A comprehensive study on the biological treatabilities of phenol and methanol—III Treatment system design

The effects of temperature, pH, salinity, and nutrients on bacterial activities were investigated and evaluated using a statistical method. The substrate utilization rate coefficient (k) decreased as pH deviated from neutral and as salinity increased, and the unfavorable pH and salinity alleviated the temperature effect on k. The modified Arrhenius equation, k_T2 = k_T1 θ(^T2−T1), was not effective in describing the temperature effect on k: the temperature coefficient (θ) ranged between 1.0–1.4 depending on the temperature range, pH, salinity, and substance (phenol or methanol). The endogeneous respiration activity was affected by various environmental factors such as pH, temperature, and salinity; however, the cell decay coefficient (k_d) turned out to be correlated to a single parameter, k. Thus, k_d = 0.066 k^0.87 and k_d = 0.0115 k^0.634, where k and k_d are based on the unit of h⁻¹, were proposed for the prediction of cell decay coefficient for phenol and methanol acclimated activated sludge, respectively. In batch treatment of 770 mg l⁻¹ of phenol and 1000 mg l⁻¹ of methanol as TOC, nitrogen and phosphorus did not have any recognizable effect on k, while trace elements such as Fe²⁺, Mg²⁺, Mn²⁺, Ca²⁺, and Zn²⁺, etc. showed a slightly perceptible effect on it. The absence of extra-cellular nitrogen and phosphorus resulted in a greater cell yield; however, the cells in this condition decayed more rapidly than normal cells. The primary factor affecting the substrate decomposition rate in natural systems was pH: phenol decomposition resulted in a considerable decrease in pH so that the buffering capacity of the water was the most important factor, and methanol decomposition did not affect pH significantly so that the initial pH of the water was the most important factor. An initial lag phase was observed in 8 out of 115 phenol batch tests and 31 out of 66 methanol batch tests.     

Evaluation of a portable bare-electrode amperometric analyzer for determining free chlorine in potable and swimming-pool waters

Chlorine in the forms of HOCl or ClO⁻ was determined rapidly and precisely in the range from 0.10 to 3.0 ppm chlorine, without titration, using a bare-electrode portable amperometric analyzer. The instrument was calibrated with a 1.00 ppm chlorine standard solution or an equivalent permanganate solution which is stable for at least 6 months. The detection limit was 0.10 ppm chlorine, and relative standard deviations (N = 10) were <6.0% in potable or swimming-pool waters containing 0.25, 1.00 and 2.50 ppm or 0.35, 1.40 and 2.70 ppm chlorine respectively. Bromine-, triiodide ion-, and Mn (VII)-generated signals were stoichiometrically equivalent to that of hypochlorite, but MnO₂ suspensions (1.5, 5.0 or 15 ppm) did not produce detectable amperometric signals.Analysis of solutions of hypochlorite with ammonium chloride or selected organic nitrogen compounds indicated that various N-chloro compounds may interfere. In the presence of N-chloroglycine (2.70 ppm chlorine) the amperometric signal was about 5% of that for the equivalent concentration of hypochlorite, but higher relative responses were obtained with NH₂Cl, NHCl₂ or NCl₃ (19, 42 and 70% at 2.60, 1.20 or 1.00 ppm chlorine respectively). Chlorinated urea (2.2 ppm N, 2.90 ppm chlorine), chlorinated bovine albumin (10 ppm albumin, 2.00 ppm chlorine) or monochloroisocyanurate (1.30 ppm chlorine) produced amperometric signals (76, <5 and 50% respectively) which are lower than those obtained by the N,N-diethyl-p-phenylenediamine (DPD) method (100, 12 and 92%).Twenty potable water samples were analyzed for free chlorine by the DPD and amperometric procedures. Statistical analysis showed no significant differences between the two sets of results (P < 0.1). Swimming-pool-water samples were also analyzed by the two methods in the field (22 samples) and in the laboratory (24 samples). In each set of results the mean free-chlorine value by the DPD procedure was significantly higher than that obtained amperometrically (P > 0.005). This discrepancy was associated with the probable presence of chlorinated urea, whose signal by amperometry is lower than that by the DPD method.The advantages of this simple procedure must be weighed against possible inaccurate results in the presence of NH₂Cl, NHCl₂ or NCl₃.     

Comportement des acides amines dissous du milieu marin apres injection de chlore

Evidence that dissolved organic matter is one of the most significant sources of chlorine demand of seawaters (Fig. 1) used in cooling circuits is now well recognized. Nevertheless the specific role of the different kinds of compounds which form this organic material has seldom been studied and even less quantified; this is not surprising as less than 20% of the organic substances are identified. In this paper our objective was to define more quantitatively the effect of the dissolved free and combined amino-acids in the oxidant decay. Two main criteria justified the choice of these solutes:

1. (i)|the reactivity of chlorine and/or bromine towards amino groups;

2. (ii)|the role of these nitrogenous compounds in some biological mechanisms.

What happens to the halogen added and to the organic species during the first 20 min was investigated. The experimental conditions selected (concentrations, salinity, temperature and acidity) are those encountered in practice.The reactivity of the amino-acids towards chlorine is of course influenced by physicochemical properties such as the pH, but is particularly dependent upon the nature of the amino group. Whereas β and γ free amino-acids (Fig. 3) as also combined species (proteins) (Table 2) yield stable halogenocompounds like those produced with aliphatic amines (Fig. 2), α free amino-acids (COOH---CH---NH₂)|R on the other hand yield unstable haloamines which decompose rapidly (Fig. 4). Regarding these results, only the reactivity of the α compounds was afterwards studied as they are the largest fraction of the free amino-acids encountered in natural waters.After investigating the role of the side groups R in the kinetics and the efficiency of the consumption of the oxidant we examined, by liquid chromatography, the depletion of the nitrogenous species (Table 3). In each case the HPLC data relative to changes in the level of the organic compounds agree with those reported for the residual oxidant decay.A few experiments carried out on samples of seawater (Table 4) treated with 1 ppm of chlorine showed that around 5% of chlorine which dissipated during the first 3 min are consumed by the dissolved free amino-acids, the depletion of which is about 50%.     

Crack coalescence in a rock-like material containing two cracks

This paper investigates the pattern of crack coalescence and strength of a sandstone-like material containing two parallel inclined frictional cracks under uniaxial compression, with changing values of inclination of preexisting cracks α, bridge angle β (inclination between the inner tips of the two preexisting cracks), and the frictional coefficient μ on the surfaces of the preexisting cracks. Three main modes of crack coalescence are observed: the shear (S) mode (shear cracking between the two preexisting cracks); the mixed shear/tensile (M) mode (propagation of both wing and shear cracks within the bridge area); and the wing tensile (W) mode (coalescence of wing cracks from the tips of the preexisting cracks). The M-mode and W-mode of crack coalescence can further be divided into two and six types, respectively. Simple regime classifications of coalescence in the α–β space are proposed for different values of μ (=0.6, 0.7 and 0.9). In general, the S-mode mainly occurs when α=β or when β<β*(α, μ)=a−bα, with both a and b depending on μ; the M-mode dominates when β_L>β>β*(α, μ) (where β_L≈82.5°); and the W-mode is only observed when β>β_L. However, more experiments are still required to refine the classification. The observed peak strength, in general, increases with μ. Our results show that the peak strength predicted by the Ashby and Hallam (1986) model basically agrees with experiments. A minimum occurs at about α=65° when the peak strength is plotted against α. For α>45°, the peak strength is essentially independent of the bridge angle β.     

Buckling analysis of trapezoidally corrugated panels using spline finite strip method

Buckling of trapezoidally corrugated panels under in-plane loading is analyzed by a spline finite strip method. The influence on the elastic buckling load of various parameters, such as geometry. loading forms and boundary conditions, etc., is studied. It is found that: (1) for longitudinal compression the buckling load increases with the corrugation angle α, and for a given α the highest buckling load is achieved when the ‘proportion parameter’ γ = 1; (2) for shear loading the buckling load increases as α increases, and for a given α the highest buckling load is obtained when γ = 2; and (3) for a combined loading of compression and shear, interactive curves can be approximated by unit circles when α = 15°, 30°, 45°, 60° and 90°. However, when α = 75° a parabola seems to be a better approximation. Based on the numerical experiments, simplified formulae and interactive curves are suggested for practical design.     

Prediction of the optimum pH for ammonia-n oxidation by nitrosomonas Europaea in well-aerated natural and domestic-waste waters

Three assumptions were needed to model whole-cell and cell-extract data showing how pH affects the rate and optimum pH of the first step of nitrification: (1) un-ionized ammonia-N is the substrate; (2) substrate ionization occurs; and (3) ampholytic ionization of only the rate-limiting enzyme-substrate complex, and not the free enzyme, controls the rate of ammonia-N oxidation. The rate was shown to obey a Michaelis-Menten rate law where the apparent maximum-velocity coefficient and the apparent half-saturation coefficient with V_m and K_m being the Michaelis-Menten maximum-velocity and half-saturation coefficients, respectively; K₁ and K₂, the acid dissociation coefficients for the enzyme; K₃, the acid dissociation coefficient for aqueous ammonium. The optimum pH (pH₀) was shown to decrease almost linearly with the logarithm of total ammonia-N concentration over the concentration range found in natural and domestic-waste waters: for N < ppm total ammonia-N.     

The effects of depressed pH on flagfish reproduction, growth and survival

Breeding communities of flagfish, Jordanella floridae, were exposed to northern Ontario lake water (hardness 28 mg l⁻¹ CaCo₃) adjusted to depressed pH levels of 6.0, 5.5, 5.0 and 4.5. Control water (pH 6.8) received no acid treatment. Egg production, egg fertility and fry growth was impaired (P < 0.05) at all exposure levels. Flagfish fry survival was reduced (P < 0.05) at pH 5.5 and 5.0 and no fry survived at pH 4.5. Variability of hatching in all treatments precluded any identifiable hatching response to depressed pH. Reduction in the reproductive processes monitored indicated the following order of sensitivity: egg production > fry survival > fry growth > egg fertility.Results of this study coincide with reproductive investigations on brook trout and fathead minnows indicating the “no effect” level of pH depression for successful reproduction to be pH 6.5.     

Natural radioactivity in various surface waters in stanbul, Turkey

Gross-α and gross-β, activities of eight well and five tap water samples taken in stanbul were determined. Ra²²⁶, Rn²²², Pb²¹⁴, Bi²¹⁴, K⁴⁰, Cs¹³⁷ activity concentrations in four lake, four sea water, one snow and one rain water samples were also analyzed in order to determine their radioactivity. The results obtained showed that, in general, natural activities in drinking water samples did not exceed WHO and ITS guidelines. In sea and lake water, four samples were over WHO and TSI guidelines. Concentrations ranging from 0.007 to 0.04 Bq l⁻¹ and from 0.02 to 0.1 Bq l⁻¹ were observed for drinking water and the gross-α and gross-β activities, respectively. For all samples the gross-β activities were higher than the corresponding gross-α activities. In order to evaluate the annual effective dose equilavent of ingestion of these waters, a conservative dosimetric calculation was carried out using dose conversion factor suggested by the ICRP. An average annual effective dose equivalent of 0.84 μSv y⁻¹ for Ra²²⁶ was calculated.     

Shear fracture (Mode II) of brittle rock

Mode II fracture initiation and propagation plays an important role under certain loading conditions in rock fracture mechanics. Under pure tensile, pure shear, tension- and compression-shear loading, the maximum Mode I stress intensity factor, K_Imax, is always larger than the maximum Mode II stress intensity factor, K_IImax. For brittle materials, Mode I fracture toughness, K_IC, is usually smaller than Mode II fracture toughness, K_IIC. Therefore, K_Imax reaches K_IC before K_IImax reaches K_IIC, which inevitably leads to Mode I fracture. Due to inexistence of Mode II fracture under pure shear, tension- and compression-shear loading, classical mixed mode fracture criteria can only predict Mode I fracture but not Mode II fracture. A new mixed mode fracture criterion has been established for predicting Mode I or Mode II fracture of brittle materials. It is based on the examination of Mode I and Mode II stress intensity factors on the arbitrary plane θ,K_I(θ) and K_II(θ), varying with θ(−180°θ+180°), no matter what kind of loading condition is applied. Mode I fracture occurs when (K_IImax/K_Imax)<1 or 1<(K_IImax/K_Imax)<(K_IIC/K_IC) and K_Imax=K_IC at θ_IC. Mode II fracture occurs when (K_IImax/K_Imax)>(K_IIC/K_IC) and K_IImax=K_IIC at θ_IIC. The validity of the new criterion is demonstrated by experimental results of shear-box testing.Shear-box test of cubic specimen is a potential method for determining Mode II fracture toughness K_IIC of rock since it can create a favorable condition for Mode II fracture, i.e. K_IImax is always 2–3 times larger than K_Imax and reaches K_IIC before K_Imax reaches K_IC. The size effect on K_IIC for single- and double-notched specimens has been studied for different specimen thickness B, dimensionless notch length a/W (or 2a/W) and notch inclination angle α. The test results show that K_IIC decreases as B increases and becomes a constant when B is equal to or larger than W for both the single- and double-notched specimens. When a/W (or 2a/W) increases, K_IIC decreases and approaches a limit. The α has a minor effect on K_IIC when α is within 65–75°. Specimen dimensions for obtaining a reliable and reproducible value of K_IIC under shear-box testing are presented. Numerical results demonstrate that under the shear-box loading condition, tensile stress around the notch tip can be effectively restrained by the compressive loading. At peak load, the maximum normal stress is smaller than the tensile strength of rock, while the maximum shear stress is larger than the shear strength in the presence of compressive stress, which results in shear failure.     

Toxicity-, accumulation- and elimination studies of α-hexachlorocyclohexane (α-HCH) with saltwater organisms of different trophic levels

A short-term study with α-HCH was carried out with saltwater organisms of different trophic levels the alga—Dunaliella, the crustacean—Artemia, and the fish—Lebistes, acclimated to water of gradually increased salinity.Within the solubility range of α-HCH in saltwater (1.4 mg l⁻¹) there was no influence on the growth of Dunaliella. The LC50 (4 days) for Artemia was 0.5 mg l⁻¹, the EC50 (2 and 4 days)—E = mortality and immobilization, for Lebistes was 1.4 and 1.3 mg l⁻¹ respectively. In the longterm study the LC10 (35 days) for Lebistes proved to be 0.5 mg l⁻¹.In the accumulation studies the concentration factor was about 60–90 with Artemia and about 500 with Lebistes; equilibrium levels were reached within 24 and 48 h respectively. In the elimination studies the α-HCH concentration was halved within 48–72 h in Artemia and within 10 h in Lebistes.     

Survie in vitro de Yersinia dans les eaux d'alimentation et recuperation par filtration sur membrane

This study was undertaken to determine the survival characters and optimal parameters for the recovery of Yersinia from drinking water samples. Experiments were done by artificial contamination of 4 different water samples with 4 Yersinia strains.The strains tested along this study are: Y. enterocolitica 4052, 0:3 and 4360, 0:9, Y. enterocolitica intermedia 3953, 0:17 and Y. pseudotuberculosis 0:1. The water samples are characterized by an increasing mineralization: Distillated water, Gerardmer water (

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), Nancy water (-4500 ω cm⁻¹—H = 10°) and Vittel water (-730 ω cm⁻¹, H = 71°).Total mineralization does not significantly affect the survival of Yersinia at 20°C, but causes a dramatic decrease of the Yersinia strains at 4°C for the most mineralized water. There is no pH effect from alkaline, neutral and acidic values until pH 4.4 but Yersinia is greatly affected by more acidic pH.The previous stay of Yersinia strains in artificially contaminated water causes a reduction of kinetic growth during cultivation on peptone-water but does not change the recovery rate by filtration method.The recovery rate of the filtration method using cellulose acetate membranes (mean porosity = 0.45 μm) is very poor, ranging from 0 to 8%. The efficiency is significantly higher with the aid of polyester membranes treated by laser (Nucleopore−0.40 μm) ranging from 12 to 53% according to the mineralization of the water. The best recovery rate is obtained with the moderately mineralized water.These results can explain the poor results obtained with the use of water bacteriology classical methods for the search of Yersinia.Thus the best results can be predicted from the concentration of fairly mineralized water by filtration on polyester membrane at neutral, alkaline or weakly acidic pH.     

Application de l'analyse des correspondances a des resultats d'essais de traitement d'eaux de surface

Many results show that if a conventional coagulation-flocculation-clarification treatment line is combined with pre-ozonation, removal efficiency as regards pariculate and dissolved organics is substantially enhanced. However, research on the optimum balance between pre-ozonation and coagulation treatment has turned out to be difficult because of the numerous parameters that are involved. In order to identify the most significant among clarification criteria it was in fact necessary to develop a more elaborate model than is required for conventional statistical analysis, capable of comparing all the intervening factors. This we finally achieved by a program based on stepwise regression analysis.Measuring samples and parametersSamples. Samples were taken from the pilot plant located at Choisy-le-Roi on premises belonging to the Paris Suburbs Water Authority, over a period of 3 months from 1 April to 24 June, i.e. exactly 43 days of research.The plant shown in Fig. 1 consists of 4 trains working in parallel arrangement. This layout allows practically two complete treatment runs daily so that 8 different ozone-coagulations could be tested each day on the same quality of raw water. 387 samples were thus taken with 344 treated waters and 43 raw waters. The campaign was designed over this rather long period to achieve two ends:

1. (1) to gather enough results to give real significance to the mathematical computation. During the 43 day experimental campaign, each ozone-WAC combination was repeated more than 10 times;

2. (2) to find a means of allowing for fluctuation in the river in relation to phenomena of great amplitude such as rises in temperature and changes in flow rate, so that acquired results could eventually be extrapolated for application to industrial treatment plant management.

Parameters. Twenty-two parameters were measured in respect of each sample of raw and treated water. The aim of the research being to define the main parameters on which to base the combination, it was essential to begin with a study of all the magnitudes normally representative of suface waters.These parameters can be divided into various types:

treatment parameters: WAC + O₃; the concentration tested are shown in mg l⁻¹ in Table 2 and Fig. 2;

parameters concerning suspended solids: total number of particles per ml (NT) and their equivalent diameter (D), turbidity (Tu) expressed in drops of mastics and zeta potential (Z_p);

parameters concerning organics: total organic carbon (COT) in mg l⁻¹ of C, KMnO₄ in mg l⁻¹ of O₂, dissolved O₂ in mg l⁻¹, u.v. absorption at 254 nm, NTK and ammonia (NH₄⁺), both in mg l⁻¹.

Besides pH and temperature which vary very little in Siene river water, total aluminium (ALT) in mg l⁻¹ and residual ozone (RO₃) were monitored.Analysis of data. The basic data represented in the following matrix (I × J), in which I is the sum of the sampling steps and J the sum of the concentrations of the different chemical elements, are too vast for conventional statistical analysis. By factor analysis, one can obtain as a final result a geometrical figure in a two-dimensional space but that simultaneously accounts for all the combinations of I and J. We thus obtain a factorial chart analysing the proximity between variables in terms of correlation and that between individual points in terms of similarity of behaviour toward these variables as a whole.Each component i of I and j of J is represented in profile form ƒ_jⁱ (or ƒ_I^j)=k(i,j)/k(i) as shown in the matrix below:

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All of the profiles and I and J, each with a volume allocated pro rata the complete line (or column), make up a set of points with a corresponding volume in a multi-dimensional space. In the case under study, each components i (sampling steps) are in a space with 22 dimensions and each variable j (concentrations) in a 387-dimensional space. The purpose of the analysis is to obtain from the cloud as true a representation as possible brought down to a 2-dimensional space. This dimensional reduction consists in finding a sub-space in which the space between individual points i or j are as close as posible to the initial distances in IR₂₂ (or IR₃₈₇). The distance used in factor analysis is the distribution distance expressed as: . The plane thus located is defined by 2 perpendicular straight lines. They are the factorial or inertia axes. Inertia measures the total dispersal area of the cloud on one axis and shows the ratio between the points projected in space and the sum of the square-roots of the distances between the initial points. It measures the dispersion of data on the axis. The axes are called “factors”.Using this method, it becomes possible to described the accumulated data and quantify the phenomena that control both the variable parameters and their components (I or J) without any preconceived hypothesis as to the relative importance of the initial data. And, furthermore, we have a simultaneous geometric representation of samples and variables.Results. The first (horizontal) axis, F₁ represent the abatement of suspended particles and organics. The second (vertical) axis enables the different treatment trains to be interpreted in terms of ozone and residual ozone. Four distinct groups appear on plane F₁ × F₂:

Group 1: Group 1 represents water with no WAC or ozone treatment nor residual ozone. Characteristics include a very high suspended particles content and a certain amount of organics (i.e. variables N, D₁, D₂…D₁₀ and KMnO₄). This group is representative of raw waters in general.

The variable KMnO₄ factor quite realistically reflects the clarification treatment, a high KMnO₄ value indicating the presence of raw water, a low content the presence of treated water.

Group 2: This is an intermediate group between raw water and the water in trains A and B. It is characterized by poor abatement of both suspended solids and organics and corresponds to the majority of waters in train D with no pre-ozonation and train A with low-rate ozonation (0.3 mg l⁻¹).

Group 3: A high WAC rate and an average ozone rate are the predominant features of this group in which residual ozone is very low. A good level of suspended solids and organic removal was obtained, as is the case of treatments in general, and as practically demonstrated by trains A and B.

Group 4: This group corresponds to the treated water with a high ozone injection rate, hence a high residual ozone content. A good level of suspended solids and organics removal is obviously obtained, most of the water having been treated on train C. This maximum ozone residual for a similar abatement of organics concentration indicates that the extra ozone added was in excess of the amount required in order to oxidize the quantity of organics in the effluent. The optimum ozone dose must therefore be somewhere near that of the previous group, i.e. trains A and B.

In conclusion, analysis by stepwise regression identified the five main variables that define the complete clarification process: N_T, KMnO₄, TOC, WAC and ozone. As regards the last two mentioned, differentiation between groups 3 and 4 provides a means of determining the optimum dose rate for ozone in the treatment concerned, i.e. less than for train C (group 3) where the residual ozone rate is higher, hence approximately the same as for trains A and B—in the region 0.3–0.8 mg l⁻¹.     

Natural radioactivity in various surface waters in stanbul, Turkey

Gross-α and gross-β, activities of eight well and five tap water samples taken in stanbul were determined. Ra²²⁶, Rn²²², Pb²¹⁴, Bi²¹⁴, K⁴⁰, Cs¹³⁷ activity concentrations in four lake, four sea water, one snow and one rain water samples were also analyzed in order to determine their radioactivity. The results obtained showed that, in general, natural activities in drinking water samples did not exceed WHO and ITS guidelines. In sea and lake water, four samples were over WHO and TSI guidelines. Concentrations ranging from 0.007 to 0.04 Bq l⁻¹ and from 0.02 to 0.1 Bq l⁻¹ were observed for drinking water and the gross-α and gross-β activities, respectively. For all samples the gross-β activities were higher than the corresponding gross-α activities. In order to evaluate the annual effective dose equilavent of ingestion of these waters, a conservative dosimetric calculation was carried out using dose conversion factor suggested by the ICRP. An average annual effective dose equivalent of 0.84 μSv y⁻¹ for Ra²²⁶ was calculated.     

A quantitative investigation of the reaction of ozone with p-toluenesulfonic acid in aqueous solution as a model compound for anionic detergents

The reaction of ozone with p-toluenesulfonic acid (PTA) at initial pH 3 and 12 in aqueous solutions (25°C) has been studied at initial concentration 1 mmol l⁻¹ and ozone dose is 24 mg min⁻¹ 1. and 11 mg min⁻¹ 1. respectively. The substrate elimination follow a zero order rate law. A 98% p-toluenesulfonic acid reduction requires at least 7 mol O₃ per mol PTA, however to remove 100% PTA the consumption of ozone increases to 16 mmol O₃ per mmol PTA. At this point a 28% reduction of DOC and a 74% COD reduction was achieved.The PTA decomposition is quicker at higher ozone flow rate, but the specific ozone consumption increases also. As oxidation products the following compounds were identified and their quantitative variations as function of ozonation time were measured: methylglyoxal, acetic acid, formic acid, pyruvic acid, oxalic acid, H₂SO₄ and H₂O₂. As byproduct mesoxalic acid was identified. At pH 12 lactic acid as a further oxidation product was observed.Balances of carbon, sulfur and methyl as well of the acid equivalents indicate one or more intermediates with a sulfonic acid group. These intermediates with a proportion of about 20% disappear after 100% PTA elimination. On account of these results a reaction mechanism is discussed.     

Variation in strength and creep life of six Japanese rocks

In this paper, variations in strength and creep life are investigated for rocks under various conditions: dry and wet, uniaxial and triaxial, and compressional and tensile. A number of parameters are introduced for this purpose; to assess the time-dependent failure under constant and monotonic loading the following parameters are used: the parameter of time dependency δ, coefficient of creep life α and coefficient of strength β. δ explains the rate dependency of strength or stress level dependency of creep life. α and β are related to each other. Variations in β have been evaluated using data from previous experiments. It is confirmed here that δ, β and variations in β determined by creep tests are in most cases identical to those determined using strength tests. Variation in β in the wet condition is almost the same as that in the dry condition; however, variation in tension increases more than in compression. Under confining pressure, variation in β is reduced for Neogene sedimentary rocks, and does not appear to change for igneous rock and welded tuff.     

Shaft resistance of a pile embedded in rock

A rational calculation procedure is proposed for establishing the shaft resistance of a pile embedded in rock, based upon the Hoek and Brown failure model. The state of the art of the calculation of the pile shaft resistance is analysed. Nearly all the recommendations that have appeared in the technical literature, for calculating the ultimate shear strength of a shaft embedded in rock (τ_ult) propose that τ_ult=ασ_c^k(σ_c;τ_ulten MN/m²) where the coefficient α, considered as a constant dimensional value, ranges from 0.1 to 0.8, if the unconfined compressive strength (σ_c) is expressed in MN/m². In most cases, the exponent k is 0.5.A comparison is made between the results yielded and the different empirical theories that have been put forward with respect to this shaft resistance. It can generally be stated that the results obtained with this theory are reasonable for long and deeply socketed piles (high confining pressures) but the results are on the safe side in some cases where short piles (low confining pressures) are involved.This paper is a continuation of the works developed by the same authors with piles working at the tip, socketed in rock.     

Coefficient of restitution and rotational motions of rockfall impacts

This paper presents experimentally obtained results for the coefficient of restitution for spherical boulders impacting on rock slopes. Plaster modeling material is used for casting both the boulders and slopes. It is observed that the normal component of the coefficient of restitution (R_n) increases with the slope angle α, which agrees with Wu's observations (Trans. Res. Rec. 1–5 (1985) 1031). However, there appears to be no clear correlation between the tangential component of the coefficient of restitution (R_t) and the slope angle α. When the ratio of the resultant velocities and the ratio of the kinetic energies before and after impacts are used to define the coefficient of restitution (i.e. R_V and R_E), a very clear increasing trend in the coefficient of restitution with α is observed. When all data are plotted onto the R_t−R_n space, our laboratory data fall into the rock slope regime proposed by Fornaro et al. (In: D.G. Price (Ed.), Proceedings of the Sixth International Congress IAEG, Amsterdam, Balkema, Rotterdam, 1990, p. 2173) and also agree with those data gleaned from literature. In addition, the rotational kinetic energy E_r, induced at each impact, increases with the slope angle α, achieves a maximum at about α=40°, before decreasing again to a negligible value at α=70°. A simple theoretical model is proposed to explain this observation based on the locking between the boulder and the slope during impact. The α-dependence of E_r differs from the recommendation by the Japanese Railway Association that the induced rotational energy is about 10% of that of the translational kinetic energy.     

Effect of pH on toxicity of kraft pulp and paper mill effluent to salmonid fish in fresh and seawater

In freshwater bioassays with juvenile rainbow trout (Salmo gairdneri), at initial pH values from 4 to 11, kraft mill effluents were considerably less toxic at pH 9–10 than at neutrality. When pH of test solutions was controlled throughout the bioassay period, the least toxic range was 8.5–9.5. Toxicity at typical receiving-water pH values was 50–67% greater.The acute toxicity of effluent samples to yearling coho salmon (Oncorhynchus kisutch) was identical for these effluents in seawater and freshwater respectively, provided that the pH was adjusted and held at the same value, and that test fish were previously acclimated to the dilution water for several months. Thus seawater constituents other than pH did not affect the acute toxicity of pulp and paper mill effluents appreciably.     

Hypochlorite oxidation of cyanate under mildly alkaline conditions

Kinetic study was carried out on the hypochlorite oxidation of cyanate, over the pH range of 8.6–10.0 and temperature range from 27 to 50°C. The decomposition reaction was found to be first order each with respect to cyanate, hypochlorite and hydrogen ion concentration. The experimental results indicate that the decomposition reaction may probably follow a series reaction in which the cyanate first hydrolyses to ammonium which then decomposes in alkaline hypochlorite solution to nitrogen. Under the range of pH and hypochlorite/cyanate molar ratio examined in this study, the stoichiometric ratio of hypochlorite to cyanate for the decomposition reaction is found to be approx. 1.5. The conversion of cyanate to nitrate is negligible compared with that to nitrogen. This study suggests that complete treatment of cyanide waste is best carried out in two stages at room temperature and in the presence of excess hypochlorite. The first stage involves the hypochlorite oxidation of cyanide to cyanate at pH 11 and the second stage involves the conversion of the cyanate to nitrogen and other stable inert products at a reduced pH of about 9.