Understanding the Essential Steps of Sewage Water Treatment
With rapid urbanization and industrialization, the need for efficient sewage water treatment is more critical than ever. Treating wastewater before releasing it back into the environment not only protects public health but also conserves water resources and reduces environmental pollution. To achieve this, sewage treatment follows a structured process designed to remove physical, chemical, and biological contaminants. In this blog, we’ll explore the essential steps of sewage water treatment, explain the different stages of sewage treatment, and highlight the specific stage of wastewater treatment for removing large particles.
Why Sewage Water Treatment Matters?
Sewage water contains a variety of pollutants—suspended solids, organic matter, pathogens, nutrients, oils, and chemicals. If untreated, it can:
- Contaminate freshwater bodies
- Harm aquatic ecosystems
- Spread diseases
- Deplete oxygen levels in water
Sewage treatment plants (STPs) use a multi-step process to purify wastewater and make it safe for discharge or reuse.
Key Steps of Sewage Water Treatment
The treatment process is typically divided into three major stages of sewage treatment:
1. Preliminary Treatment – Removing Large Particles
This is the stage of wastewater treatment for removing large particles such as rags, plastics, sticks, sand, and grit that can damage equipment or clog pipes.
Processes involved:
- Screening: Large screens trap debris like paper, plastic, and cloth.
- Grit Removal: Grit chambers slow down the flow to allow sand, gravel, and other heavy particles to settle.
Purpose: Protects pumps and downstream equipment from abrasion or blockage.
2. Primary Treatment – Settling Suspended Solids
After large particles are removed, the water moves to primary sedimentation tanks where suspended solids settle to the bottom as sludge, and lighter materials float to the surface as scum.
Processes involved:
- Sedimentation: Heavier organic and inorganic particles settle.
- Scum removal: Floating oil and grease are skimmed off.
Effectiveness: Removes about 50–60% of suspended solids and reduces Biological Oxygen Demand (BOD) by 30–40%.
3. Secondary Treatment – Biological Breakdown
This stage targets the dissolved and remaining suspended organic matter using microorganisms. It’s the most critical of the steps of sewage water treatment for reducing organic load.
Processes involved:
- Activated Sludge Process (ASP): Aerobic bacteria in aeration tanks consume organic waste.
- Trickling Filters: Wastewater trickles over rocks or media coated with microbial biofilms.
- Oxidation Ponds or Lagoons: Natural biological treatment using algae and bacteria.
Clarification: After biological treatment, water enters a secondary clarifier where microbial flocs settle and are either removed or returned to the aeration tank.
Effectiveness: Reduces BOD and suspended solids by 85–90%.
4. Tertiary (Advanced) Treatment – Polishing Effluent
This final stage enhances water quality and removes specific pollutants like nutrients, pathogens, or trace chemicals.
Processes involved:
- Filtration (sand or membrane)
- Disinfection (chlorination, UV, or ozone)
- Nutrient Removal (nitrification, denitrification, and phosphorus precipitation)
Purpose: Meets regulatory standards for discharge or reuse in irrigation, cooling, or industrial processes.
5. Sludge Treatment and Disposal
Sludge generated during primary and secondary treatment is further processed to reduce volume and pathogens.
Processes involved:
- Thickening and Dewatering (centrifuge, belt filter)
- Digestion (anaerobic or aerobic)
- Disposal (land application, incineration, landfilling)
In some cases, digested sludge is used as fertilizer or for biogas generation.
Summary: Stages of Sewage Treatment at a Glance
| Stage | Purpose | Key Methods |
| Preliminary Treatment | Remove large debris | Screening, Grit removal |
| Primary Treatment | Settle suspended solids | Sedimentation, Scum removal |
| Secondary Treatment | Biologically degrade organic matter | Activated sludge, Trickling filter |
| Tertiary Treatment | Final polishing, disinfection, and nutrient removal | Filtration, UV/chlorination, nutrient processes |
| Sludge Management | Treat and safely dispose of biosolids | Dewatering, Digestion, Reuse/Disposal |
Ion Exchange’s Advanced Sewage Treatment Solutions
Ion Exchange is a leading provider of innovative water and wastewater treatment solutions globally. Their advanced range of sewage treatment plants is designed to meet the diverse needs of the country’s growing population and industrial sectors. With a focus on sustainability and efficiency, Ion Exchange offers customized solutions that incorporate the latest technologies, ensuring optimal performance and environmental compliance.
INDION New Generation Packaged Sewage Treatment Plant (NGPSTP)
It is a state-of-the-art solution that combines the innovative technologies of lamella plate clarification and aeration, resulting in a highly efficient, ready-to-operate, prefabricated system for sewage treatment. This all-in-one single-tank packaged system is designed with a modular capacity ranging from 10 to 100 m3/d, making it both compact and user-friendly. Not only does it deliver high-quality effluent, but it also boasts features that cater to the specific needs of modern facilities. The NGPSTP’s advantages include minimal land usage, reduced power and chemical requirements, and low operating costs, making it an ideal choice for a wide range of applications while ensuring environmental sustainability and cost-effectiveness.
INDION NGPSTP-NRÂ
It is an advanced sewage treatment solution that combines a fixed film reactor with lamella clarification, resulting in a high-performance, prefabricated system that is ready to operate. This all-in-one, modular design offers compact and simple operation with minimal maintenance. Built with an MS tank lined with FRP, it ensures no corrosion, delivering high-quality effluent while being efficient and easy to manage.
Sequencing Batch Reactor (SBR)Â
It is an advanced activated sludge process that operates in true batch mode, with both aeration and sludge settlement occurring within the same tank. Unlike conventional continuous-flow systems, which separate these functions into different spaces, the SBR performs them in a time sequence, offering greater flexibility. This design allows the SBR to handle varying influent volumes, making it adaptable to changing conditions, unlike the continuous system, which relies on a fixed flow rate.
Advanced Fluidized Media Reactor (AFMR) system
It is a compact SINGLE TANK DESIGN UNIT that integrates an aeration tank with floating media, a lamella settler, and a chlorine contact tank. The AFMR media boasts a high surface area, excellent physical and chemical resistance, and minimal annual losses. INDION’s Advanced FMR offers significant advantages, including reduced space requirements, lower power consumption due to the elimination of sludge recirculation, and minimal maintenance thanks to its design without moving mechanical parts.
Conclusion
Understanding the steps of sewage water treatment is crucial for designing, operating, or upgrading wastewater systems in both municipal and industrial settings. From the stage of wastewater treatment for removing large particles to the final polishing stage, each process plays a vital role in protecting water quality, human health, and the environment.
