Activated sludge process

ACTIVATED SLUDGE PROCESS

• Activated Sludge Process (ASP) is an aerobic biological sewage treatment system
• It consists of the following units
• Aeration tank
• Secondary settling tank
• Sludge return line and
• Excess sludge waste line
• Raw sewage is give a primary treatment in Primary Settling Tank (PST) with a short detention time of 1 to 1.5  hours.
• PST removes settleable solids
• The raw sewage is mixed with activated sludge (return sludge). This mixture is called mixed liquor
• Mixed liquor is aerated and mixed for 4 to 10 hours depending on
• degree of purification required and
• strength of sewage

 

• Aerated mixed liquor is sent to final settling tank where sludge settles
• Effluent from final settling tank is disposed off
• A portion of effluent from final settling tank is mixed with raw sewage before sending it into the Primary Settling Tank (PST)
• Part of settled sewage is sent back in aeration tank for seeding the raw sewage and excess quality is treated and disposed off.