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Authors: Tesfaye, Minuta
Keywords: Activated sludge
Date Added: 4-Sep-2007
Abstract: Untreated tannery wastewaters contain high levels of organic materials and nitrogen. The principal forms of nitrogen in tannery wastewater are organic nitrogen (mainly proteins) and ammonia obtained from hides and skins. The presence of nitrogen in wastewater discharge can be undesirable because it has ecological impacts and can affect public health. Methemoglobin, eutrophication and depletion of dissolved oxygen in aquatic ecosystems are some of the major problems related to release of nitrogenous wastewater to the environment. Because of these pollution problems, nitrogenous compounds must be eliminated or reduced to the acceptable limits together with the organic carbon during wastewater treatment. The nitrogen in wastewater will be converted to the harmless nitrogen gas by microbial processes mainly through ammonification, nitrification and denitrification. The objective of this study was to evaluate sludge biomass activity obtained from alkaliphilic environment for removal of nitrogen and organic matter from tannery effluent using lab-scale predenitrification/nitrification activated sludge system. This was fed with simulated and actual tannery wastewater. The raw tannery wastewater was obtained from the Modjo Tannery. The system was inoculated with sludge biomass prepared using sediment slurry from alkaline soda lake and artificial wastewater in batch reactor. The potential of sediment sludge to remove nitrogen and organic matter was analyzed using COD, BOD, TN/TKN, NH+ 4-N, NO- 3-N, S2- and SO4 2- concentrations. The sludge activity was also tested for the occurrence of denitrifiaction and nitrification at higher pH using Nitrate and Ammonia Uptake Rates (NUR and AUR). The system was operated at three different organic loading rates (OLR) (10, 5 and 2.5 gm l-1 d-1). The influent had an average concentrations of 8193.33, 2355, 645.67, 686, 222.33 and 564.67 mg l-1 COD, BOD, TKN, NH4 +-N, S-2 and SO4 2-, respectively, at 10 gm l-1 d-1 OLR. Average effluent concentrations of the aforementioned parameters at 5 gm l-1d-1 OLR were 4209.33, 1409.33, 834, 578, 256.67 and 458.67 mg l-1 while at 2.5 gml-1d-1 OLR were 1886.67, 598.33, 672.33, 280.33, 241.67 and 401.33 mg l-1. The sediment sludge biomass was able to achieve 65.3, 89.2 and 97.1 % removal of COD and 59.7, 87.8 and 97.3 % removal of BOD at 10, 5 and 2.5 gm l-1 d-1 of OLRs, respectively. In addition, TKN removal efficiencies of 44.2, 86.7 and 96.6 % and NH4 +-N removal efficiencies of 62.2, 74.5 and 94.8 % were achieved at 10, 5 and 2.5 gm l-1 d-1 of OLRs, respectively. The removal efficiency of sulphide was 38.2, 89.7 and 92.3 % at respective OLRs. Their potential to remove nitrate and ammonia nitrogen during NUR and AUR Test were 69.5 and 82.8 % at range pH values of 10.2 and 10.21 and 9.50 and 9.75, respectively. Maximum removal efficiencies (97.1, 97.3, 96.6, 94.8 and 92.3 %) of COD, BOD, TKN, NH4 +-N and S2- were obtained at 2.5 gm l-1d-1 of OLR. At this OLR, the final COD, BOD, TKN, NH4 +-N, NO3 --N and S-2 were 55.33, 14.67, 22, 14.6, 4.53 and 18.67 mg l-1, respectively. This is in line with the effluent discharge limit values in Ethiopia. Thus, alkaliphiles could be a good alternative to be used as inoculums for nitrogen and organic matter removal from industrial wastewaters.
Description: I would like to express my deepest gratitude and appreciation to my advisors Dr. Amare Gessesse and Dr. Seyoum Leta for their consistent support, help and encouragement through out the whole study period. They were always willing to help me starting from installing the system to the end of lab work in all aspects and extremely helpful in correcting any technical problems through out the work. I would like to thank my family Kassa W/mariam, Geremew Nisrane, Kore Mersha, Adanech W/mariam, Alemnesh H/mariam, Seble G/silassie, Menbere G/silassie, Habte Neri, Deginesh Minuta, Askale Yirga, Fantaye Berta and Gizeworqe Minuta for supporting me through my graduate studies. They greatly encourage me to enroll in this program. With out their encouragement and moral the study would have been much more difficult. I would like to express my heartfelt and deepest thanks to my friend w/t Sisay Sahle for her continuous encouragement and moral throughout my study period. My greatest appreciation and full thanks must go to my friends Zewede Haile, Addisu Etifu, Nuru Bereda and Dessalegn Berga for their encouragement and moral throughout my study period. Also, appreciation is extended to my friend Abraham Mebrat for his endless support during write up the thesis. I am grateful for technical assistance of w/t Hirut Teshome and w/o Tigist Mengesha during working in laboratory. Special thanks must deserve to my friends indeed Hayal, Dereje, Essayas, Tilahun, and other graduate friends. I would also like to acknowledge SNNPRG, especially Guragae Zone education bureau for granting me the study leave. Also, thanks to Addis Ababa University for funding of the research. Lastly, above all, I want to thank God for helping me endures the rigorous of every day life and to overcome the challenges of graduate studies. Without Him nothing is happened. So I want to say Praise Lord!!
URI: http://hdl.handle.net/123456789/64
Appears in:Thesis - Biology

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