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Treating Tannery Wastewater for Nutrient Removal and Composition of Bacterial Community in Integrated SBR -Wetland System: Pilot Scale Studies

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dc.contributor.advisor Leta, Seyoum (Professor)
dc.contributor.author Lemma, Eshetu
dc.date.accessioned 2021-06-29T12:35:00Z
dc.date.available 2021-06-29T12:35:00Z
dc.date.issued 2020-05-05
dc.identifier.uri http://etd.aau.edu.et/handle/123456789/27005
dc.description.abstract This dissertation reports on developing and optimizing processes for SBR technologies for treating tannery wastewater, with special reference to degradation/removal of nutrients from tanning industries and to identify the most efficient nitrifying and denitrifying organisms in tannery wastewaters laden with toxic substances. Tannery wastewater is one of the most hazardous wastewater for the environment when discharged without any treatment. Biological treatment technologies have shown encouraging results in the treatment of toxic compounds containing wastewaters. In this study, real tannery wastewater (RTW) was treated in a pilot scale aerobic sequencing batch reactor (SBR).The main aim of this study was to investigate the effect of cycle time length, organic loading rate and sludge retention time on the performance of Sequential Batch Reactor for treating a high strength tannery wastewater. For this purpose, pilot-scale sequencing batch reactor of 50m3 volume was operated under different phases with the same conditions at different four cycle time length i.e.,6,12,24 and 48 days, five organic loading ratei.e.,0.5,1.04,2.1,3.1 and 4.2 kg COD /m3.day and five sludge retention times (SRT) i.e., 5,10,20,25 and 30 days for treating tannery wastewater. For single aerobic time SBR processes, the maximum COD (82.26%) and TKN (71.59%) removal efficiencies were obtained at the cycle time and aerobic time of 24 h and 12h, respectively. While the maximum TN (68.18%) and 14 phosphorus (58.29%) removal efficiencies were obtained at a cycle time of 24 h and aeration time of 12 h/cycle. Considering biochemical processes the volumetric loading rate for tannery wastewater should be higher than 1.5 kgCOD/ (m3*d). Higher COD input load with a COD-based volumetric loading rate of 3.1 kgCOD/(m3*d) nearly led to complete nitrogen removal. Under different operational conditions average nitrification rates up to 5.2 gNH/(m3*h) and denitrification rates up to 3.4 gNO/(m3*h) was achieved. Cycle time is another parameter that shows the effect on concentration profiles. The increasing of reacting time provides more time for biomass to react and makes the BOD effluent and ammonium concentration decrease. When cycle period decreases, nitrate has less time to transform to nitrogen gas. Total SBR-cycle times should be in between 20- 24 hours. Reduction of the cycle time from 24h to 360 minutes resulted in an increase of peak nitrogen effluent concentrations by 88 %.The results at optimum cycle length, OLR and SRT showed that over the experimental feeding phases ranged from 82-98% for the total nitrogen, 95- 98% for COD, 96-98% for BOD5, 46-95% for ammonia nitrogen, 95-99% for sulphide and 93- 99% for trivalent chromium. As a result, high cycle time (24 h), moderate aeration time as intermittently aerated SBR (12h/cycle), 3.1 kgCOD/(m3*d) and 25 -day SRT were found to be the optimal region for maximum tannery waste water carbon and nitrogen removal efficiencies using SBR. Nitrogen removal in an aerobic SBR through simultaneous nitrification-– denitrification could be a good option for tannery wastewater. SBR is a viable option for tannery wastewater compared to the conventional aerobic systems provided pollution control measures are conducted at the source level through the use of eco-friendly chemicals and cleaner processing methods to avoid nitrification inhibiting compounds in the effluent. Ammonia of the influent and effluent and MLSS of aeration tank were determined at various detention times to 15 generate data for kinetic coefficients. The kinetic coefficients k (maximum substrate utilization rate), Ks (half velocity constant), Y (cell yield coefficient) and Kd (decay coefficient) were found to be 29.41 12.24, day-1, 0.298 mg/L, and 0.058 day-1, respectively. These coefficients may be utilized for the design of activated sludge process facilities for tannery wastewater. Overall ammonia removal rate constant ‘K’ was found to be 29.41 day-1.The result of pilot scale study on the structure and diversity of microbial community in the sludges of SBR-wetland system revealed that most dominant phylum, class, order, family, genuses and species in SBR were proteobacteria (40.11%),Gammaproteobacteria (39.07), Pseudomonadales (39.04), Moraxellaceae (39.03), Psychrobacter (32.98) and pulmonis(31.89). while the most dominant phylum, class, order, family, genuses and species in wetland were proteobacteria (35.72), Gammaproteobacteria (31.81), Pseudomonadales (30.60), Pseudomonadaceae (15.58),Pseudomonas (15.55) and unclassified species from Pseudomonas genus (15.55) respectively. Therefore the prototype is now not only turning the industrial wastes into value-added products (clean water) but is also serving for university- industry linkage in developing scalable innovations for the sustainable management of all other agro-processing wastewaters in the country. en_US
dc.language.iso en en_US
dc.publisher Addis Ababa University en_US
dc.subject Treating Tannery Wastewater en_US
dc.subject Nutrient Removal en_US
dc.subject Composition of Bacterial Community en_US
dc.subject Integrated Sbr -Wetland System en_US
dc.subject Pilot Scale Studies en_US
dc.title Treating Tannery Wastewater for Nutrient Removal and Composition of Bacterial Community in Integrated SBR -Wetland System: Pilot Scale Studies en_US
dc.type Thesis en_US

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