Application of magnetic field for reduction of sludge bulking in activated sludge system

Activated sludge treatment process is the most commonly used technology in treating municipal wastewater. Nevertheless, its stable operation is always plagued by occurrence of sludge bulking. Existing control approaches have led to various drawbacks and caused more problematic issues in the treatmen...

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Main Author:	Zaidi, Nur Syamimi
Format:	Thesis
Language:	English
Published:	2016
Subjects:	TA Engineering (General) Civil engineering (General)
Online Access:	http://eprints.utm.my/id/eprint/60720/1/NurSyamimiZaidiPFKA2016.pdf
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spelling	my-utm-ep.607202021-01-03T01:50:10Z Application of magnetic field for reduction of sludge bulking in activated sludge system 2016-08 Zaidi, Nur Syamimi TA Engineering (General). Civil engineering (General) Activated sludge treatment process is the most commonly used technology in treating municipal wastewater. Nevertheless, its stable operation is always plagued by occurrence of sludge bulking. Existing control approaches have led to various drawbacks and caused more problematic issues in the treatment system. Therefore, this study investigated the use of magnetic field on activated sludge in controlling the occurrence of sludge bulking and to further enhance wastewater treatment process. The initial stage of the study involved batch tests where statistical experimental design was implemented. Factorial design was carried out first, followed by central composite design experiment. The studies showed that turbidity reduction, aggregation and settling velocity of the activated sludge were affected by factors of magnetic field, exposure time, biomass concentration and mixing intensity. Interaction effects between the factors were also observed. Statistical models describing relationship between the variables were developed. From the study, the highest turbidity reduction (89.1%), aggregation (97.8%) and settling velocity (0.68 cm/min) were achieved under optimal condition of 88.0 mT magnetic field, 16.5 hrs exposure time, 2800 mg/L biomass concentration and 300 rpm mixing intensity. The following stages of the study were conducted in 6 L column reactors. The reactors were operated under long period of sludge retention time of 20 days and in deficient dissolved oxygen of less than 2 mg/L in order to induce the sludge bulking phenomenon. After reaching its stable state, the activated sludge under the magnetic field exposure showed significant results as compared to without the exposure. The average aggregation and settling velocity for the magnetically exposed activated sludge were 89% and 0.59 m/hr as compared to 68% and 0.50 m/hr for the unexposed sludge. Such properties resulted in significant enhancement of sludge volume index at 23.7 mL/g for magnetically exposed activated sludge as compared to 72.2 mL/g for the unexposed sludge. This enhancement benefited the treatment performances whereby the average chemical oxygen demand, ammonia and total phosphorus removal were 87%, 88% and 72% under the magnetic field exposure as compared to 67%, 75% and 44%, respectively without the exposure. Magnetically exposed activated sludge also contained high content of tightly bound extra-cellular polymeric substances (95.6 mg/g VSS) compared to unexposed sludge (61.8 mg/g VSS). Finally, Next Generation Sequencing analysis indicated that magnetically exposed activated sludge showed less possibility of filamentous microorganisms presence compared to the unexposed activated sludge. Overall, analysis confirmed that magnetic field could enhance the settling property of activated sludge through improvement on its aggregation and bioflocculation capability. These imply that magnetic field is reliable for accelerating activated sludge settleability, hence enhancing performance efficiency of the treatment systems. The applied magnetic field was also proven to inhibit proliferation of filamentous microorganisms, thus has potential to inhibit occurrence of sludge bulking. 2016-08 Thesis http://eprints.utm.my/id/eprint/60720/ http://eprints.utm.my/id/eprint/60720/1/NurSyamimiZaidiPFKA2016.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:94143 phd doctoral Universiti Teknologi Malaysia, Faculty of Civil Engineering Faculty of Civil Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TA Engineering (General) Civil engineering (General)
spellingShingle	TA Engineering (General) Civil engineering (General) Zaidi, Nur Syamimi Application of magnetic field for reduction of sludge bulking in activated sludge system
description	Activated sludge treatment process is the most commonly used technology in treating municipal wastewater. Nevertheless, its stable operation is always plagued by occurrence of sludge bulking. Existing control approaches have led to various drawbacks and caused more problematic issues in the treatment system. Therefore, this study investigated the use of magnetic field on activated sludge in controlling the occurrence of sludge bulking and to further enhance wastewater treatment process. The initial stage of the study involved batch tests where statistical experimental design was implemented. Factorial design was carried out first, followed by central composite design experiment. The studies showed that turbidity reduction, aggregation and settling velocity of the activated sludge were affected by factors of magnetic field, exposure time, biomass concentration and mixing intensity. Interaction effects between the factors were also observed. Statistical models describing relationship between the variables were developed. From the study, the highest turbidity reduction (89.1%), aggregation (97.8%) and settling velocity (0.68 cm/min) were achieved under optimal condition of 88.0 mT magnetic field, 16.5 hrs exposure time, 2800 mg/L biomass concentration and 300 rpm mixing intensity. The following stages of the study were conducted in 6 L column reactors. The reactors were operated under long period of sludge retention time of 20 days and in deficient dissolved oxygen of less than 2 mg/L in order to induce the sludge bulking phenomenon. After reaching its stable state, the activated sludge under the magnetic field exposure showed significant results as compared to without the exposure. The average aggregation and settling velocity for the magnetically exposed activated sludge were 89% and 0.59 m/hr as compared to 68% and 0.50 m/hr for the unexposed sludge. Such properties resulted in significant enhancement of sludge volume index at 23.7 mL/g for magnetically exposed activated sludge as compared to 72.2 mL/g for the unexposed sludge. This enhancement benefited the treatment performances whereby the average chemical oxygen demand, ammonia and total phosphorus removal were 87%, 88% and 72% under the magnetic field exposure as compared to 67%, 75% and 44%, respectively without the exposure. Magnetically exposed activated sludge also contained high content of tightly bound extra-cellular polymeric substances (95.6 mg/g VSS) compared to unexposed sludge (61.8 mg/g VSS). Finally, Next Generation Sequencing analysis indicated that magnetically exposed activated sludge showed less possibility of filamentous microorganisms presence compared to the unexposed activated sludge. Overall, analysis confirmed that magnetic field could enhance the settling property of activated sludge through improvement on its aggregation and bioflocculation capability. These imply that magnetic field is reliable for accelerating activated sludge settleability, hence enhancing performance efficiency of the treatment systems. The applied magnetic field was also proven to inhibit proliferation of filamentous microorganisms, thus has potential to inhibit occurrence of sludge bulking.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Zaidi, Nur Syamimi
author_facet	Zaidi, Nur Syamimi
author_sort	Zaidi, Nur Syamimi
title	Application of magnetic field for reduction of sludge bulking in activated sludge system
title_short	Application of magnetic field for reduction of sludge bulking in activated sludge system
title_full	Application of magnetic field for reduction of sludge bulking in activated sludge system
title_fullStr	Application of magnetic field for reduction of sludge bulking in activated sludge system
title_full_unstemmed	Application of magnetic field for reduction of sludge bulking in activated sludge system
title_sort	application of magnetic field for reduction of sludge bulking in activated sludge system
granting_institution	Universiti Teknologi Malaysia, Faculty of Civil Engineering
granting_department	Faculty of Civil Engineering
publishDate	2016
url	http://eprints.utm.my/id/eprint/60720/1/NurSyamimiZaidiPFKA2016.pdf
_version_	1747817767276380160

Application of magnetic field for reduction of sludge bulking in activated sludge system

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