NCERT Class 7 Science Chapter 18 - Wastewater Story Notes

Chapter 18 - Wastewater Story Notes

1. Wastewater is rich in lather that is mixed with oil, black-brown water, goes down the drains from sinks, showers, toilets, laundries and is dirty.

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. Aeration is the process in which air is pumped into clarified water to help bacteria grow.

13. Aerobic bacteria require oxygen to live and grow are called aerobic bacteria.

14. Anaerobic bacteria that can survive without oxygen are called anaerobic bacteria.

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