Class 7 wastewater story notes

Questions covered are

1. What is wastewater?

Wastewater is the water that has been used in homes, industries, and other places, which now contains impurities such as food waste, detergents, human and animal excreta, and industrial chemicals.
It includes water from kitchens, bathrooms, toilets, laundries, factories, and agricultural fields.
This wastewater must be cleaned before it is released into the environment, as it can cause severe water pollution and health hazards.
The main sources of wastewater include:
- Domestic waste from households (kitchens, bathrooms, and toilets).
- Industrial waste containing chemicals and harmful substances.
- Agricultural runoff that carries pesticides and fertilizers.

Clean water is essential for human survival and for various daily activities such as drinking, cooking, bathing, and irrigation.
Contaminated water leads to serious health problems such as diarrhea, cholera, typhoid, and other waterborne diseases.
More than one billion people worldwide lack access to safe drinking water, leading to millions of deaths every year, especially among children.
The demand for freshwater is increasing due to population growth, pollution, and industrialization, making water conservation and treatment necessary.
The United Nations launched the “Water for Life” decade (2005-2015) to reduce the number of people without access to clean water.

Sewage is the wastewater released from homes, factories, hospitals, and public places.
It consists of liquid waste that contains organic and inorganic impurities, including harmful microorganisms.
Rainwater that runs off roads, carrying dirt, oil, and chemicals, also forms part of sewage.
Sewage must be properly treated before being released into rivers or seas to prevent pollution and health hazards.

Type of Impurity	Examples
Organic Impurities	Human and animal waste, oil, pesticides, food waste
Inorganic Impurities	Nitrates, phosphates, heavy metals (lead, mercury)
Nutrients	Phosphorus, nitrogen (from fertilizers)
Bacteria	Vibrio cholerae (causes cholera), Salmonella typhi (causes typhoid)
Other Microbes	Protozoa (cause dysentery), viruses (cause hepatitis)

Wastewater from households and industries is collected through underground pipes and open drains.
It is transported to a sewage treatment plant (STP), where it undergoes a series of purification processes.
The cleaned water is then released into rivers, lakes, or reused for irrigation and industrial purposes.
In many rural areas, where there is no proper sewage system, wastewater is often discharged untreated, leading to severe pollution.

Primary Treatment:
- Large debris such as plastic, rags, and sticks are removed using bar screens.
- Water flows into grit and sand removal tanks, where heavy particles settle at the bottom.
- The remaining liquid is sent to sedimentation tanks, where solid waste (sludge) settles down, and grease and oil float on top.
Secondary Treatment:
- The partially treated water is aerated by adding oxygen, which encourages the growth of bacteria that break down organic waste.
- These bacteria consume waste materials, converting them into harmless substances.
- After several hours, the activated sludge settles at the bottom, and the clean water is separated.
Tertiary Treatment:
- Water is passed through sand filters to remove remaining impurities.
- It is disinfected using chlorine or ozone to kill harmful bacteria and viruses.
- The treated water is now safe for release into water bodies or reuse.

Sludge is the solid waste that settles at the bottom of sedimentation tanks during wastewater treatment.
It contains organic matter, bacteria, and other impurities.
Treatment of sludge involves:
- Drying it using sand drying beds or mechanical presses.
- Decomposing it using anaerobic bacteria, which produce biogas (used as a fuel for electricity generation or cooking).
- Using dried sludge as manure in agriculture to improve soil fertility.

Poor sanitation leads to contamination of drinking water, spreading diseases such as cholera, typhoid, dysentery, and hepatitis.
Proper disposal of human waste, garbage management, and sewage treatment are essential for maintaining hygiene.
People should use toilets instead of open defecation, as untreated human excreta pollutes the environment and groundwater.

Septic Tanks: Used in areas without proper sewage systems; they treat waste locally.
Chemical Toilets: Use chemicals to break down waste; commonly used in airplanes and trains.
Composting Toilets: Convert human waste into compost, which can be used as fertilizer.

Install proper drainage systems in crowded areas such as railway stations and markets.
Use dustbins to dispose of garbage instead of littering.
Raise awareness about hygiene and cleanliness.
The government should enforce strict sanitation laws and implement cleanliness programs like “Swachh Bharat Abhiyan.”

Fix leaking taps and pipes to conserve water.
Use water-efficient appliances such as low-flow showers and dual-flush toilets.
Avoid throwing fats, oils, and chemicals down the drain, as they clog pipes and interfere with wastewater treatment.
Dispose of solid waste like tea leaves, food remains, and sanitary products in dustbins instead of flushing them.

Contaminated water spreads infections when used for drinking, bathing, or cooking.
Proper sanitation practices, such as using toilets, maintaining clean surroundings, and ensuring proper waste disposal, can prevent diseases.

Disease	Cause
Cholera	Drinking contaminated water with Vibrio cholerae
Typhoid	Consuming food or water contaminated with Salmonella bacteria
Dysentery	Drinking water containing harmful protozoa
Hepatitis	Viral infection caused by contaminated water sources

Wastewater treatment is essential to protect human health and the environment.
Proper sanitation practices help prevent diseases and promote hygiene.
Everyone must take responsibility for reducing water pollution and conserving clean water resources.

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CBSE CLASS 6 SOCIAL SCIENCE