The correct option is option (ii).
Two chemicals used to disinfect water are chlorine and ozone.
Our role as an active citizen should be in maintaining sanitation in neighbourhood and at public places. We can limit the type of waste and quantity of waste produced. For this every citizen should follow these steps.
Lack of sanitation may cause diseases. Large fraction of people defaecate in open, on dry river boards, railway tracks and many times directly in water. It results in pollution of water and many diseases. Diseases like typhoid, meningitis, hepatitis, dysentery, etc. are caused due to poor sanitation.
In wastewater treatment plant bar screens are used to separate large objects like rags, plastic packets, napkins, etc. by passing water through them.
Semi-solid wastes such as faeces that settle down at the bottom during wastewater treatment are called sludge. Sludge is removed with a scraper. The sludge is then transferred to a separate tank where it is decomposed by the anaerobic bacteria. In this process biogas is produced.
The biogas produced can be used as a fuel or can be used to produce electricity.
Oils and fats should not be released in the drain because they can harden and block the pipes. In an open drain the fats clog the soil pores which affect its water filtering efficiency. Therefore, oils and fats should be thrown in dustbins.
(a) Cleaning of water is a process of removing pollutants.
(b) Wastewater released by houses is called sewage.
(c) Dried sludge is used as manure.
(d) Drains get blocked by cooking oil and fats.
Untreated human excreta is a health hazard because it pollutes soil and water. Both the surface water and ground water gets polluted. Due to contamination of ground water, various water bodies such as wells, tube wells, ponds, etc. also get contaminated as ground water is the source of water for them. When water from these contaminated sources is used for domestic purposes, it may cause several water borne diseases such as cholera, dysentery, meningitis, etc.
Steps involved in getting clarified water from wastewater are as follows:
Sewage is wastewater having dissolved and suspended impurities released from homes, industries, hospitals, offices and other users.
It is harmful to discharge untreated sewage into rivers or seas because:
Therefore, it is harmful to discharge untreated sewage into rivers or seas.
Yes, the NCERT book has been designed keeping in mind the pattern of paper that will be presented in the exam to students. The NCERT book is sufficient to study for the exam as it has everything related to the exam and contains all information out of which the questions will be asked in the exam. But if you want to prepare a little bit extra, we suggest that you go through the NCERT class 7 solutions.
When you are studying the NCERT book for math and other subjects for your class 7 exams, refer to the NCERT class 7 solutions simultaneously so you can see where you are going wrong and what are you getting right in your exercises’ attempt.
The class 7th is very crucial as it is among the major middle school classes during which the child’s base is formed in math and science and even in other subjects like English. Thus, it is students must study smartly in this class and ace their exams while getting all the help they need from the NCERT 7 solutions given by Extramarks.
Yes, absolutely. The NCERT solutions provided by Extramarks for class 7 are eloquent and elaborate at best and are thus useful for students studying for the final exams of class 7. The students will have many questions and doubts regarding the NCERT solutions for class 7 and this is why the solutions have been elaborated well to help students understand the answers to exercises.
Yes, the NCERT solutions for Math and other subjects for class 7 are available for free from Extramarks.