CBSE Class 7 Science Chapter 18 Notes Wastewater Story
Forests: Our Lifeline Class 7 Notes Understanding the Lesson
1. Rich in lather, mixed with oil, black-brown water that goes down the drains from sinks, showers, toilets, laundries is dirty. This is called wastewater.
2. The suspended impurities in water are called contaminants.
3. The waste water released by homes, industries, hospitals and other users is called sewage.
4. ‘Cleaning of water’ is a process of removing pollutants before it enters a water body or is reused. This process is generally known as ‘sewage treatment’.
5. Sewage treatment plant is constructed to make wastewater or sewage reusable.
6. A complete network of sewers underlying the surface is planned to collect and send the wastewater for treatment. This is called sewerage system.
7. Treatment of wastewater involves physical, chemical and biological processes, which removes physical, chemical and biological matter that contaminates the wastewater.
8. The treated water from sewage treatment plant has a very low-level organic material and suspended matter. This is discharged into the water bodies by sometimes disinfecting with chlorine and ozone.
9. By-products of wastewater treatment are sludge and biogas.
10. Where underground sewerage systems and refuse disposal systems are not available, the low-cost on-site sanitation system can be adopted.
11. Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.
12. We must realise our responsibility in maintaining the water sources in a healthy state. Adopting good sanitation practices should be our way of life.
Class 7 Science Chapter 18 Notes Important Terms
Aeration: It is the process in which air is pumped into clarified water to help bacteria grow.
Aerobic bacteria: Bacteria that require oxygen to live and grow are called aerobic bacteria.
Anaerobic bacteria: Bacteria that can survive without oxygen are called anaerobic bacteria.
Biogas: It is a gaseous fuel produced by the fermentation of manure, plant, or crop waste under anaerobic conditions which is used to generate electricity from waste matter.
Contaminants: There are harmful substances dissolved and suspended as impurities in water.
Sanitation: The proper disposal of sewage and garbage from the houses or nearby areas is called sanitation.
Sewage: Wastewater generated by homes, offices, hospitals, industries and other areas is called sewage.
Sewer: A network of big and small pipes to carry wastewater to treatment plant is called sewer.
Sewerage: It is the drainage system of sewer.
Sludge: Sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater.
Wastewater: The water that is not fit for use is called ‘wastewater’.