what are the steps involved in cleaning
waste in sewage treatment plant
Cleaning waste in a sewage treatment plant typically involves multiple steps to ensure effective removal of solid waste, organic matter, and harmful contaminants. Here are the general steps involved:
1. Preliminary Treatment: The incoming wastewater goes through a preliminary treatment process to remove large objects and debris such as sticks, rags, and plastics. This is usually done using bar racks or screens and sometimes includes grit removal to get rid of sand and gravel.
2. Primary Treatment: In this step, the wastewater is sent to a primary sedimentation tank where the heavy solids and suspended particles settle at the bottom forming sludge. The sludge is then collected and removed using mechanisms like scrapers or pumps.
3. Biological Treatment: The partially treated wastewater (effluent) is passed into the biological treatment unit, such as an activated sludge system or a trickling filter. Microorganisms present in these units breakdown the organic matter in the wastewater. This step helps in reducing harmful bacteria, viruses, and organic pollutants.
4. Secondary Treatment: The effluent from the biological treatment unit undergoes another sedimentation process to separate the remaining suspended particles and biological solids. This is usually achieved in the secondary sedimentation tanks. The settled sludge is removed, and the clarified water moves to the next step.
5. Tertiary Treatment: Tertiary treatment is an advanced purification step, which further treats the effluent to remove any remaining fine solids, nutrients (like nitrogen and phosphorus), and trace contaminants. Methods like sand filtration, disinfection with chlorine or UV rays, or membrane filtration (such as reverse osmosis) can be used.
6. Sludge Treatment: Throughout the process, sludge is collected and treated separately. Sludge is usually thickened, stabilized, and dewatered to reduce the volume and make it suitable for proper disposal or further treatment (like incineration or conversion to biogas).
7. Disinfection: Before final discharge or reuse, the treated wastewater is disinfected to kill any remaining disease-causing organisms. Common disinfection methods include chlorination, ultraviolet (UV) radiation, or ozone treatment.
It's important to note that the exact steps and processes may vary depending on the type of sewage treatment plant and the level of treatment required to meet environmental regulations and local standards.