FR :

Les réservoirs volgiens ont pour but de retenir les eaux de fonte de printemps pour les redistribuer dans le cadre de l'année hydrologique (avril-mars). Cette fonction implique des variations de niveau des lacs de retenue et ceci est à l'origine de conséquences négatives. Le remplissage de printemps peut être une menace hydrologique sérieuse pour l'agriculture. Le déstockage qui suit est mené en saison de navigation (il intéresse donc tous les secteurs impliqués dans l'aménagement) ou en hiver (il n'intéresse plus que l'hydroélectricité). D'après les règles établies, le déstockage devrait être mené selon un rythme précis et devrait être régulier d'une année sur l'autre pour ne pas porter préjudice à la pèche dans les réservoirs et pour ne pas entretenir l'érosion sur les rives. Depuis vingt ans, la pèche attribue toutefois ses mauvais résultats au non-respect des règles. D'autres ministères se plaignent du même fait. Les règles sont-elles respectées? Seule l'étude des niveaux réels des réservoirs permet de répondre à cette question. Elle fait apparattre depuis vingt ans des remplissages de printemps anarchiques, d'importantes et imprévisibles variations de niveau en saison de navigation, des déstoclcages massifs d'hiver. Cette pratique est partiellement responsable du développement en URSS d'un puissant mouvement de contestation écologique.

EN :

Since 1962, the Volga River has become a series of cascades of eight reservoirs. Initially, the main object of the development was hydro-electricity but fishing, irrigation and transport became more and more important. Sine 1962, the function of Volgian reservoirs has been to retain spring water for its redistribution during the navigation season - for all the sectors involved in the management - and during the winter - only for hydro-electricity. This function implies lake level variations, which can generate negative environmental effects.

According to Soviet economic principles, each Ministry manages its own equipment, which means that the Volga development is controlled from Moscow by different Ministries. The Ministry of Energy, controlling dams and turbines, has an enormous power. Hence, there are rules for defending the interests of the other economic sectors. The Ministry of Energy, allegedly, is concerned only about its own plans and does mot comply with the rules, which naturally it denies. These ruses have mot been published but their main lines are well-known as they are largely referred to in scientific publications concerning the Volga management problem. The only way to check is to compare the rules with the available hydrological data on lake levels.

The most significant part of annual Volgian runoff proceeds from the spring melting of snow. This water must be used to fill the Volgian reservoirs and to satisfy the Lower-Volga artificial flood (110 km³). Actual data about Kuybyshev dam water discharge shows that the lower-Volga water requirements are mot satisfied. The true data about Kuybyshev and Rybinsk lakes shows disorganized fillings : the reservoirs are filled up to different levels every year, which contributes to activate bank erosion and prevents the constitution of aquatic vegetation. Bank erosion supplies a lot of sediments which, certain years, obstruct access to storm shelters or, sometimes, to harbours (Dimitrovgrad, for example). The lack of aquatic vegetation reduces the possibilities of fish reproduction.

By raising the level of groundwaters around the reservoirs, this spring filling jeopardizes agriculture, so it is mot allowed to full reservoirs over the maximum water level. Yet, the data shows that the Kuybyshev reservoir, right in the middle of the agricultural zone of the USSR, was filled more than 16 years out of 26.

The drawdown must be carried out with moderation and according to a specific rhythm particularly before winter in order to force the fish to leave the shallows. During the winter it is better to avoid massive drawdowns. The study of winter levels reveals very deep drawdowms. In This case the lake surfaces reduce and the tee collapses down to the lake bottom causing very important prejudice to the aquatic fauna.

According to the numerous scientific publications by Soviet fishing Institutes, the non-observation of the rules accounts for the poor production of fish. (500-600 kg a year per km² on Kuybyshev and Kybinsk lakes) and for the increase of bank erosion. The study of the lake levels shows that the Volgian water is used only in the interest of hydro-electricity and without any care for the other users (agriculture, fishing, navigation) or for the effects on the environment. The Energy lobby is so strong that 25 years of scientific protest bas not changed anything.

Such inconsistent management bas played a great part in the determination of an environmental movement In the USSR. Over the last forty years significant areas of territory have been submerged under the large reservoirs (on the Volga alone more than 300,000 people have been resettled on account of submersion) so the scientific protest met with the approval by a show of hostility to hydro-energy. Since the instauration of the « glasnost », the protest against the « hydro-lobby » has taken a symbolical value, a facet of the opposition to the « old order », and the poor management of Volga development largely contributed to this.

FR :

L'origine et le mécanisme de l'augmentation de la concentration en manganèse dans l'eau de la nappe phréatique de Beaucaire ont été recherchés afin d'orienter le choix d'un procédé de démanganisation adapté aux conditions du site.

L'aquifère est caractérisé par son déficit en oxygène et par la présence de dépôts d'oxyde de manganèse (Mn(IV)) sur les sédiments. Dans ces conditions la microflore utilise les oxydes de manganèse conne accepteur final d'électrons (démontré dans les expériences in vitro) et le manganèse réduit passe alors en solution.

Lors des essais d'application du procédé Vyredox le potentiel d'oxydoréduction de la nappe augmente et la concentration en manganèse dissous diminue. Rien n'indique une précipitation du manganèse et donc un colmatage à la périphérie de la partie oxygénée de la nappe.

EN :

The origin and the mechanism of the increase of the dissolved manganese concentrations have been investigated to choose a system of demanganization well fitted b the site conditions.

The aquifer characteristics are a depletion of the dissolved oxygen amount and deposits of manganese oxides (Mn(IV)) on the detriments. Under these conditions the microflora utilizes these manganese oxides as a final electron acceptor (as demonstrated by in vitro experiments) and the solubilization of manganese takes place.

The field application of the Vyredox system increases the redox potential of the groundwater and the manganese concentration decreases. Nothing indicates that manganese precipitation and consequently warping of the water table takes place at the periphery of the oxygenated part of the aquifer.

FR :

Le présent article a pour but de montrer l'importance dune analyse intégrée des problèmes d'estimation hydrologique et des problèmes de décisions d'aménagements pour tenir compte rationnellement des diverses incertitudes intervenant dans ces problèmes. La méthode d'analyse est basée sur les techniques bayesiennes qui permettent des évaluations économiques comparées des divers types d'informations locales ou régionales mobilisées. Un cas d'application schématique est présenté.

EN :

This paper aims to show the importance of an integrated analysis of hydrological problems of estimation and of decision in water resource fields. Such an analysis is necessary to take into account the various uncertainties involved. The analysis is based on bayesian techniques which allow comparisons between the economical values of various types of information. This information can be both local and regional. A schematic example is presented.

FR :

Afin de modéliser efficacement la persistance dans les séries chronologiques rencontrées en hydrologie, des développements récents autour du modèle fractionnaire auto-régressif à moyenne mobile (FARMA) (fractional autoregressive-moving average model) sont présentés. On s'intéresse particulièrement ici à de nouvelles procédures permettant d'estimer les paramètres du modèle FARMA d'une manière efficace au point de vue calcul. Pour obtenir les distributions d'échantillons des estimateurs des paramètres à partir de petits échantillons, une technique faisant appel au bootstrap peut être utilisée. Des applications pratiques à des séries de débits en rivière, de précipitations et de températures, montrent l'utilité des modèles FARMA.

EN :

In order to model effectively persistence in hydrologic tune series, recent developments in fractional autoregressive-moving average (FARMA) models are presented. A time series possesses persistence or long memory if it has an autocorrelation structure that attenuates slowly to zero with increasing lags. Based on the controversy surrounding the Hurst phenomenon, some hydrologists claim that it is important to employ stochastic models which have the ability to model long memory when it is present in a given time series. Fractional Gaussian noise models and approximations thereof were developed within the field of hydrology in order to be able to model long memory. However, a particularly flexible set of models having the capability to describe long memory is the FARMA family of models, which constitutes a direct generalization of autoregressive integrated moving average (ARIMA) models.

In particular, like an ARIMA model, a FARMA model contains autoregressive and moving average parameters. Whereas the differencing operator d is restricted to be zero or take on positive integer values in an ARIMA model, the parameter d in a FARMA model can have real values and is estimated along with the other model parameters. For a specified range of values for the d parameter, a FARMA model has long memory. Besides reviewing the background and main theoretical properties of FARMA models, simulation and forecasting techniques are presented. Additionally, procedures for estimating the parameters of a FARMA model are given and a bootstrapping technique is described to obtain the small sample distributions of the estimated parameters.

To explain how to apply FARMA models in practice and demonstrate their usefulness, they are fitted to riverflow, precipitation and temperature time series.

FR :

Cette étude de laboratoire a eu pour but d'examiner la réactivité du bioxyde de chlore sur un acide humique d'origine aquatique en solution aqueuse et en milieu neutre (pH = 7,5) et de préciser en particulier l'incidence d'une préoxydation chimique au CIO₂ sur les potentiels de formation de composés organohalogénés (trihalométhanes, acides dicloroacétique et trichloroacétique, chlore organiquement lié) et sur l'adsorbabilité du carbone organique sur charbon actif.

Les résultats obtenus montrent que radian du bioxyde de chlore sur racide humique Pinail à l'obscurité, conduit à des faibles abattements du carbone organique dissous (< 10 %) et de l'absorbance UV à 254 nm (de l'ordre de 30 %) et conduit à des productions potentiel es en composées organohalogénés très nettement inférieures à celles formées par chloration. De plus, une préoxydation chimique au bioxyde de chlore permet de diminuer d'une manière très significative la production de composés organohalogénés au cours d'une post-chloration et semble améliorer l'adsorbabllité du carbone organique sur charbon actif.

L'oxydation de l'acide humique par le bioxyde de chlore s'accompagne, par ailleurs, de la formation de chlorites (0,65 mg/mg de CIO₂ consommé) qui peuvent ensuite être oxydés en chlorates au cours d'une post-chloration ou réduits en chlorures par un traitement au charbon actif.

Enfin, les résultats obtenus font apparaître que le mécanisme d'oxydation de composés organiques parle bioxyde de chlore en présence de la lumière ainsi que les interactions entre le bioxyde de chore, les chlorites, la matière organique et le charbon actif méritent d'être plus précisément étudiés.

EN :

Chlorine dioxide has drawn much recent attention as an alternative disinfectant and oxidant for drinking water to replace chlorine because of its powerful disinfecting ability and its limited capacity to produce organohalogenated compounds. However, the use of chlorine dioxide leads to chlorite (ClO₂-) and chlorate (ClO₃-) as inorganic oxidation by-products which are reported to have toxic effects on humans. The reactions of ClO₂ with simple organic compounds (phenols, aliphatic and aromatic amines...) produce polar compounds such as quinone, ketones, aldehydes and carboxylic acids while oxydation by-products of dissolved organic matter of surface waters (in particular humic substances) are largely unknown. Consequently, the aim of this work was to obtain a better understanding of the effects of the use of chlorine dioxide in drinking water treatment To this end, experiments were carried out with dilute aqueous solutions of an isolated aquatic humic acid (Pinail humic acid, PHA) and the objectives of this present study were :- To evaluate the ClO₂ demand and to determine the productions of chlorite, chlorate and of organohalogenated compounds such as trihalomethanes (THMs), dichloroacetic and trichloroacetic acids (DCA, TCA) which are the main organohalogenated products formed by chlorination.- To show the effects of chlorine dioxide preoxidation on organic halide formation potentials (postchlorination) and on the removal of dissolved organic carbon (DOC) by activated carbon. In addition, reactions of chlorite with chlorine or with activated carbon were also examined.

EXPERIMENTAL

Pniail humic acid was dissolved in phosphate buffered ultra-pure water (pH = 7.5). Oxidation and adsorption experiments were carried out in headspace-free bottles, at 20 ± 1 °C and in the dark. Stock solutions of chlorine dioxide (4-6 g l^-1) and of chlorine (6-10 g l^-1) were prepared in the laboratory and titrated by iodometry. Residual chlorine dioxide concentration in PHA solutions was determined by spectrophotometric measurement at 360 nm and by two colorimetric methods : the chlorophenol red and the ACVK methods. Concentrations of DOC and of total organic chlorine or halogen (TOCI, TOX) were measured using a DOHRMANN DC 80 carbon analyser and a DOHRMANN DX 20 A TOX analyser equipped with a microcoulometric cell, respectively. THMs, DCA and TCA were determined by a gas chromatograph equipped with a ⁶³ Ni electron capture detector after extraction by pentane for the THMs, and methylation in ether phase for DCA and TCA. Inorganic chlorine species were analysed by HPLC with a UV detector (ClO₂-) or by chromatography (Cl-, ClO₃-).

RESULTS

• Oxidation of PHA by ClO2

The results showed that PHA consumed about 2 mg of ClO₂/mg of DOC after a reaction time of 24 hours (fig. 1) and that there is a rapid consumption of ClO₂ during the first 30 minutes of the reaction (fig. 2) Oxidation by ClO₂ had no effect on DOC concentration (DOC removal : < 10 %) and led to a significant decrease (about 30 %) of the UV-absorbance at 254 or 270 nm (fig. 1 and 2), and to productions of ClO₂- (0,65 mg of ClO₂-/mg of ClO₂ consumed) which were independant of the applied oxidant dose and of the reaction time.

Furthermore, after a 72 hour reaction time in the dark, chlorine dioxide ([ClO₂]₀ = 5 mg l^-1, [PHA]0 = 5 mg l^-1, DOC = 2,6 mg l^-1) produces very small amounts of chloroform (< 5 µg l^-1), DCA (5 µg l^-1) and TCA (5 µg l^-1) and organochlorinated compounds (TOCl : 36 µg/mg DOC) compared to chlorine oxidation (tableau 1). However, in the presence of sunlight, ClO₂ is rapidly photodecomposed (fig. 3) and the photodegradation products of ClO₂ allow bromide oxidation (fig. 11) and lead to higher productions of organohalogenated compounds such as THMs (fig. 4).

• Chlorine dioxide preoxidation followed by chlorination

As shown in figure 5, chlorine dioxide preoxidation reduces the production of organohalogenated compounds and the chlorine demand during postchlorination. For a preoxidant dose corresponding to the ClO₂ demand of PHA, the decrease in the formation potentials of CHCl₃, DCA, TCA and TOCl was about 40-50 %. These results confirm the similarity of the action of chlorine dioxide and chlorine on aromatic structures which have high electron density carbons and which constitute probably the most reactive precursors of organohalogenated by-products.

As far as chlorite concentration is concerned, the results showed that chlorite formed during the preoxidation step was completely oxidized to chlorate during postchlorination, under the experimental conditions used in this study (chlorine dose : 40 mg l^-1; contact time : 24 or 72 hours). Because of the reactions of chlorine eh chlorine and with residual chlorine dioxide, a small increase in the chlorine demand was observed when PHA solutions were heavily preoxidized (fig. 5).• Chlorine dioxide preoxidation followed by activated carbon treatment

Batch experiments were carried out with a powdered activated carbon (PAC, granulometry : < 80 µm) which was obtained by crushing a commercial granular activated carbon (CECA 40,12 x 40 mesh). Once equilibrium was achieved (contact time : 10 days), adsorption isotherms indicated that chlorine dioxide preoxidation increases the absorbability of DOC on activated carbon (fig; 4 tableau 2). Furthermore, chlorite in oxidized PHA solutions was reduced by PAC to chloride. The capacity of CECA 40 activated carbon for ClO₂- reduction to Cl- was about 170 mg ClO₂-/g of PAC (fig. 7). Other experiments showed that chlorite may react with specific surface groups on PAC to produce inorganic carbon (fig. 7) and with PHA only in the presence of PAC as shown the DOC and UV-absorbance curves in figure 8 and the increase of TOX concentration in the liquid phase in figure 9. Thus the observed increase in DOC absorbability on PAC after a chlorine dioxide preoxidation may be attributed to cheminal interactions between PAC, chlorite, residual chlorine dioxide and adsorbed organic matter and requires further study.

FR :

Les apports contaminants d'origine continentale jouent un rôle fondamental dans le processus de contamination du milieu marin. Une étude a été réalisée sur le site de Barcelone, afin de réaliser un inventaire des sources de pollution et de déterminer l'influence de ces apports sur la contamination des sédiments marins; ce lieu d'expérimentation ayant été retenu du fait de la multiplicité des types de rejets effectués en mer : eaux usées, boues de station d'épuration... Les sédiments ont été prélevés à partir du navire océanographique au cours de 3 campagnes de novembre 1987 à juin 1988 à des distances de 50 mètres à 4 km de la côte et à des profondeurs de 10 à 52 métres. Globalement 88,8 % des échantillons analysés renfermaient des oeufs d'helminthes (Nématodes et/ou Cestodes) à des concentrations variant de 5 à 256 oeufs 100 g^-1 de sédiments Si des oeufs de Nématodes (Ascaris, Toxocara, Trichuris, Capillaria) sont retrouvés dans tous les échantillons positifs, seulement 44,4% renferment des oeufs de Cestodes (Taenia, Hymenolepis). Chez les Nématodes, les oeufs de Toxocara ont été retrouvés avec une très grande fréquence (66,6 %) chez les Cestodes des oeufs de Tenia (38,8 %) prédominent Il faut donc noter la moindre résistance des oeufs de Cestodes dans le milieu marin. Quant à la viabilité réalisée sur les oeufs d'Ascaris, elle s'échelonne selon les prélèvements de 5 à 100 %. Des études ultérieures devraient être poursuivies pour vérifier si ces oeufs viables ont encore conservé leurs potentialités infectieuses.

EN :

Microbiological pollution of the marine environment is often the result of man's presence in the coastal zone (offshore flow of sewage sludge or effluents from raw or treated wastewater).

Although many studies have been carried out on the viral and bacteriological pollution of the marine environment, very little is known about parasitological contamination of this important resource. This investigation is aimed at the problem of parasitological contamination by examining its sources and their effect on the contamination of marine sediments of a specific coastal region.

Barcelone was selected as the study site because of the many types of effluent flowing into the sea. These are due to : two highly polluted rivets (the Besos river and the Llobregat river), treated and raw wastewater. Sewage sludge is transported offshore front Barcelone through a deep conduit.

Marine sediments were collected at distances between 50 m. to 4 km of the shores of urban Barcelone at depths varying from l0 to 52 m. Samples obtained by the oceanographic vessel « Garcia del Cid » required use of a Reineck device.

Parasite density was too low for direct microscopic examination, thus all the samples underwent an enrichment procedure. A preliminary study had shown that, out of all the various concentration methods available, the one described by Janeckso-Urbanyl was the best adapted 10 the samples investigated here. This method uses a high density (d = 1.44) potassium lodomercurate solution with low viscosity so that the eggs rise rapidly to the surface. The slides were enlarged 100 times and numbered with a Mac Master slide. The determination of the viability of Ascaris eggs was studies after a n-butanol treatment. The results are expressed as number of eggs per 100 g-1 sample.

Helminth eggs were found in 88,8 % of 36 samples analysed with levels ranging from 5 to 256 eggs per 100 g^-1 of sediment. During the 3 campaigns, in November 1987 (first campaign) was obtained the smallest number of positive samples (9/12) and in March 1988 (second campaign) the highest number of positive samples seize all these samples contained helminth eggs. These eggs were of the Nematode and/or the Cestode class. All the positive samples (32/36) contained Nematode eggs whereas Cestode eggs are found only in 16 samples. The Nematode eggs were Ascaris, Toxacara and Trichuris, Capillaria; Cestode eggs Hymenolepis and Taenia. All the samples with Nematode eggs contained in decreasing amounts Toxocara (66,6 %), Ascaris (61 %) and Trichuris, Capliaria (22,2 %). Cestodes were predominantly Taenia (38,8 %), Hymenolepis (16,6%). The difference in behaviour between Nematode and Cestode eggs, the latter being much less frequent, was probably due to the greater fragility of Cestodes in a marine environment. The viability of the Ascaris eggs found on samples at the Besos area was 100 %. The samples from the effluent zone contained Ascaris eggs with viability ranging from 0 to 100 %. In the Barcelonetta area, 5 to 42 % of Ascaris eggs were viable.

These results obtained front seawater emphasize the necessity of further investigation into the extent of parasitological pollution on the marine environment by offshore flowing of treatment plant sludge, paying particular attention to the viability and the infection potential of the helminth eggs.