ITA recommendations on contractual sharing of risks/AITES recommandations sur le partage contractuel des risques

This report summarizes two recommendations prepared by the International Tunnelling Association Working Group on Contractual Sharing of Risks. The recommendations were officially approved by the International Tunnelling Association at its annual meeting in Toronto, Canada, in September 1989.     

ITA recommendations on contractual sharing of risks/AITES recommendations sur le partage contractuel des riques ITA Working Group on Contractual Sharing of Risks/ AITES Groupe de Travail “Partage Contractuel des Risques”

This report summarizes two recommendations prepared by the International Tunnelling Association Working Group on Contractual Sharing of Risks. The recommendations were officially approved by the ITA at its annual meeting in Acapulco, Mexico, in May 1992.     

Utilisation de l'algue oocystis sp. Pour le traitement tertiaire des eaux usees-II. Effet du conditionnement prealable des cellules en cyclostat sur leur vitesse de prise en charge de l'azote lors d'incubations de longue duree

In an attempt to examine if the rapid uptake of nitrogenous nutrients by “starved” cells occurs also during the prolonged incubation required for complete removal of nutrient from wastewater, ammonia uptake rates for Oocystis sp., in preconditioning phase (phase I) and incubation phase (phase II) are compared.When equilibrium is reached in phase I, phytoplankton cells have a relatively constant N-ammonia uptake rate per cell; this rate varies with the different water stocks used in different experiments, but it is always lower (2–6 times) than the uptake rate exhibited by these cells in phase II.At the end of the second phase (12 h) the cell nitrogen content is up to 3.5 times higher than the initial content.These characteristics of alga Oocystis sp. are discussed and commented.     

Influence sur la survie jusqu'a eclosion des embryons de carpe commune (cyprinus carpio l.) apres traitement, pendant la fecondation et le developpement precoce, par le carbendazime, un fongicide antimitotique de synthese

The toxicity of the systemic antimitotic fungicide carbendazim, a benzimidazol compound, was studied both by trout and common carp insemination, as well as on the early development of the common carp.The toxicity is several grades of magnitude higher for these stages of the vital cycle compared with the effect on the adult stages: whereas The Pesticide Manual states that for the adult Carp, an LC₁₀₀ (24 h) > 1000 mg 1⁻¹ we find, during insemination at pH 9: LC₁₀₀ (30 min) < 5 mg l⁻¹ and during insemination at pH 7: LC₁₀₀ (30 min) <2.5 min l⁻¹.During early development we find, for instance, LC₁₀₀ (30 min) < 5 mg 1⁻¹ before the end of activation and LC₁₀₀ (24 h) < 1 mg l⁻¹ before the end of epiboly.In the course of insemination, the egg is more sensitive to carbendazim at pH 7 than at pH 9: this difference may be attributed to a greater solubility of the non ionic form of the molecule in the biological membranes.The resistance of the embryo to short treatment grows at the end of activation. This may be attributed to the decrease of the shell permeability during activation.Before the end of activation, the resistance to short intoxication seems to be able to fluctuate, which perhaps corresponds to the existence of sensitive stages in the mitotic cycle.The resistance to an over 24-h exposure increases abruptly at the end of epiboly, which could correspond to a protective part played by the enveloping layer.We suggest the possibility of classifying aquatic pollutants by correlating their physiological mode of action to the resistance profile of the fish embryo.The carp egg seems to be a favourable biological model for studying the effects of aquatic pollutants.     

Adsorption de colorants ioniques sur le dechet lainier de carbonisageAdsorption of ionic dyes on wool carbonizing waste

Wool carbonizing waste is not used although large amounts are available in the countries where wool is processed. Wool carbonizing waste is made up of two components: the plant particles can be considered as sulfo lignins; the short-size wool fibres have undergone chemical modifications. Owing to its physical structure and to the polar as well as apolar properties of its macromolecules, this waste is liable to adsorb ionic organic solutes. The adsorption of ionic dyes on wool carbonizing waste was therefore investigated so as to evaluate its possible use for the decolourization of dyeing effluents. The effect of the solution-substrate reaction time on the adsorption at various temperatures was studied first. Temperature had a marked effect on the adsorption of the acid dye (AB 80) (Fig. 1) whereas the basic dye (BR 22) (Fig. 2) was characterized by its faster diffusion within the wool carbonizing waste particles. These differences can be ascribed to the higher steric hindrance of the AB 80 molecules and to their possible aggregation. The L-type adsorption isotherms corroborated the temperature effect already mentioned as well as the high affinity of the wool carbonizing waste with acid (Fig. 3) and basic (Fig. 4) dyes. The shape of the adsorption isotherms suggests that the adsorption proceeds through ionic bonding; as the dye molecules are oriented flatwise on the surface of the waste, the dye-substrate hydrophobic interactions can be maximum. The amounts adsorbed were 0.744 mmol g^?1 (i.e. 52.5%) for AB 80 at pH 2 and 0.193 mmol g^?1 (i.e. 5.5%) for BR 22 at pH 4. Higher amounts of basic dyes might however be expected to be adsorbed since the adsorption maximum is reached at pH 9 in the case of BR 22 (Fig. 5), as a result of the increasingly electronegative charge of the substrate. The Langmuir and Freundlich equations (Table 1) were used to have a mathematical model for the operation of a waste water processing unit. As shown by the L-type adsorption isotherms, the wool carbonizing waste used is suitable for the processing of low concentration effluents, such as dyeing waste waters: the decolourization of synthetic solutions was therefore considred. The column processing of an AB 80 solution showed the effect of the reaction time on the efficiency of the material used (Table 2). Investigation of the processing of a BR 22 solution in a stirred reactor led to the determination of the optimum carbonizing waste concentration (Fig. 6). as well as of the optimum effluent-substrate reaction time and the number of reactors to be used (Fig. 7). Eventually, the adsorptive power of the wool carbonizing waste used was compared with that of various materials (Table 3): the uptake capacity of wool carbonizing waste is lower than or equal to that of other substrates in the case of basic dyes but it is 6–10-fold higher in the case of acid dyes.     

Chloration de composés organiques: demande en chlore et réactivite vis-a-vis de la formation des trihalométhanes. Incidence de l'azote ammoniacalChlorination of organic compounds: Chlorine demand and reactivity in relationship to the trihalomethane formation. Incidence of ammoniacal nitrogen

The purpose of this work is to contribute to knowledge of the condition of formation of volatile and non-volatile organochlorinated compounds during surface water chlorination. With this aim in view, the chlorination of a number of organic substances in diluted aqueous solutions (10⁻⁶-10⁻⁵ moll ⁻¹) and in a neutral medium was studied. Special attention was given to their reactivity in relation to the formation of trihalomethanes.The results obtained show great differences in the reactivity of chlorine towards chemical substances liable to be present in the waters. The high chlorine demands, 5–12 mol of chlorine per mol of compound after a 15 h reaction at pH 7, where obtained with those aromatic compounds having activating groups such as — OH and — NR₂ (phenol and aniline derivatives). On the other hand, a number of compounds (alipahitcs in general; acids, aldehydes, alcohols…) are relatively inert towards chlorination.As far as chloroform production is concerned, the study shows that many organic compounds are liable to lead to the production of low quantities of chloroform in a neutral medium (molar yields < 5%). However, only a few specific structures such as metapolyhydroxybenzenes and metachlorophenols constitute good precursors of the haloform reaction.The study of the formation kinetics of chloroform, carried out with some precursors of different reactivity: acetone, acetylacetone, resorcinol, phloroglucinol and 3,5-dichlorophenol allowed us to determine the kinetic constants of chloroform formation at pH 7.5 and 20° C:

The results obtained during this work also show that the chlorine found in the chloroform produced from a precursor, represents only a small proportion of the chlorine demand. Even with a highly reactive precursor such as resorcinol. It was shown that the liberation of chloroform is accompanied by the formation of trichloroacetic acid (molar yield < 10%) and of monochloromaleic acid (molar yield 60%). Moreover, tetrahalogenated and pentahalogenated hydrocarbons (C₃Cl₄ and C₃ HCl₅) resulting from 3,5 -dichlorophenol chlorination were made manifest. As for the chlorin- ation of acetylacetone, a mechanism passing through the formation of 1,1-tri- chloroacetone was proposed.Lastly, in the general framework of the interactions between chlorine, ammonia nitrogen and the organic compounds which are frequently found in surface water chlorination, the study allowed us to show that the chlorination of highly reactive precursors (such as metapolyhydroxybenzenes and metachlorophenols) can lead to the production of important amounts of chloroform before reaching breakpoint. These results compared to the values of the velocities of the various reactions between chlorine and the ammoniacal compounds.     

Influence of daily surface temperature fluctuations on rock slope stability: case study of the Rochers de Valabres slope (France)

The present paper describes a rockfall that has affected the Rochers de Valabres slope (France's Southern Alps region) and discusses one possible mechanism for the occurrence of this rockfall, along with the potential for future ones. In the absence of an obvious explanatory trigger factor, we set out to examine whether natural daily surface temperature changes could have played a role in this event. In particular, it is suspected that these slight, yet repeated, perturbations may be a preparatory factor for rockfalls, with a day-to-day cumulative effect. A numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position. To investigate this notion more thoroughly, a currently vulnerable part of the Rochers de Valabres slope has been instrumented with a high-precision geodetic monitoring system (total station). It is believed that this device is able to capture thermally induced movements if specific precautions are taken. The instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability. Measured data (with a precision level never before achieved on rock slopes) are compared herein with numerical modelling results. The initial conclusions of the long-term study we are conducting indicate that surface temperature changes play an important, while not easily quantifiable, role in preparing rockfalls.