16 Questions
Define sewage.
A complex mixture containing suspended solids, organic and inorganic impurities, nutrients, and disease-causing bacteria and other microbes.
What is wastewater?
Contaminated water after activities like washing, bathing, and mopping.
What is the composition of sewage?
It includes organic impurities (animal waste, urea, etc.), inorganic impurities (metals, phosphates), bacteria (cholera, typhoid), nutrients (nitrogen, phosphorus), and other disease-causing microbes.
What is a sewer?
A pipe that carries wastewater.
Explain sewage treatment.
It involves processes like aeration, sedimentation, and disinfection to remove impurities and disease-causing agents from sewage.
What is the purpose of wastewater treatment?
To clean water by removing pollutants before it enters a water body or is reused.
What are the three main stages of water treatment described in the text?
Aeration, filtration, chlorination
Why should cooking oil and fats not be thrown down the drain?
They can harden and block the pipes.
What are the potential consequences of throwing paints, solvents, insecticides, motor oil, and medicines down the drain?
They may kill microbes that help in the purification of water.
Why should solid food remains, soft toys, and sanitary towels not be thrown in drains?
They can choke the drains and do not allow free flow of oxygen.
What are the consequences of poor sanitation, according to the text?
Poor sanitation causes a large number of diseases. It leads to water and soil pollution.
Where do large numbers of people defecate in the open, according to the text?
Dry river beds, railway tracks, and directly in water.
What is the significance of proper sanitation in public areas such as railway stations, bus depots, and airports?
Proper sanitation is important to prevent epidemics from breaking out.
What is the purpose of the waste water treatment plant (WWTP) described in the text?
To remove large objects, grit, sand, and settle solids from the water.
What happens to the water in the large tank in the waste water treatment plant?
Solids like faeces settle at the bottom and are removed with a scraper.
How is water decomposed in the waste water treatment plant?
Water is decomposed by anaerobic bacteria in a tank, and air is passed to help in the process.
Study Notes
- Wastewater is contaminated water resulting from various activities like washing, bathing, mopping, etc.
- Wastewater treatment is the process of cleaning water by removing pollutants before it enters a water body or is reused.
- Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, bacteria, and other microbes.
- Organic impurities in sewage include animal waste, urea, pesticides, herbicides, fruits, vegetables, etc. Inorganic impurities consist of metals, phosphates, nitrates.
- Sewage treatment involves several processes such as aeration, filtration, and chlorination.
- A sewer is a pipe that carries wastewater. Sewerage is a network of big and small pipes called sewers.
- In sewage treatment, water is passed through screens to remove large objects, then to a grit and sand removal tank.
- Water is then allowed to settle in a large tank where solids settle at the bottom and are removed.
- Water is decomposed by anaerobic bacteria in a tank and air is passed. Microbes settle down at the bottom as activated sludge and water from the top is removed.
- Better housekeeping practices include not throwing cooking oil, fats, paints, solvents, insecticides, etc., down the drain.
- Solid food remains, soft toys, sanitary towels, etc., should be thrown in the dustbin instead of drains.
- Poor sanitation leads to numerous diseases and both water and soil get polluted.
- Large amounts of waste are generated in public places like railway stations, bus depots, and airports, and must be disposed of properly to prevent epidemics.
- We should throw litter in dustbins instead of public places.
Test your knowledge on the topics covered in Chapter 18 'Wastewater Story' of Class 7th Science. Explore concepts such as wastewater, sewage treatment, wastewater treatment plants, sanitation, and more.
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