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Title: Enhancing nitrogen and organic matter removal from tannery wastewater using efficient proteolytic bacterial isolates and their enzymes in lab-scale anoxic-oxic process
Authors: Yemisirach, Mulugeta
Advisors: Dr. Amare Gessesse
Dr. Seyoum Leta
Copyright: Feb-2008
Date Added: 19-Dec-2008
Publisher: Addis Ababa University
Abstract: Tannery wastewater contains high level of protein, which, as a macromolecule takes longer residence time for its microbial degradation. The objectives of this study were to see the effect of adding protease and bio-augmentation of proteolytic organisms on protein hydrolysis and on total nitrogen removal rate using anoxic/oxic lab-scale reactor feeded with synthetic wastewater. Eighty five proteolytic organisms were isolated from tannery wastewater sludge sample of which proteases extracted from three best isolates (ETY-19, YE-25 and YE-33). The temperature and pH characteristics of proteases of the three selected isolates showed optimum activity at around neutral pH range and at mesophilic temperature. Protease from YE-33 was used to see the effect of adding enzyme on protein hydrolysis and the same organism was used to test the effect of bio-augmentation on protein hydrolysis. Ammonium production, total nitrogen and chemical oxygen demand (COD) removal were determined for 120h experimental time. Increasing protease activity didn’t considerably affect the overall COD removal where, removal efficiencies were 89- 91%, 89-90% and 90-91% for no enzyme, 10 and 30U/ml protease supplements respectively. Anoxic system ammonium concentration increased from 65-70mg/l, 61- 109mg/l and 74-153mg/l for the non enzyme supplemented, 10 and 30U/ml protease supplements respectively. The 120h average total nitrogen removal efficiencies were 55.4- 56.8%, 54.5-61.3% and 54.7-73% in the non enzyme supplemented, 10 and 30U/ml protease supplemented experiments respectively. In the bio-augmentation experiments in addition to colony forming unit count Ammonium production, total nitrogen and COD removal efficiency were determined for 120h experimental time. There was very little variation in COD removal efficiencies where 90-93%, 89-91% and 90.5-91.5 % COD removal efficiencies observed in non augmented, 10 x107 and 10x109 cfu/ml cell density augmentations respectively. Ammonium concentrations in the anoxic tank were 77-79mg/l, 78.2-100mg/l and 101-104mg/l in the non augmented, 10x107 and 10x109 cfu/ml augmentations respectively. Little improvement 56-58%, 58-64% and 65.68% in total nitrogen removal efficiencies were observed in the non augmented, 10x107 and 10x109 cfu/ml cell density augmentations respectively. In general exogenous protease and proteolytic bio-augmentation found to improve protein hydrolysis and nitrogen removal rates.
Description: A Thesis Submitted to the School of Graduate Studies Addis Ababa University In Partial Fulfillment of the Requirement for the Degree of Master of Science in Environmental Science
URI: http://hdl.handle.net/123456789/1821
Appears in:Thesis - Environmental Sciences
Thesis - Environmental Sciences

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