Primary and Final Settlement Tanks
A new range of advanced design hopper bottom GRP settlement tanks for small wastewater treatment plants.
Efficient solids removal is the cornerstone of any effective wastewater process. KEE’s range of Primary Settlement Tanks and Final Settlement Tanks is designed to provide optimal hydraulic conditions for the separation of settleable solids.
Constructed from high-quality GRP and featuring advanced hopper-bottom designs, our settlement tank solutions ensure regulatory compliance and protect the integrity of your downstream biological processes. Trust KEE’s 70+ years of engineering expertise to deliver a system tailored to your site’s specific flow and load requirements.
The Role of the Settlement Tank in Modern Wastewater Management
Effective wastewater treatment relies on the physical separation of solids from liquid. Whether you are installing a new system or upgrading an existing facility, selecting the right settlement tank is critical to the plant’s overall performance and the quality of the effluent.
At KEE, we offer a range of advanced-design hopper-bottom GRP tanks engineered for rapid installation and long-term structural integrity.
Primary Settlement Tanks (PST): The First Line of Defence
Primary Settlement Tanks represent the first major stage in the treatment process following preliminary screening. By reducing the velocity of the incoming wastewater, these tanks allow heavier organic solids to settle at the bottom as sludge, while lighter fats and oils accumulate on the surface.
- Load Reduction: Efficient primary settlement can remove up to 60% of suspended solids, significantly lowering the organic load on the secondary biological treatment stage.
- Protection: By capturing grit and heavy solids early on, PSTs help protect downstream pumps and Rotating Biological Contactors (RBCs) from excessive wear and potential blockages.
Final Settlement Tanks (FST): Ensuring Effluent Clarity
Following biological treatment, Final Settlement Tanks (also known as secondary clarifiers) perform the crucial task of separating treated effluent from the biological “floc” or biomass.
- Polished Output: Our FSTs are designed to capture even the finest particles, resulting in clear effluent that meets or exceeds Environment Agency discharge consents.
- Sludge Return & Management: The hopper-bottom design facilitates easy removal of settled humus sludge, which can then be returned to the primary stage or removed from the site.
Why Choose KEE GRP Settlement Tanks?
Our tanks are manufactured from Glass-Reinforced Plastic (GRP), providing a superior alternative to traditional concrete structures:
- Corrosion Resistance: Fully resistant to the aggressive chemical environment of raw sewage.
- Watertight Integrity: Precision-engineered joints ensure a 100% watertight seal, preventing groundwater infiltration.
- Modular & Scalable: Available in various diameters and depths to accommodate populations ranging from single households to large commercial developments.
- Ease of Installation: The lightweight GRP construction allows for faster site assembly and lower crane costs, even in remote locations.
Technical Expertise and Support
Choosing KEE means more than just purchasing equipment. Our British Water-accredited engineers provide comprehensive support, from initial hydraulic sizing and design to installation and commissioning. We also offer fixed-price maintenance contracts to ensure your settlement tank continues to operate at peak efficiency for its 30-year design life.
Protect your processes with KEE. Contact our technical team today to discuss your project requirements.
FAQs
What is the difference between a primary settlement tank and a secondary settlement tank?
The primary settlement tank and secondary settlement tank serve different stages and functions in the wastewater treatment process, targeting specific materials for removal.
| Feature | Primary Settlement Tank (PST) | Secondary Settlement Tank (SST) |
|---|---|---|
| Stage in Process | Follows preliminary treatment (screens/grit removal). | Follows the biological treatment stage (e.g., Activated Sludge). |
| Primary Purpose | To physically remove coarse, settleable solids (raw sewage solids) from the incoming wastewater. | To separate the biological sludge (flocculated microbial biomass) from the treated water. |
| Output Sludge Use | Sludge is sent to further sludge treatment (e.g., anaerobic digestion). | Sludge is mostly returned to the biological reactor to maintain the cleaning process. |
| Removal Efficiency | Removes about 60% of suspended solids and 30-40% of Biological Oxygen Demand (BOD). | Removes fine, non-settling particles and the biological floc remaining after aeration. |
Is a septic tank a settling tank?
A septic tank serves as a settlement tank, specifically functioning as a single-stage primary treatment unit. It is a watertight container designed to hold wastewater for a sufficient period, allowing solids to settle at the bottom and form sludge, while lighter materials, such as grease and oils, float to the top, creating scum.
The liquid effluent then exits the tank for further dispersal or treatment. Unlike a treatment plant, which uses multiple designated primary settlement tanks to handle high flow volumes, a septic tank performs the same basic physical separation process for a single household or facility.
What is a GRP tank?
GRP stands for Glass-Reinforced Plastic (or Glass-Reinforced Polymer). A GRP tank is a container made from a composite material that consists of plastic resin reinforced with fine glass fibres (fibreglass).
GRP tanks are commonly used in wastewater treatment for various applications, including pump stations, emergency storage, and settlement tanks. They offer several key advantages:
- Corrosion Resistance: GRP tanks are highly resistant to chemicals and corrosive environments common in sewage and wastewater.
- Lightweight: These tanks are easier to transport and install compared to traditional concrete or steel tanks.
- Durability: GRP tanks provide excellent structural strength and offer a long service life with minimal maintenance.
