Among all nanomaterials, which are intentionally manufactured and applied, nanosilver (nAg) is one of the most frequently applied nanomaterials. It is introduced into wastewater treatment plants (WWTPs) due to its use as antimicrobial resource in household and medical care products and hence concern raised regarding its impact on activated sludge organisms and their purification efficiency. Within this thesis, the effects of nAg on single species, simple food chains and communities related to activated sludge were investigated. Among all tested species in this thesis, the gammaproteobacteria R. planticola was the most sensitive organism regarding the tested nAg material, NM-300K. The environmental risk assessment (ERA), based on an assumed predicted environmental concentration derived from modeled concentrations of other types of nAg, revealed no risk for the activated sludge. This result should be interpreted with care, considering the tolerantly chosen safety factor for calculation of the predicted no effect concentration and the assumptions which were made concerning environmental concentrations. Differences in acute toxic effects of nAg on the ciliate P. tetraurelia were observed depending on the type of medium and the exposure pathway (via medium or via bacterial food). More detailed investigations are required to analyze the distribution, availability and uptake of nAg into ciliates in the respective tests. In chronic experiments concentration response was very steep in the range between the effect concentration determined in acute toxicity testing (resulting in 100% mortality) and a tenfold lower concentration (no effect observed) for both exposure pathways. Community experiments with activated sludge exposed to realistic and high concentrations of nAg revealed acute effects on the protozoan community at high nAg concentration using multivariate statistics for data analysis. In contrast, the sludge biotic index was not meaningful for data interpretation, as no differences were observed between the samples of different treatments. For chronic testing, more preliminary work is required to develop a protocol for artificial wastewater which serves the needs of activated sludge organisms over longer time periods and which retains a typical composition of the activated sludge community.

Pharmaceutical residues are passing our wastewater treatment plants and flowing out in to the nature. The medical substances are built to affect different processes in our bodies, but also affect other species and increase the risk of developing multi resistant bacterial strains, not curable with antibiotics. This has made wastewater treatment plants (WWTPs) interested in investing in pharmaceutical removal. This study describes what criteria that are important to consider when choosing technology for pharmaceutical removal, and presents a model for the WWTPs to use when choosing pharmaceutical removal technology. Secondly, the study presents a reasoning regarding business model concepts. These concepts are presented to aid suppliers of pharmaceutical removal technology, when designing their business models. The method of choice is a qualitative research study based on interviews and document analysis. / Aktiva läkemdelssubstanser passerar idag våra reningsverk oförändrade och rinner ut i naturen. Dessa substanser är tillverkade för att påverka olika biologiska processer i våra kroppar, men de påverkar också andra arter och ökar risken för att utveckla antibiotikaresistenta bakterier som vi inte kan bota oss från. Dessa risker har gjort reningsverk intresserade av att investera i läkemedelsrening. Denna studie beskriver vilka kriterier som är viktiga att överväga vid val av teknik för läkemedelsrening och presenterar sedan en modell som reningsverk kan använda när de väljer teknik för läkemedelsrening. Ett resonemang förs också kring olika affärsmodellskoncept som kan nyttjas av leverantörer av teknik för läkemedelsrening, när de utvecklar sina affärsmodeller. Den valda metoden för studien är baserat på ett kvalitativt förhållningssätt med intervjuer och dokumentanalyser.

Industrial effluents with high concentrations of heavy metals are widespread pollutants of great concerns as they are known to be persistent and non-degradable. Continuous monitoring and treatment of the effluents become pertinent because of their impacts on wastewater treatment plants. The aim of this study is to determine the correlation between heavy metal pollution in water and the location of industries in order to ascertain the effectiveness of the municipal waste water treatment plant. Heavy metal identification and physico-chemical analysis were done using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and multi-parameter probe respectively. Correlation coefficients of the measured values were done to investigate the effect of the industrial effluents on the treatment plants. Heavy metal resistant bacteria were identified and characterised by polymerase chain reaction and sequencing. Leeuwkuil wastewater treatment plants were effective in maintaining temperature, pH, and chemical oxygen demand within South Africa green drop and SAGG Standards whereas the purification plant was effective in maintaining the values of Cu, Zn, Al, temperature, BOD, COD, and TDS within the SANS and WHO standard for potable water. This findings indicated the need for the treatment plants to be reviewed.The industrial wastewater were identified as a point source of heavy metal pollution that influenced Leeuwkuil wastewater treatment plants and the purification plants in Vaal, Vereenining South Africa. Pseudomonas aeruginosa, Serratia marcescens, Bacillus sp. strain and Bacillus toyonensis that showed 100% similarity were found to be resistant to Al, Cu, Pb and Zn. These identified bacteria can be considered for further study in bioremediation. / Environmental Sciences / M. Sc. (Environmental Science)

South Africa is a water-scarce country and over the years, the quality of water resources has deteriorated due to poor effluent discharge, agricultural, industrial, mining and human activities. The major contributing factors of poorly-treated or inadequately treated wastewater may be attributed to: (a) the poor design and construction of wastewater treatment plants; (b) lack of qualified process controllers; (c) non-compliance with applicable legislation; (d) lack of proper monitoring; and (e) management issues with regard to wastewater treatment plants. Water quality is important as many communities depend on water resources for their daily activities and livelihood. There is a need therefore to build and manage wastewater treatment plants effectively as they have an impact on water quality. Wastewater treatment plants in South Africa are regulated by the Constitution of the Republic of South Africa, 1996, the National Environmental Management Act 107 of 1998, the National Water Act 36 of 1998, the Water Services Act 108 of 1997, Provincial legislation, Municipal by-laws and other Government policies applicable to Local Government. Chapter 7 of the Constitution inter alia, provides that Local Government has the duty to provide a safe and healthy environment to its community in a sustainable manner. Schedule 4B of the Constitution imposes the function of delivering water, sanitation and wastewater treatment services on Municipalities. This responsibility rests on District Municipalities but may be performed by a Local Municipality if the district municipality lacks the capacity to do so. Although Local Government has the right to govern on its own initiative the affairs of its communities, it needs support and monitoring from other spheres of Government (National and Provincial) to ensure the delivery of wastewater treatment services in a sustainable manner. In this study, Ba-Phalaborwa Local Municipality is used as an example of a Municipality in the Limpopo Province faced with challenges related to the operation and management of its wastewater treatment plant. This study aims to determine who should be responsible for the regulation of wastewater treatment plants in Ba-Phalaborwa Local Municipality area in order to ensure service delivery to communities in a sustainable manner. In order to deal with the challenges experienced by Local Government in dealing with wastewater treatment plants, the study considers Best Practice Guidelines and external service delivery mechanisms, specifically in the form of Public-Private Partnerships. The study concludes with recommendations based on Best Practice Guidelines which Municipalities can use to avoid wastewater pollution and proposes management mechanisms in managing a Public-Private Partnership effectively in order to ensure that they provide service delivery in a sustainable manner. / LLM (Environmental Law and Governance), North-West University, Potchefstroom Campus, 2014

South Africa is a water-scarce country and over the years, the quality of water resources has deteriorated due to poor effluent discharge, agricultural, industrial, mining and human activities. The major contributing factors of poorly-treated or inadequately treated wastewater may be attributed to: (a) the poor design and construction of wastewater treatment plants; (b) lack of qualified process controllers; (c) non-compliance with applicable legislation; (d) lack of proper monitoring; and (e) management issues with regard to wastewater treatment plants. Water quality is important as many communities depend on water resources for their daily activities and livelihood. There is a need therefore to build and manage wastewater treatment plants effectively as they have an impact on water quality. Wastewater treatment plants in South Africa are regulated by the Constitution of the Republic of South Africa, 1996, the National Environmental Management Act 107 of 1998, the National Water Act 36 of 1998, the Water Services Act 108 of 1997, Provincial legislation, Municipal by-laws and other Government policies applicable to Local Government. Chapter 7 of the Constitution inter alia, provides that Local Government has the duty to provide a safe and healthy environment to its community in a sustainable manner. Schedule 4B of the Constitution imposes the function of delivering water, sanitation and wastewater treatment services on Municipalities. This responsibility rests on District Municipalities but may be performed by a Local Municipality if the district municipality lacks the capacity to do so. Although Local Government has the right to govern on its own initiative the affairs of its communities, it needs support and monitoring from other spheres of Government (National and Provincial) to ensure the delivery of wastewater treatment services in a sustainable manner. In this study, Ba-Phalaborwa Local Municipality is used as an example of a Municipality in the Limpopo Province faced with challenges related to the operation and management of its wastewater treatment plant. This study aims to determine who should be responsible for the regulation of wastewater treatment plants in Ba-Phalaborwa Local Municipality area in order to ensure service delivery to communities in a sustainable manner. In order to deal with the challenges experienced by Local Government in dealing with wastewater treatment plants, the study considers Best Practice Guidelines and external service delivery mechanisms, specifically in the form of Public-Private Partnerships. The study concludes with recommendations based on Best Practice Guidelines which Municipalities can use to avoid wastewater pollution and proposes management mechanisms in managing a Public-Private Partnership effectively in order to ensure that they provide service delivery in a sustainable manner. / LLM (Environmental Law and Governance), North-West University, Potchefstroom Campus, 2014

Thesis (MPA)--Stellenbosch University, 2014. / The asset management process and strategy has been adopted and implemented within the public sector. Although the National Treasury developed the Capital Asset Management Guidelines to assist with the development and implementation of the asset management system the guidelines have received very little attention over the years. The Auditor General’s findings indicate a lack of proper implementation of the asset management process. The study provides a clear indication of the implementation of the asset management process by most government entities, local government municipalities and the public sector. The outcome is that while most entities have made progress with regards to the implementation, much remains to be done. Most entities implement the asset management process selectively. This does not yield positive and sustainable results and they end up abandoning the whole asset management system. The report provides the process of successful development and implementation of asset management, it also indicate that if there are element that are missed or not properly done the process will not yield constant results or performance and the impact on the organization performance will not be positive. The management of the organization must ensure that asset management is aligned with strategic objectives of the organization and performance measurement must be directly linked with asset management, performance measurement should be used to determine progress and implementation. Service level agreements must be established between all relevant departments including the finance department and there must be agreement on the objectives between all stakeholders. The key to proper implementation is the alignment of the asset management process with the strategic objectives of the organization.

Submitted in complete fulfillment for the degree of Doctor of Philosophy (Biotechnology), Durban University of Technology, Durban, South Africa, 2016. / Seasonal nitrification breakdown is a major problem in wastewater treatment plants which makes it difficult for the plant operators to meet discharge limits. The present study focused on understanding the seasonal impact of environmental and operational parameters on nitrifiers and nitrification, in a biological nutrient removal wastewater treatment works situated in the midlands of KwaZulu Natal. Composite sludge samples (from the aeration tank), influent and effluent water samples were collected twice a month for 237 days. A combination of fluorescent in-situ hybridization, polymerase chain reaction (PCR)-clone library, quantitative polymerase chain reaction (qPCR) were employed for characterizing and quantifying the dominant nitrifiers in the plant. In order to have more insight into the activated sludge community structure, pyrosequencing was used in profiling the amoA locus of ammonia oxidizing bacteria (AOB) community whilst Illumina sequencing was used in characterising the plant’s total bacterial community. The nonlinear effect of operating parameters and environmental conditions on nitrification was also investigated using an adaptive neuro-fuzzy inference system (ANFIS), Pearson’s correlation coefficient and quadratic models. The plant operated with higher MLSS of 6157±783 mg/L during the first phase (winter) whilst it was 4728±1282 mg/L in summer. The temperature recorded in the aeration tanks ranged from 14.2oC to 25.1oC during the period. The average ammonia removal during winter was 60.0±18% whereas it was 83±13% during summer and this was found to correlate with temperature (r = 0.7671; P = 0.0008). A significant correlation was also found between the AOB (amoA gene) copy numbers and temperature in the reactors (α= 0.05; P=0.05), with the lowest AOB abundance recorded during winter. Sanger sequencing analysis indicated that the dominant nitrifiers were Nitrosomonas spp. Nitrobacter spp. and Nitrospira spp. Pyrosequencing revealed significant differences in the AOB population which was 6 times higher during summer compared to winter. The AOB sequences related to uncultured bacterium and uncultured AOB also showed an increase of 133% and 360% respectively when the season changed from winter to summer. This study suggests that vast population of novel, ecologically significant AOB species, which remain unexploited, still inhabit the complex activated sludge communities. Based on ANFIS model, AOB increased during summer season, when temperature was 1.4-fold higher than winter (r 0.517, p 0.048), and HRT decreased by 31% as a result of rainfall (r - 0.741, p 0.002). Food: microorganism ratio (F/M) and HRT formed the optimal combination of two inputs affecting the plant’s specific nitrification (qN), and their quadratic equation showed r2-value of 0.50. This study has significantly contributed towards understanding the complex relationship between the microbial population dynamics, wastewater composition and nitrification performance in a full-scale treatment plant situated in the subtropical region. This is the first study applying ANFIS technique to describe the nitrification performance at a full-scale WWTP, subjected to dynamic operational parameters. The study also demonstrated the successful application of ANFIS for determining and ranking the impact of various operating parameters on plant’s nitrification performance, which could not be achieved by the conventional spearman correlation due to the non-linearity of the interactions during wastewater treatment. Moreover, this study also represents the first-time amoA gene targeted pyrosequencing of AOB in a full-scale activated sludge is being done. / D

Les troubles reliés à la dépression, l’épuisement professionnel et l’anxiété sont de plus en plus répandus dans notre société moderne. La consommation croissante d’antidépresseurs dans les différents pays du monde est responsable de la récente détection de résidus à l’état de traces dans les rejets urbains municipaux. Ainsi, ces substances dites « émergentes » qui possèdent une activité pharmacologique destinée à la régulation de certains neurotransmetteurs dans le cerveau suscitent maintenant de nombreuses inquiétudes de la part de la communauté scientifique. L’objectif principal de ce projet de doctorat a été de mieux comprendre le devenir de plusieurs classes d’antidépresseurs présents dans diverses matrices environnementales (i.e. eaux de surfaces, eaux usées, boues de traitement, tissus biologiques) en développant de nouvelles méthodes analytiques fiables capables de les détecter, quantifier et confirmer par chromatographie liquide à haute performance couplée à la spectrométrie de masse en tandem (LC-QqQMS, LC-QqToFMS). Une première étude complétée à la station d’épuration de la ville de Montréal a permis de confirmer la présence de six antidépresseurs et quatre métabolites N-desmethyl dans les affluents (2 - 330 ng L-1). Pour ce traitement primaire (physico-chimique), de faibles taux d’enlèvement (≤ 15%) ont été obtenus. Des concentrations d’antidépresseurs atteignant près de 100 ng L-1 ont également été détectées dans le fleuve St-Laurent à 0.5 km du point de rejet de la station d’épuration. Une seconde étude menée à la même station a permis l’extraction sélective d’antidépresseurs dans trois tissus (i.e. foie, cerveau et filet) de truites mouchetées juvéniles exposées à différentes concentrations d’effluent dilué traité et non-traité à l’ozone. Un certain potentiel de bioaccumulation dans les tissus (0.08-10 ng g-1) a été observé pour les spécimens exposés à l’effluent non-traité (20% v/v) avec distribution majoritaire dans le foie et le cerveau. Une intéressante corrélation a été établie entre les concentrations de trois antidépresseurs dans le cerveau et l’activité d’un biomarqueur d’exposition (i.e. pompe N/K ATPase impliquée dans la régulation de la sérotonine) mesurée à partir de synaptosomes de truites exposées aux effluents. Une investigation de l’efficacité de plusieurs stations d’épuration canadiennes opérant différents types de traitements a permis de constater que les traitements secondaires (biologiques) étaient plus performants que ceux primaires (physico-chimiques) pour enlever les antidépresseurs (taux moyen d’enlèvement : 30%). Les teneurs les plus élevées dans les boues traitées (biosolides) ont été obtenues avec le citalopram (1033 ng g-1), la venlafaxine (833 ng g-1) et l’amitriptyline (78 ng g-1). Des coefficients de sorption expérimentaux (Kd) calculés pour chacun des antidépresseurs ont permis d’estimer une grande sorption des composés sertraline, desméthylsertraline, paroxetine et fluoxetine sur les solides (log Kd > 4). Finalement, un excellent taux d’enlèvement moyen de 88% a été obtenu après ozonation (5 mg L-1) d’un effluent primaire. Toutefois, la caractérisation de nouveaux sous-produits N-oxyde (venlafaxine, desmethylvenlafaxine) par spectrométrie de masse à haute résolution (LC-QqToFMS) dans l’effluent traité à l’ozone a mis en lumière la possibilité de formation de multiples composés polaires de toxicité inconnue. / Mood disorders such as depression, burn-out and anxiety have increased in our modern society. Increasing amounts of antidepressant prescriptions around the world are now suspected to be the main cause of the recent detection of traces of antidepressant residues within urban wastewaters. These so-called “emerging” substances that possess pharmacological activity towards neurotransmitter regulation in the brain have raised serious concerns from the scientific community. The initial goal of the study was to better understand the fate of various classes of antidepressants present in different environmental matrices (e.g. surface waters, wastewaters, treatment sludge, and biological tissues) by developing novel reliable analytical methods that can detect, quantify and confirm antidepressants using high performance liquid chromatography coupled to tandem-mass spectrometry (LC-QqQMS,LC- QqToFMS). A preliminary study completed at the Montreal sewage treatment plant (STP) confirmed the presence of six antidepressants and four N-desmethyl metabolites in raw sewage (2 – 330 ng L-1). For this primary treatment (physico-chemical), low removal rates (≤ 15%) were obtained. Concentrations of antidepressant close to 100 ng L-1 were also detected directly in the St. Lawrence River at 0.5 km of the effluent outfall. A second study conducted at the same STP allowed the selective extraction of antidepressants in three biological tissues (e.g. liver, brain, and filet) dissected from juvenile brook trouts previously exposed to diluted untreated and treated effluents with ozone. Bioaccumulation of antidepressants was readily observed in fish tissues (0.08-10 ng g-1) for the specimens exposed to untreated effluent (20% v/v), with major distribution in liver and brain. During experiments, a significant correlation was established between the concentrations of three antidepressant detected in brain tissues and the activity of a selected biomarker of exposition (e.g. an N/K ATPase pump involved in the serotonin regulation) measured within dissected synaptosomes from trout exposed to effluents. Investigation of estimated treatment removal efficiencies from various Canadian STPs operating different disinfection modes showed that secondary treatments (biological) were more efficient than primary (physico- chemical) to remove antidepressants (mean removal rates : 30%). The highest amounts detected in treated sludge (biosolids) were obtained respectively with citalopram (1033 ng g-1), venlafaxine (833 ng g-1), and amitriptyline (78 ng g-1). Experimental calculated sorption coefficients (Kd) of each antidepressant predicted fairly good sorption capacities for sertraline, desmethylsertraline, paroxetine, and fluoxetine to solid matters (log Kd > 4). Finally, an excellent mean removal rate of 88% was obtained after ozonation (5 mg L-1) of a primary effluent. However, the characterization of new N-oxide side-products (venlafaxine, desmethylvenlafaxine) in ozonized effluent by high-resolution mass spectrometry (LC-QqToFMS) highlighted the possibility of formation of multiple polar compounds with unknown toxicity.

L’estuaire de la Gironde est le plus grand estuaire macrotidal d’Europe formé par la confluence de la Garonne (où se situe l’agglomération de Bordeaux) et de la Dordogne. L’une de ses principales caractéristiques est la présence d’une zone à forte turbidité (bouchon vaseux) où les processus hétérotrophes (dégradation de la matière organique) sont favorisés et où au contraire les processus autotrophes (production primaire) sont limités par le manque de lumière. Ainsi, des déficits en oxygène pouvant être préjudiciables à la vie aquatique se développent systématiquement dans la zone du bouchon vaseux de la Garonne estuarienne. Ces préoccupations environnementales ont donc conduit à étudier en détail dans le cadre de ce travail de doctorat, les facteurs environnementaux qui provoquent ces hypoxies estuariennes. Dans un premier temps, j’ai réalisé un suivi sur le réseau d’eaux urbaines partiellement séparatif et unitaire de la Communauté Urbaine de Bordeaux, de ses stations d’épurations et déversoirs d’orage afin d’appréhender les apports urbains de matières organique et azotées et de les comparer à ceux en provenance du bassin versant amont. Bien que les deux stations d’épuration réalisent des abattements très significatifs sur la matière organique et l’ammonium, il s’avère que les flux vers le milieu naturel restent importants, notamment durant les périodes estivales, pendant lesquelles des orages peuvent engendrer des déversements d’effluents non traités. Ensuite, des expériences d’incubations ont permis de mettre en évidence le caractère fortement labile de cette matière organique urbaine. Le carbone organique dissous et l’ammonium, contenus dans les eaux usées, sont des composés fortement consommateurs en oxygène. Des expériences de respirométrie ont également permis d’estimer les taux de consommation en oxygène nettement plus importants dans les effluents urbains que dans les eaux de la Gironde. Enfin, l’analyse des données du réseau de mesures en continu de la qualité physico-chimique des eaux MAGEST (MArel Gironde ESTuaire) a démontré que l’estuaire subit dans sa section garonnaise des périodes d’hypoxie lors d’étiages prononcés, la masse d’eau la plus affectée par ces désoxygénations étant celle qui oscille aux alentours de l’agglomération de Bordeaux. Si ces résultats démontrent l’impact significatif de l’agglomération Bordelaise, le traitement statistique des données MAGEST pour la période 2005-2011 montre que les phénomènes de désoxygénation sont accrus en période d’étiage prononcé, en présence du bouchon vaseux et lorsque la température de l’eau est élevée. Dans ces conditions, l’oxygène dissous, déjà présent en faible quantité, peut être rapidement consommé lors d’apports supplémentaires d’eaux urbaines non traitées qui ont lieu pendant de fortes précipitations orageuses. Ce travail démontre également que le type de traitement biologique des eaux usées employé par les stations d’épuration et les capacités de stockage temporaire d’eaux d’orages ont un rôle critique sur les bilans de ces composés rejetés dans le milieu naturel. Enfin, ce travail permet de proposer aux gestionnaires des stratégies de rejets des effluents à court et moyen terme, en fonction des conditions hydrologiques et physico-chimiques du milieu, dans le but de limiter leur impact sur l’oxygénation des eaux estuariennes de la Garonne. / The Gironde Estuary is the largest macrotidal estuary in Western Europa, formed by the Garonne River (where the urban area of Bordeaux is located) and the Dordogne River. One of its main characteristics is the presence of a Turbidity Maximum Zone (TMZ) where heterotrophic processes (organic matter decomposition) are favored and where low penetration of light limits autotrophic processes (photosynthetic activity). Low dissolved oxygen (DO) that could impact aquatic biota occurred exclusively in the fluvial, low salinity and high turbidity sections of the estuary. These environmental concerns have led to study in detail in this work factors that cause estuarine hypoxia. First, I have estimated organic matter and ammonium fluxes from urban inputs in separate and combined sewer network of the Urban Community of Bordeaux, its wastewater treatment plants (WWTP) and combined sewer overflow, to compare them to the upstream watershed inputs. Even if the two WWTPs succeed in significant reduction in organic matter and ammonium contents of effluents, discharges into estuarine waters are important especially during summer, periods while storm events can generate untreated effluent inputs. This work demonstrates the high lability of this urban organic matter through incubation experiments. The dissolved organic carbon and ammonium contents in wastewater consume oxygen. Respirometry experiments allowed us to estimate higher oxygen uptake rates in wastewater than in the waters of the Gironde Estuary. Finally, the analysis of 7-yr data series from the continuous monitoring of the physico-chemical water quality (MAGEST network: MArel Gironde ESTuary) highlights periods of hypoxia in the upstream section of the estuary during pronounced low water around the Bordeaux conurbation. Statistical treatments of the 7-yr time series of DO concentration demonstrate the significant impact of the Bordeaux metropolitan area as it appears that the under-oxygenations increase during marked low water, in the presence of the TMZ, when the water temperature is high, and where the dissolved oxygen content is already low and can be quickly consumed after untreated storm water discharges. This study also shows that the nature of biological treatment used by the WWTPs and the temporary storage capacity of storm water have a critical role in the release of such compounds into the environment. This work finally provides strategies for effluent discharges to water managers, to short and medium terms, based on hydrological and physico-chemical conditions of the environment in order to limit their impact on the water oxygenation of the Garonne River.

Objetivo. Examinar a pertinência de utilização de abordagem multicritério como ferramenta de planejamento em reúso de água. Metodologia. As etapas são: (1) levantamento bibliográfico; (2) caracterização do Distrito Federal (área de estudo); (3) definir as áreas passíveis de serem irrigadas com água de reúso por sobreposição de mapas temáticos; (4) trabalho com decisores; (5) utilização do Método ELECTRE III; (6) apresentar e discutir resultados; (7) avaliar o trabalho desenvolvido. Resultados: (1) Os esgotos sanitários tratados de todas as estações de tratamento de esgotos (ETEs) não apresentaram qualidade satisfatória para irrigação irrestrita. Sugere-se seu uso na irrigação das grandes culturas do Distrito Federal (DF): milho, soja, café e trigo; (2) identificaram-se seis alternativas relacionadas às ETEs para se realizar reúso no Distrito Federal: Brazlândia, Samambaia/Melchior, Gama, Sul, Planaltina e São Sebastião; (3) as seis alternativas têm capacidade para irrigar todos os canteiros ornamentais, como também 4.268 ha de áreas agrícolas - correspondentes a 38% das áreas irrigadas das grandes culturas do DF; (4) Após a aplicação do Método ELECTRE III, as alternativas mais vantajosas relacionaram-se às ETEs Sul e Samambaia/Melchior. Conclusões: (1) a implementação do reúso de água no DF deve ser considerada no gerenciamento dos recursos hídricos; (2) a abordagem multicritério mostrou-se ferramenta apropriada ao planejamento em reúso de água; (3) o Método ELECTRE III adequou-se ao problema e foi sensível às preferências dos decisores. / Objective. To examine the relevance of adopting the multi-criterion approach as a planning tool when water is reused. Methods. It consisted of the following stages: (1) a bibliographical survey; (2) description of the Federal District (area under study); (3) determining the areas liable to irrigation with reused water by overlaying thematic maps: (4) working with decision makers; (5) applying the ELECTRE III Method; (6) presenting and discussing results; (7) assessing the work undertaken. Results: (1)The quality of the sewage treated in all the wastewater treatment plants (WTPs) was found to be unsuitable for unrestricted irrigation. It was suggested that it be reused in irrigating the Federal District´s major crops: maize, soy bean, coffee and wheat; (2) six alternatives, with regard to wastewater treatment plants, were identified for undertaking water reuse in the Federal District: Brazlândia, Samambaia/Melchior, Gama, Sul, Planaltina and São Sebastião; (3) the six alternatives are capable of irrigating all public flower beds, as well as 4,268 hectares of farmland - representing 38% of the Federal District´s irrigated lands under major crop cultivation; (4) after applying the ELECTRE III Method, the most advantageous alternatives were those related to Sul and Samambaia/Melchior wastewater treatment plants. Conclusions: (1) water reuse should be considered in water resources management in the Federal District; (2) the multi-criterion approach proved to be a suitable tool when planning water reuse; (3) the ELECTRE III Method was a suitable solution to the problem and met the requirements of the decision makers.