Etude de la circulation dans les bassins d'aeration a boues activeesStudy of the circulation pattern in aeration tanks

Keeping the mixed liquor in suspension is one of the critical problems in aeration tanks. This can only be assured by adequate circulation of the liquid. A hydrodynamic study in different laboratory and industrial scale aeration tanks, has been carried out to characterise the circulation (bottom velocity, V_f, mean circulation velocity) using the following parameters i.e. tank geometry and air flow rate G. This study also proposes a scale-up criterion for aeration tanks. All the dimensions of these tanks are given in Table 1.     

Gonflement de la chaux dans les briques

Le problème de l'éclatement des briques dû à l'action de la chaux devient grave dans la fabrication des briques en différents endroits de l'lnde et d'ailleurs. Des briques cuites tombent en poussière lorsqu'elles sont exposées à l'air libre, du fait de la présence de particules de chaux. L'Institut central de recherche de la construction de Roorkee s'est attachée à l'étude du mécanisme par lequel les chlorures peuvent prévenir cet inconvénient.     

Etude de l'inhibition de la nitrification par les composes organiques

Organic compounds likely to inhibit nitrification are numerous. The literature is rich in quantitative results but interpretation of these results is rarely attempted. Our study presents the inhibition constant determination of some phenolic and naphtholic products and proposes a theoretical approach of inhibition with emphasis on the structure.On a nitrifying mixed biomass, we have studied, in batch experiments, the effects of following organic pollutants on the nitrification: phenol; 2,4,5 trichlorophenol; 1-naphthol; 2 chloro-1-naphthol; 4 chloro-1-naphthol; 2,4 dichloro-1-naphthol. Our trials were conducted with mixed biomass (not only nitrifying bacteria) and, for the phenol, we observed inhibition that disappears when phenol is degraded. The phenol is highly toxic for nitrifying bacteria (Figs 1 and 2).For non biodegradable naphtholic components the model: allows the determination of K_I (inhibition constant) (Fig. 3).In dynamic experiments on biological filters, the study of the support role in nitrifying fixed bacteria inhibition has been carried out by comparing two different organics in particular: methanol (very little adsorbable aliphatic compound) and phenol (aromatic compound very well adsorbed on activated carbon). The two supports compared were expanded clay and activated carbon. The results obtained show that an adsorbing support can retain adsorbable compounds, removing toxicity observed for non supported or fixed or non adsorbing material ones (Fig. 4).For the naphthol family, we have calculated electronic structures using the M.N.D.O. method. We obtained also energies of low unoccupied molecular orbitals (L.U.M.O.) and high occupied-molecular orbitals (H.O.M.O.) Relations between the energy of L.U.M.O., the energy difference between the two frontier orbitals, pK_a and toxicity have been established. We show a correlation of K_i with pK and E_BV and ΔE (Fig. 5, Table 4).     

Metaux lourds dans les sediments de l'estuaire de la loire

Estuaries, being interfaces between fluviatile and marine environments, are the scene of considerable physico-chemical and biological gradients which can have an effect on the distribution of metallic elements between the solid and dissolved phases. The purpose of the present study was to determine the relative influence of each parameter in this distribution.The study included two series of samples (ICOLO 26 and ICOLO 32) taken by means of the Schipeck grab at 19 selected points of the estuary as indicated in Fig. 1.Within the framework of this study we first investigated and were able to determine the origin and evolution of the metallic elements in the Loire estuary.Pollution levelTable 1 and Fig. 2 summarize the results: firstly, the metallic element contents are relatively low, indicating that pollution is not very strong. Secondly, the contents measured in the different samples vary considerably due to the great heterogeneity of sample composition and particle-size distribution.Upstream-downstream evolutionFigure 2 shows that the longitudinal profiles for metals are very similar to those obtained for the different characteristics of the sediments. Such an observation has already been made by various authors. Owing to the existence of these relationships, we believe, as do Boust et al. (1981), that it is preferable to interpret the results relative to metals obtained on a given site in terms of the various characteristics of the sediment. In Fig. 3, the metallic element contents (ICOLO 26 samples) is thus plotted against organic carbon. As shown in the figure, there is a very good relationship between the two parameters. Figures 2 and 3 indicate that the contents are uniform throughout the estuary with no evidence of further significant sedimentation this uniformity being due to tidal action. Owing to this uniformity, the impact of significant discharges is highly localized except for the wastewater from the city of Nantes as a whole, whose impact which is felt along the entire estuary.The relationship between copper and volatile matter for the ICOLO 32 samples, as represented in Fig. 4, shows that the points fall into two groups, which are the same whatever the explanatory parameter involved. Though the results are more uniform for the ICOLO 26 than for the ICOLO 32 samples, Fig. 6 clearly shows that the “marine” points stand out in both series of samples. This is indicative of a reduction in contents in the downstream direction, especially noticeable beyond point B (Zn, Cr, Ni) or even M (Cd, Cu, Pb).The seasonal evolution is clearly shown on the “metal-characteristic of sediment” graphs by the comparison of the slopes of the lines linking the same point sampled during the two sampling campaigns. The example of copper is shown in Fig. 7.On the whole, analysis of the results derived from the study of one characteristics of the sediment, indicates that only limited enrichment or depletion occurs at a point over a period of time. This probably reflects a good constancy over time of the metallic flux in the estuary. There is little doubt that changes in the composition of the sediment, will cause changes in the trapping of the metallic flux. In this case, variations in contents do not reflect alterations in the metallic flux over the sediment, but the varying capacity of the sediment under investigation to trap the same polluting flux according to is own composition.This study was also productive in the investigation of the various phenomena responsible for the reduction in metal contents during estuarial transit, which phenomenon can be expected to occur in a large number of estuaries.The impact depends on the chemical properties of the element under investigation.Solubilization of metallic elements due to to increased salinity occurs but plays only a secondary role in the upstream-downstream reductions. This is presumably because of the low percentages of metal absorbed in relation to the total amount of metals associated with the sediments.The reduction in metal contents related to the degradation of organic matter also occurs but it is of little significance compared with the overall phenomenon. The disappearance of metals associated with organic matter could well be related to salinity.The considerable reduction of contents in the lower estuary markedly occurs downstream of the salinity front and precisely where the first sediments characteristic of the marine environment are encountered. Consequently, the most obvious parameter responsible for the reduction in the metallic element contents is the mixing of relatively laden fluviatile sediment with “clean” marine sediments.     

Etude de l'inhibition de la nitrification par les cations de métaux lourds

The aim of this work was to make a contribution to the knowledge of inhibition by some inorganic pollutants of nitrifying bacteria which are free or fixed on an adsorbant support.For the inhibition tests, we used the following inorganic salts: Nickel, Ni²⁺; Copper, Cu²⁺; Cadmium, Cd²⁺ and Zinc, Zn²⁺ as sulphates (Figs 1, 2).The preliminary tests give the solubility of the cations in the feed solutions to the pilot units (biological filters and activated sludge). The other experiments, dynamic or in batch, try to establish the inhibitory effects observed with respect to a nitrifying biomass inactivation.     

Etude de l'inhibition de la nitrification par les composes organiquesInhibition study of the nitrification by organic compounds

Organic compounds likely to inhibit nitrification are numerous. The literature is rich in quantitative results but interpretation of these results is rarely attempted. Our study presents the inhibition constant determination of some phenolic and naphtholic products and proposes a theoretical approach of inhibition with emphasis on the structure.

On a nitrifying mixed biomass, we have studied, in batch experiments, the effects of following organic pollutants on the nitrification: phenol; 2,4,5 trichlorophenol; 1-naphthol; 2 chloro-1-naphthol; 4 chloro-1-naphthol; 2,4 dichloro-1-naphthol. Our trials were conducted with mixed biomass (not only nitrifying bacteria) and, for the phenol, we observed inhibition that disappears when phenol is degraded. The phenol is highly toxic for nitrifying bacteria (Figs 1 and 2).

For non biodegradable naphtholic components the model:

allows the determination of K_I (inhibition constant) (Fig. 3).

In dynamic experiments on biological filters, the study of the support role in nitrifying fixed bacteria inhibition has been carried out by comparing two different organics in particular: methanol (very little adsorbable aliphatic compound) and phenol (aromatic compound very well adsorbed on activated carbon). The two supports compared were expanded clay and activated carbon. The results obtained show that an adsorbing support can retain adsorbable compounds, removing toxicity observed for non supported or fixed or non adsorbing material ones (Fig. 4).

For the naphthol family, we have calculated electronic structures using the M.N.D.O. method. We obtained also energies of low unoccupied molecular orbitals (L.U.M.O.) and high occupied-molecular orbitals (H.O.M.O.) Relations between the energy of L.U.M.O., the energy difference between the two frontier orbitals, pK_a and toxicity have been established. We show a correlation of K_i with pK and E_BV and ΔE (Fig. 5, Table 4).     

Metaux lourds dans les sediments de l'estuaire de la loireHeavy metals in the sediments of the loire estuary

Estuaries, being interfaces between fluviatile and marine environments, are the scene of considerable physico-chemical and biological gradients which can have an effect on the distribution of metallic elements between the solid and dissolved phases. The purpose of the present study was to determine the relative influence of each parameter in this distribution.The study included two series of samples (ICOLO 26 and ICOLO 32) taken by means of the Schipeck grab at 19 selected points of the estuary as indicated in Fig. 1.Within the framework of this study we first investigated and were able to determine the origin and evolution of the metallic elements in the Loire estuary.Pollution levelTable 1 and Fig. 2 summarize the results: firstly, the metallic element contents are relatively low, indicating that pollution is not very strong. Secondly, the contents measured in the different samples vary considerably due to the great heterogeneity of sample composition and particle-size distribution.Upstream-downstream evolutionFigure 2 shows that the longitudinal profiles for metals are very similar to those obtained for the different characteristics of the sediments. Such an observation has already been made by various authors. Owing to the existence of these relationships, we believe, as do Boust et al. (1981), that it is preferable to interpret the results relative to metals obtained on a given site in terms of the various characteristics of the sediment. In Fig. 3, the metallic element contents (ICOLO 26 samples) is thus plotted against organic carbon. As shown in the figure, there is a very good relationship between the two parameters. Figures 2 and 3 indicate that the contents are uniform throughout the estuary with no evidence of further significant sedimentation this uniformity being due to tidal action. Owing to this uniformity, the impact of significant discharges is highly localized except for the wastewater from the city of Nantes as a whole, whose impact which is felt along the entire estuary.The relationship between copper and volatile matter for the ICOLO 32 samples, as represented in Fig. 4, shows that the points fall into two groups, which are the same whatever the explanatory parameter involved. Though the results are more uniform for the ICOLO 26 than for the ICOLO 32 samples, Fig. 6 clearly shows that the “marine” points stand out in both series of samples. This is indicative of a reduction in contents in the downstream direction, especially noticeable beyond point B (Zn, Cr, Ni) or even M (Cd, Cu, Pb).The seasonal evolution is clearly shown on the “metal-characteristic of sediment” graphs by the comparison of the slopes of the lines linking the same point sampled during the two sampling campaigns. The example of copper is shown in Fig. 7.On the whole, analysis of the results derived from the study of one characteristics of the sediment, indicates that only limited enrichment or depletion occurs at a point over a period of time. This probably reflects a good constancy over time of the metallic flux in the estuary. There is little doubt that changes in the composition of the sediment, will cause changes in the trapping of the metallic flux. In this case, variations in contents do not reflect alterations in the metallic flux over the sediment, but the varying capacity of the sediment under investigation to trap the same polluting flux according to is own composition.This study was also productive in the investigation of the various phenomena responsible for the reduction in metal contents during estuarial transit, which phenomenon can be expected to occur in a large number of estuaries.The impact depends on the chemical properties of the element under investigation.Solubilization of metallic elements due to to increased salinity occurs but plays only a secondary role in the upstream-downstream reductions. This is presumably because of the low percentages of metal absorbed in relation to the total amount of metals associated with the sediments.The reduction in metal contents related to the degradation of organic matter also occurs but it is of little significance compared with the overall phenomenon. The disappearance of metals associated with organic matter could well be related to salinity.The considerable reduction of contents in the lower estuary markedly occurs downstream of the salinity front and precisely where the first sediments characteristic of the marine environment are encountered. Consequently, the most obvious parameter responsible for the reduction in the metallic element contents is the mixing of relatively laden fluviatile sediment with “clean” marine sediments.     

Utilisation de la photographie de moire pour mesurer l'usure des granulats dans les couches superficielles de chaussees

The author describes a rapid and non-destructive method of following and measuring the evolution of the shape of aggregates used in wearing courses of roads. The method is based on the moiré phenomenon which, in the present example, allows us to draw graphic curves, with a precision up to a few tenths of millimeters on a vertical cut. The article describes:

- the method and equipment necessary to obtain a workable moiré on a photograph,

- a computer-programmed chain which, during a series of topographical cross-cuts, measures and studies the distribution of spacings of contour lines. The spacings vary according to the rounded nature of the aggregates which are classified according to their shape.

The road studied is then characterized by drawing graphs of the distribution of the lengths of cuts of the road, occupied by the different shapes of the selected aggregates. The author gives a few examples of the uses of the method in studying the evolution of surface dressings and embedded stone on concrete. The author also shows that his method can be used in other fields than civil engineering.     

Effects of aeration patterns on the flow field in wastewater aeration tanks

Due to the high energy input of aeration, the spatial distribution of air diffusers largely determines the flow field in aeration tanks. This has consequences on the efficiency of the aeration system, the performance of the aeration tank and on tank operation and control. This paper deals with these effects applying both Computational Fluid Dynamics (CFD) enhanced with a biokinetic model and full scale validation using velocity and reactive tracer measurements with high temporal and spatial resolution. It is shown that small changes in the diffuser arrangement drastically change the overall flow field. Using different aeration patterns in the same tank may lead to large scale instabilities in the flow field that lower plant performance and produce strong variations in concentration signals impeding their use for plant control. CFD is a valuable tool to analyze the interaction of flow field and aeration and their effects on plant performance and operation. But, in complex flow situations experimental validation is needed and strongly suggested.     

Etude du transfert DE Cd, Pb, Cu ET Zn dans les chaines trophiques neritiques et estuariennes—I. Etat dans l'estuaire interne de la loire (France) au cours de l'ete 1978

In order to determine the behaviour of some trace elements (Cd, Pb, Cu, Zn) in estuarine biota, different species of crustaceans and fishes were taken up from the Loire estuary. The concentrations of metals were determined by atomic absorption.Except for Zn, the accumulation of metals is higher in crustaceans than in fishes and the phenomenon is particularly important for copper, a constituent of crustaceans respiratory pigment. The concentrations of metals are no more important for bottom-feeders than for other fishes. The highest levels are encountered for Zn followed by Cu, Pb and Cd. The Loire organisms are not so contaminated than those of the same species taken up from heavily polluted estuaries (Severn and Medway, G.-B.).Transfers in food chains were quantified with the transfer factor: f.t. = Concentration in the consumer/Concentration in the prey.For Cd, Pb and Cu, the transfer factor is generally inferior to 1, attaining exceptionally 2.01. Except in one case, it is higher than 1 for Zn. The concentration of trace elements in intestine content is higher than in stomach content, probably as a consequence of faeces enrichment by unassimilated metals. So, there is probably no biomagnification in estuarine food chain for Cd, Pb and Cu, the case of Zn being more ambiguous.     

Recherches sur les risques pouvant resulter de la pollution chimique des eaux d'alimentation—I. Etude de la toxicite a long terme chez le rat et la souris des micropolluants organiques chloroformo-extractibles a partir d'eaux livrees a la consommation humaine

Groups of 50 weaning mice and 50 weaning rats of both sexes received organic micropollutants (extracted from drinking water by chloroform at neutral pH) in their diet for their whole life span. The doses were calculated from a 31 water daily intake by a man of 60 kg, with application of safety factors of 100 and 200. Long term toxicity studies showed:

1. 1. Biochemical changes: increase of transaminases and ornithine carbamyl-transferase activities in blood serum, which, taking into account the variation of activities of the same enzymes in liver parenchyma do not appear to be caused only by hepatic cytolysis.

2. 2. Histopathological changes: (a) liver enlargement, cellular hypertrophy of the liver, steatosis and cirrhosis; (b) significant increase of the incidence of malignant tumours in female mice and in male and female rats with, in the latter, a dose response relationship.

3. 3. Significant increase in mortality rates, in both species, beginning much earlier in males than in females.

A critical discussion is given of results in relation to their value as alarm signs regarding prediction of eventual manifestation of such toxic potentialities in man from consumption, of drinking water containing organic micropollutants.

Résumé

Des micropolluants organiques, obtenus par extraction au chloroforme à pH neutre à partir d'une eau offerte à la consommation humaine (obtenue par traitements classiques, comportant une préchloration, une ozonation et une post-chloration terminale, d'une eau brute de riviére), ont été administrés, ˜a partir du sevrage, après incorporation au régime, á des lots de 50 rats et de 50 souris, par moitié mâles et femelles. Les doses ont été calculées à partir de la consommation quotidienne moyenne de 31 d'eau pour un homme de 60 kg, avec application de facteurs de sécurité de 100 et 200.Les résultats obtenus mettent en evidence les faits principaux suivants:

1. 1. Sur le plan biochimique: Augmentation des activités des transaminases et de l'ornithine transférase au niveau du sérum sanguin traduisant une atteinte du foie qui, d'aprés les observations relatives á l'évolution des taux des mêmes enzymes au niveau du parenchyme hépatique, ne parait pas pouvoir être rapportée à une simple action cytolytique.

2. 2. Sur le plan histologique: (a) phénoménes d'hypertrophie cellulaire au niveau du tissu hépatique avec tendance à la dégénérescence graisseuse et lésions de type cirrhotique; (b) augmentation significative du nombre des tumeurs chez les souris femelles et chez rats des deux sexes avec, au moins chez cette derniére espéce, une corrélation avec la dose.

3. 3. Parallélement, accroissement significatif du taux de mortalité chez les deux espéces, augmentation débutant beaucoup plus précocément chez les mâles.

Discussion critique des résultats obtenus en ce qui concerne notamment leur valeur comme signes d'alarme quant à la manifestation éventuelle de potentialités toxiques pouvant résulter, chez l'homme, de l'ingestion prolongée d'eaux d'alimentation renfermant des traces de micropolluants.     

Propagation des ondes dans les roches anisotropes sous contrainte évaluation de la qualité des schistes ardoisiers

The propagation velocity of longitudinal waves has been measured on slates with various fissilities. The cylindrical bars used for those measurements were cut along the characteristic lines of the fabric of those schists and were submitted to an axial stress. This method clearly points out the influence of the fabric (orientation of the minerals and discontinuities) and of the development of the stress cracking. It may be usefully applied for the evaluation of the quality of schists used for the production of roofing slates.     

Capteur de resine chelatante pour le prelevement la preconcentration et la determination de metaux traces toxiques (Zn, Cd, Hg, Pb) dans les eaux

The subject of this article is the elaboration of a catcher of toxic metals (Zn, Cd, Hg, Pb) which enables them to be determined at μg 1⁻¹ level.It is known that, at these low concentrations, it is advisable to prevent the sample from being altered in any way between the time of taking and the time of analysis; moreover, it is necessary to proceed, on the one hand, to the pre-concentration of the wanted elements and, on the other hand, to the elimination of the main elements present in water and likely to interfere at the time of analytical determination.We therefore made a catcher which makes it possible to achieve these two desired effects by chromatographic separation and to carry out the conditioning of the sample, in the field, in a well-defined, chemical form, stable in time as a small volume in a solid state, easy to carry and to store.The catcher is in the shape of a small, cylindrical capsule (diameter = 29 mm, thickness = 10 mm) in Makrolon (Lexan) whose bases are made of a nylon cloth and which contains a chelating resin load (Chelex-100, 100–200 mesh).At the time of use, the catcher is put into a dismountable filtering-apparatus which permits percolation of the solution containing the wanted metal traces.Then, to proceed to the analytical determination of the elements it is possible to use two methods: analysis in solution after elution;X-ray fluorescence spectrometry, or else activation analysis on the catcher dried and then pelletized when hot in an hydraulic press.The experimentation has included the following points:

1. 1. Determination of the conditions of chromatographic separation on Chelex-100 resin which permits optimal fixation of Zn, Cd, Hg and Pb and the elution of the main elements Ca, Mg and Fe. We chose soda-citrate medium 7.1 · 10⁻² M at pH = 7.00;

2. 2. Determination of the conditions of use of the catcher and its efficiency according to the main elements in the sample of water.

The process we chose involves a sample of 1 l. of water which is acidified at pH 1 by concentrated HNO₃ and then filtered through a membrane (0.45 μm).The solid residue is examined by X-ray fluorescence spectrometry.To the filtrate are added 100 ml of soda-citrate buffer 7.1 · 10⁻¹ M and the pH is set to seven by addition of NaOH. Then the filtrate is percolated through the Chelex-100 resin catcher (flux = 1.5 ml min⁻¹).Then, it is possible to proceed: either to the elution of toxic metals by HNO₂ 2M to determine them in solution (atomic absorption spectrophotometry, anodic stripping voltammetry); or to pelletizing of the catcher and to the analytical determination by X-ray fluorescence spectromy or activation analysis.The results of these methods are compared with different water: (1) spring warer: (2) over waters and (3) sea-water. The elution method as well as direct analysis of the pelletized catcher gave satisfactory agreement.