The most common type of nitrogen removal in wastewater treatment plant is to use abiological treatment. When biological treatment is used, the two most common processes fornitrogen removal is pre and post denitrification. In the biological treatment A (BA) atKungsängsverket the nitrogen removal process used is intermittent aeration. Whenintermittent aeration is used, the wastewater is aerated at specific time intervals. This allowsboth nitrification and denitrification to occur in the same water volumes. It is of great interestto find a control strategy for controlling the air supply which is both cost effective and leadsto low emissions of nitrogen. The aim of this project was to improve the intermittent aeration at Kungsängsverket, Uppsala.The project was divided into two parts. The first part consisted of experiments carried out infull scale on the plant and the second part was a simulation study. In the experimental partdifferent time intervals for aeration were evaluated. The aim of the simulation part was toevaluate different control parameters and to find which parameters that should be used for anoptimal control strategy. The results showed that the best combination of aerated time and un-aerated time is 50minutes aerated and 50 minutes unaerated. It is recommended that the wastewater should beadded in the beginning and after half of the plant. The simulation results showed that thecontrol strategy can be improved by using a PI-regulator. The experiments and thesimulations both showed clear signs of variations in the inflow during the day. Because of thisit is recommended to establish a control strategy which easily can change the aeration timedepending on low and high flows. / Biologisk rening av avloppsvatten är den vanligaste typen av kväverening vidavloppsreningsverk. Bioblock A, Kungsängsverket Uppsala, har efter en renovering fått dettidigare driftsättet, kaskadkväverening, utbytt mot intermittent luftning. Intermittent luftninginnebär att nitrifikation och denitrifikation sker i samma zoner. Luftningen startas och stängsav med jämna tidsintervall vilket skapar en miljö för både nitrifikation och denitrifikation. Detär av stort intresse att finna en fungerande styrstrategi för luftningen som både ärkostnadseffektiv och som ger låga halter av kväve i utgående vatten. Syftet med examensarbetet var att effektivisera den intermittenta luftningen vid bioblock Avid Kungsängsverket, Uppsala. Tillvägagångsättet var att genom en utvärdering av detnuvarande driftsättet se vad som kunde förbättras. Det ställdes därefter upp ett antal försöksom var inriktade på att finna bättre driftparametrar. Dessa experiment genomfördes ifullskala. Därefter genomfördes en simuleringsstudie där dagens relästyrning jämfördes medtre regleralternativ. Det första alternativet var att reglera luftningen med hjälp av en PIregulator.De andra två alternativen var att styra luftningsperioderna efter utgåendeammonium-respektive nitrathalt. Fullskaleförsöken indikerade att luftning påslagen i 50 minuter följt av avslagen i 50 minutergav den högsta kvävereduktionen av de undersökta alternativen. Bioblock A är uppdelad ifem olika linjer vilka i sin tur är uppdelade i zoner. Utifrån försöken kan det rekommenderasatt avloppsvattnet tillsätts till första zonen och efter hälften av linjen, istället för som vid dennuvarande driften då vattnet tillsätts efter en fjärdedel och efter hälften av linjen. Simuleringsstudien visade att om dagens relästyrning byttes ut mot en PI-regulator skullesyretopparna minskas och syrehalten stabiliseras vid det förinställda börvärdet. Resultatenfrån både simuleringsstudien och fullskaleförsöken visar att en tidsstyrning avluftningsperioderna är av intresse för att spara energi och få en bättre kväverening.

Approximately 25% of households in the U.S. treat their wastewater onsite using conventional onsite wastewater treatment systems (OWTS). These systems typically include a septic tank or a series of septic tanks followed by a soil absorption system. They effectively remove biochemical oxygen demand (BOD), total suspended solids (TSS), fats and grease but are not designed to remove significant amounts of nitrogen. High nitrogen loading to coastal and ground waters can be dangerous to aquatic life and public health. Hence, there is a need for advanced onsite wastewater treatment systems that can effectively remove nitrogen. Making enhanced nitrogen removal for OWTS as our primary goal, a laboratory scale Hybrid Adsorption and Biological Treatment Systems (HABiTS) was developed and upon observation of its effective nitrogen removal capacity, a pilot demonstration study with two side-by-side HABiTS, one with recirculation and one without recirculation (only forward flow) were constructed and tested at the Northwest Regional Water Reclamation Facility in Hillsborough County (Florida). HABiTS employ biological nitrogen removal and ion exchange for effective nitrogen removal. HABiTS is a two-stage process which uses nitrification for the oxidation of ammonium to nitrate and ion exchange for ammonium adsorption that helps buffer transient loading and also acts as a biofilm carrier in its stage 1 biofilter and it uses tire-sulfur hybrid adsorption denitrification (T-SHAD) in its stage 2 biofilter. These sulfur pellets help promote sulfur oxidation denitrification (SOD) and tire chips are used for nitrate adsorption during transient loading conditions, as biofilm carriers for denitrifying bacteria, and can also be used as organic carbon source to promote heterotrophic denitrification because they leach organic carbon. For this research, HABiTS without recirculation is considered as the control system and the performance of HABiTS with recirculation was tested for its ability to further enhance nitrogen removal from HABiTS. Nitrified effluent recirculation is a common strategy employed in wastewater treatment for enhanced nitrogen removal. It is the reintroduction of semi-treated wastewater to pass through an anoxic pre-treatment chamber to achieve better quality effluent. Recirculation is said to improve and consistently remove nitrogen at any hydraulic loading rate and/or nitrogen concentration. This is because of the dilution of high BOD septic tank effluent with nitrified effluent which lowers COD:TKN ratio and also improves mass transfer of substrates in the stage 1 biofilter. Recirculation also provides some pre-denitrification in the pre-treatment chamber, thereby reducing nitrogen load on the system. The HABiTS with recirculation (R) was run at 1:1 ratio of nitrified effluent recirculation rate to the influent flow rate for 50 days, and at 3:1 ratio for the remaining period of this research (200 days). The forward flow system (FF) was run under constant conditions throughout the research and comparisons between the two systems were made for different water quality parameters (pH, DO, conductivity, alkalinity, TSS, chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and various nitrogen species). The final effluent ammonium results showed that the system with recirculation removed consistently > 80% NH4+-N during 1:1 and 3:1 recirculation ratios whereas the forward flow system achieved 57% removal. Further, an average of 81% total inorganic nitrogen (TIN) removal from the system influent was seen in the recirculation system’s final effluent when compared to an average of 55% in forward flow system’s final effluent. This research explains in detail, the impact of nitrified effluent recirculation on enhanced nitrogen removal in onsite systems and the results presented in this thesis proved that nitrified effluent recirculation provides promising enhanced nitrogen removal in an onsite wastewater treatment system.

High strength wastewater (HSWW) generated in food processing industries is characterized by high organic carbon and nitrogen content, and thus high oxygen demand. Biological nitrogen removal (BNR) is a technology widely used for the treatment of HSWW. Food processing facilities practice sanitation to keep food contact surfaces clean and pathogen-free. Benzalkonium chlorides (BACs) are cationic quaternary ammonium antimicrobial compounds (QACs) common in industrial antimicrobial formulations. BAC-bearing wastewater generated during sanitation applications in food processing facilities is combined with other wastewater streams and typically treated in BNR systems. The poor selectivity and target specificity of the antimicrobial BACs negatively impact the performance of BNR systems due to the susceptibility of BNR microbial populations to BAC. Objectives of the research were: a) assessment and quantification of the inhibitory effect of QACs on the microbial groups, which mediate BNR in HSWW treatment systems while treating QAC-bearing HSWW; b) evaluation of the degree and extent of the contribution of QAC adsorption, inhibition, and biotransformation on the fate and effect of QACs in BNR systems. A laboratory-scale, multi-stage BNR system was continuously fed with real poultry processing wastewater amended with a mixture of three benzalkonium chlorides. The nitrogen removal efficiency initially deteriorated at a BAC feed concentration of 5 mg/L due to complete inhibition of nitrification. However, the system recovered after 27 days of operation achieving high nitrogen removal efficiency, even after the feed BAC concentration was stepwise increased up to120 mg/L. Batch assays performed using the mixed liquors of the BNR system reactors, before, during, and post BAC exposure, showed that the development of BAC biotransformation capacity and the acquisition of resistance to BAC contributed to the recovery of nitrification and nitrogen removal. Kinetic analysis based on sub-models representing BNR processes showed that BAC inhibition of denitrification and nitrification is correlated with BAC liquid-phase and solid-phase concentrations, respectively. Simulations using a comprehensive mathematical BNR model developed for this research showed that BAC degradation and the level of nitrification inhibition by BAC were dynamic brought about by acclimation and enrichment of the heterotrophic and nitrifying microbial populations, respectively. The fate and effect of BACs in the BNR system were accurately described when the interactions between adsorption, inhibition, and resistance/biotransformation were considered within the conditions prevailing in each reactor. This work is the first study on the fate and effect of antimicrobial QACs in a continuous-flow, multi-stage BNR system, and the first study to quantify and report parameter values related to BAC inhibition of nitrification and denitrification. Results of this study enable the rational design and operation of BNR systems for the efficient treatment of QAC-bearing wastewater. The outcome of this research provides information presently lacking, supporting the continuous use of QACs as antimicrobial agents in food processing facilities, when and where needed, while avoiding any negative impacts on biological treatment systems and the environment.

Non-point sources (NPS) of pollution are non-discernable, diffuse sources of pollution that are often difficult to localize and in turn mitigate. NPS can include stormwater runoff, agricultural/aquaculture wastes and wastes from small decentralized wastewater treatment systems, such as conventional septic systems. The mitigation of these NPS is imperative to reduce their potential detrimental effects on the water environment. This dissertation addresses novel treatment technologies for the mitigation of nutrients, particularly nitrogen, in Recirculating Aquaculture Systems (RAS) and onsite wastewater treatment systems (OWTS). The removal of trace organics limiting RAS production and water reuse were also investigated. The first question this dissertation addressed is: Can the application of a UV-TiO2 reactor reduce the concentration of off-flavor compounds in RAS? In the UV-TiO2 reactor, spray-coated TiO2 plates were placed in an aluminum reactor and exposed to UV light. The process was applied in both a full-scale sturgeon RAS and a bench-scale RAS for the degradation of Geosmin (GSM) and 2-methylisoborneol (MIB). Improved performance on the removal of GSM and MIB was observed when the UV-TiO2 was applied as a batch reactor since it allowed for a longer treatment time without the effect of constant production of the compounds in the biological treatment processes. Treatment performance of UV-TiO2 was affected by GSM and MIB concentrations and dissolved oxygen. No harmful effects were observed on other water quality parameters when the UV-TiO2 reactor was operated as a batch or side stream process. The second question this dissertation addressed is: Does the application of Tire-Sulfur Hybrid Adsorption Denitrification (T-SHAD) in RAS improve nutrient and off-flavor compound removal when compared to conventional heterotrophic denitrification? T-SHAD combines tire mulch as an adsorbent and sulfur oxidizing denitrification for the removal of NO3--N from the aquaculture waters. Adsorption studies showed the tire has significant adsorption capacity for the off-flavor compounds GSM and MIB but can be limited by contact time and, possibly, the presence of competing organic matter in RAS. The application of T-SHAD as an effluent polishing step in RAS with a high empty bed contact time (EBCT) of 720 min removed 96.6% of NO3--N and 69.6% of GSM. The application of T-SHAD within RAS as denitrification side treatment for NO3--N removal resulted in lower EBCT (185 min) that limited NO3--N removal to 21% and showed no significant removal of off-flavor compounds. The comparison between T-SHAD and a molasses fed heterotrophic upflow packed bed reactor (UPBR), showed no significant differences in N species concentrations as well as off-flavor compound removal. However, high production of SO42- resulted from sulfur oxidizing denitrification (SOD) processes was noted. Hybrid Adsorption and Biological Treatment Systems (HABiTS), is composed of two biofilters in series employing ion exchange (IX) and nitrification for removal of NH4+ and tire scrap coupled with sulfur chips and oyster shells for both adsorption and SOD of NO3-. The third question addressed in this dissertation is: What IX/adsorption media best balances both ammonium removal and cost effectiveness for application in OWTS? Adsorption isotherms performed with different media materials showed that the zeolite material, clinoptilolite, was the best medium for the nitrification stage of HABiTS due to its high IX capacity for NH4+and cost. An adsorption capacity of 11.69 mg g-1 NH4+-N when in competition with other cations present in septic tank effluents was determined by the IX model fit to the data. The cost of clinoptilolite is significantly higher than the other media materials tested. However, the high adsorption capacity would allow for low dosages that can be combined with non-adsorptive material reducing overall costs. The fourth question this dissertation addressed is: How is the BNR process within HABiTS affected by IX? Results from side-by-side biofilter studies with HABiTS and a conventional nitrification/denitrification biofilter showed that the combined IX and nitrification in HABiTS can allow for faster startup, sustain variable loading, and achieve over 80% removal of NH4+ at a hydraulic loading rate of 0.34 m3 m-2-d-1 when compared to the conventional biofilter with 73% removal. Under lower loading rates the biological treatment was enhanced and dominated the NH4+ removal processes in both columns. The addition of a denitrification stage decreased Total Inorganic Nitrogen (TIN) by 53.54% and 40.97%, for the HABiTS treatment and the control treatment, respectively, under loading rates of 0.21 m3 m-2-d-1. Further decrease of NH4+-N loading rates results in high desorption of exchanged NH4+ in the clinoptilolite, resulting in lower TIN removal efficiencies (28.7%) when compared to the conventional control treatment (62%). The final question addressed in this dissertation is: Does the proposed hybrid system enhance the removal of TIN in OWTS under transient loading conditions? Further studies with HABiTS and the conventional biofilter were performed to determine N removal performance on an hourly basis. It was found that the performance of HABiTS varies with daily and hourly loads, particularly when recovering from periods of very low loading to high loadings and vice versa. If recovering from low loading periods, IX is observed for HABiTS and the biofilter outperforms the conventional treatment in overall TIN removal. However, recovery from a high loading period results in release of NH4+-N stored in the clinoptilolite and increased production of NO3--N that could affect the performance of the denitrification stage.

Data from Hampton Roads Sanitation District was used to calculate nitrification and denitrification rates for the A²/O mode (1987) and the VIP mode (1988) of operation. Nitrification and denitrification rates compared to literature values for similar sludge ages. The mean VIP nitrification rate was eight percent less compared to the A²/O mode. Denitrification varied with the amount of nitrate loading to the anoxic zone and the rate of total nitrate recycle. The amount of denitrification that occurred in each zone during the different operations was determined. Process mode variations caused different percentages in each zone. Anaerobic and anoxic denitrification was a linear function of the mass of nitrate recycled to the anoxic zone. Fifty to seventy-five percent of the denitrification took place in the aerobic basin during both process modes, but more aerobic denitrification occurred for the A²/O operation. Secondary clarifier nitrate varied inversely with the nitrate recycle similarly for both process modes. The differences in sludge production between the VIP and A²/O process could be explained by the differences in mean cell residence time. / Master of Science

No description available.

Groundwater and surface water contamination has been linked in the past to inadequate or failing on-site wastewater treatment and disposal systems. The on-site wastewater systems installed in coastal areas have more potential for inflicting this kind of environmental damage. This work studied the regulatory compliance and environmental protection of the four types of on-site wastewater disposal systems found on the Mississippi Gulf Coast; i.e., vegetative rock filter, subsurface drip irrigation, sand mound, and sprinkler systems, by statistical techniques. Compliance was also evaluated for groundwater samples collected from monitoring wells installed at four corners of a disposal field. This work eventually culminated in formulation of strategy for modifying the aerobic treatment prior to disposal to help reduce nitrogen loading on the discharging environment. Process modeling and simulations were performed to optimize conditions for biological nitrogen reduction in the treatment unit by efficient management of aeration. Two separate proposals were developed, such as either running the aerator unit in a low operating dissolved oxygen concentration or intermittent aeration mode.

A ampla ocorrência de contaminação de águas por compostos de nitrogênio em concentrações superiores às recomendadas pela legislação tem suscitado interesse no desenvolvimento de tecnologias viáveis de remoção desses compostos. A remoção biológica de nitrogênio apresenta como principais vantagens os custos relativamente reduzidos e a possibilidade de maior eficiência. Compostos reduzidos de enxofre como sulfetos podem ser oxidados a enxofre elementar ou a sulfato por bactérias oxidantes de sulfeto que utilizam nitrato ou nitrito como receptor de elétrons. Esta desnitrificação reduz os requerimentos globais de carbono para a remoção de nutrientes, com menor produção de lodo, proporcionando grande economia. O objetivo desta pesquisa consistiu em contribuir para o conhecimento acerca dos aspectos microbiológicos do processo de desnitrificação com o uso de sulfeto. Foram avaliados os efeitos dos modos de operação dos reatores desnitrificantes sobre a biomassa em cada uma das diferentes configurações e monitorada a colonização microbiana por meio de técnicas de Biologia Molecular como PCR/DGGE, sequenciamento e análises filogenéticas. Os fragmentos do gene RNAr 16S foram relacionados aos gêneros Pseudomonas, Aeromonas, Acidobacteria, Chlroroflexi, Clostridium, Cupriavidus e Ralstonia. Filotipos dos clones para o sistema piloto foram associados a bactérias não cultiváveis e Firmicutes envolvidos na digestão anaeróbia em reatores tratando água residuária, Synergistetes, Deferribacteria e Proteobacteria. Foram identificados micro-organismos presentes nos reatores com reconhecida capacidade para desnitrificação: Pseudomonas, Desulfovibrio desulfuricans e Ralstonia. Amostras de ambos os reatores desnitrificantes apresentaram reações de amplificação positivas com primers específicos para bactérias semelhantes a Thiomicrospira associados a primers universais: 100% das amostras amplificaram com OST1F/1492R e 75% com EUB8F/OSTR1R. Para duas condições de operação do reator em escala de bancada foram identificados micro-organismos semelhantes a Sulfurimonas denitrificans, bactéria autotrófica redutora de nitrato e oxidadora de sulfeto. Chloroflexi também foram encontrados em digestores localizados em plantas de tratamento de águas residuárias recebendo essencialmente efluente doméstico e Propionibacterium foi associada a comunidade microbiana de reatores UASB tratando água residuária industrial. Bactérias em associações sintróficas com participação no ciclo do enxofre e/ou na digestão anaeróbia foram igualmente identificadas: Clostridium sulfidigenes e outros Firmicutes, Synergistetes, clones de bactérias de cultura de enriquecimento e bactérias do gênero Syntrophorhabdus. Os resultados deste trabalho proporcionaram associar a colonização microbiana com o desempenho e as características metabólicas de alguns micro-organismos com reatores desnitrificantes combinados para o tratamento de águas residuárias. / The widespread nitrate contamination in concentrations higher than recommended by legislation has raised interest in technologies for water and wastewater treatment. Biological nitrogen removal is relatively low cost and higher efficiency. Sulfide as electron donor can be oxidized to elemental sulfur or sulfate by sulfide oxidizing bacteria that can use nitrate or nitrite as electron acceptor. This type of denitrification reduces the overall requirements for removal of carbon nutrients and less sludge is produced. The aim of this research was to contribute to microbiological knowledge about denitrification using sulfide. The effects of operation conditions on the denitrifying biomass were monitored through molecular biology techniques such as PCR/DGGE, sequencing and phylogenetic analysis. 16S rRNA gene fragments were related to Pseudomonas, Aeromonas, Acidobacteria, Chlroroflexi, Clostridium, Cupriavidus and Ralstonia. Phylotypes of clones from samples of pilot-scale reactor were associated with non-cultivable bacteria and Firmicutes involved in anaerobic digestion of wastewater, Synergistetes, Deferribacteria and Proteobacteria. Microorganisms with ability to denitrification were identified in both reactors: Pseudomonas, Desulfovibrio desulfuricans and Ralstonia. Samples of denitrifying reactors showed positive amplification with specific primers for Thiomicrospira associated to universal primers: 100% of the samples amplified with OST1F/1492R and 75% EUB8F/OSTR1R. Sulfurimonas denitrificans-like were identified for two operational conditions of the bench scale reactor. Chloroflexi were also found in treatment plants digesters receiving domestic wastewater and Propionibacterium was associated with microbial community of UASB reactors treating industrial wastewater. Syntrophic bacteria participating in the sulfur cycle and/or anaerobic digestion were also identified: Clostridium sulfidigenes and other Firmicutes, Synergistetes, clone enrichment culture bacteria and Syntrophorhabdus. These results provide to associate this microbial colonization and metabolic characteristics of some microorganisms with performance of combined denitrifying reactors for treatment of wastewater.

Population growth and aspects related to management water resources, make it extremely important to search for simple wastewater treatment systems, low cost and simplicity operational, capable of producing effluent with potential use for compatible many purposes. In this scenario, the use of aerated reactors as post-treatment of anaerobic effluent is shown quite promising for Brazilian reality. This work contributes to the development of new biofilter system for aerobic treatment of sewage, which is being developed at the Federal University of Rio Grande do Norte. The reactor uses corrugated conduit as cut filler, providing a high void ratio, and is capable of producing effluent with turbidity UT order of 1, 2 mg / L of TSS and COD of below 40 mg / L. IT IS objective of this work to investigate the nitrogen removal capacity by simultaneous nitrification and denitrification. The work was divided into four phases, in which has been changed air flow in the filters, and during step 4, introduced a supplementary source of carbon. The system proved to be effective regarding the removal of nitrogen. In the most efficient configuration It was able to remove 56% of the influent nitrogen, and the less efficient phase removal was 40%. The principal component analysis showed that the nitrification was the most important factor for the process. It was concluded that the system is able to remove nitrogen through nitrification and simultaneous denitrification. Furthermore, it is also important to mention that during the more than three years of the experiment duration was not required removal of retained sludge. / O crescimento da populaÃÃo e aspectos relacionados ao gerenciamento de recursos hÃdricos, fazem com que seja extremamente importante a busca por sistemas de tratamento de esgoto simples, de baixo custo e simplicidade operacional, capazes de produzir efluentes com potencial de utilizaÃÃo para diversos fins compatÃveis. Neste cenÃrio, a utilizaÃÃo de reatores aerados como pÃs-tratamento de efluente anaerÃbio mostra-se bastante promissor para a realidade brasileira. Este trabalho contribui para o desenvolvimento de novo sistema de biofiltros aerÃbios para tratamento de esgotos sanitÃrios, que està sendo desenvolvido na Universidade Federal do Rio Grande do Norte. O reator utiliza eletroduto corrugado cortado como material de enchimento, proporcionando elevado Ãndice de vazios, e à capaz de produzir efluente com turbidez da ordem de 1 UT, 2 mg/L de SST e DQO abaixo de 40 mg/L. à objetivo deste trabalho investigar a capacidade de remoÃÃo de nitrogÃnio pelo processo de nitrificaÃÃo e desnitrificaÃÃo simultÃnea. O trabalho foi dividido em quatro fases, nas quais foi alterada a vazÃo de ar nos filtros, e, durante a fase 4, introduzida uma fonte suplementar de carbono. O sistema mostrou-se eficiente em relaÃÃo à remoÃÃo de nitrogÃnio. Na configuraÃÃo mais eficiente foi capaz de remover 56% do nitrogÃnio afluente, e na fase menos eficiente a remoÃÃo foi de 40%. A anÃlise de componentes principais mostrou que a nitrificaÃÃo foi o fator mais relevante para o processo. Concluiu-se que o sistema à capaz de remover nitrogÃnio pelo processo de nitrificaÃÃo e desnitrificaÃÃo simultÃnea. AlÃm disso, à importante mencionar tambÃm que durante os mais de trÃs anos de duraÃÃo do experimento nÃo foi necessÃria a remoÃÃo do lodo retido.

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. / QC 20101028