How is Water Purified at a Sewage Treatment Plant

Water is essential for human life and serves various purposes, such as drinking, cooking, and cleaning. However, water can get contaminated with various unwanted substances, making it unfit for consumption. Sewage treatment plants play a critical role in purifying water to make it safe for human use. Here is a breakdown of the process of water purification at sewage treatment plants:

Preliminary Treatment

The first step in water purification at a sewage treatment plant is the removal of large solids and debris from the water. The water passes through a series of screens to trap any large objects, such as sticks, leaves, and rocks. The screens also remove non-biodegradable materials like plastics and metals. Afterward, the water flows into a grit chamber where sand, gravel, and other small-sized solids settle down. The settled solids, also known as grit, are then removed using mechanical scrapers, and the water moves to the next stage of treatment.

Primary Treatment

Next, the water undergoes primary treatment, where the remaining solids, known as organic matter, are removed. In this stage, the water flows into a sedimentation tank where it is slowed down to allow heavier materials like human waste, suspended fecal matter, and food particles to settle at the bottom. The waste material forms a sludge-like substance called primary sludge, which is removed using large mechanical scrappers. After primary treatment, about 40-50% of the impurities in the water are removed, and the water moves to the next stage.

Secondary Treatment

The third stage of water purification is secondary treatment, where the remaining organic matter is removed. In this stage, the water flows into aeration tanks where bacteria and other microorganisms are added to break down the remaining organic matter present in the water. The microorganisms consume the organic matter and convert it to carbon dioxide and water. This process is known as biological oxidation, and it removes about 90-95% of the impurities contained in the water. The water then moves to the next stage for further treatment.

Tertiary Treatment

The fourth and final stage of water purification is tertiary treatment, where the water undergoes further purification to remove any remaining impurities. The water may pass through filters or other specialized equipment, depending on the water source and the intended use. It may also be treated with chlorine or other disinfectants to kill any remaining bacteria and viruses. In some cases, the water may be filtered through activated carbon to remove any remaining odor or taste from the water. After the final stage of treatment, the water is safe for human consumption and can be used for various purposes such as drinking, cooking, and cleaning.

Conclusion

In conclusion, sewage treatment plants play a crucial role in ensuring that water is purified to make it safe for human use. The purification process involves four stages, namely preliminary treatment, primary treatment, secondary treatment, and tertiary treatment. Each stage serves a unique purpose in removing impurities, and the end result is clean and safe water for human consumption.