Stages of Making a Health Facility Wastewater Treatment Plant
In almost all WWTP systems, the clarifier is the unit that ensures water quality before entering the next process. Without a properly functioning clarifier, suspended solids (TSS) will carry over to the filtration or disinfection units, causing blockages, increased operational costs, and even potential compliance failure.
A clarifier is not just a place to “settle sludge,” but a system that functions to:
- Maintain the stability of the active sludge (sludge blanket)
- Produce clear overflow water
- Return biomass to the biological process
- Prevent TSS carry-over
Its function is crucial, especially for biological processes such as Activated Sludge, MBBR, and SBR.
2. Basic Principles of Sedimentation in Clarifiers
The clarifier works based on the principle of gravity, separating solids from liquids by utilizing differences in density. When water flows into the clarifier:
- Heavier solids sink
- Clear water rises to the top
- Oil/grease can be skimmed from the surface
However, the success of this process depends heavily on maintaining laminar flow so particles are not lifted back up.
- Clarifier Process Flow from Inlet to Effluent
The clarifier process takes place across several interconnected zones:
- Inlet Zone: Flow is slowed; turbulence energy is reduced.
- Settling Zone: Particles begin to settle under laminar flow conditions.
- Sludge Zone: Sludge accumulates and thickens; some is pumped back (return sludge).
- Skimming Zone: Oil and light particles float to be removed.
- Effluent Zone: Clear water is discharged in a controlled manner.
The success of the clarifier depends on the balance among these zones.
- Clarifier Design Elements and Their Functions
Table: Clarifier Components and Their Roles
| Component | Function |
| Inlet Baffle | Reduces incoming turbulence to allow calmer flow |
| Tube Settler / Lamella Plate | Accelerates settling by increasing surface area |
| Sludge Hopper | Collects sludge for easy pumping |
| Scraper (Rotary Arm) | Directs sludge to the center of the tank |
| Scum Skimmer | Removes oil and light particles from the surface |
| Weir (Overflow Channel) | Distributes clean water evenly during discharge |
Proper design ensures optimal sedimentation while maintaining effluent clarity.
5. Effect of Material on Clarifier Performance
The clarifier tank material determines durability, efficiency, and maintenance costs. Some common material options include:
- Carbon Steel → strong but requires periodic coating
- Stainless Steel → corrosion-resistant, high initial cost
- FRP / Composite → lightweight, chemical-resistant, low maintenance
- Modular Bolted Tank (SUPRAX-style) → quick installation, flexible, suitable for industries needing scalability
The right material can extend tank lifespan while reducing operational costs.
Clarifier Optimization with Chemical Treatment Support
In many cases, clarifiers require the help of coagulation and flocculation to speed up settling. Chemicals enlarge particles, making them easier to settle at the bottom.
Other common optimization methods include:
- Adjusting pH to improve coagulation
- Polymer dosing to strengthen flocs
- Very light aeration to prevent septic conditions in the sludge zone
- Maintaining optimal MLSS in biological units to avoid over-sludging
With proper chemical support, clarifier performance can improve significantly.
Signs That a Clarifier Needs Maintenance
A clarifier that is becoming less optimal typically shows the following signs:
- Effluent appears cloudy
- Oil layer accumulates on the surface
- Sludge settles too fast or too slow
- The rotating arm moves irregularly
- Sludge becomes too dilute or too thick
- Effluent TSS increases even if other processes are normal
These signs must be detected early to prevent system failure.
The clarifier is one of the most important units in wastewater treatment. With proper design, adequate chemical support, and the right material selection, a clarifier can deliver optimal separation results and maintain overall system stability.
If you need clarifier performance evaluation, material recommendations, or sedimentation system improvements for industrial WWTPs, PJL Enviro is ready to provide accurate technical solutions tailored to your process needs.
