
STP Plant Overview
A Sewage Treatment Plant (STP) is a vital infrastructure designed to purify wastewater, making it safe for discharge into the environment or reuse. It employs a series of physical, chemical, and biological processes to remove pollutants and contaminants from sewage. Here's a breakdown of how an STP plant operates:
How It Works
- Pre-Treatment: Raw sewage enters the STP plant and undergoes preliminary treatment, which involves the removal of large objects, such as debris, plastics, and grit, through screening and grit chamber processes.
- Primary Treatment: The pre-treated sewage then flows into primary settling tanks, where heavy solids settle to the bottom as sludge, and lighter materials float to the surface as scum. Mechanical scrapers or skimmers remove these layers for further processing.
- Biological Treatment: The partially treated sewage moves into biological treatment units, such as activated sludge or trickling filters, where microorganisms break down organic matter present in the sewage into simpler, harmless substances through aerobic or anaerobic digestion processes.
- Secondary Clarification: After biological treatment, the sewage undergoes secondary clarification, where remaining suspended solids and biological sludge settle out in settling tanks. Clear effluent rises to the top and is separated from the settled sludge.
- Tertiary Treatment: In some advanced STP plants, tertiary treatment processes such as filtration, disinfection (chlorination, UV treatment), and chemical precipitation are employed to further polish the effluent, ensuring it meets stringent water quality standards.
- Effluent Discharge or Reuse: The treated effluent, now substantially free from pollutants and contaminants, is either discharged into receiving water bodies like rivers or oceans, or reused for non-potable purposes like irrigation, industrial processes, or groundwater recharge, depending on local regulations and requirements.
By effectively treating sewage, STP plants play a crucial role in safeguarding public health, protecting the environment, and conserving water resources.