Chapter 18 (Wastewater Story) of Class 7 Science NCERT Book (PDF) is available here for download in PDF format. Download now & prepare for CBSE Class 7 Science exam in academic session 2021-22. It is one of the most important chapters of the CBSE Class 7th Science NCERT textbook & many essential questions are framed from this chapter.
Snapshot from Chapter 18 of Class 7 Science NCERT Textbook:
Important topics of this chapter:
⇒ Aerobic bacteria
⇒ Anaerobic bacteria
Important points of this chapter:
⇒ Used water is wastewater. Wastewater could be reused.
⇒ Wastewater is generated in homes, industries, agricultural fields and in other human activities. This is called sewage.
⇒ Sewage is a liquid waste which causes water and soil pollution.
⇒ Wastewater is treated in a sewage treatment plant.
⇒ Treatment plants reduce pollutants in wastewater to a level where nature can take care of it.
Where underground sewerage systems and refuse disposal systems are not available, the low cost on-site sanitation system can be adopted.
⇒ By-products of wastewater treatment are sludge and biogas.
⇒ Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.
⇒ We should not defecate in the open. It is possible to have safe disposal of excreta by low cost methods