| Abstract: |
The application of anaerobic processes has tended to be restricted to strong industrial wastewaters. The success of anaerobic processes as a treatment technology for high strength, industrial wastewater has meant that the potential of these processes for the treatment of low strength wastewater has been evaluated. However, one of the main challenges to anaerobic technology remains its applicability to low-strength wastewaters like sewage. The upflow anaerobic sludge blanket (UASB) reactor is the most widely and successfully used high rate anaerobic system for sewage treatment.There is a need to develop methodologies enabling one to determine UASB reactor performance, not only for designing more efficient UASB reactor but also for estimating the performance of UASB reactor under various conditions of influent wastewater flows and characteristics.An experimental investigation has been performed in order to investigate the effect of some selected variables on performance of UASB reactor, namely hydraulic retention time, organic loading rate, upflow velocity and effect of mixing the seeding sludge with clay minerals. Kaolinite and Montmorillonite are utilized in the present study as clay minerals, while COD, BOD, SS, DS and TS are selected as assessment parameters of the treatment process. The influence of inoculation on the effluent quality has been assessed as well.Two identical pilot-scale models simulating ”Upflow Anaerobic Sludge Blanket” reactors (UASBs) were built and operated continuously within the work-frame of the present work in order to investigate its performance and efficiency in treating raw domestic wastewater. These two models were operated under the same operation conditions and scenario, one of them was seeded with a mixture of sludge and kaolinite while the other was seeded with a mixture of sludge and monmorillonite. Different mixing ratios (weight-basis) of clay minerals and sludge (Wc:Ws) ranged from 0% to 80% were applied in the present study to achieve its global objective.Based on the results obtained from the experimental program executed within the scope of this study and limited to the conditions under which the experimental runs had been run, it is found that the UASB achieves substantially different removal efficiencies in removing COD, BOD and SS. Also, it is found that inoculation enhances the efficiency of the UASB in removing these pollutants especially in the start-up period. The capability of the UASB reactor to cope with the variations in the influent characteristics has been found as well. The study showed that, the best conditions for organic matter removal in the UASB reactor were at 20 hr HRT, 0.72 kg COD/m3/d OLR and 0.10 m/hr Vup, where the efficiency of COD removal was 62.1%. It is also found that the substantial enhancement in the efficiency of UASB treating raw sewage upon mixing the seeding sludge with clay minerals. An enhancement amount up to about 24% in the UASB efficiency in removing COD. The optimum mixing ratio of clay (which achieved the maximum removal ratio of organic matters) for kaolinite was 80 %, and for montmorillonite was 60 %. The maximum efficiency of COD removal was 86.2 % in the case of kaolinite, while in the case of montmorillonite this efficiency was 83.3 %.This work explores the feasibility of application the artificial neural network (ANN) for simulating the performance of the UASB reactor. Accordingly, a neural network model was designed and trained to calculate the effluent BOD or COD in UASB reactor treating domestic wastewater under different conditions.
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