06/12/2025
a cross-section of a small-scale sewage treatment system, likely an Activated Sludge Plant or a Biodigester, often used for individual homes or small communities where connection to a municipal sewer system isn't feasible.
It is divided into two tanks, Tank A and Tank B, which correspond to the primary and secondary treatment stages.
Here is a detailed breakdown of the system components and processes:
💧 SEWAGE TREATMENT SYSTEM DESIGN
The system has six key numbered points and three main chambers: Primary Settlement, Biological Chamber, and Secondary Settlement.
TANK A: PRIMARY SETTLEMENT CHAMBER
This is the first stage where physical separation occurs.
• 1. INLET: Raw sewage enters the tank.
• Process: The flow slows down significantly, allowing Suspended Solids to settle to the bottom, forming Fine Sludge. Lighter material (grease, oils, etc.) floats to the surface and forms a Crust (or scum layer). This chamber removes a large percentage of solids before biological treatment.
• Dimensions: It has a volume of 1850 Litres and a chamber width of 1570 mm.
TANK B: BIOLOGICAL AND SECONDARY CHAMBERS
This tank houses the secondary (biological) and tertiary (final settlement) treatment stages.
1. BIOLOGICAL CHAMBER
This is where the wastewater is cleaned by microorganisms.
• 2. COMPRESSOR/Air Line: Air is pumped into the chamber from an external compressor (located on top).
• 3. DIFFUSER: Air is released into the water through a diffuser, which creates fine bubbles. This process is called aeration.
• 4. MEDIA: The tank contains plastic or stone Media (often Bio-Media) which provides a large surface area for beneficial aerobic bacteria to grow. The bacteria consume the organic pollutants in the wastewater. This specific setup is often referred to as a Submerged Aerated Filter (SAF) or similar fixed-film process.
2. SECONDARY SETTLEMENT CHAMBER
This is the final stage of separation.
• Process: The treated water, which now contains biological "sludge" (floccul
