NCERT Solutions for Class 7 Science Chapter 18
Important NCERT Questions
7th Chapter 18 Wastewater Story
NCERT Books for Session 2022-2023
CBSE Board and State Board
Questions No: 5
What is sludge? Explain how it is treated.
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NCERT Solutions for Class 7 Science Chapter 18
Important NCERT Questions
7th Chapter 18 Wastewater Story
NCERT Books for Session 2022-2023
CBSE Board and State Board
Questions No: 5
Sludge is human waste (like faeces) in waste water left during sewage treatment. Since it is organic waste, it is used to produce bio gas and manure.
Sludge is collected by a scrapper. It is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel. After the aerator tank, microbes and human waste settle down and form activated sludge. The activated sludge is about 97% water. The water is removed by sand drying beds or machines. Dried sludge is used as manure, returning organic matter and nutrients to the soil.
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Sludge is the solid residue separated from wastewater during treatment. It undergoes thickening to reduce volume, followed by anaerobic digestion where microorganisms break down organic matter. Then, dewatering removes more water, reducing its volume. Treated sludge can be disposed of in landfills, incinerated, or reused as fertilizer in agriculture. The process aims to stabilize sludge, reduce its volume, and make it safer for disposal or beneficial for reuse, following environmental guidelines for responsible waste management.