STP Plant: Sewage Treatment Plant for Efficient Wastewater Management
An STP Plant (Sewage Treatment Plant) is a wastewater treatment system designed to treat sewage generated from residential societies, commercial complexes, hotels, hospitals, and industries. With increasing urban development and strict discharge norms issued by the Central Pollution Control Board, installing a sewage treatment plant has become essential for sustainable infrastructure projects.
This blog explains the working process, technology types, benefits, and importance of an STP plant.
What is an STP Plant?
An STP plant is a facility that treats domestic and commercial wastewater to remove contaminants, organic matter, suspended solids, and harmful microorganisms. After proper treatment, the water can be safely discharged or reused for non-potable applications such as:
Gardening
Toilet flushing
Cooling towers
Industrial cleaning
Construction activities
The main objective is to reduce BOD, COD, TSS, oil & grease, and pathogens from wastewater.
STP Plant Treatment Process
The sewage treatment process is divided into three major stages:
1. Preliminary and Primary Treatment
Screening removes large solids and debris
Grit chamber removes sand and heavy particles
Primary settling tank allows sludge to settle
This stage physically separates solid waste from liquid sewage.
2. Secondary (Biological) Treatment
Aeration tank supplies oxygen
Microorganisms break down organic matter
Clarifier separates treated water from sludge
This stage significantly reduces organic pollution and improves water quality.
3. Tertiary Treatment
Pressure sand filtration
Activated carbon filtration
Disinfection using chlorine or UV
Tertiary treatment ensures the treated water meets discharge or reuse standards.
Types of STP Technologies
Choosing the right technology depends on space, capacity, and water quality requirements.
MBBR (Moving Bed Biofilm Reactor)
Compact and efficient
Low sludge production
Suitable for apartments and commercial buildings
SBR (Sequen