From the Proceedings of the 1977 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 15-16, 1977, Las Vegas, Nevada / The purpose and operation of the Central Arizona Project water allocation model system are described, based on a system analysis approach developed over the past 30 years into an interdisciplinary science for the study and resolution of complex technical management problems. The system utilizes mathematical and other simulation models designed for computer operations to effectively solve such problems as the CAP faces including those concerned with social and economic considerations. The model is composed of two major components: (1) a linear program designed to determine the optimal allocation of all sources of water to all demands and, (2) a hydrologic simulator capable of reflecting the impact of distribution alternatives on per-unit cost of delivery. The model, currently being use, has substantially contributed to a greater understanding of water usage potential in Arizona.

From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / The recently- created Arizona Groundwater Management Study Commission is mandated to propose a reform of Arizona's groundwater laws. A number of issues must be addressed by this Commission in order to deal with urban problems with present groundwater law. These include: a comprehensive set of regulations on groundwater use to enhance the public interest and benefit in scarce groundwater resources; a permanent mechanism to permit transfer of water rights away from specific parcels of land; an effective system of management which considers differing types of water problems in various parts of the state; a method of quantifying existing rights and measuring use of groundwater; an extraction tax to recognize public costs associated with groundwater mining and the need for replenishment; a reevaluation of existing preferences and subsidies which encourage the mining of groundwater. Failure by Arizona to reform its groundwater laws threatens future funding for the Central Arizona Project and increases the possibility of federal intervention in state water management.

From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / Tucson's "Beat the Peak" program implemented in the summer of 1977 effectuated a reduction in peak day water usage from 151.5 million gallons per day on July 9, 1976, to 114.0 million gallons per day on July 8, 1977. This twenty-five percent reduction, if maintained, will allow a three -year deferral of a new remote wellfield and transmission pipeline estimated to cost between $25 and $50 million. More time will be available to analyze the cost effectiveness of solutions to the region's water resources supply problems (such as imported groundwater, Central Arizona Project water, effluent reuse, and their interrelationships). Although conservation was not promoted, the successful peak management program resulted in a 13.3 percent reduction in 1977 water use during the summer months (May through August) compared to usage during the same period in 1976. This resulted in water sales revenues less than projected, but the combination of less utility expenses and deferred capital improvements will yield lower customer rates and monthly bills than would have otherwise been necessary without the program.

This thesis analysis the funding possibilities from structural funds for the development of water management in villages as well as different legal acts and international covenants whose regulations corresponds the project The Development of the System for Collecting Waste Water in Kirdoniai Village of Birzai District. It also analysis whether this project corresponds the SPD, its impact on the environment and the EU horizontal politics. In this thesis a lot of data are used, which were processed using ordinary statistical methods along with cost-benefit analysis recommended by the European Commission and the method proposed by the Environmental Project Management Agency used for financial and economic analysis. For data processing DAM and the MS Excel programmes were used. During the research the characteristics of Kirdoniai Village territory in Birzai district were analysed as well as the existing situation of drink water supply and the collection of waste water. It was also examined who could benefit from this project, what problems could this project solve. The formulation of the investment project was carried out. The research results were used by the Municipality Administration of Birzai district, which submitted the application according to the 1st priority “The development of social and economic infrastructure”, the 1.3 measure “The improvement of environment’s quality and the prevention of environmental damage” of activities’ group “The supply of drink water and... [to full text]

L’objectif de ce mémoire est d’examiner l’accès à l’eau d’un point de vue non pas technologique mais social. Toute société humaine a eu à régler la question de l’accès à l’eau. C’est particulièrement le cas des populations vivant sous un climat aride comme au Sahel, où cette ressource est rare. Le village d’étude est situé au nord du Burkina Faso, dans la région du Yatenga. J’examinerai d’abord la répartition temporelle et spatiale des groupes et des puits sur le territoire, puis la question de la régulation de l’accès à l’eau en tant qu’enjeu politique au sein des structures traditionnelles. Je montrerai qu’il permet tantôt de renforcer les hiérarchies sociales existantes, et tantôt de les dépasser. J’examinerai enfin l’accès à l’eau de différents groupes d’usagers : femmes, hommes, jeunes, vieux, agriculteurs, éleveurs. Je montrerai que leur condition d’accès est implicitement régulée, et limite les possibilités d’expansion économique de certains d’entre eux. Dans cette société en mutation, les usagers désavantagés peuvent développer des tactiques leur permettant de contourner ces contraintes. L’accès à l’eau est alors pris dans un jeu de stratégies antagonistes, celle de la reproduction sociale et celle du changement. / The purpose of this report is to examine access to water, not from a technological but from a social point of view. Any human society has had to cope with the issue of access to water. This is especially true for the people living under arid climates such as in Sahel, where water is a limiting resource. The village under study is located in the Yatenga region, north of Burkina Faso. I will first examine the space and time distribution of wells and of human groups in this territory, then I will question the regulation of access to water as a political issue within traditional structures. I will show that it contributes to sometimes strengthen and sometimes circumvent patterns of social hierarchy. Then I will study access to water in different social groups: women, men, younger and older people, elders, farmers, herders. I will show that their access to water is implicitly checked, thus limiting opportunities of economical improvement for some of them. In this developing society, disadvantaged users may develop tactics to circumvent these constraints. Thus access to water is taken between conflicting strategies, pertaining to social reproduction as opposed to social change.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

China has undertaken a vast engineering project: the large-scale transfer of water from the south of the country to the north, the intention being to alleviate flooding in the south and water shortages in the north. It may take up to fifty years to complete. This thesis examines the broad outline of the scheme, the planning that has gone into it, its historical and political background, and the political, social, and ecological problems that it has encountered and may be likely to cause in the future. The political context of a 'pro-technology' policy amongst today's Chinese leaders is highlighted. The Chinese study is made in the light of water-transfer schemes that have been implemented, or proposed, in other countries; and also ideas about sustainable development, policy processes, and natural resource management. Five case studies are considered: the Aral Sea (Central Asia), the Snowy Mountain Scheme (Australia), the National Hydrological Plan (Spain), the Central Arizona Project (the United States) and the South-to-North Water Transfer Project (China). They are examined as a basis for understanding policy problems and processes in water resource management, and also to make some suggestions for their resolution in the Chinese case―though finding a permanent or definitive solution lies beyond the scope of the present inquiry. The difficulties for traditional policy processes to manage uncertainty and complexity are particularly acute in the area of natural resource management. For example, climate change issues challenge present water management systems and diversion projects. Therefore, uncertainty and complexity issues, beyond the 'ideal' policy cycle, are considered, particularly in relation to climate change, but also the water diversion schemes themselves. Climate change presents a particularly important challenge to the Chinese Project.

The aim of this thesis was to identify the denitrifying microbial communities in activated sludge from full-scale treatment plants and from small-scale reactors exposed to acetate or methanol as external carbon sources. Biological denitrification is currently the most widely used, sustainable and cost-effective process to remove nitrogen from wastewater. Increasingly strict effluent discharge standards are posing significant challenges to plant operators to reduce effluent NO3--N concentrations to levels as low as 2-3 mg L-1 or even lower. The lack of sufficient influent carbon in many municipal wastewater treatment plants makes it very difficult to achieve such low NO3--N concentrations in the effluent. An effective solution to the problem is to introduce additional external carbon sources to enhance denitrification. The selection of external carbon sources is not purely based on costs but is also dependent on the possible microbial transformations that these carbon sources may bring about in activated sludge. The most common carbon source used is methanol due to its low cost, but it has been found to cause long delays until an improvement in denitrification performance is observed. On the other hand, acetate has been found to improve denitrification almost instantaneously when added, but it has a significantly higher cost. In this study, methanol and acetate utilising denitrifiers were investigated in activated sludge with and without enrichment in laboratory scale bioreactors. The relevant denitrifiers were identified and evaluated in situ using culture independent methods particularly stable isotope probing (SIP), 16S rDNA cloning, fluorescence in situ hybridisation (FISH) and microautoradiography (MAR). Activated sludge collected from a biological nutrient removal plant exhibiting good denitrification was enriched in an anoxically-operated sequencing batch reactor (SBR) by feeding methanol as the sole carbon source and nitrate as the electron acceptor. The SBR was operated over a duration of 7 months and the SBR denitrification rate improved from 0.02 mg NO3--N mg mixed liquor volatile suspended solids (MLVSS)-1 h-1 to a steady-state value of 0.06 mg NO3-N mg MLVSS-1 h-1. At steady state operation the enriched biomass was subjected to SIP with 13C-methanol to biomark the denitrifiers capable of utilising methanol under anoxic conditions. The separated 12C-DNA and 13C-DNA fractions from the SIP experiment were individually subjected to full cycle rRNA analysis. The dominant 16S rRNA gene phylotype (Group-A clones) in the 13C-library was closely related to the obligate methylotrophs Methylobacillus and Methylophilus in the order Methylophilales of the Betaproteobacteria (96-97% sequence identities), while the most abundant clone groups in the 12C-library mostly belonged to the family Saprospiraceae in the Bacteroidetes phylum. Oligonucleotide probes were designed for FISH to target the Group-A clones and Methylophilales (probes DEN67 and MET1216, respectively) and the Saprospiraceae clones (probe SAP553). Application of these probes on SBR biomass over the enrichment period demonstrated a strong correlation between the level of SBR denitrification and relative abundance of DEN67-targeted bacteria in the SBR community. By contrast, no correlation was found between denitrification rate and the relative abundances of the well known denitrifying genera Hyphomicrobium and Paracoccus nor the Saprospiraceae-clones visualised by FISH in the SBR biomass. FISH combined with microautoradiography independently confirmed that the DEN67-targeted cells were the dominant bacterial group capable of anoxic [14C] methanol uptake in the enriched biomass. As observed in full-scale operations, the methanol-fed SBR experienced a lag period of several weeks before denitrification performance increased. Using FISH quantification, it was shown that this coincided with the lag phase in the growth of the DEN67-targeted denitrifying population. It was therefore concluded that the Methylophilales bacteria dominant in our SBR system are likely to be important in full-scale methanol-fed denitrifying sludges. The acetate utilising microbial consortium in activated sludge was investigated without prior enrichment using stable isotope probing (SIP). 13C-acetate was used in SIP to biomark the DNA of the denitrifiers. The extracted 13C-DNA fraction was subjected to a full cycle rRNA analysis. The dominant 16S rRNA gene phylotypes in the 13C-library were closely related to bacterial families Comamonadaceae and Rhodocyclaceae of class Betaproteobacteria (96-97% sequence identities). Seven oligonucleotide probes (DEN444, DEN220, DEN581, DEN441, DEN124, DEN220a and DEN1454) for use in FISH was designed to specifically target the identified phylotypes. Application of these probes on the sludge of a continuously fed denitrifying sequencing batch reactor (CFDSBR) operated over a duration of 16 days indicated a strong correlation between the level of CFDSBR denitrification and relative abundance of all probe-targeted bacteria in the CFDSBR community. FISH combined with microautoradiography (FISH-MAR) further confirmed that the DEN581- and DEN124-targeted cells dominating the CFDSBR were capable of taking up [14C] acetate under anoxic conditions. The initial occurrence of the DEN444- and DEN1454-targeted bacteria and the final dominance of DEN581- and DEN124-targeted bacteria in the CFDSBR community were likely related to the changing in-reactor nitrite concentrations during the first few days of CFDSBR operation. Hence, the DEN444- and DEN1454-targeted bacteria were hypothesised to have low affinities for nitrite while DEN124- and DEN581-targeted bacteria have higher nitrite affinities. However, it was clear that all probe-targeted bacteria were denitrifiers capable of utilising acetate as a carbon source. The rapid increase in numbers of the probe-targeted organisms positively correlates with the immediate increase in denitrification rates. The rapid response and community shifts observed when acetate was used to enhance denitrification suggest that an intermittent application of acetate is quite effective to temporarily enhance the denitrification capacity of a treatment plant. However, the importance of a bacterial impact assessment of activated sludge subjected to intermittent acetate supplementation is recommended prior to the wide use of acetate in the wastewater industry. The acetate utilising denitrifying microbial communities investigated in the previous chapter were characterised according to their eco-physiological properties using the r- and K-selection criteria. The electron donor (acetate) and acceptor (nitrite) affinities of these probe-identified denitrifiers were used as traits for this characterisation. The substrate to microorganism (S/M) ratio was manipulated to provide high and low substrate concentrations in the reactor to create conditions favourable for r- and K-strategists, respectively. Two factors, namely feeding regimes and sludge retention times, were studied to achieve the desired S/M ratios and enable r/K characterisation. The high substrate affinities and high specific growth rates of two probe-identified denitrifiers (DEN124 and DEN581) did not enable resolution of these two organisms with the feeding regimes used in this study. However, the application of different sludge retention times as a control strategy to maintain constant high and low in-reactor S/M ratios enabled characterisation of the two probe-targeted denitrifiers DEN124 and DEN581 as K- and r-strategists, respectively. The in-reactor S/M ratios applied in this study did not facilitate the characterisation of populations targeted by probes DEN444 and DEN1454. The minor fluctuations of the S/M ratios during a cycle in the SBR operation was considered as a drawback, but conclusive results could still be obtained from the study. A chemostat reactor operation with constant loading and variable flow rates is suggested as an alternative. Conclusively, this study was able to identify specific groups of denitrifying microorganisms in activated sludge when exposed to acetate and methanol. Unlike most previous studies, which relied on culture dependent methods, this study adopted a pure culture independent approach to identify microorganisms in relation to their function, i.e. denitrification. Moreover, acetate denitrifiers were in situ characterised based on eco-physiological properties. The identification of denitrifying communities in this study has paved the way to a larger research project on the optimisation of denitrification processes with external acetate, methanol and other carbon supplements. As such, this study has contributed significantly to the understanding of the denitrification processes by linking process data with microbial investigations.

The aim of this thesis was to identify the denitrifying microbial communities in activated sludge from full-scale treatment plants and from small-scale reactors exposed to acetate or methanol as external carbon sources. Biological denitrification is currently the most widely used, sustainable and cost-effective process to remove nitrogen from wastewater. Increasingly strict effluent discharge standards are posing significant challenges to plant operators to reduce effluent NO3--N concentrations to levels as low as 2-3 mg L-1 or even lower. The lack of sufficient influent carbon in many municipal wastewater treatment plants makes it very difficult to achieve such low NO3--N concentrations in the effluent. An effective solution to the problem is to introduce additional external carbon sources to enhance denitrification. The selection of external carbon sources is not purely based on costs but is also dependent on the possible microbial transformations that these carbon sources may bring about in activated sludge. The most common carbon source used is methanol due to its low cost, but it has been found to cause long delays until an improvement in denitrification performance is observed. On the other hand, acetate has been found to improve denitrification almost instantaneously when added, but it has a significantly higher cost. In this study, methanol and acetate utilising denitrifiers were investigated in activated sludge with and without enrichment in laboratory scale bioreactors. The relevant denitrifiers were identified and evaluated in situ using culture independent methods particularly stable isotope probing (SIP), 16S rDNA cloning, fluorescence in situ hybridisation (FISH) and microautoradiography (MAR). Activated sludge collected from a biological nutrient removal plant exhibiting good denitrification was enriched in an anoxically-operated sequencing batch reactor (SBR) by feeding methanol as the sole carbon source and nitrate as the electron acceptor. The SBR was operated over a duration of 7 months and the SBR denitrification rate improved from 0.02 mg NO3--N mg mixed liquor volatile suspended solids (MLVSS)-1 h-1 to a steady-state value of 0.06 mg NO3-N mg MLVSS-1 h-1. At steady state operation the enriched biomass was subjected to SIP with 13C-methanol to biomark the denitrifiers capable of utilising methanol under anoxic conditions. The separated 12C-DNA and 13C-DNA fractions from the SIP experiment were individually subjected to full cycle rRNA analysis. The dominant 16S rRNA gene phylotype (Group-A clones) in the 13C-library was closely related to the obligate methylotrophs Methylobacillus and Methylophilus in the order Methylophilales of the Betaproteobacteria (96-97% sequence identities), while the most abundant clone groups in the 12C-library mostly belonged to the family Saprospiraceae in the Bacteroidetes phylum. Oligonucleotide probes were designed for FISH to target the Group-A clones and Methylophilales (probes DEN67 and MET1216, respectively) and the Saprospiraceae clones (probe SAP553). Application of these probes on SBR biomass over the enrichment period demonstrated a strong correlation between the level of SBR denitrification and relative abundance of DEN67-targeted bacteria in the SBR community. By contrast, no correlation was found between denitrification rate and the relative abundances of the well known denitrifying genera Hyphomicrobium and Paracoccus nor the Saprospiraceae-clones visualised by FISH in the SBR biomass. FISH combined with microautoradiography independently confirmed that the DEN67-targeted cells were the dominant bacterial group capable of anoxic [14C] methanol uptake in the enriched biomass. As observed in full-scale operations, the methanol-fed SBR experienced a lag period of several weeks before denitrification performance increased. Using FISH quantification, it was shown that this coincided with the lag phase in the growth of the DEN67-targeted denitrifying population. It was therefore concluded that the Methylophilales bacteria dominant in our SBR system are likely to be important in full-scale methanol-fed denitrifying sludges. The acetate utilising microbial consortium in activated sludge was investigated without prior enrichment using stable isotope probing (SIP). 13C-acetate was used in SIP to biomark the DNA of the denitrifiers. The extracted 13C-DNA fraction was subjected to a full cycle rRNA analysis. The dominant 16S rRNA gene phylotypes in the 13C-library were closely related to bacterial families Comamonadaceae and Rhodocyclaceae of class Betaproteobacteria (96-97% sequence identities). Seven oligonucleotide probes (DEN444, DEN220, DEN581, DEN441, DEN124, DEN220a and DEN1454) for use in FISH was designed to specifically target the identified phylotypes. Application of these probes on the sludge of a continuously fed denitrifying sequencing batch reactor (CFDSBR) operated over a duration of 16 days indicated a strong correlation between the level of CFDSBR denitrification and relative abundance of all probe-targeted bacteria in the CFDSBR community. FISH combined with microautoradiography (FISH-MAR) further confirmed that the DEN581- and DEN124-targeted cells dominating the CFDSBR were capable of taking up [14C] acetate under anoxic conditions. The initial occurrence of the DEN444- and DEN1454-targeted bacteria and the final dominance of DEN581- and DEN124-targeted bacteria in the CFDSBR community were likely related to the changing in-reactor nitrite concentrations during the first few days of CFDSBR operation. Hence, the DEN444- and DEN1454-targeted bacteria were hypothesised to have low affinities for nitrite while DEN124- and DEN581-targeted bacteria have higher nitrite affinities. However, it was clear that all probe-targeted bacteria were denitrifiers capable of utilising acetate as a carbon source. The rapid increase in numbers of the probe-targeted organisms positively correlates with the immediate increase in denitrification rates. The rapid response and community shifts observed when acetate was used to enhance denitrification suggest that an intermittent application of acetate is quite effective to temporarily enhance the denitrification capacity of a treatment plant. However, the importance of a bacterial impact assessment of activated sludge subjected to intermittent acetate supplementation is recommended prior to the wide use of acetate in the wastewater industry. The acetate utilising denitrifying microbial communities investigated in the previous chapter were characterised according to their eco-physiological properties using the r- and K-selection criteria. The electron donor (acetate) and acceptor (nitrite) affinities of these probe-identified denitrifiers were used as traits for this characterisation. The substrate to microorganism (S/M) ratio was manipulated to provide high and low substrate concentrations in the reactor to create conditions favourable for r- and K-strategists, respectively. Two factors, namely feeding regimes and sludge retention times, were studied to achieve the desired S/M ratios and enable r/K characterisation. The high substrate affinities and high specific growth rates of two probe-identified denitrifiers (DEN124 and DEN581) did not enable resolution of these two organisms with the feeding regimes used in this study. However, the application of different sludge retention times as a control strategy to maintain constant high and low in-reactor S/M ratios enabled characterisation of the two probe-targeted denitrifiers DEN124 and DEN581 as K- and r-strategists, respectively. The in-reactor S/M ratios applied in this study did not facilitate the characterisation of populations targeted by probes DEN444 and DEN1454. The minor fluctuations of the S/M ratios during a cycle in the SBR operation was considered as a drawback, but conclusive results could still be obtained from the study. A chemostat reactor operation with constant loading and variable flow rates is suggested as an alternative. Conclusively, this study was able to identify specific groups of denitrifying microorganisms in activated sludge when exposed to acetate and methanol. Unlike most previous studies, which relied on culture dependent methods, this study adopted a pure culture independent approach to identify microorganisms in relation to their function, i.e. denitrification. Moreover, acetate denitrifiers were in situ characterised based on eco-physiological properties. The identification of denitrifying communities in this study has paved the way to a larger research project on the optimisation of denitrification processes with external acetate, methanol and other carbon supplements. As such, this study has contributed significantly to the understanding of the denitrification processes by linking process data with microbial investigations.

The aim of this thesis was to identify the denitrifying microbial communities in activated sludge from full-scale treatment plants and from small-scale reactors exposed to acetate or methanol as external carbon sources. Biological denitrification is currently the most widely used, sustainable and cost-effective process to remove nitrogen from wastewater. Increasingly strict effluent discharge standards are posing significant challenges to plant operators to reduce effluent NO3--N concentrations to levels as low as 2-3 mg L-1 or even lower. The lack of sufficient influent carbon in many municipal wastewater treatment plants makes it very difficult to achieve such low NO3--N concentrations in the effluent. An effective solution to the problem is to introduce additional external carbon sources to enhance denitrification. The selection of external carbon sources is not purely based on costs but is also dependent on the possible microbial transformations that these carbon sources may bring about in activated sludge. The most common carbon source used is methanol due to its low cost, but it has been found to cause long delays until an improvement in denitrification performance is observed. On the other hand, acetate has been found to improve denitrification almost instantaneously when added, but it has a significantly higher cost. In this study, methanol and acetate utilising denitrifiers were investigated in activated sludge with and without enrichment in laboratory scale bioreactors. The relevant denitrifiers were identified and evaluated in situ using culture independent methods particularly stable isotope probing (SIP), 16S rDNA cloning, fluorescence in situ hybridisation (FISH) and microautoradiography (MAR). Activated sludge collected from a biological nutrient removal plant exhibiting good denitrification was enriched in an anoxically-operated sequencing batch reactor (SBR) by feeding methanol as the sole carbon source and nitrate as the electron acceptor. The SBR was operated over a duration of 7 months and the SBR denitrification rate improved from 0.02 mg NO3--N mg mixed liquor volatile suspended solids (MLVSS)-1 h-1 to a steady-state value of 0.06 mg NO3-N mg MLVSS-1 h-1. At steady state operation the enriched biomass was subjected to SIP with 13C-methanol to biomark the denitrifiers capable of utilising methanol under anoxic conditions. The separated 12C-DNA and 13C-DNA fractions from the SIP experiment were individually subjected to full cycle rRNA analysis. The dominant 16S rRNA gene phylotype (Group-A clones) in the 13C-library was closely related to the obligate methylotrophs Methylobacillus and Methylophilus in the order Methylophilales of the Betaproteobacteria (96-97% sequence identities), while the most abundant clone groups in the 12C-library mostly belonged to the family Saprospiraceae in the Bacteroidetes phylum. Oligonucleotide probes were designed for FISH to target the Group-A clones and Methylophilales (probes DEN67 and MET1216, respectively) and the Saprospiraceae clones (probe SAP553). Application of these probes on SBR biomass over the enrichment period demonstrated a strong correlation between the level of SBR denitrification and relative abundance of DEN67-targeted bacteria in the SBR community. By contrast, no correlation was found between denitrification rate and the relative abundances of the well known denitrifying genera Hyphomicrobium and Paracoccus nor the Saprospiraceae-clones visualised by FISH in the SBR biomass. FISH combined with microautoradiography independently confirmed that the DEN67-targeted cells were the dominant bacterial group capable of anoxic [14C] methanol uptake in the enriched biomass. As observed in full-scale operations, the methanol-fed SBR experienced a lag period of several weeks before denitrification performance increased. Using FISH quantification, it was shown that this coincided with the lag phase in the growth of the DEN67-targeted denitrifying population. It was therefore concluded that the Methylophilales bacteria dominant in our SBR system are likely to be important in full-scale methanol-fed denitrifying sludges. The acetate utilising microbial consortium in activated sludge was investigated without prior enrichment using stable isotope probing (SIP). 13C-acetate was used in SIP to biomark the DNA of the denitrifiers. The extracted 13C-DNA fraction was subjected to a full cycle rRNA analysis. The dominant 16S rRNA gene phylotypes in the 13C-library were closely related to bacterial families Comamonadaceae and Rhodocyclaceae of class Betaproteobacteria (96-97% sequence identities). Seven oligonucleotide probes (DEN444, DEN220, DEN581, DEN441, DEN124, DEN220a and DEN1454) for use in FISH was designed to specifically target the identified phylotypes. Application of these probes on the sludge of a continuously fed denitrifying sequencing batch reactor (CFDSBR) operated over a duration of 16 days indicated a strong correlation between the level of CFDSBR denitrification and relative abundance of all probe-targeted bacteria in the CFDSBR community. FISH combined with microautoradiography (FISH-MAR) further confirmed that the DEN581- and DEN124-targeted cells dominating the CFDSBR were capable of taking up [14C] acetate under anoxic conditions. The initial occurrence of the DEN444- and DEN1454-targeted bacteria and the final dominance of DEN581- and DEN124-targeted bacteria in the CFDSBR community were likely related to the changing in-reactor nitrite concentrations during the first few days of CFDSBR operation. Hence, the DEN444- and DEN1454-targeted bacteria were hypothesised to have low affinities for nitrite while DEN124- and DEN581-targeted bacteria have higher nitrite affinities. However, it was clear that all probe-targeted bacteria were denitrifiers capable of utilising acetate as a carbon source. The rapid increase in numbers of the probe-targeted organisms positively correlates with the immediate increase in denitrification rates. The rapid response and community shifts observed when acetate was used to enhance denitrification suggest that an intermittent application of acetate is quite effective to temporarily enhance the denitrification capacity of a treatment plant. However, the importance of a bacterial impact assessment of activated sludge subjected to intermittent acetate supplementation is recommended prior to the wide use of acetate in the wastewater industry. The acetate utilising denitrifying microbial communities investigated in the previous chapter were characterised according to their eco-physiological properties using the r- and K-selection criteria. The electron donor (acetate) and acceptor (nitrite) affinities of these probe-identified denitrifiers were used as traits for this characterisation. The substrate to microorganism (S/M) ratio was manipulated to provide high and low substrate concentrations in the reactor to create conditions favourable for r- and K-strategists, respectively. Two factors, namely feeding regimes and sludge retention times, were studied to achieve the desired S/M ratios and enable r/K characterisation. The high substrate affinities and high specific growth rates of two probe-identified denitrifiers (DEN124 and DEN581) did not enable resolution of these two organisms with the feeding regimes used in this study. However, the application of different sludge retention times as a control strategy to maintain constant high and low in-reactor S/M ratios enabled characterisation of the two probe-targeted denitrifiers DEN124 and DEN581 as K- and r-strategists, respectively. The in-reactor S/M ratios applied in this study did not facilitate the characterisation of populations targeted by probes DEN444 and DEN1454. The minor fluctuations of the S/M ratios during a cycle in the SBR operation was considered as a drawback, but conclusive results could still be obtained from the study. A chemostat reactor operation with constant loading and variable flow rates is suggested as an alternative. Conclusively, this study was able to identify specific groups of denitrifying microorganisms in activated sludge when exposed to acetate and methanol. Unlike most previous studies, which relied on culture dependent methods, this study adopted a pure culture independent approach to identify microorganisms in relation to their function, i.e. denitrification. Moreover, acetate denitrifiers were in situ characterised based on eco-physiological properties. The identification of denitrifying communities in this study has paved the way to a larger research project on the optimisation of denitrification processes with external acetate, methanol and other carbon supplements. As such, this study has contributed significantly to the understanding of the denitrification processes by linking process data with microbial investigations.