Wastewater Management Class 7 Notes Science

Wastewater is water that has become dirty due to human activities. It is generated from various sources, including agriculture, construction, industries, hospitals, hotels, offices, domestic activities, and mining.

Sources of Wastewater

• Agriculture: farms generate wastewater containing harmful pesticides, biocides, and animal waste.
• Construction: large amounts of wastewater are generated during the construction of buildings.
• Industries: paint and dye industries generate wastewater containing harmful chemicals such as lead and chromium.
• Hospitals, hotels, offices: wastewater from hospitals can contain disease-causing germs.
• Domestic activities: wastewater from houses contains detergents, food waste, human faeces, plastics, paper, metal objects, etc.
• Mining: wastewater is generated as a result of mining operations.

Sewage and Contaminants
All wastewater released from various sources contains suspended impurities and is called sewage. The impurities present in sewage are called contaminants.

Eutrophication
Eutrophication is the excessive growth or blooms of algae in lakes rich in nutrients such as phosphates. Human activities have enhanced this process greatly by adding excessive amounts of plant nutrients (primarily phosphorus, nitrogen, and carbon) to streams and lakes in various ways. Runoff from agricultural fields and urban lawns and untreated domestic sewage discharged into lakes are major sources of these nutrients. Eutrophication leads to oxygen depletion, resulting in the death of many fish, birds, and other animals and the stinking of water.

Domestic Wastewater Management
Domestic wastewater is in our direct control. Domestic wastewater goes through a treatment process before releasing it into rivers, streams, and other water bodies.

WHERE DOES DOMESTIC WASTEWATER GO?

Domestic wastewater contains various impurities and needs to be treated before being discharged into water bodies. Wastewater treatment plants are used to treat wastewater from domestic and industrial sources. The process of wastewater treatment involves primary, secondary, and tertiary stages.

• The Sewer System
  A channel system of pipelines used to carry sewage is called the sewer system. Sewage leaves houses through drain pipes and flows to the sewer mains of the city. Sewer mains flow into progressively larger pipes until they reach the wastewater treatment plant. Manholes are used to access the sewer system in case of leaks or blockages.
• Wastewater Treatment Plant
  A facility that treats wastewater from domestic and industrial sources is called a wastewater treatment plant. The treatment process involves three stages - primary, secondary, and tertiary.
• Primary Treatment
  The primary treatment is a mechanical process that involves screening and settling of large particles. Sewage is passed through screens of vertical bars to remove larger impurities such as metal cans, plastic bags, cloth pieces, etc. The wastewater is then passed through a grit and sand removal tank called the grit chamber. The water is then passed through huge sedimentation tanks, where solid wastes such as faeces settle down, and light floatable wastes such as soaps, oils, plastics, and grease rise. Solid waste that settles at the bottom in the primary treatment is called the sludge. Light waste that rises to the top and floats is called the scum. The water that comes out of the sedimentation tanks is called clarified water.
• Secondary Treatment
  Secondary treatment is a biological process in which the organic matter in the clarified water is broken down with the help of bacteria. Biogas is produced during the digestion process, which can be used as a fuel or to produce electricity. The treatment at this stage can be speeded up by allowing water to flow into large aeration tanks, where air is blown onto the sewage.
• Tertiary Treatment
  Tertiary treatment is a chemical process in which chemicals are used to remove phosphorus and nitrogen from the water. Addition of chlorine and exposure to ultraviolet light kills any remaining bacteria and disinfects the water. The treated water is then discharged into water bodies.

What Happens to the Treated Water?
The treated water is released into water bodies such as streams and rivers. The water can be used again for various purposes such as supplying drinking water, fertilizers for growing crops, and for aquaculture.

What Happens to the Sludge?
Sludge consists of human faeces and other organic matter and needs to be treated before disposal. Sludge can be incinerated, dewatered, or composted to produce fuel or fertilizers. Incineration involves burning sludge into ash that can be used as soil conditioner or construction material. Dewatering involves removing water from sludge and combining it with other wastes to make fertilizers. Solid composting involves processing sludge to produce gases that can be used as fuel.

Controlling Sewage Generation

A. Measures to control sewage generation
1. Use flushes with low capacity
2. Proper disposal of household products
a. Cleansers, beauty products, medicine, automobile oil, and paint
b. Reason for proper disposal
3. Disposal of excess cooking oil, butter, meat fats, and plastic
a. Consequences of improper disposal
4. Fixing leakages in sewer pipes
a. Potential contamination of drinking water
b. Breeding of disease-causing insects

Green Corner: Promoting Environmental Awareness
A. Importance of avoiding pollutant discharge into water bodies
B. Actions to promote environmental conservation
1. Carrying reusable bags while shopping
2. Minimizing packaging waste
Wastewater management is essential for maintaining a clean and healthy environment. In this chapter, we will explore the importance of controlling sewage generation and adopting measures to protect our water resources.

Controlling Sewage Generation
To control the generation of sewage, certain measures should be adopted. Firstly, using flushes with low capacity can help reduce the amount of water used for flushing, thereby reducing the volume of wastewater produced.
Secondly, it is crucial to dispose of household products properly. Pouring cleansers, beauty products, medicine, automobile oil, and paint down the drain should be avoided. These substances contain chemicals that wastewater treatment plants may not be able to remove effectively. Thus, they should be disposed of through appropriate channels.
Furthermore, excess cooking oil, butter, meat fats, and plastic should never be disposed of in sinks or toilets. These materials can clog pipes, leading to sewage overflow in homes or public areas. Such overflow poses health and environmental risks.
Leakages in sewer pipes should also be addressed promptly. These leaks not only contaminate drinking water but can also seep into the water table, affecting the quality of groundwater. Additionally, stagnant sewage in certain areas can become breeding grounds for disease-causing insects like flies, cockroaches, and mosquitoes.

Green Corner: Promoting Environmental Awareness
Cleaning wastewater is a laborious, time-consuming, and costly process. Therefore, it is essential to avoid discharging pollutants into water bodies. As responsible citizens, we can take small but impactful actions to protect the environment.
One way to contribute is by carrying our own bags when we go shopping and refusing plastic bags. This simple step reduces the consumption of single-use plastic, which often ends up polluting water bodies. Additionally, we should strive to choose products with minimal packaging, minimizing the amount of waste generated.
By practicing these environmentally conscious habits, we can play our part in wastewater management and contribute to the conservation of our precious water resources.

LTERNATIVE METHODS OF SEWAGE DISPOSAL 

• Septic Tanks
  • Description and working of septic tanks
  • Advantages and disadvantages of septic tanks
• Biogas Plants
  • Description and working of biogas plants
  • Advantages and disadvantages of biogas plants
• Vermi-composting Toilets
  • Description and working of vermi-composting toilets
  • Advantages and disadvantages of vermi-composting toilets

Septic Tanks

• Septic tanks as an alternative method of sewage disposal
• Household wastewater management through septic tanks
• Bacteria's role in partially decomposing solid waste
• Discharge of liquid waste through pipes into the ground
• Importance of regular cleaning and maintenance of septic tanks

Biogas Plants

• Biogas plants as an alternative method of waste disposal
• Use of human and animal excreta to produce biogas
• Microorganisms' role in breaking down waste materials
• Use of biogas to produce electricity
• Advantages of biogas plants for waste disposal and energy generation

Vermi-composting Toilets

• Vermi-composting toilets as an innovative method for waste disposal
• Use of earthworms to convert human excreta into compost
• Minimal use of water in the process
• Safe and hygienic way of processing human waste
• Advantages of vermi-composting toilets for waste management

Improper Management of Sewage

Discharge of untreated or partly treated sewage into water bodies is a common cause of water pollution. Improper sewage handling processes of municipal bodies can contribute to the discharge of untreated sewage into water bodies. Faulty sewer lines can cause dirt to flow into the open and contaminate the water supply. Consuming contaminated water can lead to diseases like gastroenteritis, dysentery, and typhoid.

• Sanitation in Public Places
  Proper sanitation should be maintained at public places such as bus depots, railway stations, airports, malls, and fairs. Waste generated at public places is usually large and should be disposed of properly. Public conveniences and dustbins have been built by the government to help in maintaining sanitation in public places. We should maintain cleanliness even outside our homes by throwing wastes in bins meant for them.
• Case Study: Ganga Action Plan (GAP) and Namami Gange Programme
  The Ganga Action Plan was launched by the government of India in 1986 to improve the water quality of river Ganga. The GAP plan included diversion of waste water flowing directly into Ganga, installing sewage treatment plants, and other pollution control measures. The plan laid emphasis on public awareness and participation to keep the Ganga clean, but it was not fully successful. The plan has been revived again under the Namami Gange Programme in 2014 to not only arrest the pollution of Ganga but also to revive it.
• Green Corner: Help Us Green
  Help Us Green is an initiative started in 2015 by Ankit Agrawal and Karan Rostogi. The initiative collects floral waste from temples, mosques, and gurudwaras situated on the banks of Ganges. Around 80% of the waste is converted into vermi-compost and used in natural and chemical-free lifestyle products. This initiative promotes cleanliness and sustainability.

Key Words

Activity

Title: Water Conservation
Aim: To promote water conservation among students
Materials: Posters, stickers, and educational materials
Method: Students can create posters and stickers that promote water conservation. They can also participate in educational activities such as water audits and water-saving competitions.