Application of constant recycle solid concentration in the pure oxygen activated sludge system | |
| Author | Lin, Li-jen |
| Call Number | AIT Thesis no. 888 |
| Subject(s) | Sewage disposal Sewage--Purification--Activated sludge process |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand. |
| Publisher | Asian Institute of Technology |
| Abstract | Due to the increasing application of pure oxygen activated sludge process in practical usage, the understanding of kinetic and performance of the pure oxygen system is necessary. HSU (1975) conducted the studies of kinetic of microbial growth in the pure oxygen system for batch and once-through system. The main purpose of this research is to investigate the kinetic and performance of a continuous flow pure oxygen process with cell recycle. The model for completely-mixed activated sludge with constant recycle cell concentration was used to investigate the performance of continuous flow oxygenation process. An actual soft drink industrial waste, i.e., Pepsi-Cola combined wastewater, was used as the substrate. Short-term experiments were conducted at various dilution rates for two recycle cell concentration values, i.e., 5000 g/l and 10,000 mg/l. The influent substrate concentration was maintained at 1000 mg/l COD, and the hydraulic recycle ratio, a, at 0.3. A laboratory fermenter was used as aerator. The aerator biological solids and effluent filtrate COD were observed and remained in the steady state. Very high COD removal efficiency was obtained even at very high dilution rate (low detention time), e.g. 92.3% at D(dilution rate) = 2 hr-1 for XR = 10,000 mg/l and 84.9% at D = 1 hr-1 for XR = 5,000 mg/l. No obvious dilute-out point was observed. Neither bulking nor rising sludge occurred during the period of experiment. The SVI values of the mixed liquor was very low within the range of 31.9 to 58.5. The carbohydrate and protein content of the cells has a slightly increasing trend as dilution rate increases, and they are independent of XR. The carbohydrate content was at the average value of 44.8% within the range of 10.1% to 21.6%, and the protein content was at the average value of 45% within the range of 35.6% to 52.2% for dilution rate vary from 1/9 hr-1 to 1/0.5 hr-1 and XR vary from 5000 mg/l to 10,000 mg/l. Cell yield was not related to the dilution rate and sludge loading. The average observed sludge yield was 0.55 (D varied from 1/9 to 1/0.5 hr-1 ', .XR was in the range of 5000 to 10,000 mg/l). Comparing with air activated sludge processes, CMOAS system (pure oxygen system). can provide better performance higher treatment efficiency, better settling characteristics of sludge and no bulking and rising sludge. No significant differences were observed in carbohydrate and protein content of the cells for oxygenation system and air system. The values of µm and ks are related to dilution rates. The higher dilution rate is, the higher values of µm and ks are. Two sets of µm and ks are found for the present CMOAS process, one is µm = 0.4 hr-1 and ks = 92 mg/l for dilution rate higher than 1/3 hr-1 , the other is µm = 0.05 hr-1 and k = 11.1 mg/l for dilution rate below 1/6 hr-1. The maintenance coefficient, kd, appears to have no effect on predicted values of effluent COD, but it influences the biological solids at low dilution rates (below 1/3 hr-1 ). |
| Year | 1976 |
| Type | Thesis |
| School | Student Research Before 1980 |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Thesis (Year <=1979) |
| Chairperson(s) | Yang, Ping Yi |
| Examination Committee(s) | Pescod, M.B. ;Nguyen Cong Thanh ;Htun, Maung Nay ;Samorn Muttamara |
| Scholarship Donor(s) | The Government of Republic of China |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1976 |