Secondary Treatment of Wastewater: Next-Gen Purity
Clean water is essential for life, yet urbanization and industrialization continue to increase the burden on our natural water bodies. Wastewater treatment ensures that contaminated water from households, businesses, and industries is purified before being released back into the environment. Among the various stages of treatment, the secondary treatment of wastewater plays a vital role in achieving high-quality, safe, and reusable water. With next-generation technologies, this stage is becoming more efficient, sustainable, and resource-friendly.
What is Secondary Treatment of Wastewater?
To put it simply, what is secondary treatment of wastewater? It is the stage where biological processes are used to remove dissolved and suspended organic matter that cannot be eliminated through basic physical methods. Unlike primary treatment, which focuses on screening, grit removal, and sedimentation, secondary treatment uses microorganisms to break down pollutants in an oxygen-rich (aerobic) or oxygen-free (anaerobic) environment.
This step ensures the removal of harmful organic compounds, significantly improving water quality before discharge or further treatment.
Primary and Secondary Treatment of Wastewater
Understanding the distinction between primary and secondary treatment of wastewater is key:
- Primary Treatment – Removes large solids, oils, grease, and some suspended matter through physical processes like screening and sedimentation.
- Secondary Treatment – Targets dissolved and colloidal organic matter through biological processes, ensuring a much higher level of purification.
While primary treatment prepares water for biological processes, secondary treatment brings it closer to environmental discharge standards and, in many cases, reuse applications.
What Happens in the Secondary Stage of Wastewater Treatment?
So, what happens in the secondary stage of wastewater treatment? The focus here is on biological decomposition. Microorganisms consume organic pollutants, breaking them down into simpler, harmless compounds like carbon dioxide, water, and biomass (sludge).
This stage usually takes place in aeration tanks, bio-reactors, trickling filters, or lagoons. After the biological action, clarifiers separate the clean water from the biomass. The result is effluent that is much clearer and safer for release or advanced tertiary treatment.
What Are the Steps Involved in the Secondary Treatment of Wastewater?
The steps involved in the secondary treatment of wastewater vary depending on the technology, but typically include:
- Aeration or Biological Contact – Oxygen is supplied (in aerobic processes) to stimulate microorganisms that digest organic matter.
- Microbial Decomposition – Bacteria and other microbes break down organic pollutants into simpler forms.
- Sedimentation/Clarification – The treated water is passed into settling tanks, where microbial biomass (sludge) is separated.
- Disinfection (Optional) – In some cases, treated water undergoes disinfection before being discharged or reused.
These steps together ensure a high level of purification, reducing biochemical oxygen demand (BOD) and chemical oxygen demand (COD) to acceptable limits.
Next-Gen Approaches in Secondary Treatment
With advances in technology, modern plants are improving the secondary treatment of wastewater by adopting:
- Membrane Bioreactors (MBR) – Combining biological treatment with membrane filtration for higher-quality effluent.
- Moving Bed Biofilm Reactors (MBBR) – Using carriers to increase microbial surface area and efficiency.
- Sequencing Batch Reactors (SBR) – Compact systems that treat wastewater in batches with automated cycles.
- Energy Recovery Systems – Anaerobic processes that generate biogas for power, making treatment more sustainable.
These innovations reduce energy use, improve efficiency, and enable water reuse, aligning with sustainability goals.
Ion Exchange’s Advanced Sewage Treatment Solutions
Ion Exchange is a leading provider of innovative water and wastewater treatment solutions. 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
The secondary treatment of wastewater is the backbone of modern purification, ensuring that harmful organic pollutants are removed before water is discharged or reused. By understanding what happens in the secondary stage of wastewater treatment and what steps are involved in the secondary treatment of wastewater, it is clear that this stage is essential for protecting both human health and the environment.
As new technologies enhance efficiency, primary and secondary treatment of wastewater are evolving into smarter, greener systems. With next-gen approaches like MBRs and MBBRs, secondary treatment is not just about cleaning water—it is about driving sustainability and ensuring a future where every drop counts.
