Understand the key differences between STP and ETP plants. Learn which treatment system suits your needs based on waste type, compliance requirements, and operational costs.
Both STPs (Sewage Treatment Plants) and ETPs (Effluent Treatment Plants) treat wastewater, but they serve fundamentally different purposes. Understanding these differences is crucial for regulatory compliance and effective waste management. This guide explains when to use each system and how to make the right choice.
What is an STP (Sewage Treatment Plant)?
STPs treat domestic sewage—wastewater from toilets, kitchens, bathrooms, and laundry. The waste is primarily organic (biodegradable) with consistent composition. STPs are mandatory for residential complexes above 10,000 sq.m (as per local building bylaws), hotels, hospitals, educational institutions, and commercial buildings.
What is an ETP (Effluent Treatment Plant)?
ETPs treat industrial effluents—wastewater from manufacturing processes. This includes heavy metals, chemicals, oils, acids, alkalis, and complex organic compounds. Each industry generates unique effluents requiring customized treatment solutions. ETPs are mandatory for industries classified as Red/Orange category by CPCB.
Key Differences at a Glance
Waste Source: STP handles domestic/sanitary waste; ETP handles industrial process waste. Treatment Complexity: STP uses standard biological processes; ETP requires industry-specific treatment trains. Regulatory Authority: Both must comply with CPCB/SPCB norms, but discharge standards differ. Capital Cost: ETPs typically cost 2-5x more than equivalent capacity STPs due to specialized equipment.
STP Treatment Processes
Common STP technologies include: Activated Sludge Process (ASP), Sequential Batch Reactor (SBR), Moving Bed Biofilm Reactor (MBBR), and Membrane Bioreactor (MBR). These biological processes efficiently break down organic matter, achieving BOD removal of 95%+ and producing reusable treated water.
ETP Treatment Processes
ETPs employ multi-stage treatment: Physical (screening, oil separation, equalization), Chemical (neutralization, coagulation, precipitation), Biological (for biodegradable organics), and Tertiary (filtration, carbon adsorption, advanced oxidation). For zero liquid discharge, evaporation and crystallization may be added.
Making the Right Choice
For residential and commercial buildings generating only domestic waste, STP is the answer. For industries, ETP is mandatory—and often a Combined Effluent Treatment Plant (CETP) serves industrial estates. Greenify designs and installs both STP and ETP systems with CPCB compliance, IoT monitoring, and water reuse capabilities.