Which process is used in the primary treatment of sewage to remove floating debris by passing it through wire mesh screens?

filtration

The correct answer is Option (1)-filtration

Primary treatment of wastewater involves the physical removal of particles, both large and small, from the sewage through filtration and sedimentation processes. This treatment step is typically the first stage in the wastewater treatment process.

During primary treatment, the wastewater undergoes a series of steps to remove different types of solid materials. Initially, floating debris, such as sticks, leaves, and plastics, is removed through sequential filtration. This process involves passing the wastewater through screens or filters to capture and remove these larger particles.

After the removal of floating debris, the wastewater proceeds to the sedimentation tanks. In these tanks, the velocity of the water is reduced, allowing the smaller particles, including soil, sand, and small pebbles, to settle to the bottom under the force of gravity. This settling process is called sedimentation. The settled solids, known as primary sludge, are collected and removed from the bottom of the tanks.

The liquid portion of the wastewater, known as the supernatant, is the clarified effluent. It contains reduced levels of suspended solids compared to the original sewage. The effluent from the primary settling tank then proceeds for further treatment in the secondary treatment stage.

Primary treatment primarily focuses on the physical removal of solid materials from wastewater. It helps to reduce the presence of solid particles, organic matter, and other contaminants, making the wastewater more amenable to subsequent treatment processes. While primary treatment alone is not sufficient to fully purify wastewater, it plays a crucial role in the overall wastewater treatment process by preparing the wastewater for further treatment stages, such as secondary and tertiary treatment, to achieve higher levels of purification.

In summary, primary treatment involves the physical removal of particles, including floating debris and sedimentable solids, from wastewater through filtration and sedimentation processes. It helps in reducing solid content and prepares the wastewater for subsequent treatment steps to achieve cleaner effluent.