Optimization of Up-flow Anaerobic Sludge Blanket Reactor: A case of Kality Wastewater Treatment Plant, Ethiopia
| dc.contributor.advisor | Agizew Nigussie (PhD) | |
| dc.contributor.advisor | Asie Kemal (PhD) | |
| dc.contributor.author | Johnny Girma | |
| dc.date.accessioned | 2025-01-14T13:59:17Z | |
| dc.date.available | 2025-01-14T13:59:17Z | |
| dc.date.issued | 2024-08 | |
| dc.description.abstract | Enhancing the performance of an up-flow anaerobic sludge blanket reactor (UASB) for unregulated sewage treatment by optimising its operating parameters at a moderate temperature is contingent upon controlling variables like temperature, pH, organic loading rate (OLR), and hydraulic retention time (HRT). The primary goal of the study was to improve the performance of the Kality Wastewater Treatment Plant (WWTP), which uses a UASB reactor through optimization of operational parameters. To do this, controllable operational parameters were optimised, toxic heavy metals concentrations were measured in the unit processes like UASB reactor, Trickling filter, and secondary clarifier. Samples were also tested at downstream irrigated soil and plants for toxic heavy metals concentration. Eventually, the UASB reactor was modelled using general process simulation (GPS-X). Sixty experimental data sets were collected during the rainy seasons (June, July and August) and dry seasons (February, March and April). Central composite design-response surface method (CCD-RSM) tool was used for optimization of operational parameters. Using this CCD-RSM, a temperature of 21.58°C, OLR of 2.99kg COD/m3.d, HRT of 4.37hrs and pH of 6.3 operational parameters were achieved during the rainy seasons. Experimental triplications were conducted using the rainy seasons optimized parameters and about 92.70% Chemical Oxygen Demand(COD), 99.06% Total Suspended Solid(TSS), and 94.50% volatile suspended solid (VSS) were achieved . For dry season’s data, CCD-RSM gave raise optimized operational parameters of temperature (23.04°C), OLR (2.23kg COD/m3.d), pH (7.5), and HRT (11.43hrs). Using optimized operational parameters, experimental triplications were conducted and achieved a removal efficiencies 84.07%COD, 99.89%TSS, and 100%VSS which is much higher than the removal efficiency set by Kality WWTP manual (55% COD, 55%BOD5 and 70%TSS). At the halfway point of the HRT, the reactor's process wellbeing was assessed by measuring the VFA to alkalinity ratio, VSS to TSS ratio, mixed liquor suspended solids (MLSS), and mixed liquor volatile suspended solids (MLVSS). Moreover, because of point and non-point sources of wastewater to the treatment plant multiple issues that have public and environmental health significance could be observed. One of the issue is the evaluation of the WWTP’s unit processes for toxic heavy metals. They were evaluated for toxic heavy metals removal since the existence of higher concentration of these metals in WWTP’s unit processes significantly affects the wellbeing of microorganisms through significant change of pH and the formation of complex compound which precipitate and corrodes the distribution pipes. The second issue is associated with the prevalent use of the treated effluent for irrigation by local farmers. Data were collected to identify and quantify toxic heavy metals in treatment plant’s effluent, irrigated soil, and vegetables. The laboratory tests revealed that majority of the toxic heavy metals were present in the samples analyzed (Chromium, Cadmium, Arsenic, Copper, Lead, and Manganese) and the unit processes were inefficient to remove these metals. Furthermore, a model describing the main biological processes occurring in the UASB reactors was developed. General Process Simulation-X (GPS-X) was used in this experimental research since it is the best tool for simulation and optimization of WWTP processes. Before simulation, influent characterization was done for mass balance around the secondary clarifier which was helpful for calibrating the GPS-X model. The sensitivity analysis result showed that model parameters like kinetic (Maximum Specific Growth Rate on Substrate, Maximum Growth Rate for Ammonia Oxidizer, Maximum Growth Rate for nitrite Oxidizer, Maximum growth rate of PAO) and stoichiometric (Ammonia-oxidizer yield, and Nitrite-Oxidizer yield) values were the most sensitive parameters to calibrate the UASB reactor but the most influential model parameter was kinetic value (heterotrophic maximum specific growth rate). Average absolute relative error (ARE) was used to evaluate the best fit between the measured and simulated data sets. ARE values for COD, TSS and ammonia-nitrogen being less than 7-15% showed that the model was calibrated. Finally the calibrated model was validated based on actual dry seasons data sets collected experimentally. As the simulated results showed acceptable model performances, the developed model can be used by operators, designers and researchers for further studies. | |
| dc.identifier.uri | https://etd.aau.edu.et/handle/123456789/4107 | |
| dc.language.iso | en_US | |
| dc.publisher | Addis Ababa Univeristy | |
| dc.subject | GPS-X | |
| dc.subject | mathematical model | |
| dc.subject | operational parameters | |
| dc.subject | optimization | |
| dc.subject | moderate temperature | |
| dc.subject | up-flow sludge blanket reactor | |
| dc.subject | toxic heavy metal | |
| dc.subject | and wastewater. | |
| dc.title | Optimization of Up-flow Anaerobic Sludge Blanket Reactor: A case of Kality Wastewater Treatment Plant, Ethiopia | |
| dc.type | Dissertation |