Water Treatment Plant: Removing Dissolved Iron and Manganese

Introduction:
Water treatment plants are facilities designed to remove impurities from water, making it safe for consumption. These impurities could include minerals, bacteria, viruses, and other contaminants. In this question, we are focusing on the removal of dissolved iron and manganese from water.

Methods:
There are several methods that can be used to remove dissolved iron and manganese from water. These include:

1. Aeration:
Aeration involves the introduction of air into the water. This can help to oxidize the dissolved iron and manganese, causing it to form a solid that can be filtered out. However, this method is not always effective as some forms of iron and manganese may not be easily oxidized.

2. Coagulation:
Coagulation involves the addition of chemicals that cause the dissolved iron and manganese to clump together, forming larger particles that can be filtered out. This method is effective but can be expensive and may require the use of large amounts of chemicals.

3. Flocculation:
Flocculation is similar to coagulation, but instead of adding chemicals to clump the particles together, the water is stirred or agitated to encourage the particles to clump naturally. This method is less expensive than coagulation but may require more time to achieve the desired results.

4. Sedimentation:
Sedimentation involves allowing the water to settle, allowing the larger particles to sink to the bottom of the tank. The water is then filtered, removing the particles that have settled at the bottom. This method is simple and effective but may require a large amount of space to allow the particles to settle properly.

Correct Answer:
The correct answer to the question is option D - aeration and sedimentation. This method involves the introduction of air into the water to oxidize the dissolved iron and manganese, followed by allowing the water to settle to allow the particles to sink to the bottom of the tank. The water is then filtered to remove the particles that have settled at the bottom. This method is effective and relatively simple, making it a popular choice in many water treatment plants.