Simulation of water-bloom in a eutrophic lake—I. Photosynthetic characteristics of Microsystis aeruginosa

A perspective of how to simulate “emergence and/or disappearance of the water-bloom… dense population of a blue-green alga, Microcystis aeruginosa at the surface of eutrophic waters… ” was presented.The algal photosynthetic activity. Q_o2 as a function of irradiation light intensity. I, could be represented by the Blackman model, taking the algal content. C of chlorophyll-α and water temperature. 0 as parameters.When the cells that had been cultured under dim light were transferred to a new environment, wherein the light intensity was from 0 (dark) to the level much brighter than the dim light, the value of C exhibited various responses against time. Subtracting the rate of chlorophyll-α degradation from that of chlorophyll-α synthesis, the rate of change in C values during the light-adaptation period was studied.     

Enhancement of Nitrobacter activity by heterotrophic bacteria

The present work shows that a supply which is not sterile and which contains organic matter does not interfere with the performance of a column filled with a support previously inoculated with Nitrobacter winogradskyi serotype agilis.Measurements of oxidation rates give results higher than those obtained under axenic conditions (maximum oxidation rate: 220 mg NO₂⁻ h⁻¹ l⁻¹ of reactor volume under non-sterile conditions: 160 mg NO₂⁻ h⁻¹ l⁻¹ of reactor volume under axenic conditions).This finding has concentrated our work on the effect of heterotrophic bacteria and of organic matter on the growth of Nitrobacter. We show that a fermentation filtrate of a heterotrophic bacterium (Pseudomonas sp.) added to a fermenter culture of Nitrobacter produces an increase of activity. Experimental results indicate an appreciable reduction in the latence period (15-0 h) and a considerable increase in the rate of growth of Nitrobacter. (Maximum growth rate with 10% of heterotrophic filtrate: 0.044 h⁻¹; without filtrate: 0.032 h⁻¹.)     

Influence de la duree d'exposition sur la bioaccumulation par voie directe de deux derives du mercure par Salmo gairdneri (alevins) et relation “poids des organismes-concentration en mercure”

In the context of ecotoxicological research on the contamination of continental aquatic systems by mercury compounds, the analysis of bioaccumulation at different consumer levels (especially fish) shows that the weight of the organism affects the concentration factors measured. However, after a bibliographic synthesis it is not possible to define precisely what this effect might be, since published results show either an absence of any relationship, or a positive or negative correlation, depending on the authors and on the conditions of intoxication.Our research is based on the direct contamination of newly hatched rainbow trout (weight when time factor = zero : 0.20 g); concentration of mercury in the water was 1 μg l⁻¹ (1 ± 0.1 ppb for the duration of the experiment). Two compounds were studied : HgCl₂ and CH₃HgCl. By using automated contamination modules we were able to maintain constant biotic conditions (number of fish per tank) and abiotic conditions (temperature: 15 ± 0.5°C; photoperiod; 16h/8h; concentration of Hg in the water) for the two contaminants.An analysis of the mercury bioaccumulated was carried out after 15, 30, 60 and 83 days of exposure. For each experimental condition—e.g. HgCl₂, 15 days—25 fish were kept at time factor zero. The mercury concentration was determined by flameless atomic absorption spectrophotometry (VARIAN AA 475). A polynomial regression method, with or without transgeneration of the dependent variable, was used in order to demonstrate a possible relationship between the “weight of organism” and “concentration of mercury” parameters.A comparison of the development in weight of the organisms in all the different populations contaminated by HgCl₂ and CH₃HgCl (Fig. 1) shows that this is identical up to 30 days. Between 30 and 83 days it may be seen that methylmercury has a very strong influence on this parameter which is coupled with a reduction in food intake and a considerable increase in mortality.The dynamics of the average mercury content—μg per organism—and the corresponding concentrations (μg g⁻¹ fresh weight) over the 83 days exposure period (Fig. 2) show that the mercury content and concentration in the fish are much higher for methylmercury than for mercuric chloride and this does not depend on the length of exposure period, e.g. at 60 days the ratio between CH₃HgCl and HgCl₂ concentrations is about 7.Although the concentration of the two contaminants in the environment was kept constant (1 ppb), the curves representing mercury accumulation—expressed as a concentration—are not linear and show a fairly pronounced plateau.The relationship between “organism weight” and “concentration of mercury” was studied for both two mercury compounds during each experimental exposure period (Figs 3 and 4).The noticeable grouping of points corresponding to each population studied indicates a relationship between the weight and concentration parameters; in both contaminants the concentration factor develops in relation with the exposure period. Although it is rather simple and approximate, the linear model displays quite satisfactorily the phenomenon we are studying and its development (Table 1). However a logarithmic relationship gives a better adjustment of the results.Analysis of the results shows:A negative correlation between the weight of the organisms and their mercury concentration for both compounds. This correlation decreased as the exposure period increased. In the case of HgCl₂, after 83 days exposure, the weight no longer seemed to have an influence on the amounts of metal bioaccumulated by the fish.A difference between the adjusted straight lines for HgCl₂ and CH₃HgCl, the organism weight has a greater influence on concentration in the case of contamination by the organic compound.Observations conducted in a natural environment usually show a positive relationship between concentration and the weight of the organisms. When compared with these, our experimental results cannot be said to be contradictory since they deal with different biotic conditions: contamination methods, growth rate and age of individuals.An assessment of the level of contamination in aquatic ecosystems is usually based on an estimation of concentration levels found in the organisms, and, especially for fish, in the skeletal muscles. Our results however, show the necessity of taking organism weight into consideration; the influence of this parameter on the processes of bioaccumulation is particularly important in the case of mercury contamination in the newly hatched stage, and probably in other species with a rapid growth rate. In the case of experimental research into these processes influence of organism weight is considerable and therefore necessitates its examination especially when the object of the study is the development of a standardised toxicological test.     

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.     

The crayfish as a “biological indicator” of aquatic contamination by heavy metals

Cu, Cd. Mg, Mn and Ni concentrations in whole Cambarus bartoni, trapped from Nepahwin Lake, Joe Lake and Wizard Lake, lying at distances of 10, 30 and 150 km, respectively, from the Sudbury smelters in Northeastern Ontario, showed an inverse relationship with the distance of the habitat from the emission site. Highest concentrations of Cu were observed in the hepatopancreas, Cd in the hepatopancreas and the gut, Fe and Mn in the gut, and Mg in the exoskeleton. Tissue concentrations of Ni and Zn were highly variable. Differences between males and females at each sampling site were not significant at the 5% level. The general relationship between crayfish tissue metal concentrations at the three sites was Cu > Mg > Mn > Zn > Ni > Cd. This observed relationship, except for Mg and Mn, agreed with the concentration relationship of these metals in the water and the sediments (top 10–20 cm) in the three lakes. In laboratory studies, Cu concentrations in the hepatopancreas, gills, exoskeleton and the viscera increased significantly over the control during the 4-weeks exposure to 125,250 and 500 μg Cu 1⁻¹. Hepatopancreas, in general, had the highest Cu concentration, and the exoskeleton, the lowest. Relationship between Ni exposure and the tissue Ni concentrations in the four treatments was 800 μg Ni l⁻¹ > 400 μg Ni l⁻¹ = 200 μg Ni l⁻¹ > control, while between the exposure periods and the tissue Ni concentrations was week 4 > week 1 > week 3 = week 2. Highest Ni concentrations at the end of the 4-week exposure to Ni were observed in the gut, gills and the hepatopancreas, and the lowest in the viscera. The present study suggests that Cambarus bartoni is a reliable indicator of the presence of class B and borderline elements with specific gravity > 5 in the aquatic environment. However, their value as biomonitors of variations in Cu and Ni concentrations in freshwater ecosystems is debatable.     

A toxicity testing system for exposing small invertebrates and fish to short square-wave concentrations of chlorine

We describe a flow-through toxicity testing system which can be manipulated to deliver a “square-wave” chlorine concentration curve for short exposure times to small invertebrates and fish. The system consists of a series of test containers, each with dual input delivery lines (dilution water alone or toxicant plus dilution water), a syringe pump for addition of toxicant to one of the two delivery lines, a constant head tank, and reservoir tanks. Control of valves on the delivery lines and on the test chamber drains caused chlorine concentration to rise to the target value in 1 min and to fall below detection limits (0.01 mg 1⁻¹) in 2 min at the beginning and end of the exposure period, respectively. Using this system, we determined the toxicity of 30- and 60-min exposures of total residual chlorine (85–95% free residual to Daphnia magna and Gambusia affinis. The 30- and 60-min LC 50 values were 0.097 and 0.063 mg 1⁻¹, respectively, for Daphnia and 1.59 and 0.84 mg 1⁻¹, respectively, for Gambusia. Use of this (or a similar) system can provide the readily comparable data base which is important for developing chlorine criteria for power plants.     

A preliminary study of metal distribution in three waterhyacinth biotypes

Two waterhyacinth (Eichhornia crassipes (Mart.) Solms) biotypes from Broward County, Florida, were collected and analyzed for chlorophyll content and metal distribution (potassium, calcium, magnesium, cobalt, copper, manganese and iron) in roots, stems and leaves. Two biotypes were distinguished by size (medium or “stunted”, and large or “super”) and by whether they were or were not eaten (“stunted” and ”super”, respectively) by the waterhyacinth weevil, Neochetina eichhorniae Warner. Results are compared with a third biotype (small or “normal”): i.e. plants from the Hillsborough and Peace Rivers where the weevils have not been released. The data indicate abnormal concentration of cobalt and iron in the leaves of the “super” plants relative to the third biotype. Fractions of calcium, magnesium, manganese, iron and copper in roots showed a significant, negative linear correlation coefficient, r, with solubility product constant (log K_sp) for metal carbonates of the small and medium biotypes.     

Towards a better understanding of high rate biological film flow reactor theory

On the assumption that performance of biological film flow reactors is independent of oxygen transfer, a theoretical extension of a mathematical model (after Ames) is described. This predictive and interpretive model incorporates both mass transfer-limitations between biomass and liquid film, and kinetic biological reaction rate of organic “food” utilization.Given general boundary conditions for the differential equations describing the mass transfer process, it is shown that: C_e = C_r + (C_l − C_r.exp(−K_m D/Q) where by definition: C_t = α C_s + C_r1/K_m = 1/K_LA_γ + α/Kx.For an influent concentration biochemical oxygen demand (C_i) and resultant effluent concentration (C_e) obtained during film flow through a packed media depth (D), the Model proposes that the residual concentration (C_r) is a function of surface irrigation rate (Q) and biomass activity. If this term is negative, adsorption occurs; while if positive, desorption from the biomass film at concentration (C_s) takes place.An overall mass transfer coefficient (K_m) is defined by a series equation where the usual mass transfer coefficient (K_L) is primarily a function of Reynolds Number [surface irrigation rate (Q) and specific surface area (A_V)], Schmidt Number (diffusivity of organic “Food”) and concentration. “Food” utilization at active sites on the biological film is governed by a specific adsorption coefficient (α) and explained by a Langmuir analogy. Biological conversion of “food” is described by a kinetic rate constant (K), while the necessary oxygen is defined by (X).This predictive model was developed from a wide range of pilot plant data, successfully tested further on a variety of published results and on actual full scale operating plants.Parameters derived from this Model, in terms of Height of Transfer Unit and Kinetic Reaction coefficient, characterize organic “treatability” for a variety of wastes.     

An incubator method for estimating the actual daily planktonalgae primary production

Based on the knowledge of the sun/shade adaptation mechanism of algae a computer program has been developed which makes it possible to transform potential estimated primary production values to ‘normal’ daily primary production values. The potential production is measured in an incubator at a temperature equal to that at the sampling locality. Necessary light energy is delivered by fluorescence lamps (Philips TL 20 W/33). The transformation calculations are based on the actual transmission of green light and the light conditions during a ‘normal irradiance year’. This means that the determined production values represent the ‘normal’ production and thus the eutrophic state of the water body. An intercalibration with the traditional in situ method shows good agreement. If an incubation period of half a light day is used with the in situ method then the method described in this paper is less time consuming.     

Quantitative three-dimensional description of a rough surface and parameter evolution with shearing

The choice of a general criterion to determine the shear strength of rough rock joints is a topic that has been investigated for many years. The major problem is how to measure and then to express the roughness with a number (e.g., joint roughness coefficient) or a mathematical expression in order to introduce the morphology of the joint into a shear strength criterion. In the present research a large number of surfaces have been digitised and reconstructed using a triangulation algorithm. This approach results in a discretisation of the joint surface into a finite number of triangles, whose geometric orientations have been calculated. Furthermore, during shear tests it was observed that the common characteristic among all the contact areas is that they are located in the steepest zones facing the shear direction. Based on this observations and using the triangulated surface data, it is possible to describe the variation of the potential contact area versus the apparent dip angle with the expression A_θ^*=A₀[(θ_max^*−θ^*)/θ_max^*]^C, where A₀ is the maximum possible contact area, θ_max^* is the maximum apparent dip angle in the shear direction, and C is a “roughness” parameter, calculated using a best-fit regression function, which characterises the distribution of the apparent dip angles over the surface. The close agreement between analytical curves and measured data therefore suggests the possibility of defining the influence of roughness on shear strength by the simple knowledge of A₀, C and θ_max^*. Based on the samples studied here, the values of these parameters capture the evolution of the surface during shearing. Moreover, they tend to be characteristic for specific rock types, indicating that it might be possible to determine ranges for each rock type based on laboratory measurements on representative samples.     

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.     

Evaluation of geosmin and 2-methylisoborneol on the histidine dependence of TA98 and TA100 Salmonella typhimurium tester strains

Low (ca 0.01 ppb) concentrations of the naturally occurring terpene derivatives geosmin (1α, 10β-dimethyl-9α-decalol) and 2-methylisoborneol [(1-R-exo)-1,2,7,7-tetramethyl-bicyclo-(2,2,1)-heptan-2-ol] (MIB), impart earthy/muddy “off-flavors” to many water and food resources. The presence of these “off-flavors” often elicits public concern over the safety of the affected resources. The “Ames test”, assesses the induction of reverse mutation at the histidine locus in specially constructed Salmonella typhimurium tester strains, and is a widely used index of mutagenicity. This investigation indicated that neither MIB nor geosmin, when tested up to cytotoxic levels in both the presence and absence of exogenous metabolic activation, induced a mutagenic response in either strain TA98 or TA 100 compared to controls. Doses of MIB and geosmin above 45.2 and 18.1 ppm, respectively, inhibited tester strain growth, indicating that high concentrations of these metabolites may exhibit an antimicrobial activity, possibly by a mechanism similar to that reported for certain other terpene derived alcohols. Food or water resources containing similar concentrations of geosmin or MIB would be extremely unpalatable and would probably not be consumed.     

Sludge viability in a biological reactor

The volatile suspended solids (VSS) concentration cannot be used as a measure for the active biomass in a reactor which operates under a wide range of operating conditions since the viable organism content of the VSS is not constant. Using substrate saturation conditions the kinetic parameters maximum substrate removal rate ( ) and oxygen uptake rate (J)—both per mass of VSS—were determined in an experimental pulse fed batch biological reactor. It was found that and J both doubled during the experimental period (6 h). It was concluded that the increases in and J values were due to the increase in the sludge viability which are here defined as the percentage of VSS which is active biomass. Using the variations in and J values during each experiment, it was possible to calculate sludge viability. During a 6 h experimental period at substrate saturation level the sludge viability increased on average from 8.9 to 23.3%.In a loop type sewage conduits system operated as a plug flow reactor and enriched with biomass and air, it is possible to achieve high specific substrate removal rates when step feeding creates saturation conditions. This is further attenuated by a marked increase in the sludge viability.     

A Bayesian method for establishing fatigue design curves

From a reliability viewpoint, the simple conventional procedure for establishing design S−N curves from laboratory fatigue test data suffers from two important limitations. Firstly, the calculated fatigue reliability on the design curve only reflects the observed “physical” uncertainty associated with the fatigue process itself. “Statistical” uncertainties, connected with estimating the parameters of the fatigue model, are not considered. Secondly, it is not possible to account for fatigue run-outs (non-failures) in a rational manner.A new procedure, based on Bayesian statistical inference, is presented which is capable of handling both the above problems. Its use is illustrated via the analysis of some typical fatigue data sets and a number of general points arising from the results are discussed.     

The biodegradability of para-dichlorobenzene and its behaviour in model activated sludge plants

Confirmation of the ready and ultimate biodegradation of para-dichlorobenzine (pDCB) was obtained from the Organisation for Economic Cooperation and Development (OECD) closed bottle test. The fate of pDCB during primary sedimentation of raw sewage was investigated in a simple laboratory study, and the results indicated that the major proportion of the material (> 67%) remained in the supernant liquor, and would therefore undergo biological treatment. The removal of pDCB in the OECD confirmatory test was found to be consistently high (97.1 ± 2.3%). Mass balance results indicated that, at a high aeration rate (21 min⁻¹), the major mechanism for removal of pDCB was volatilization (66.6 ± 19.3%). The fate of pDCB in a modified porous pot test, operated at a lower aeration rate, and at temperatures of 8, 15, and 20°C and sludge retention times (SRT) of 3 and 6 days, was also investigated. Once again the overall removal was found to be consistently >95%. Mass balance results suggested that, under normal operating conditions, the major proportion of pDCB (>76%) had been removed by biodegradation. The amount of pDCB removed by volatilization showed a slight dependence on aeration rate, but only became significant (63 ± 4%) when adverse operating conditions prevailed (i.e. 8°C, at a 3 day SRT). Radioisotopic studies confirmed the presence of pDCB degrading bacteria in activated sludge taken from a porous pot continuously dosed with pDCB. The results of a similar test using sludge from an undosed porous pot suggested that acclimatization to pDCB was rapid, occurring within 2 days. No adverse effects on sewage treatment processes, due to the presence of pDCB, were observed.     

An evaluation of the potential toxicity of treated bleached kraft mill effluent to striped bass (Morone saxatilis walbaum) larvae exposed through metamorphosis to the juvenile stage

Twenty-day-old striped bass (Morone saxatilis) larvae were exposed to a range of treated bleached kraft mill effluent (BKME) concentrations from 0 to 20% effluent by volume (v/v) under continuous flow test conditins. The experimental test concentrations in the 2–20% BKME test aquaria had a BOD₅ which ranged from < 1 to 5 mg l⁻¹, TSS 12–17 mg l⁻¹, and true color 35–416 mg l⁻¹. Bleached kraft mill effluent did not kill larvae exposed to it for 20 days through metamorphosis to the juvenile stage. The BKME did not alter growth in length, weight or condition factor in larvae over the 20-day exposure period as determined by multiple regression analysis. A linear regression analysis on the dry weight data at Day 20 only, however, indicated a trend of decreasing weight with increasing BKME concentration. Effluent-exposed larvae also developed normally during the 20-day study. All individuals examined completed the transformation from postlarvae to juveniles by the age of 40 days.     

Effects of mercury accumulation on the electrophoretic patterns of the serum, haemoglobin and eye lens proteins of Tilapia mossambica (Peters)

Two test concentrations of mercury (0.01 and 0.04 ppm) were used for studies on the uptake of mercury by the tissues and alteration in the electrophoretic patterns of blood serum, haemoglobin and eye lens proteins. Haemoglobin showed an increase in protein in the faster moving band. Significant changes were seen in the patterns of serum protein with respect to number, mobility and intensity of the protein fractions in the fish exposed to higher concentration of mercury (0.04 ppm). The patterns of eye lens protein were quite constant throughout the period of exposure.Short-term experiments on the fish serum electrophoresis were carried out using higher concentrations of mercury in the medium (0.4, 0.6 and 0.8 ppm). These were just below the lethal level. Sampling was done at 3, 24, 48 and 72 h intervals. From 24 h onwards there was a significant increase in the intensity of the lower mobility bands and there was a decrease in the higher mobility bands. After 48 and 72 h, a distinct extra band was seen between the first two fast-moving bands at all the three high concentrations of mercury used. These patterns were very similar to the pattern observed with the lower concentration of mercury in the medium (0.04 ppm) after the 11th week exposure period, which was found to affect the survival or growth potential of the fish. This study shows that exposure to a large amount of mercury over a short period has an effect similar to small amounts over a long period. The serum electrophoretic patterns obtained after 48 and 72 h exposures to sublethal concentrations of mercury, and which were similar to the one obtained in 0.04 ppm mercury concentration after the 11th week exposure period, can be regarded as the “stress pattern” of T. mossambica serum. The use of fish blood morphology as a biological index of water quality has been indicated.     

Use of photosynthetic bacteria for hydrogen sulfide removal from anaerobic waste treatment effluent

The feasibility of using photosynthetic bacteria to remove H₂S from anaerobic waste treatment effluent was investigated by growing fixed films of photosynthetic bacteria in a packed column or in a submerged tube system (“phototube”). Growth and enrichment for these organisms depended on constant illumination, anaerobic conditions and a substratum for attachment of the bacteria. Both systems were operated as flow-through processes using effluent from anaerobic (upflow) filters.Results showed that photosynthetic bacteria in fixed films can be effectively used for H₂S removal. Removal efficiencies of 81–95% were obtained on a 24-h retention time. Residual H₂S remained in the process effluent. The submerged “phototube”, showed dramatic improvement over the column, yielding a final effluent completely devoid of H₂S, at significantly shorter retention times and higher loading rates than the column. Performance appeared dependent on cell-H₂S contact and adequate illumination. The green photosynthetic sulfide-oxidizing bacterium, Chlorobium, was identified as a common organism in this phototube.This biological sulfide removal process offers the following advantages over currently used physical-chemical techniques: simplicity, no need for aeration or chemical additives and odor-free. Much research in process design is necessary before pilot or full scale application of the technique is possible.     

Toxicity of sodium selenite to rainbow trout fry

In a study designed to examine the long-term effects of inorganic selenium (IV) on early life stages of rainbow trout (Salmo gairdneri), survival was significantly reduced at selenium concentrations of 47 and 100 μg l⁻¹ after 90 days of exposure. Length and weight were significantly reduced after 90 days of exposure to 100 μg l⁻¹. Whole-body residues of selenium increased with increasing exposure concentrations but appeared to decline between 30 and 90 days of exposure. Analyses of trout backbone indicated little change in bone development with exposure to selenium (IV) with one exception; calcium concentrations were significantly decreased in fish exposed to 12 μg l⁻¹ of selenium. Results of our study indicates that a recommended safe level of 10 μg l⁻¹ for inorganic selenium would not significantly affect growth and survival of rainbow trout; however, concentrations of selenium near this level can reduce the levels of calcium in the backbones of trout.