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Water is an indispensable resource for the survival of every human being; it’s essential for the health and a fundamental human right. So, in order to provide enough quality water to populations whatever the context, researchers are now further focusing on innovative procedures of easy and cheap exploitation allowing access to enough quality water at the user end. Therefore, one of the innovative techniques used in various area in science is three-dimensional (3D) printing. Thus for this study, a 3D printer, “Ultimaker 1”, initially designed for plastic printing has been tailored for the confection of ceramic filters. These filters can treat the water to be consumed at the user end. From this experience we can notice that this innovative concept, could very soon become a reliable alternative in the provision of enough and quality water in developing countries., L’eau est une ressource indispensable à la survie de tout être vivant, essentiel pour la santé, et constitue un droit fondamental pour tout homme. Ainsi, afin de fournir de l’eau de qualité en quantité suffisante aux populations quels que soient les contextes, les recherches scientifiques s’orientent actuellement vers le développement de procédés novateurs, d’exploitation facile et peu coûteux. L’objectif étant de permettre l’accès à de l’eau de qualité en quantité suffisante au point d’utilisation. À cet effet, une des techniques novatrices qui aujourd’hui retrouve son application dans divers domaines de la science est l’impression tridimensionnelle (3D). Ainsi au cours de cette étude une imprimante 3D, l’ «Ultimaker 1» destinée initialement à l’impression à base de matière plastique a été adaptée afin de servir à la fabrication de filtres en céramiques. Ces filtres pourront retrouver des applications en traitement de l’eau destinée à la consommation au point d’utilisation. Il ressort de cette expérience que ce concept novateur, pourrait devenir dans un avenir proche, une alternative viable à la fourniture d’eau potable en quantité et qualité suffisante dans les Pays en Développement.

Depuis plus de 15 ans, la Direction de la Recherche et du Développement du Syndicat Interdépartemental pour l’Assainissement de l’Agglomération Parisienne (SIAAP) étudie le procédé de biofiltration des eaux résiduaires urbaines. Les différents travaux de recherche et développement, menés à l’échelle industrielle et semi-industrielle (stations d’épuration/ prototypes/pilotes) ont permis au SIAAP d’acquérir une réelle expérience sur ce procédé de traitement. L’objectif de cet article de synthèse est d’extraire de ces 15 années de travail des informations clés sur les performances et les limites des biofiltres (charges éliminées et influence des conditions d’exploitation sur l’élimination de la pollution) ainsi que sur les mécanismes de colonisation et d’encrassement des massifs filtrants., For more than 15 years, the interdepartmental association for sewage disposal in Paris conurbation (SIAAP) research center has studied wastewater treatment by biofiltration. Such studies, carried out at industrial and semi-industrial scales (wastewater treatment plants/pilot and prototype units), have allowed SIAAP to expand its knowledge of this wastewater treatment technology. This paper aims to review the available information on the performance and limits of these immersed biological systems (purification performances and effects of the operating conditions on the pollution abatement efficiencies) and about the mechanisms of colonization of filter media by bacteria populations.

Cet article présente les résultats d'une étude menée sur le traitement d'effluents fortement chargés (DCO > 1,5 kg.m-3) par un procédé à boues activées. L'objectif principal de ce travail est de montrer qu'une alimentation séquentielle d'un réacteur parfaitement agité avec maintien permanent du recyclage des boues et de l'oxygénation permet d'obtenir une bonne épuration tant du point de vue de l'élimination de la pollution carbonée que de la maîtrise de la décantabilité des flocs microbiens. Les essais sont menés sur un pilote de laboratoire constitué d'une colonne à bulles et d'un décanteur, alimenté avec un substrat synthétique. Contrairement à une alimentation continue, la mise en place de cycles d'alimentation permet d'obtenir des flocs de bonne décantabilité de manière constante dans le temps. Ainsi une concentration élevée en biomasse peut être maintenue dans le réacteur. De plus, le suivi d'un cycle 1 h/1 h confirme que la mise en œuvre d'un cycle court n'entraîne pas de variations importantes des performances d'épuration. Par ailleurs, le suivi d'un long cycle (24 h/24 h) montre des variations significatives des concentrations en DCO, polysaccharides dans la phase liquide et exopolysaccharides dans les flocs microbiens. Ceci semble indiquer que des produits microbiens sont relargués des flocs vers la phase liquide pendant l'arrêt de l'alimentation et que des exopolysaccharides sont produits dans les flocs pendant l'alimentation., The overall efficiency of an activated sludge wastewater treatment system depends both on the ability of the activated sludge culture to remove the soluble organic pollution and on the efficiency of the separation of the treated water from the biomass. In the treatment of a high-strength wastewater (COD > 1.5 kg .m-3), ultrafiltration or crossflow filtration systems can sometimes substitute for the final clarifier, the separation of the sludge from the effluent water being very good regardless of changes in sludge settleability. Because of the high pollutant concentrations, the biomass must be more concentrated in the bioreactor than in the usual aerobic processes (10 to 20 kg.m-3 rather than 4 kg.m-3), whatever the separation system (settler or filtration system). Thus, with this biomass concentration, the volumetric loading rate can be increased while the organic loading rate is maintained at a low level.The use of a clarifier is preferable because it is cheaper than ultrafiltration or crossflow filtration systems, which have very high investment and operation costs, on the other hand, and some fouling problems, on the other hand. However, its use requires a very good biomass settleability. Results from the literature show that there is no general relation between sludge settleability and such wastewater treatment operating parameters as dissolved oxygen concentration in the aeration basin, organic loading rates, pH, or low relative influent nitrogen and phosphorus contents. On the other hand, the separation ability of the clarifier depends on the hydraulic configuration of the aerated reactor: biomass settleability can be controlled by completely stirred reactors in series, plug-flow reactors or intermittently-fed systems. Indeed, this spatial or temporal staggering should allow microorganisms to consume their accumulated substrate and thus restore their accumulation capacity. In the case of high-strength wastewater treatment, temporal staggering is better than spatial staggering. Indeed, higher organic loading rates require a higher number of reactors. Thus, the COD concentration significantly increases in the first reactors of the cascade and some toxic or inhibitory problems could appear. For this reason, a temporal staggering was chosen.Biomass settleability is linked to the extracellular polymers that are the third component of the sludge flocs, after the cells and the water. These polymers are composed largely of microbial exopolysaccharides. Measurements of exopolysaccharides could be used to characterize sludge settleability. A too low level of exopolysaccharides indicates a sludge defloculation problem, whereas a too high level of exopolysaccharides means that sludge settleability could be hindered because of an excessive growth of filamentous organisms.The purpose of the present work is to show that the use of only one completely stirred reactor, fed in a cyclic way with permanent oxygenation and return sludge flow, leads to good sludge settleability and effluent quality. The experiments have been performed with a laboratory pilot-plant composed of a 11.3 litre bubble column, which is a completely stirred reactor, and a secondary settling tank of 14.8 litres. The reactor is fed with an equilibrated synthetic substrate consisting mainly of meat extract, saccharose and ethanol (COD:N:P=100:5:1 and 1 kg COD=1 kg meat extract + 0.444 kg saccharose + 0.2 kg ethanol). The feeding cycle is a set of consecutive periods of feeding and starvation. For example, during a 1h/2h feeding cycle, the substrate feeding is continuous during 1 hour and stopped during 2 hours.The sludge comes from the Nancy-Maxéville wastewater treatment plant and its acclimation to the synthetic substrate begins with an aeration without feeding during 12 hours. Afterwards, the experimental system is fed during 1 hour every 2 hours with the substrate (first concentration of COD=0.1 kg.m-3). Then, the inlet COD is increased by steps of 0.1 kg.m-3 every day until the required concentration is reached. Once the biomass is acclimated to the influent and sufficiently concentrated, the experiment can begin.In order to show the positive influence of cyclic feeding on wastewater treatment quality, we have carried out one experiment with continuous feeding and two experiments with cyclic feeding (see Table 1). For these experiments, the volumetric loading rate is about 4 kg COD.m-3.d-1. With an appropriate feeding cycle, the settleability of the sludge and the effluent quality remain good: the diluted sludge volume index is 56 cm3.g-1 and 96% of the inlet COD is removed. Thus, the biomass concentration remains high in the reactor (19 kg.m-3). This is not the case with a continuous feeding where the biomass settleability rapidly deteriorates. The principal advantage of sequential feeding is the maintenance of good sludge settleability and a high biomass concentration in the aeration basin. Moreover, during the short feeding cycles, the variations of the concentrations of COD, polysaccharides in the bulk phase and extracellular polysaccharides in the microbial aggregates are very low. This augurs well for system stability.In contrast, monitoring of a long cycle (24 h of feeding and 24 h of starvation) shows great variations in the concentrations of COD, polysaccharides and extracellular polysaccharides in the system. When the feeding is stopped, the COD and polysaccharide concentrations in the bulk phase increase whereas the exopolysaccharide concentration in sludge flocs decreases. Reciprocally, after the feeding is begun, the COD and polysaccharide concentrations in the bulk phase decrease, and then remain constant, whereas the exopolysaccharide concentration increases. As 1 kg of measured polysaccharides represents 0.9 kg COD, and as in the bulk phase the COD concentration is equivalent to 4 times the polysaccharide concentration, it seems that microbial products other than polysaccharides are released in the bulk phase during starvation, these products being slowly biodegradable. Extracellular polysaccharides in the microbial aggregates are formed during the feeding phase.

We present in this paper an empirical evaluation of a contract-based environmental regulation under asymmetric information. An imperfect pollution tax results in the necessity of regulating industrials by a contract-based policy, in order to promote a higher level of pollution removal. The local regulatory agency has imperfect information on costs of abatement and must design a feasible mechanism providing incentives for industrials to extend their wastewater treatment plant capacity. The optimal policy consists in regulating only the most efficient industrials in the abatement activity. Empirical evidence reveals that the pollution tax should be more than twice its present level to attain the fully internalizing Pigouvian tax level.

Solid-liquid separation : the membranes This work gives the state of the art in the applications of membrane filtration to the liquid-solid separation field. The general features of the membranes used in this type of application are briefly presented. The fouling phenomenon in industrial conditions is thouroughly analysed and the control methods are presented. Last the most frequent applications of membrane filtration to water treatment are breifly summarized., On présente l'état de l'art relatif à l'application de certaines techniques de filtration par membranes à la séparation solide-liquide. Après une présentation succincte de ce que sont les membranes et de leur mode de fonctionnement, le phénomène de colmatage dans les applications industrielles est analysé et les techniques utilisées poux sa gestion sont présentées. Enfin, on donne un bref aperçu des applications les plus fréquentes des membranes au traitement des eaux., Bersillon Jean-Luc. Séparation solide-liquide : les membranes. / Solid-liquid separation : the membranes. In: Sciences Géologiques. Bulletin, tome 46, n°1-4, 1993. Minéraux finement divisés, sous la direction de Jacques Yvon. pp. 175-182.

The Australian Alps are the most significant mainland catchment but the many rivers and streams in the Alps are under increasing pressure due to recreational use and as a source of water supplies for the increasing urban developments in the region. The deteriorating quality of the waters of the alpine streams has become a major management issue. A major river (Thredbo River) is discussed in the paper as an example of the problems of water quality management., Résumé : Cet article pose le problème de la qualité des eaux dans les Alpes australiennes et de l'état des connaissances sur ce sujet pour les Parcs Nationaux où des mesures de protection sont nécessaires. La pollution des eaux, qu'elle soit naturelle ou anthropique, pose des problèmes spécifiques de gestion de ces territoires protégés. Le cas de la rivière Thredbo est exposé, tout particulièrement en ce qui concerne les mesures chimiques de concentration en phosphore et nitrates en amont et en aval d'une station de retraitement des rejets en eaux usées. Le problème de la croissance des algues en période d'étiage est également étudié ainsi que les mesures de protection contre ce phénomène., Cullen P. 15 — Gestion de la qualité des eaux dans les Alpes australiennes / Management of water quality in the Australian Alps. In: Revue de géographie alpine, tome 80, n°2-3, 1992. pp. 425-449.