Important Questions Test: Waste Water Story - Class 7 MCQ

because using pesticides on plants is no way useful to reduce water pollution and use of unleaded petrol in cars is related to air pollution. So, statement (1) and (4) is correct

The international decade for action on "water for life" was proclaimed by the United Nations General Assembly on 22 March 2005. Initiative aims to address the global water crisis and improve access to safe drinking water.

- Sewage contains various impurities, including:
- Organic Substances: These include biodegradable materials like food waste, oils, human waste, and plant material.
- Inorganic Substances: Comprising minerals, salts, metals, and other non-living chemical compounds.
- Nutrients: Such as nitrogen and phosphorus, which are essential for plant growth but can cause environmental issues when present in excess.
- Therefore, the correct answer is D: All of the above, as sewage contains a mix of all these impurities.

Sludge refers to the semi-solid waste material that settles at the bottom of sedimentation tanks during the treatment of sewage. It primarily consists of faecal matter, which originates from toilets. Therefore, the correct source of sludge is toilets.
Therefore,Correct Answer- Option A

Sewage is wastewater that originates from homes, offices, and other places. It includes waste materials like human excreta, kitchen waste, and liquid waste, which need proper treatment before being released into the environment.

A skimming tank is a chamber so arranged that the floating matter like oil, fat, grease etc., rise and remain on the surface of the waste water.

Sludge is a type of semi-solid waste.

The treatment method involves anaerobic digestion, which is a biological process.

• This process breaks down organic matter without oxygen.
• It reduces the volume of waste.
• It produces biogas, which can be used as energy.

The function of sedimentation in wastewater treatment is primarily

Settling Suspended Particles: Sedimentation allows suspended particles, such as silt, sand, and organic matter, to settle at the bottom of a tank due to gravity and then decant can be taken out which will be free of these impurities. 

The text highlights that open defecation, poor sewage disposal, and untreated human excreta contribute to water pollution, leading to waterborne diseases like cholera, typhoid, and hepatitis. Therefore, the correct answer is (D) All of the above.