There has been a growing concern about environmental pollution and the adverse effects of releasing untreated wastewater into rivers and other natural water bodies. There are stringent regulations in India and other parts of the world to ensure proper sewage treatment. These regulations safeguard the environment and public health. Sewage water treatment plants help treat wastewater before releasing it into the environment. There are different technologies available. This blog sheds light on the types of sewage treatment plant available.
Table of content
- Stages in sewage water treatment
- Sequence Batch Reactor (SBR)
- Membrane Bioreactors
- Moving Bed Biofilm Reactor (MBBR)
- Activated Sludge Process (ASP)
- Top Sewage Treatment plant manufacturers on our platform
Stages in sewage water treatment
Sewage treatment facilities generally follow several stages to remove contaminants before discharging the water. Stages may differ depending on the type of sewage water treatment:
- Primary treatment: The first, or primary sedimentation stage, involves a large chamber where wastewater flows. Heavy sediments settle at the bottom, while oil and grease that float to the top can be skimmed off. The wastewater leaving the chamber is called effluent.
- Secondary treatment: The secondary, or biological, treatment removes organic matter and pollutants from the wastewater. Microorganisms introduced into the effluent convert pollutants into cell tissue, water, and nitrogen. Aeration and activated sludge are key components of this process.
- Tertiary treatment: Removes more than 99% of impurities from the wastewater, making it suitable for discharge. This stage may use a combination of biological and chemical methods and use advanced equipment if required.
Sequence Batch Reactor (SBR)
The sequence batch reactor (SBR) method treats wastewater in batches. It is a popular types of sewage treatment plant. There are five distinct phases:
- Fill: The tank fills with wastewater.
- React: Microorganisms break down organic matter during this reaction phase.
- Oxygen is bubbled through the wastewater mixture, and activated sludge reduces the organic matter content. We measure this reduction as biological oxygen demand (BOD) or chemical oxygen demand (COD).
- Settle: Solids settle at the bottom, allowing the treated effluent to clarify at the top.
- Decant: The clear, treated effluent is discharged.
- Idle: The tank prepares for the next cycle by allowing any remaining solids to settle.
| Advantages | Disadvantages |
|---|---|
| Since it is a batch operation, there is excellent operational flexibility. | Sludge removal can be challenging. |
| Smaller footprint compared to other sewage treatment methods. | Complex operational cycles |
| Effective in removing nutrients, such as nitrogen and phosphorus. | Requires experienced operators to monitor and operate the system. |
Membrane Bioreactors
Municipalities and industrial wastewater treatment plants use membrane bioreactors (MBR), which combine microfiltration or ultrafiltration with biologically activated sludge to purify sewage water.
Components of the membrane bioreactors include:
Bioreactors: The Bioreactor chamber is designed for wastewater treatment and supports a biologically active environment for bacteria and protozoa to grow and consume substances. Bioreactors can be aerobic, anoxic, or anaerobic, depending on the presence or absence of oxygen and nitrates. There are three types of bioreactors:
- Suspended growth bioreactors: grow biomass into flocs.
- Attached growth bioreactors: grow biomass attached to carriers
- Hybrid bioreactors: combine suspended and attached growth bioreactors.
Membrane: Membranes play a crucial role in the Multi-Body Reactor (MBR) process, acting as a solid-liquid separation device to keep biomass within the bioreactor before discharging treated effluent, and are installed after the anaerobic and aerobic reactors. They replace clarifiers in the conventional activated sludge (CAS) process. Two membranes conventionally used are:
- Microfiltration
- Ultrafiltration – preferred due to its superior separation characteristics and lower fouling tendency.
| Advantages | Disadvantages |
|---|---|
| Produces high-quality effluents free of bacteria and pathogens | More expensive compared to conventional STPs. |
| MBR can be fully automated and can be implemented at decentralized sites. | Requires regular maintenance |
| Compact footprint compared to conventional STPs. | Energy-intensive process |
Moving Bed Biofilm Reactor (MBBR)
A moving bed biofilm reactor (MBBR) is a biological wastewater treatment process that uses plastic carriers to increase the amount of microorganisms that can treat wastewater. Microorganisms consume organic material and attach to the carriers to grow. MBBR is a combination of the conventional activated sludge process and biofilm media.
Components of MBBR include:
- Basin: The MBBR reaction takes place in the basin, aeration tank, or reactor. The reactor’s size depends on the plant’s filtration requirements. The effluent can then move to another basin for further treatment. The aeration tanks are open, exposing the water to air for aerobic filtration.
- Media: The basin contains thousands of small plastic chips called media or carriers, occupying 50-70% of the tank. These carriers have a similar density of water and can mix throughout the fluid without floating or sinking.
- Sieve: The MBBR system uses a sieve attached to the tank to prevent media from escaping through the exit. The mesh material allows water to pass through while keeping the plastic carriers inside the basin, ensuring a secure environment for media.
| Advantages | Disadvantages |
|---|---|
| Compact | The MBBR can function independently but is usually integrated into a larger treatment facility. |
| Easy to maintain | Improper operation can cause the biofilm to thicken, hindering oxygen and nutrient diffusion to the cells within the biofilm’s middle layers. |
| High efficiency of 98% after 8 hours of treatment | Managing carrier media can pose challenges due to its nature. |
| MBBR is a highly efficient water treatment system, offering a rapid removal of BOD and nitrogen in just three to four hours due to its low hydraulic retention time (HRT) due to the continuous movement of media and large biofilm. |
Activated Sludge Process (ASP)
Municipalities widely use the activated sludge wastewater treatment process, employing a multi-chamber reactor unit where microorganisms remove nutrients from the wastewater, and is one of the top types of sewage treatment plant. According to the Central Pollution Control Board, nearly 70% of municipalities use ASP.
Oxygen helps establish aerobic conditions and suspends the solid. This treatment is effective for large volumes of water and involves blowing air or oxygen into raw sewage. Wastewater is mixed and aerated in a special tank, oxidizing organic matter in the wastewater, producing new cells, carbon dioxide, and water. The sludge particles are then removed through gravity settling. This treatment is ideally completed in a centralized facility.
| Advantages | Disadvantages |
|---|---|
| Simple and reliable process | High initial capital cost |
| Effective in reducing the quantity of BOD and COD | Require skilled personnel to operate and maintain the activated sludge system. |
| Produces high-quality effluent as long as the sewage is uniform. | High-energy cost. |
| Very few odours produced | Disposal of sludge can be difficult. |
Top Sewage Treatment plant manufacturers on our platform
Leadec India Private Limited
Leadec, established in 2008, is a technical service specialist with revenue between INR 100 Cr. – 500 Cr. Operating in Madhya Pradesh, Maharashtra, Uttar Pradesh, and other key regions. They excel in sewage treatment plant (STP) services and offer comprehensive utility equipment operation and maintenance, ensuring efficient and environmentally compliant STP operations. Serving diverse industries such as power, chemicals, and automotive, their key customers include Asian Paints, JSW Steel, and Tata Motors.
A.t.e. Huber Envirotech Private Limited
Established in 2000, A.t.e Huber specializes in sewage treatment plants (STPs) and other wastewater treatment systems, including packed STPs, ETP plants, and sludge dewatering systems. Serving key regions like Maharashtra, Uttar Pradesh, and Tamil Nadu, the company partners with OEMs like BT and caters to industries such as oil & gas, power, and chemicals. Notable clients include Cipla Patalganga, BHEL, and Infosys.
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