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Distribution and activity of ammonium-oxidizing bacteria in Nakivubo wastewater channel and wastewater treatment wetland,Uganda
KTH, School of Biotechnology (BIO).
KTH, School of Biotechnology (BIO).
2006 (English)In: Acta Hydrochimica et Hydrobiologica, ISSN 0323-4320, E-ISSN 1521-401X, Vol. 34, no 1-2, 137-145 p.Article in journal (Refereed) Published
Abstract [en]

The pollution profiles of Nakivubo channel and wetland, and the spatial distribution of ammonium-oxidizing bacteria and the corresponding ammonium-oxidation activities along Nakivubo channel and wetland are presented. A set of physico-chemical and biochemical variables was monitored, and numbers and activity of ammonium-oxidizing bacteria in the water, sediment and epiphyton were quantified to estimate their influence on the nitrification and nitrogen bio-conversions in general, and to determine the factors influencing the distribution of ammonium-oxidizing bacteria in Nakivubo channel and wetland. Considerable numbers of ammonium-oxidizing bacteria and ammonium-oxidation activities were found upstream of Nakivubo channel suggesting that the physico-chemical conditions were suitable for the survival of nitrifying bacteria. However, the longitudinal decline in numbers and activity of ammonium-oxidizers was probably due to (1) high biodegradable organic matter input which supported proliferation of heterotrophs, consuming the little available oxygen, (2) hydro-sedimentary conditions of the channel, (3) die-off due to presence of toxic and inhibitory chemicals and metal compounds. The removal of biochemical oxygen demand was significantly higher than that of nitrogen indicating lower self-purification efficiency for nitrogen. A comparison of the ammonium-oxidation activity of the different phases indicated that epiphytic nitrification was more important than that of sediment and water compartments of the wetland, whereas sediment and suspended nitrifiers were equally important for nitrification upstream of Nakivubo channel.

Place, publisher, year, edition, pages
2006. Vol. 34, no 1-2, 137-145 p.
Keyword [en]
Ammonium-oxidation activity, Epiphyton, Nitrogen, Sediment, Self-purification
National Category
Other Environmental Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4947DOI: 10.1002/aheh.200400617ISI: 000237151300013Scopus ID: 2-s2.0-33646228655OAI: oai:DiVA.org:kth-4947DiVA: diva2:7172
Note
QC 20100909. Uppdaterad från Submitted till Published (20100909). Tidigare titel: "Distribution and activity of ammoniumoxidizing bacteria in Nakivubo channel and wetland systems". Available from: 2005-02-20 Created: 2005-02-20 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Optimizing processes for biological nitrogen removal in Nakivubo wetland, Uganda
Open this publication in new window or tab >>Optimizing processes for biological nitrogen removal in Nakivubo wetland, Uganda
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The ability of Nakivubo wetland (which has performed tertiary water treatment for Kampala city for the past 40 years) to respond to pollution and to protect the water quality of Inner Murchison Bay of Lake Victoria was investigated. The aim of this study was to assess the capacity of Nakivubo wetland to remove nitrogen from the wastewater after its recent encroachment and modification, in order to optimize biological nitrogen removal processes using constructed wetland technology.

Field studies were performed to assess the hydraulic loading, stability and water quality of this wetland. The distribution and activity of ammonium-oxidizing bacteria (AOB) in Nakivubo channel and wetland were also investigated, and the significance of the different matrices in biological nitrogen transformations within the two systems elucidated. Studies to optimize nutrient removal processes were carried out at pilot scale level both in container experiments and in the field using substrate-free constructed wetlands (CWs) planted with Cyperus papyrus and Miscanthidium violaceum which were adapted to the local ecological conditions.

Results showed that Nakivubo wetland performs tertiary treatment for a large volume of wastewater from Kampala city, which is characterised by large quantities of nutrients, organic matter and to a lesser extent metals. Mass pollutant loads showed that wastewater effluent from a sewage treatment plant constituted a larger proportion of nitrogen and phosphorus and biochemical oxygen demand (BOD) discharged into the wetland. The upper section of Nakivubo wetland exhibited high removal efficiencies for BOD, whereas little or no ammonium-nitrogen and metals except Lead were removed by wetland. Studies further showed that nitrifying bacteria existed in the wetland but their activity was limited by oxygen depletion due to the high BOD in the wastewater and heterotrophic bacteria from the sewage treatment plant. Distributional studies indicated the presence of more AOB in surface sediments than the water column of the lower section of Nakivubo channel, an indication that nitrifiers settled with particulate matter prior to discharge into the wetland, and thus did not represent seeding of the wetland. The significant reductions in concentrations of BOD compared to ammonium and total nitrogen in the channel and wetland wastewater confirmed this finding. Whereas suspended nitrifiers upstream of Nakivubo channel equally influenced total nitrogen balance as those in surface sediments, epiphytic nitrification was more important than that of sediment/peat compartments in the wetland, and thus highlighted the detrimental impacts of wetland modification on the water quality Inner Murchison Bay and Lake Victoria as a whole.

Performance assessment of pilot-scale container experiments and field-based CWs indicated highly promising treatment efficiencies, notably in papyrus-based treatments. Plant biomass productivity, nutrient storage, and overall system treatment performance were higher in papyrusbased constructed wetlands, and resulted in effluent that met national discharge limits. Thus, papyrus-based CWs were found to be operationally efficient in removing pollutants from domestic wastewater.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. viii, 62 p.
Keyword
Environmental technology, Ammonium-oxidizing bacteria, Biological nitrogen removal, Coliform retention, Constructed wetlands, Cyperus papyrus, Miljöteknik
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-134 (URN)91-7283-962-7 (ISBN)
Public defence
2005-02-25, Kollegiesalen, Valhallavägen 79, Stokcholm, 14:00
Opponent
Supervisors
Note
QC 20101028Available from: 2005-02-20 Created: 2005-02-20 Last updated: 2010-10-28Bibliographically approved

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