Replacement for Primary Settling Tanks

Replacing the primary clarifier with a fine screen – HUBER CarbonWin®

In the HUBER CarbonWin® process, the primary clarifier is replaced by a fine screen. This results in the following advantages:

• Only 1/10 of the space required compared to conventional primary clarifiers
• Minimised investment and operating costs
• Suitable to be integrated into existing plants

The primary clarifier is the last stage of the mechanical pre-treatment of a wastewater treatment plant and works according to the anaerobic sludge stabilisation process.

In the primary settling tank, undissolved organic and inorganic substances settle at low flow velocities and with sufficient retention time and thus build the primary sludge. This is then added to the digester – usually after mechanical thickening – together with the excess sludge. In the anaerobic process, the sludge is converted into digester gas, which can be used for energy generation.

Sewage treatment plants that work according to the principle of aerobic sludge stabilisation usually do not have a primary clarifier. However, the advantage of the simpler process technology is offset by high energy consumption, because sludge stabilisation takes place simultaneously with biological wastewater treatment through a correspondingly long aeration period (high sludge age).

Aerobic sludge stabilisation is more common in smaller wastewater treatment plants up to about 20,000, sometimes up to 50,000 population equivalents (p.e.).

Driven by constantly rising energy costs and technical innovations in the field of sludge digestion and digester gas utilisation, anaerobic sludge treatment is gaining in importance also for smaller sewage treatment plants designed for fewer than 50,000 PE. For an economic and energy-optimised conversion from aerobic to anaerobic sludge stabilisation, the use of a primary clarifier is usually unavoidable.