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O Φώσφορος είναι βασικό συστατικό των αστικών αποβλήτων, ο οποίος συγκεντρώνεται στους υδάτινους αποδέκτες προκαλώντας κυρίως προβλήματα ευτροφισμού. Τα παγκόσμια αποθέματα ορυκτού φωσφόρου μειώνονται λόγω της αυξημένης ζήτησης, έτσι κρίνεται απαραίτητο η κατά κάποιον τρόπο ανακύκλωση του. Μια από τις εναλλακτικές και πολλά υποσχόμενες μεθόδους για την ανάκτηση του φωσφόρου από την επεξεργασία των υγρών αποβλήτων είναι η δέσμευση του φωσφόρου, μέσω της κρυστάλλωσης, υπό την μορφή φωσφορικών αλάτων όπως ο στρουβίτης (ΜgNH4PO4.6H2O). O στρουβίτης χρησιμοποιείται απευθείας ως βραδέως αποδεσμευόμενο λίπασμα, το οποίο λόγω της χαμηλής του διαλυτότητας, εξασφαλίζει, την ελεγχόμενη παροχή θρεπτικών συστατικών φωσφόρου και αζώτου, απαραίτητων για την ανάπτυξη των φυτών. Στη παρούσα εργασία, δοκιμάστηκαν δύο τύποι αντιδραστήρων, ένας αντιδραστήρας ρευστοποιημένης κλίνης (FBR) και ένας αντιδραστήρας διαλείποντος έργου (Batch) με συνθετικό απόβλητο σε pH 6.50 στους 25οC. Η στοιχειομετρική αναλογία 1:1:1 των πλεγματικών ιόντων του στρουβίτη, Mg:N:P, διατηρήθηκε σε όλα τα πειράματα. Η καταβύθιση στρουβίτη σε υπέρκορα διαλύματα εξαρτάται κυρίως από τον υπερκορεσμό της καταβυθιζόμενης φάσης, τη θερμοκρασία και τη παρουσία ξένων ιόντων ή επιμολύνσεων. Πραγματοποιήθηκαν πειράματα αυθόρμητης καταβύθισης του στρουβίτη σε συνθήκες σταθερού pH για τον καθορισμό του εύρους της μετασταθούς περιοχής. Η γνώση αυτή είναι απαραίτητη για τον καθορισμό των συνθηκών διεξαγωγής πειραμάτων. Τα αποτελέσματα από τους δύο τύπους αντιδραστήρων, δεν παρουσίασαν διαφορές στους χρόνους επαγωγής γεγονός το οποίο υποδεικνύει την αυξημένη σημασία της πυρηνογένεσης και την μικρότερη σημασία της ρευστοδυναμικής του συστήματος. Στους δύο τύπους αντιδραστήρων μελετήθηκε ο ετερογενής σχηματισμός του στρουβίτη σε συνθήκες σταθερού pH 6.50, σε σταθερά υπέρκορα διαλύματα συνθετικού αποβλήτου, χρησιμοποιώντας ως φύτρα για την εκκίνηση της κρυσταλλικής ανάπτυξης, quartz, άμμο και στρουβίτη. Με υπόστρωμα quartz, παρατηρήθηκε μείωση του ρυθμού καταβύθισης αυξανομένης της ποσότητας τόσο σε αντιδραστήρα batch όσο και σε FBR, λόγω της επιβραδυντικής δράσης των πυριτικών ιόντων. Με υπόστρωμα άμμου, παρατηρήθηκε υπερδιπλάσια αύξηση του ρυθμού καταβύθισης για τη διπλάσια ποσότητα φύτρων, το οποίο συνηγορεί στην υπόθεση της δευτερογενούς πυρηνογένεσης. Τα μεγαλύτερα ποσοστά ανάκτησης φωσφόρου της τάξεως ~40% και καταβύθισης στρουβίτη από 70-100% είχαμε σε αντιδραστήρα ρευστοποιημένης κλίνης με υπόστρωμα στρουβίτη. Η χρήση υποστρώματος άμμου είχε αποτελέσματα παραπλήσια με τα αντίστοιχα τα οποία ελήφθησαν με την χρησιμοποίηση φύτρων κρυσταλλικού στρουβίτη. Η εισαγωγή σωματιδίων quartz στα υπέρκορα διαλύματα για την δημιουργία πυρήνων κρυστάλλωσης στρουβίτη είχε ως αποτέλεσμα την συγκριτικά μικρότερη απομάκρυνση φωσφόρου και κρυστάλλωση στρουβίτη. Σε λιγότερα από 700min λειτουργίας των αντιδραστήρων, στα υπέρκορα διαλύματα στα οποία είχαν εισαχθεί φύτρα στρουβίτη, η καταβυθιζόμενη ποσότητα στρουβίτη ήταν η μέγιστη δυνατή. Συγκρίσιμα αποτελέσματα ελήφθησαν με την εισαγωγή άμμου στα υπέρκορα διαλύματα. Το καταβυθιζόμενο στερεό χαρακτηρίστηκε με μεθόδους περίθλασης ακτίνων-X και ηλεκτρονική μικροσκοπία σάρωσης. Στα πειράματα batch, το καταβυθιζόμενο στερεό ήταν στρουβίτης, ενώ στα FBR σε υπόστρωμα 20g quartz σε χαμηλό υπερκορεσμό καταβυθίστηκε μικρή ποσότητα φωσφορικού μαγνησίου και σε υπόστρωμα 5g στρουβίτη σε υπερκορεσμό Ω=1.65 παρατηρήθηκε μικρή ποσότητα newberyite. / Phosphorus is one of the main components in the municipal wastewater, which can lead to problems such as eutrophication in the water reservoirs. The known reserves of phosphorus rocks are decreasing because of the high worldwide demands. Thus, it is necessary to recycle phosphorus from wastewater. Τhe crystallization of struvite is An attractive and new alternative method for phosphorus recovery. Struvite may be used as a slow-release fertilizer because of its relatively low solubility and the presence of both ammonia and phosphorus which through dissolution nutrients available to plants. In the present work, two types of reactors, a fluidized bed reactor (FBR) and a stirred tank reactor were used for the investigation of phosphorus recovery in synthetic wastewater at pΗ 6.50, 25οC. The stoichiometric molar ratio at the constituent ions was 1:1:1 through out the experiments of the present work. The extent of struvite precipitation depends on the solution supersaturation with respect to the precipitating solid, the temperature and the presence of foreign ions or substrates in the solution. The spontaneous precipitation of struvite was studied in both types of reactors at a constant pH 6.50 in order to determine the metastable zone width. This provided knowledge of the stable supersaturated solutions domain where heterogenous nucleation experiments can be done, in order to evaluate nucleation experiments can be done, in order to evaluate the relative ability of substrates to induce the crystallization of struvite. For the two type’s reactors, no significant differences were measured for the induction time, preceding precipitation. This suggested that hydrodynamics is not very important for the conditions of the present work. The heterogeneous formation of struvite was investigated at constant supersaturation and of pH in synthetic wastewater in both types of reactors. The seeds included quartz, sand and synthetic struvite. A decrease in the rate of struvite precipitation was found in both reactors with the use of quartz seeds due to the retardation effect of silicon ions. The use of sand seeds increased the rate of precipitation, while increasing the amount of substrate, resulted in a disproportionate increase at the respective rates of precipitation, suggesting a secondary nucleation process. Phosphorus recovery reached almost 40% and precipitation of struvite from 70 to 100% in the FBR filled with struvite. Sand gave similar results with struvite. The recovery of phosphorus and precipitation with quartz seeds were low, perhaps because of the inhibition effect of the silicon ions. Experiments, in which struvite seeds were used to seed supersaturated solutions, resulted in the precipitation the maximum amount of struvite in less than 700min. The experiments with sand seeds were quite close from the previous experiments especially in high supersaturation values. Finally, the precipitated solid characterized with XRD and SEM. In the batch series, the precipitated solid was struvite but for the FBR experiments a small amount of magnesium phosphate, for supersaturation Ω= 1.65 with 20g quartz seeds and a small amount of newberyite for 5g struvite seeds in supersaturation value 1.65, were obtained. These findings suggested that the problem is complex and kinetic stabilization of metastable mineral phases may be formed at very specific conditions.

There is a regulatory tension within wastewater treatment, between the requirement to meet tightening consents and the need to reduce the carbon footprint of treatment processes. With 75% of wastewater treatment works serving populations of less than 2,000, low-energy tertiary treatment options suitable to small rural works need to be developed. One option that lends itself particularly well to small works is land-based wastewater treatment (LBWWT). The aim of this research was to evaluate the role of LBWWT in the UK water industry and investigate the impact ridge-and-furrow enhanced microtopography (MT) may have upon a particular type of LBWWT - slow-rate (SR) infiltration. This was achieved through meeting three objectives. Firstly, the use of LBWWT was reviewed and assessed. Secondly, the impact of ridge-and-furrow enhanced MT upon the vegetation diversity and nutrient removal of a SR- LBWWT was established by means of a three year field trial. Finally, the cost- effectiveness of SR-LBWWT and the impact of ridging and furrow irrigation upon cost-effectiveness were evaluated using Cost-Effectiveness Analysis (CEA). The first objective comprised of a review of the historical and current use of LBWWT, a review of the relevant changing legislation to identify what may be required of LBWWT and an assessment of LBWWT’s potential to meet these requirements. The result of the evaluation found that, based upon the literature, SR-LBWWT is ‘fit-for-purpose’ as tertiary treatment for small treatment works. To meet the second objective, a SR-LBWWT system trial was established at a small wastewater treatment works in Knowle, Hampshire. The trial consisted of three clay-loam grass plots irrigated with secondary treated effluent. There were two configurations of trial plot - flat and ridge-and-furrowed. Effluent (sub- surface soil water) nutrient concentrations were monitored as was vegetation diversity. In addition a number of physical, hydrological and biogeochemical parameters were monitored and hydrological modelling carried out. Mean nutrient removal performances of 90% for ammonia, 72% for nitrate, and 91% for phosphate were observed with the ridge-and-furrowed plot. Ridging and furrow irrigation was found to not have a significantly detrimental effect upon the trial plots’ removal performance for ammonia, nitrate or phosphate. Extrapolation modelling suggested, however, that this would not be the case for LBWWT systems on predominantly clay or sand soils. Ridging and furrow irrigation was found to have a statistically significant positive effect upon the vegetation diversity of the LBWWT trial plots; with mean final year Shannon-Wiener values of 0.96 and 0.69, for the ridge-and-furrowed and non-ridged plots, respectively. For the final objective, analysis found that SR-LBWWT are cost-effective when compared to horizontal sub-surface flow constructed wetlands (HSSFCW), an established low-energy treatment option. Mean cost-effectiveness ratio values of £208.5 and £262.7 per % effectiveness were observed for LBWWT and HSSFCW, respectively. Following the field trial CEA was extended to include ridge-and-furrowed SR-LBWWT systems. This found that ridging and furrow irrigation improves the cost-effectiveness of SR-LBWWT serving small populations, reducing the mid cost-effectiveness ratio to £193 per % effectiveness. This is a result of the cost-reducing effect of ridge-and-furrowing over laser-level grading; and based upon the findings of the trial that ridging and furrow irrigation can be achieved (in clay-loam soil slow-rate systems) without significant detriment to the water treatment effectiveness of LBWWT. The main conclusions of this thesis are: that SR-LBWWT has a role to play in the UK water industry, as tertiary treatment for small wastewater treatment works. That SR-LBWWT is cost-effective in relation to HSSFCW. That ridging and furrow irrigation increases that cost-effectiveness by reducing the construction and operational costs. That ridging and furrow irrigation can be employed without significant detriment to a SR-LBWWT system’s water treatment performance. And finally, that ridging and furrow irrigation can have a positive impact upon the establishment vegetation diversity of a SR-LBWWT system.

As populations grow and urban centres expand, meeting water demand and wastewater management requirements will become increasingly difficult. Goal 6 of the Sustainable Development Goals is to: 'Ensure availability and sustainable management of water and sanitation for all'. Part of the approach to achieving this will be reusing wastewater and will require a greater understanding of the institutional arrangements that support or obstruct reuse. This research was designed to achieve this and aimed to develop a set of factors that investors could use to assess the institutional feasibility of reuse in a given setting. The methodology combined a case study approach, focusing on wastewater systems in Bangalore, India and Hanoi, Vietnam, with triangle analysis to assess: the content of policies and laws; the structures (formal and informal) to implement laws and reuse projects; and the culture around acceptance and engagement in reuse. The reuse practices observed in Bangalore were treatment and use within apartments, centralized treatment and sale to industries, use in agriculture after natural attenuation, groundwater recharge and lake regeneration. In Hanoi the only reuse was indirect use from rivers feeding fish ponds and fields, although formal treatment and use is planned. Critically, both cities have environmental and water resources policies and laws that advocate reuse, as well as related local legislation. However, support for reuse is not reciprocated in industrial, agricultural or fisheries law, the result being that reuse does not always take place as planned. Legislation is required along the whole sanitation chain to the point of wastewater use. Structures to implement reuse are also vital. In Bangalore the water board has initiated reuse projects and established the New Initiatives Division but resources are a limiting factor. Effective institutions include expertise, manpower and financing mechanisms, which are lacking in both cities. The environment agency is also engaged in reuse though legislation on recycling in residential and commercial complexes but guidance for users is inadequate, expectations are perceived to be excessive and monitoring is almost impossible. The driver for reuse is increasingly the benefits observed by users. In the case of apartments this is a reliable water source and reduced costs of water supply. As a result, a private sector in wastewater treatment is becoming established. The active civil society and strong, independent media are instrumental in providing information to potential users and holding authorities to account in Bangalore. Their absence in Hanoi is notable. In summary, institutional elements to be considered are: supportive legislation across all sectors; details of acceptable reuse, deterrents and inducements; budget allocation; structures to enable reuse; strong civil society, NGOs, courts, media and universities providing evidence of suitability and safety; donors and finance mechanisms; and stakeholders willing to use the products. Encumbrances are inconsistent or uncoordinated legislation, lack of cooperation and insufficient benefit sharing or perceptions of benefits along the reuse chain.

L’élimination des produits agrochimiques indésirables des eaux de drainage agricole dans les bassins versants peut être réalisée par des zones humides ouvragées. Les oxy-hydroxydes de fer sont parmi les composés les plus réactifs chimiquement dans les sols tempérés et pourraient être un support idéal en mélange avec un support traditionnel pour la végétation dans ces systèmes. Le présent mémoire expose un travail de recherche visant à tester l’efficacité d’un procédé novateur d’élimination du glyphosate par un filtre minéral planté qui utilise les propriétés d’un support de grande surface spécifique composé d’oxy-hydroxyde ferrique et de végétaux adaptés aux zones humides et tolérants au glyphosate. Ce travail présente trois axes principaux qui sont : • la caractérisation physico-chimique de deux supports synthétiques choisis pour leur potentiel à retenir le glyphosate et de choisir le plus approprié pour notre étude • une étude mécaniste approfondie de l’adsorption du glyphosate sur le support retenu a été faite, suivie d’une analyse comparée de l’adsorption de glyphosate avec celle du phosphate sur ce même support. • la culture de différentes associations à partir de deux espèces végétales de milieu humide (Lythrum salicaria et Phragmites australis) sur un mélange de (sable, support adsorbant) arrosées par irrigation en présence ou en absence de glyphosate et de phosphate afin de vérifier l’efficacité du dispositif sur la dégradation de glyphosate. Les résultats obtenus de la caractérisation nous ont dirigés vers le minéral synthétique GEH®104, (GEH Wasserchemie GmbH & Co. KG, Heinrich-Hasemeier-Straße 33, D-49076 Osnabrück) qui est presque une akaganeite pure avec une surface spécifique de 350 m2.gr-1. Les cinétiques d’adsorption ont suggéré que le temps d’équilibre était plus long (15 j) que le temps déclaré dans la littérature pour des phases similaires. Cela est attribué à la nature mésoporeuse du support utilisé. L’akaganeite adsorbe le glyphosate fortement suivant deux modes : le premier est presque irréversible suivi par un mode hyperbolique, suivant l’équation de Langmuir double, alors que l’adsorption du phosphate suit plutôt l’équation de Bradley. La grande capacité d’adsorption de glyphosate et de phosphate par l’akaganeite en fait un candidat approprié pour une implication dans des zones humides ouvragées devant traiter des eaux contenant ces polluants. Les expériences de culture ont montré que Phragmites australis et la Lythrum Salicaria L. peuvent supporter de fortes concentrations de glyphosate par irrigation et qu’ils bénéficient de l’association mutuelle. Il semblerait que les plantes et leurs micro-organismes associés assurent l’essentiel de la disparition du glyphosate en solution car une fois bien installées, le glyphosate et ses métabolites ne sont pratiquement plus détectables en solution. Le système complet empêche le glyphosate de percoler lorsque celui-ci est présent avec ou sans phosphate dans les eaux d’irrigation / The elimination of undesirable agrochemicals of agricultural drainage water in watersheds can be achieved through engineered wetlands. Iron oxy-hydroxides are among the most chemically reactive compounds in temperate soil and they could be an ideal support in admixture with a traditional holder for vegetation in these systems. This work aimed to test the effectiveness of an innovative method of removing glyphosate mineral planted by a filter that uses the properties of a high surface area carrier composed of ferric oxyhydroxide and plants adapted to wetlands and tolerant to glyphosate. This work has three main axis which are: • The physicochemical characterization of two synthetic materials chosen for their potential to retain glyphosate and choose the most suitable for our study. • A profound mechanism study of the adsorption of glyphosate on the chosen support has been made, followed by a comparative analysis of the glyphosate with the adsorption of phosphate on the same support. • culture of different associations based on two plant species of wetland (Lythrum salicaria and Phragmites australis) on a mixture of (sand, adsorbent support) watered by irrigation in the presence or absence of glyphosate and phosphate to verify the effectiveness of the device on the degradation of glyphosate. The results of the characterization directed us to the synthetic mineral GEH®104 (GEH Wasserchemie GmbH & Co. KG, Heinrich-Hasemeier Straße 33, D-49076 Osnabrück) which is almost a pure akaganeite with a surface area of 350 m2.gr-1. The adsorption kinetics suggested that the equilibrium time was longer than (15 days), which is longer than the time reported in the literature for similar phases. This is attributed to the mesoporous nature of the support used. Akaganeite strongly adsorbs glyphosate in two modes: the first is almost irreversible followed by a hyperbolic mode, according to the Dual Langmuir’s equation while the phosphate adsorption follows the Bradley’s equation. The large capacity of adsorption of glyphosate and phosphate by actually akaganeite makes it a suitable candidate for involvement in wetlands engineered to treat water containing these pollutants. The experimental cultural showed that reed and purple loosestrife can support high concentrations of glyphosate by irrigation and they benefit from membership organization. It appears that plants and their associated microorganisms are responsible for most of the disappearance of glyphosate in solution because once properly installed, glyphosate and its metabolites are practically no longer detectable in solution. The complete system prevents glyphosate from percolating when it is present with or without phosphate in the irrigation water

Anaerobic digestion of source segregated domestic food waste (SS-DFW) offers a sustainable management route for reclaiming potential energy in the form of a fuel gas, and nutrients which can be recycled back to land. However, the biochemical characteristics of SS-DFW can lead to free ammonia nitrogen (FAN) concentrations that are inhibitory to the digestion process causing unstable operation and in some cases complete process failure, particularly in thermophilic systems. With the purpose of reducing the total ammoniacal nitrogen (TAN) in the digester, side-stream and in situ biogas stripping technologies were tested. Mesophilic and thermophilic temperatures were evaluated under moderate and complete biogas mixing rates (0.4 l min-1 – 2.6 l min-1) in a batch system. Laboratory investigations showed that TAN reductions in an in situ bubbling reactor with moderate and complete gas mixing rates were non-existent at mesophilic temperatures and minimal at thermophilic temperatures. For this reason, it is unlikely that in situ biogas stripping would be adequate to prevent TAN concentrations greater than 2500 mg N l-1 in a food waste digester and thus will not mitigate ammonia inhibition in a thermophilic system. Semi-continuous trials carried out on SS-DFW in laboratory-scale digesters, fed daily at an organic loading rate (OLR) of 2 kg VS m-3 day-1 and coupled to stripping columns at low bleed rates (2 – 3.5 % digester volume per day treated in the stripping process) were effective in reducing ammonia concentrations to below thermophilic toxic levels (TAN concentration of 2500 – 3500 mg N l-1). The experiments also confirmed that removal of a proportion of the digester contents and their exposure to thermophilic conditions with pH adjustment to 10 had no adverse effects on performance in terms of biogas production (0.83 ± 0.03 l g-1 VS without stripping, 0.84 ± 0.05 l g-1 VS with stripping) or VS destruction (81.8 % without stripping, 88.5 % with stripping). The process required high pH and temperature (≥70 ⁰C) to achieve a TAN concentration below the toxic threshold for thermophilic digestion, and it is unlikely that stripping at 55 ⁰C and pH 10 would achieve the target reduction. The research showed the way forward for the application of side-stream stripping to prevent the build-up of ammonia under thermophilic conditions, if the digester is started up with a non-inhibitory FAN concentration in the inoculum.

Achieving microbial compliance levels in biosolids storage is complicated by the unpredictable increase of Escherichia coli (E. coli), which serves as an important indicator for pathogen presence risk. Meeting required microbial specifications validates sludge treatment processes and ensures that a safe product is applied to agricultural land. Controlled indicator monitoring provides confidence for farmers, retailers and the food industry, safeguarding the sludge-to-land application route. Following mechanical dewatering biosolids products are stored before microbial compliance testing permits agricultural application. During storage, concentrations of E. coli bacteria can become elevated and prevent the product from meeting the conventional or enhanced levels of treatment outlined in The Safe Sludge Matrix guidelines. Literature research identified innate characteristics of sludge and ambient environmental parameters of storage which are factors likely to influence E. coli behaviour in stored biosolids. The research hypothesis tested whether E. coli growth and death in dewatered sewage sludge can be controlled by the modification of physical-chemical factors in the cake storage environment. Parameters including nutrient availability, temperature, moisture content and atmospheric influences were investigated through a series of laboratory-scale experiments. Controlled dewatering and the assessment of modified storage environments using traditional microbial plating and novel flow cytometry analysis have been performed. At an operational scale, pilot trials and up-scaled monitoring of the sludge storage environment have been conducted enabling verification of laboratory results. Understanding the dynamics of cell health within the sludge matrix in relation to nutrient availability has provided a valuable understanding of the mechanisms that may be affecting bacterial growth post-dewatering. The importance of elevated storage temperatures on E. coli death rates and results showing the benefits of a controlled atmosphere storage environment provide important considerations for utilities.

Ces dernières décennies, la pollution de l’eau est devenue un problème se posant avec insistance dans le monde entier. En effet, la forte croissance des besoins en eau due à l’accroissement démographique ainsi qu’aux évolutions industrielles, agricoles et urbaines, engendrent des quantités énormes de rejets d’eaux usées. Ces derniers sont déversés dans la nature avec ou sans traitement et peuvent constituer un danger via la transmission de maladies ainsi que pour l’irrigation des terres qui se trouvent aux alentours du site de rejet. L’objectif de cette étude est le traitement des rejets aqueux par l’utilisation d’une nouvelle technologie appelée « photocatalyse hétérogène ». Ce procédé est basé sur l’utilisation d’un semiconducteur irradié par une source lumineuse de longueur d’onde appropriée et est simple à mettre en œuvre et peu coûteux. Des semiconducteurs ZnO/Fe2O3, ZnO de morphologie « bâtonnets » et ZnO dopé Mn2+ ont été synthétisés et testés dans diverses applications photocatalytiques. Les résultats obtenus ont montré une amélioration de l’efficacité catalytique par rapport au ZnO commercial. Les matériaux développés permettent de réduire la recombinaison des charges et, par conséquent, d’améliorer l’activité photocatalytique lors de la dégradation des polluants chimiques (acide salicylique, Orange II) et biologiques (bactéries) sous l’irradiation solaire. De plus, nous avons démontré la recyclabilité de ces catalyseurs sans traitement particulier. Dans la seconde partie de notre travail, nous avons étudié le mécanisme de la photocatalyse solaire sur une souche de référence E. coli MG 1655 en utilisant les bâtonnets ZnO soit en suspension soit immobilisés sur un support inerte. Les résultats montrent une perte de cultivabilité de la bactérie E. coli avec des dommages essentiellement localisés au niveau membranaire et des protéines, le matériel génétique restant intact. La réponse de trois souches bactériennes (Escherichia coli, Pseudomonas aeruginosa et Salmonella enterica Typhi) au stress oxydant de la photocatalyse a montré des différences pouvant être attribués aux différences morphologiques, métaboliques et génétiques des souches (certaines souches peuvent se réactiver après traitement). Des études réalisées sur la souche Pseudomonas aeruginosa (ATCC 4114) montrent qu’il y a une perte de cultivabilité mais que la bactérie conserve sa capacité de se réactiver ainsi que ses caractères de virulence après traitement / In recent decades, the water pollution has become a problem worldwide. Indeed, the strong growth in water demand due to population growth as well as industrial developments, agricultural and urban, generates huge amounts of waste water discharges. These are released into nature with or without treatment and may constitute a danger via the transmission of diseases as well as for irrigation of lands that are surrounding the site of release. The objective of this study is the treatment of aqueous waste through the use of a new technology "heterogeneous photocatalysis." This method is based on the use of a semiconductor irradiated by a light source of appropriate wavelength and is simple to implement and inexpensive. ZnO / Fe2O3 semiconductors, ZnO morphology "nanorods" and Mn2+ doped ZnO were synthesized and tested in various photocatalytic applications. The results showed an improvement in catalytic efficiency compared to the commercial ZnO. The developed materials can reduce the recombination of charges and, therefore, improve the photocatalytic activity when the degradation of chemical pollutants (salicylic acid, Orange II) and biological (bacteria) under solar irradiation. Furthermore, we have demonstrated recyclability of these catalysts without specific treatment. In the second part of our work, we studied the solar photocatalysis mechanism on a reference strain E. coli MG1655 using ZnO nanorods either in suspension or immobilized on an inert support. The results show a loss of cultivability of E. coli with damage essentially localized in cell membranes and proteins. The genetic material remaining intact. The response of three bacterial strains (Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica Typhi) to oxidative stress of photocatalysis showed differences can be attributed to morphology, metabolism and genetics of each strain. (Some strains can be reactivated after treatment). Studies performed on the strain Pseudomonas aeruginosa (ATCC 4114) show that there is a loss of cultivability but that the bacterium retains its ability to activate its virulence and characters after treatment

Modelling wastewater temperature variations in a network of 3048 sewer pipes was achieved in this project. Recovering heat from sewers presents attractive options for producing clean energy. However, heat recovery from sewerage may result in wastewater temperature drops which may reduce the influent temperature at the wastewater treatment plant (WWTP). This drop in the WWTP influent temperature may result in the degradation of the biological treatment stage. Therefore, it is vital to predict the impact of recovering heat from sewers on the wastewater temperature. Sewer temperatures along with hydraulic data were measured for up to a year in four different Belgian sites. The measured data was utilised to calibrate a deterministic sewer pipe model that estimates the wastewater temperature variation along the sewer pipe profiles. The latter model was calibrated using data from two sites and then validated using independent data from the other two sites. The sewer pipe model was then further developed to model wastewater temperature variations in a large (3048 pipe) network. The large network model was tested by implementing three different heat recovery scenarios. It was observed that 9 MW may be recovered from the 3048 pipe network, serving a catchment with a population equivalent of 79500 inhabitants, without impacting negatively on the biological processes.

Le développement de systèmes d’assainissement spécifiques et décentralisés peut apporter des réponses à une double problématique : l’amélioration des conditions sanitaires dans les zones les plus pauvres du monde et le développement de sources renouvelables de nutriments essentiels pour l’agriculture. L’objectif de cette thèse est de développer des connaissances scientifiques sur une filière de traitement et valorisation de l’urine couplant une cristallisation à une séparation membranaire. Il a été démontré que la précipitation de phosphore sous forme de struvite permet de récupérer la quasi-totalité du phosphore et une partie de l’azote en 20 secondes environ suite à l’ajout de magnésium avec un ratio Mg :P=1,3 :1. L’influence des conditions d’agitation, de l’apport en magnésium, des conditions de stockage de l’urine et de la présence de matières organiques et de cristaux initiaux a été étudié en réacteur batch et continu.L’ultrafiltration de différents types d’urine (fraichement excrétée, stockée, stockée puis cristallisée) a été réalisée avec des membranes en PES, PAN et PVDF. Les mécanismes responsables de cette chute de flux ainsi que l’influence spécifique des fractions particulaires colloïdales et particulaires ont été étudiés. En se basant sur ces résultats différents procédés ont été proposés et discutés / The development of decentralized and specific sanitation system is an issue that concerns both the improvement of sanitary conditions in the poorest area of the world and the development of renewable sources of nutrients for agriculture. This study aims to provide some elements about a treatment line including crystallization and membrane separation for the treatment and valorization of urine. Crystallization allows to recover phosphorus and part of nitrogen contained in urine. Membrane separation is used in order to remove bacteria and viruses from urine. To check the potentialities of these processes some tests were performed at labscale with synthetic and real human urines.It was shown that the struvite crystallization by magnesium addition with a ratio Mg:P=1,3:1 allows recovering most of the phosphorus from urine with a very rapid kinetics (about 20s). Influence of mixing conditions, urine storage, organic matter and initial crystals in urine was studied in batch and continuous reactor. Ultrafiltrations of different pretreated urines (no pretreatment, stored urine, stored and crystallized urine) were performed with PES, PAN and PVDF membranes. Mechanisms responsible for an important flux decline during urine flitration were studied. Specific influence of particular, colloidal and soluble fraction on the flux decline was also evidenced. On these basis different possible treatment lines of urines are proposed and discussed