Sewage Treatment Plant (STP)
A Sewage Treatment Plant (STP) is a facility designed to treat domestic wastewater, also known as sewage or sanitary wastewater, before it's discharged into the environment or back into municipal water bodies. The primary goal of an STP is to remove contaminants and pollutants from the sewage to protect public health and the environment. Here's an overview of the components and processes commonly found in an STP:
Preliminary Treatment:
- Screening: : Large solid objects like sticks, rags, and plastics are removed using screens.
- Grit Removal: Smaller heavy particles like sand and gravel are settled out to prevent damage to downstream equipment.
Primary Treatment:
- Sedimentation Treatment: Wastewater is allowed to sit in a tank, allowing heavier solids to settle at the bottom as sludge while lighter substances float to the top as scum.
Secondary Treatment:
- Aeration and Biological Treatment: Beneficial microorganisms (activated sludge) are introduced to break down organic matter in the wastewater. Aeration provides the necessary oxygen for microbial activity.
- Aerobic vs. Anaerobic Treatment: Some STPs use aerobic treatment, where oxygen is supplied to the microorganisms, while others use anaerobic treatment, which occurs in the absence of oxygen.
Tertiary Treatment:
- Filtration: Additional solids and fine particles are removed by passing the wastewater through sand, gravel, or other filtration media.
- Disinfection: Chemicals like chlorine or ultraviolet (UV) light are used to kill remaining pathogens and harmful microorganisms in the treated water. Additional solids and fine particles are removed by passing the wastewater through sand, gravel, or other filtration media.
Sludge Treatment and Disposal:
- Sludge Thickening: The sludge from primary and secondary treatment is often thickened to reduce its volume.
- Sludge Digestion: Biological processes (aerobic or anaerobic) break down organic matter in the sludge, reducing its volume and producing biogas.
- Dewatering: Further removal of water from the digested sludge to produce a more manageable material.
- Sludge Disposal: The dewatered sludge can be incinerated, landfilled, or used for agricultural purposes if treated and safe.
Effluent Quality Monitoring:
- Regular Testing: The quality of the treated effluent is monitored to ensure it meets regulatory standards before discharge.
Control and Automation: