All questions of Wastewater story for Class 7 Exam

Wastewater treatment, also called sewage treatment, the removal of impurities from wastewater, or sewage, before they reach aquifers or natural bodies of water such as rivers, lakes, estuaries, and oceans. Since pure water is not found in nature (i.e., outside chemical laboratories), any distinction between clean water and polluted water depends on the type and concentration of impurities found in the water as well as on its intended use. In broad terms, water is said to be polluted when it contains enough impurities to make it unfit for a particular use, such as drinking, swimming, or fishing.

Understanding the Process of Clarifying Water from Wastewater
Clarifying water from wastewater is a crucial process that ensures safe and clean water is returned to the environment or reused. The correct answer to the steps involved in this process is option 'B': Sedimentation, Aeration, Chlorination.

1. Sedimentation
- This is the first step in the clarification process.
- Wastewater is allowed to sit in a large tank where heavier particles settle at the bottom.
- This process removes solids and larger impurities from the water.

2. Aeration
- After sedimentation, the water undergoes aeration.
- During aeration, air is pumped into the water, promoting the growth of beneficial bacteria.
- These bacteria help break down organic matter and further purify the water by consuming dissolved pollutants.

3. Chlorination
- The final step involves chlorination, where chlorine is added to the water.
- This step is crucial for killing any remaining harmful bacteria, viruses, or pathogens.
- Chlorination ensures that the treated water is safe for discharge or reuse.

Conclusion
By following these steps—sedimentation, aeration, and chlorination—wastewater can be effectively clarified, making it suitable for various applications. Each process plays a vital role in ensuring the water is clean and safe, highlighting the importance of proper wastewater treatment in environmental conservation.

Understanding Filtration Plants
Filtration plants are essential in the water treatment process, but the materials they use are often misunderstood.
Why the Statement is False
- Use of Filter Paper:
- Filtration plants do not primarily use filter paper for large-scale water treatment.
- Instead, they typically utilize larger and more robust filtration systems, including sand filters, membrane filters, and activated carbon filters.
- Large-Scale Operations:
- Filtration plants are designed to treat significant volumes of water, which cannot be efficiently managed with regular filter paper.
- The materials used in these plants are engineered for durability and effectiveness in removing contaminants from water.
- Types of Filters:
- Common filtration methods include:
- Sand Filtration: Utilizes layers of sand to trap particles.
- Membrane Filtration: Uses semi-permeable membranes to separate impurities.
- Activated Carbon Filtration: Adsorbs organic compounds and chemicals.
Conclusion
In conclusion, while filter paper is a useful tool for laboratory experiments and small-scale applications, it is not a practical solution for the operations of a filtration plant. Therefore, the correct answer to the statement is indeed False (option B). Understanding the scale and complexity of water treatment helps clarify why more robust materials are employed.

What is Sludge?
Sludge is a semi-solid waste material that is typically a byproduct of various industrial processes, wastewater treatment, and sewage treatment. It consists of organic and inorganic solids that settle out from liquids during treatment processes.
Characteristics of Sludge
- Composition: Sludge contains a mixture of water, microorganisms, and suspended solids, making it thick and gooey.
- Sources: It can originate from sewage treatment plants, industrial processes, or even stormwater runoff.
Treatment of Sludge
The treatment of sludge is crucial to minimize environmental impact and recover useful resources. One of the most effective methods is anaerobic digestion.
What is Anaerobic Digestion?
- Process: This is a biological process that breaks down organic matter in the absence of oxygen.
- Microorganisms: Specific bacteria work to decompose the sludge, producing biogas (which can be captured and used for energy) and digestate (which can be used as fertilizer).
Benefits of Anaerobic Digestion
- Energy Production: The biogas generated can be used to produce electricity or heat.
- Reduced Volume: The process significantly reduces the volume of sludge, making it easier to manage.
- Nutrient Recovery: The remaining digestate is rich in nutrients and can be used to enrich soil.
In summary, the correct answer is option 'C' because sludge is a semi-solid waste that undergoes treatment through anaerobic digestion, effectively converting waste into useful energy and reducing environmental impact.

Understanding Water Cleaning
Cleaning of water is essential for ensuring its safety and suitability for consumption and other uses. The process involves removing various unwanted substances that may compromise water quality.

What Are Contaminants?
- **Contaminants** refer to any physical, chemical, or biological substances that can degrade water quality.
- They can include a wide range of harmful pollutants such as heavy metals, pesticides, industrial chemicals, and organic matter.

Importance of Removing Contaminants
- Removing contaminants is crucial for:
- **Protecting Health**: Contaminated water can lead to diseases and health issues.
- **Environmental Safety**: Pollutants can harm aquatic ecosystems and biodiversity.
- **Ensuring Potability**: Safe drinking water must be free from harmful substances.

Other Substances in Water Cleaning
While sediments, microorganisms, and bacteria are also removed during water cleaning, the term "contaminants" encompasses a broader category, making it the most appropriate answer.
- **Sediments**: These are solid particles that settle at the bottom but do not necessarily pose a health risk.
- **Microorganisms**: While they can be harmful, they are often a subset of contaminants.
- **Bacteria**: Like microorganisms, bacteria are a specific group that can be harmful but are included within the broader category of contaminants.

Conclusion
In summary, while sediments, microorganisms, and bacteria are important, the term "contaminants" effectively captures the wide range of harmful substances removed during the water cleaning process. This is why option 'B' is the correct answer.

Understanding Wastewater Treatment
Wastewater treatment is a crucial process that ensures the safe disposal and recycling of used water. It helps protect the environment and public health.
Processes Involved
Wastewater treatment utilizes three main types of processes:

• Physical Processes: These involve the removal of solids and large particles from wastewater. Techniques include screening, sedimentation, and filtration. Physical methods help to separate contaminants without altering their chemical state.
• Chemical Processes: In this stage, chemicals are added to the wastewater to facilitate the removal of pollutants. Common methods include coagulation, flocculation, and disinfection (like chlorination). These processes help to break down harmful substances chemically.
• Biological Processes: This involves the use of microorganisms to break down organic matter in wastewater. Bacteria and other microbes consume pollutants, converting them into harmless byproducts. Biological treatment is effective in reducing the organic load of wastewater.

Conclusion
In summary, wastewater treatment is an integrated approach that incorporates physical, chemical, and biological methods to ensure that water is cleaned effectively before being released back into the environment or reused. Therefore, the statement "Wastewater treatment involves physical, chemical, and biological processes" is indeed true.

Sludge, when dried, is rich in nutrients and organic matter, making it a valuable manure for agriculture. It helps improve soil fertility and plant growth.

Reasons for blocked drains:
Hair and Soap:
- Hair can easily get stuck in drains, especially in the shower or bathroom sink.
- Soap scum can build up over time and contribute to blockages in the pipes.

Cooking oil and fats:
- Pouring cooking oil and fats down the drain can lead to blockages as they solidify and stick to the pipes.
- Over time, these substances can accumulate and create a clog in the drain.

Prevention tips:
- Use drain filters or strainers to catch hair and debris before they enter the pipes.
- Avoid pouring cooking oil and fats down the drain; instead, dispose of them in the trash.
- Regularly clean drains with hot water or a mixture of vinegar and baking soda to prevent build-up.
By being mindful of what goes down the drain and taking preventative measures, you can help avoid blockages and keep your drains running smoothly.

Biogas produced from sludge is a renewable source of energy. It can be used for heating, cooking, and generating electricity, providing a sustainable energy option and reducing dependence on fossil fuels.

Oils and fats can solidify in pipes and drains, leading to blockages and clogs. These substances do not easily break down and can cause severe plumbing issues.