A study was conducted to evaluate the feasibility of activated sludge process for the treatment of tannery wastewater in a lab scale model under local conditions. Wastewater was collected from chromium stage, Elmontazah tannery, Ein Elsira tanneries, Cairo, Egypt. The reactor was operated with the activated sludge process under batch mode using a tannery wastewater as feed. A lab scale model comprised of primary sedimentation tank (5 L), aeration tank (5 L) and final clarifier (5 L). The model was operated continuously for 120 hours of contact. The pH of wastewater was firstly adjusted till pH 6.5 to enhance biosorption capacity. The wastewater samples of the effluent were analyzed after time interval 2h, 6h, 12h, 24h, 48h, 72h, 96h and finally 120 h to find process efficiency. Results of the study demonstrated that the removal efficiency of about 98.3% and 98.4% for BOD5 (Biological Oxygen Demand) and COD (Chemical Oxygen Demand) respectively, could be obtained under a HRT of 120 h. Results were also showed decrease in chromium ion, ammonia nitrogen, phosphorous and oil & grease concentrations up to 99.3%, 98.8%, 98.6% and 99.1%, respectively. Results were also showed decrease in the color absorbance. Activated sludge was characterized using SEM examination with EDAX analysis and FT-IR technique. The kinetic coefficients k (maximum substrate utilization rate), Ks (half velocity constant), Y(cell yield coefficient) and Kd (decay coefficient) were found to be 1.2 day-1, 209 mg/L, 0.18 and 0.039 day-1, respectively. These coefficients may be utilized for the design of activated sludge process facilities for tannery wastewater. |
