The major portion of the pollution load carried in wastewater is removed by the biological treatment section of the plant. This section consists of the activated sludge tanks and the final clarifiers, forming together a functional unit. The treatment process is governed by the biomass generated in the aeration tank. This biomass must be separated in the final clarifiers from the wastewater stream and returned to the aeration tank.
From this functional interdependence, the following tasks can be determined for final clarifiers:
• Suspended solids in the effluent must be the lowest possible
• The separated biosolids should be withdrawn at the highest possible concentration
• Biomass should be held and stored in tank when hydraulic swells occur
• Floating solids should not escape in effluent
The final clarifiers determining the overall efficiency of a biological wastewater treatment system, Aqua Engineering always has intensively and systematically investigated in problems related to this treatment step.
At this time, Aqua Engineering has a comprehensive knowledge on equipment design and sizing criteria for different types of clarifier tanks and sludge removal systems:
• Circular center feed clarifiers with peripheral effluent trough. Rotating blade scrapers for sludge removal. Tank diameter up to 60 m.
• Circular clarifiers with peripheral feed and takeoff. Rotating suction header for sludge removal. Tank diameter up to 60 m
• Longitudinal flow rectangular clarifiers. Submersed pipe system or open air troughs for effluent. Scraper sludge collectors with non-metallic chains, Aqua Engineering design. Maximum tank size: length 100 m, width 9 m.
• Cross flow rectangular clarifiers. Sludge withdrawal by suction header suspended to traveling bridge. Maximum tank size: length 70 m, width 20 m