consists of faeces, urine and laundry waste. These pollutants cause a rise in several bacteria and microorganisms that disrupt aquatic life and affects human health by causing diseases like cholera, diarrhoea, and typhoid.
  2. Industrial Chemical Wastes: Potentially harmful contaminants—from arsenic to copper to lead and toxic chemicals are often dumped into water bodies contaminating the water directly.
  3. Agricultural Effluents: The agricultural sector is the biggest consumer of global freshwater resources and a severe water polluter. Every time it rains, fertilizers, pesticides, and animal waste from farms and livestock operations wash nutrients and pathogens—such as bacteria and viruses—into our waterways. Nutrients such as nitrogen and phosphorus degrade water quality worldwide and lead to algal blooms.
  4. Oil Spills: Accidents and leakages of tankers lead to oil spillage in the sea. This dramatically affects marine life. Oil causes blockages in the respiratory system and leads to the loss of aquatic life.
  5. Thermal Wastes: Warm water from thermal industries often spilt in the water bodies leading to a rise in the temperature of the water body, which is not suitable for aquatic animals. Hence, it causes the loss of aquatic life.

What is Sewage?

Any liquid waste is called Sewage. The wastewater from houses, offices, industries, hospitals and other sources all forms of Sewage. Rainwater that flows into the drains during heavy rainfalls also forms Sewage because it contains pollutants that wash off the roads. The contaminants present in sewage water are:

A network of large and small pipes that carry sewage water is known as Sewerage, and the individual pipes through which Sewage flows is known as sewers.

The process in which contaminants or pollutants present in Sewage are removed from it before it reaches a water body or before it is used again is known as Sewage Treatment.

Wastewater Treatment Plant (WWTP)

We know wastewater is used water that includes substances such as food scraps, human waste, oils, soaps and chemicals. It also includes water from sinks, toilets, showers, bathtubs, dishwashers and washing machines. Industries and businesses also contribute their share of used water that must be cleaned before being dumped into water bodies.

Nature can cope with small amounts of water waste and pollution. However, it would be burdening and overwhelming if we didn’t treat the billions of gallons of wastewater we produce every day before releasing it back into the environment. Pollutants in wastewater are reduced to a level that nature can tolerate in treatment plants.

The fundamental goal of wastewater treatment is to remove as many suspended solids as possible before returning the leftover water, known as effluent, to the environment. Treatment of wastewater includes physical, chemical and biological processes of removal of the contaminants.

The physical and biological process of treatment of water:

1. Separation of Large Objects from Sewage Water

The wastewater is first made to pass through bar screens which remove big objects from the water like napkins, plastic bottles, cans, rags and sticks.

2. Separation of Sand and Dirt

The wastewater from the bar screens is sent to a grit and sand removal tank. The speed of the water is kept low to allow the sand, pebbles and dirt to settle down.

3. Removal of Solids

The water from the grit and sand removal tank cycles in a tank called Clarifier, which is sloped at the centre.

Solids like faeces settle at the bottom of the tank to form Sludge that is separated from the water with the help of a scrapper.

Floatable substances like oil and grease are removed with the help of a Skimmer to obtain clarified water.

The Sludge so obtained is transferred to a separate tank where the anaerobic bacteria decompose it. Biogas is produced in this process that can be used as fuel or can be used to produce electricity.

4. Suspended Sludge Removal

The clarified water obtained after removing the Sludge is moved to an aerator that pumps air into it. This process is called aeration. In this process, air allows aerobic bacteria to grow faster in the water.

The clarified water consists of organic waste, food waste, soaps and other elements. Aerobic bacteria decompose these wastes present in the clarified water.

This water is allowed to settle for several hours for these waste materials to settle down in the tank. This is called Activated Sludge.

After the solid has settled in the tank, the water is removed from the top of the activated Sludge with the help of machines or sand-drying beds. The dried Sludge can be further used as manure.

This treated water contains suspended matter and fewer amounts of impurities. The water so obtained can be safely dumped in a water body or under the ground. It is then discharged into rivers, seas or underground and left for nature to clean up.

Chemical Treatment of Wastewater

Sometimes disinfection of the treated water needs to be done even after treating them physically and biologically. Disinfectants such as chlorine and Ozone are used to remove harmful chemicals from the treated water.

Eucalyptus Plant and Cleaning of Water

Eucalyptus plants are planted along with the sewage ponds. This is because Eucalyptus plants absorb wastewater rapidly and release pure water vapour into the atmosphere. Hence, they act as a natural water purifier.

Better Housekeeping Practices

The best way to address the issue of sewage water is to check what is being released in the drains. Proper disposal of waste is essential to reduce sewage accumulation. Some housekeeping practices are:

  1. Oils and fats should never be put into sinks. This is because oil and fats harden and clog drains. Moreover, it isn’t easy to separate them from water.
  2. Chemicals like insecticides, pesticides, medicines and paints should not be drained off. They can kill the microbes in the water that help in its purification.
  3. A dustbin should be used to dispose of tea leaves, cotton, food remains, soft toys etc. These substances block pipes and clog drains.

Sanitation and Disease

A large number of people in low and middle-income countries die due to inadequate access to sanitation, water and hygiene each year, representing \(60\% \) of total diarrhoeal deaths. Out of these, around \(43200\) of these deaths is due to poor sanitation.

Better sanitation, water, and hygiene can prevent the deaths of children aged under five years each year.

Unsafe hygiene practices are widespread, compounding the effects on people’s health. Open defecation should be discouraged, and people should be encouraged to use toilets. Exposed faecal matter enters into the food chain and water resources, helping to spread serious diseases such as cholera. The lack of adequate sewerage or waste disposal systems can contaminate ecosystems and contribute to disease pandemics.

Benefits of Improving Sanitation

Improved sanitation extends beyond reducing the risk of diarrhoea. These include:

  1. reducing the spread of intestinal worms and the impact of malnutrition;
  2. promoting dignity and boosting safety, particularly among women and girls;
  3. promoting school attendance: girls’ school attendance is mainly boosted by the provision of separate sanitary facilities; and
  4. potential recovery of water, renewable energy and nutrients from faecal waste.

Alternative Arrangement for Sewage Disposal

Onsite sewage disposal methods such as septic tanks, compost pit toilets and chemical toilets are being used nowadays. The onsite sewage treatments treat and dispose of the wastewater or sewage using natural techniques.

  • Septic Tanks – Septic tanks are commonly constructed underground in houses or buildings to allow anaerobic microorganisms to decompose sewage from the household.
  • Chemical Toilets – A chemical toilet is a toilet with a separate chamber that uses chemicals to treat human waste and minimise odour.
  • Composting Toilets – A composting toilet uses aerobic bacteria in a storage tank to treat human waste. These bacteria digest garbage and convert it to compost.


Access to safe drinking water is a prerequisite for development. People are better able to practise good hygiene and sanitation when they have access to clean water. The most vulnerable to diseases caused by contaminated water are women and children.

Unfortunately, this elixir of life is being butchered at the hands of the most intelligent creations of God. Instead of conserving water, we are wasting it.

It’s high time that we educate the general public about the significance of recycling, storing and reusing water, or else clean water is destined to become one of the rarest commodities soon.

FAQs on Wastewater Story

Let’s look at some of the commonly asked questions about wastewater stories:

Q.1. What are the possible origins of wastewater?
The possible origins of wastewater are from homes that comprise domestic Sewage, from industries that make up industrial sewage and storm sewage.

Q.2. What happens to the wastewater after being released from the treatment plants?
The treated wastewater is released into local waterbodies. It is used again for many purposes, such as supplying drinking water, irrigating crops, and sustaining aquatic life.

Q.3. What is removed from wastewater?
Organic, inorganic and suspended solids are removed from wastewater after being treated at wastewater treatment plants. Harmful bacteria and pathogens, including chemicals, are removed by using certain disinfectants such as chlorine and Ozone.

Q.4. What is the difference between wastewater and Sewage?
The terms’ wastewater’ and ‘sewage’ are used interchangeably. However, the prime difference is that ‘sewage’ is considered to be a subset of wastewater.

Q.5. Why is wastewater more expensive?
The wastewater we produce may go back to water bodies and cause great damage to our ecosystem. Therefore, it is necessary to treat used water before releasing it to a water body. However, the treatment of effluent is not simple and costs money more than the treatment of drinking water.

Study Sources of Water Here

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