Physico-chemical activated sludge enhanced treatment in CEPT process

摘要

The elevated chemical cost is one of main concerned issues in the Chemically Enhanced Primary Treatment (CEPT) nowadays. The sludge gotten from the coagulation-flocculation-sedimentation process shows a high concentration of ions and high potential of adsorption capability. Therefore, the sludge after activated with acid or aeration could be reused to enhance flocculation in CEPT process. In this study, CEPT sludge produced after sedimentation was recycled after aerated and adjusted pH to reduce fresh ferric chloride dose and promote the organic removal efficiency. It was found that the enhanced removal efficiencies of turbidity, UV254, COD, total phosphorus (TP) and PO4-P were about 98%, 66%, 51%, 96% and 100% respectively as 16 mg/L of ferric chloride and 75 mg/L aerated chemical sludge were added, which exceeded the chemical flocculation process by 13%, 32%,8.6%, 3.7% and 1.3%, respectively. The pH played a significant role in the sludge reuse process. Experiments showed that the ferric ions could be dissolved out richer from the sludge at initial pH 3-4.