An STP (Sewage Treatment Plant) works in stages—preliminary, primary, secondary, and tertiary treatment—using physical, biological, and chemical processes to remove contaminants from wastewater, making it safe for release or reuse. It starts with screening large debris, then uses sedimentation to settle solids, employs bacteria in aeration tanks to break down organic matter, and finishes with filtration and disinfection (like UV or chlorination) to remove pathogens and polish the water.

STP (Sewage Treatment Plant) treats domestic waste (sewage from homes/offices) focusing on organic matter, while ETP (Effluent Treatment Plant) handles complex, chemically contaminated industrial wastewater (effluents) from factories, using more customized processes to remove toxic substances like heavy metals and oils. The main difference is the waste source and composition, making ETP processes much more complex and varied than the standardized biological treatment of STPs, with STP water often reused for non-potable uses like gardening, and ETP treated water for industrial processes or safe discharge.STP (Sewage Treatment Plant) Source: Domestic sewage from residential complexes, hotels, offices, municipalities. Waste Type: Human waste, organic matter, pathogens, soap, kitchen/bathroom water. Process: Simpler, primarily biological treatment (aeration, sedimentation, clarification) to break down organic material. Reuse: Irrigation, flushing, cleaning, landscaping. ETP (Effluent Treatment Plant) Source: Industrial wastewater from manufacturing, textile, pharmaceutical, chemical plants, etc. Waste Type: Toxic chemicals, heavy metals, oils, dyes, industrial residues. Process: Complex, tailored processes including chemical neutralization, coagulation, flocculation, and specialized biological/physical treatments. Reuse: Industrial cooling, process water, or safe environmental discharge. Key Differences Summarized Focus: STP on organic/biological, ETP on chemical/toxic. Complexity: STP is simpler; ETP is highly customized and complex. Application: STP for homes/commercial; ETP for industries. Regulation: ETPs face stricter, industry-specific discharge standards.