Consider the following statements regarding "Sewage": 1. It consists exclusively of industrial effluents. 2. It includes rainwater that washes off roads. 3. It is a complex mixture of solids, organic and inorganic impurities. Which of the statements given above is/are correct?

The correct option is (c). Explanation Sewage is liquid waste generated from various sources, including households, industries, and agricultural activities. It is a major cause of water pollution and requires treatment before being discharged into water bodies. - Statement 1 is Incorrect: Sewage does not consist exclusively of industrial effluents. It is wastewater released by homes, industries, hospitals, offices, and other users. Domestic wastewater is a significant component of sewage. - Statement 2 is Correct: The definition of sewage encompasses rainwater that runs down streets during storms or heavy rain. This surface runoff washes off roads and rooftops, carrying harmful substances and impurities into the wastewater system. - Statement 3 is Correct: Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprophytes, and disease-causing bacteria. These dissolved and suspended impurities are collectively referred to as contaminants. Key Takeaway: Sewage is a form of liquid waste containing dissolved and suspended contaminants derived from domestic, industrial, and medical sources, as well as stormwater runoff.

NCERT Class 7 Environment & Ecology — Chapter 2: Wastewater story

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Consider the following statements regarding "Sewage":

It consists exclusively of industrial effluents.
It includes rainwater that washes off roads.
It is a complex mixture of solids, organic and inorganic impurities.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 and 2 only
B2 only
C2 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (c).

Explanation

Sewage is liquid waste generated from various sources, including households, industries, and agricultural activities. It is a major cause of water pollution and requires treatment before being discharged into water bodies.

Statement 1 is Incorrect: Sewage does not consist exclusively of industrial effluents. It is wastewater released by homes, industries, hospitals, offices, and other users. Domestic wastewater is a significant component of sewage.
Statement 2 is Correct: The definition of sewage encompasses rainwater that runs down streets during storms or heavy rain. This surface runoff washes off roads and rooftops, carrying harmful substances and impurities into the wastewater system.
Statement 3 is Correct: Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprophytes, and disease-causing bacteria. These dissolved and suspended impurities are collectively referred to as contaminants.

Key Takeaway:

Sewage is a form of liquid waste containing dissolved and suspended contaminants derived from domestic, industrial, and medical sources, as well as stormwater runoff.

Your note

More from Chapter 2: Wastewater story

With reference to the composition of sewage, consider the following statements: 1. It is a liquid waste consisting entirely of dissolved impurities. 2. It contains nutrients such as phosphorus and nitrogen. 3. It is devoid of any saprophytic or disease-causing bacteria. Which of the statements given above is/are correct?

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Consider the following statements regarding the impurities found in sewage: 1. Urea and pesticides are classified as organic impurities. 2. Nitrates and phosphates are classified as organic impurities. 3. Vegetable waste and animal waste are classified as organic impurities. Which of the statements given above is/are correct?

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Consider the following statements regarding the physical treatment of wastewater: 1. Bar screens are used to remove large objects like rags and sticks. 2. The speed of wastewater is increased in the grit and sand removal tank to facilitate filtration. 3. Sedimentation tanks are designed to increase the flow speed to prevent settling of solids. Which of the statements given above is/are correct?

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With reference to unit operations used in wastewater treatment, the role of a skimmer is to:

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Consider the following statements regarding "Activated Sludge": 1. It consists of suspended microbes that settle at the bottom of the tank after aeration. 2. It contains a very low percentage of water, being mostly solid. 3. A part of it is pumped back into the aeration tank to serve as an inoculum. Which of the statements given above is/are correct?

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The correct option is (c).

Explanation

Statement 1 is Incorrect: Sewage does not consist exclusively of industrial effluents. It is wastewater released by homes, industries, hospitals, offices, and other users. Domestic wastewater is a significant component of sewage.
Statement 2 is Correct: The definition of sewage encompasses rainwater that runs down streets during storms or heavy rain. This surface runoff washes off roads and rooftops, carrying harmful substances and impurities into the wastewater system.
Statement 3 is Correct: Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprophytes, and disease-causing bacteria. These dissolved and suspended impurities are collectively referred to as contaminants.

Key Takeaway:

Sewage is a form of liquid waste containing dissolved and suspended contaminants derived from domestic, industrial, and medical sources, as well as stormwater runoff.