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Anaerobic treatment of wastewater in a UASB reactor
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The anaerobic treatment of waste water has been studied with an emphasis on the Up- flow Anaerobic Sludge Blanket (UASB) reactor. A model to describe the processes occurring in a UASB reactor was developed and an experimental study of the anaerobic wastewater treatment systems in Nicaragua was also performed.

Experimental work was carried out in order to link the study to the wastewater treatment situation in Nicaragua, a developing country. In order to assess the performance of the treatment plants, the methanogenic activity of sludge from seven anaerobic wastewater treatment plants was first addressed. Due to a lack of Standards for the measurement of methanogenic activity, a laboratory method was developed based on the methods found in the literature. An additional aim of this study was to find adequate inoculum for the wastewater treatment plant in a brewery using an anaerobic reactor. Physic-chemical characteristics of the sludge were also determined to provide a basis for decisions regarding the agricultural employment of the sludge from the treatment plants.

A one-dimensional model describing the physical and biological processes occurring in an Up-flow Anaerobic Sludge Blanket reactor has been developed. These processes are advection, dispersion and reaction in the granule, including mass transport at the interface and diffusion within the particle. The advection-dispersion equation is used to describe these phenomena in the reactor. Dispersion is mainly caused by the gas bubbles rising up through the reactor and the granules in the ascending flow. The extent of the dispersion is expressed by the dimensionless Peclet (Pe) number. It is assumed that the biological degradation takes place at the surface and within the granules. The processes occurring in the granules formed by the microorganisms are described in detail; they include diffusion in the stagnant film around the granule, diffusion within the particle, and a degradation reaction. From these processes, the reaction term is analytically determined. The granules were modelled as spherical porous biocatalysts of different sizes. The biochemical degradation reactions were assumed to follow Monod type kinetics of the first order. For the numerical solution of the model, a standard program was used (Within MATLAB). The model was applied to some experimental data taken from the literature.

An important characteristic of the model is that it can simultaneously take into account reactions in granules of different sizes. At present, the parameters of the model are calculated using data from the literature; but experimental measurements of the main parameters are planned. The impact of the different parameters was studied by numerical simulation and its validity was tested using experimental data reported in the literature. The model could be a useful tool in the performance optimization of UASB reactors by predicting the influences of different operational parameters.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , v, 63 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:71
Keyword [en]
Anaerobic treatment, UASB, granular biomass, methanogenic activity, modelling, axial dispersion
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9633ISBN: 978-91-7415-178-7 (print)OAI: oai:DiVA.org:kth-9633DiVA: diva2:126778
Presentation
2008-11-11, K51, Teknikringen, KTH, Stockholm, 10:00 (English)
Supervisors
Note
QC 20101116Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-16Bibliographically approved
List of papers
1. Wastewater treatment in Nicaragua
Open this publication in new window or tab >>Wastewater treatment in Nicaragua
2003 (English)In: Proceedings of the 9th Annual IWA Specialised Conference "Design, Operation and Economics of Large Wasewater Treatment Plants", 2003Conference paper, Published paper (Other academic)
Keyword
Municipal wastewater, wastewater treatment, appropriate technologies
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9628 (URN)
Note
QC 20101116Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-16Bibliographically approved
2. Alternatives of Sludge Use in Nicaragua
Open this publication in new window or tab >>Alternatives of Sludge Use in Nicaragua
2005 (English)In: Proceedings of the 27th Annual HWEA Conference "New Technical Knowledge for Clean Water", 2005Conference paper, Published paper (Other academic)
Keyword
Municipal sludge, sludge disposal, sludge use, heavy metals, wastewater treatments
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9629 (URN)
Note
QC 20101116Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-16Bibliographically approved
3. Evaluation of anaerobic sludge activity in wastewater treatment plants in Nicaragua
Open this publication in new window or tab >>Evaluation of anaerobic sludge activity in wastewater treatment plants in Nicaragua
2006 (English)In: Water Pollution VIII: Modelling, Monitoring and Management / [ed] Carlos Alberto Brebbia; J. S. Antunes do Carmo, 2006, 571-579 p.Conference paper, Published paper (Refereed)
Abstract [en]

Sludge of three municipal anaerobic wastewater treatment plants was evaluated. This study was initiated due to the low activity observed in the anaerobic wastewater treatment plants in Nicaragua. An additional goal to select one of them, if possible, as an inoculum for the brewery treatment plant was proposed. Two of these plants work with an Imhoff tank and one with a Septic tank followed by an anaerobic upflow filter. The study consisted in the characterization of biomass in terms of Specific Methanogenic Activity (SMA), Volatile Suspended Solids (VSS), density, pH, and redox potential (RP). The treated waters were also analysed for nutrients, heavy metals and the organic load. The substrate used in the experiments for determining the methanogenic activity was acetic acid. NaHCO3 was added to maintain pH in the normal range of operation. The tests were carried out at a sludge load of 1.5 g VSS/l. The results indicate that treated wastewater does not have any impediment to proper development of microorganisms; no presence of toxic substances and enough essential nutrients were detected. The specific methanogenic activity of sludge (SMA) in the Imhoff tanks is relatively close and oscillates between 0.16-0.28 g CH4-COD/g VSS/day, and in the septic tank is 0.09 g CH4-COD/g VSS/day. These values agree with the methanogenic activity found in the literature for septic tanks (0.02-0.1 g CH4-COD/gVSS/day). The highest methanogenic activity measured during the test was 0.28g CH4-COD/g VSS/day in the sludge of the Imhoff tank in The Viejo city, so this sludge could be proposed as a seed for the brewery treatment plant.

Series
WIT Transactions on Ecology and the Environment, ISSN 1746-448X ; 95
Keyword
anaerobic treatment, sludge, municipal wastewater, specific methanogenic activity, inoculum
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9631 (URN)10.2495/WP060561 (DOI)000242618600056 ()2-s2.0-36248931507 (Scopus ID)1-84564-042-X (ISBN)
Conference
8th International Conference on Modelling, Monitoring and Management of Water Pollution, Bologna, ITALY, SEP, 2006
Note
QC 20101116Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-16Bibliographically approved
4. A Model of kinetics and mass transfer in an UASB reactor
Open this publication in new window or tab >>A Model of kinetics and mass transfer in an UASB reactor
2008 (English)In: Environmental Science and Technology 2008: vol. 1, 2008, 426-433 p.Conference paper, Published paper (Other academic)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9632 (URN)978-0-9768853-0-6 (ISBN)
Conference
The Fourth International Conference on Environmental Science and Technology, July 28-31, 2008, Houston, Texas, USA
Note
QC 20101116Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-16Bibliographically approved

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