Toxicities of total and chelex-labile cadmium to salmon in solutions of natural water and diluted sewage with potentially different cadmium complexing capacities

The LC₅₀ for total Cd averaged 4.8 and 8.0 μg1⁻¹ in river water and 33% sewage-treatment-plant effluent (STPE), respectively, and for Chelex-labile Cd, 3.9 and 5.6 μg1⁻¹, respectively. The LC₅₀ values for total Cd were significantly (P < 0.05) different, indicating a reduction in toxicity of Cd in the presence of 33% STPE, presumably due to complexation of Cd²⁺. The similarity of LC₅₀ values for Chelex-labile Cd indicates that that fraction contained toxic species of Cd at approximately the same concentration(s) in both river water and 33% STPE; it is therefore considered a better measure of Cd toxicity than total Cd. Furthermore, mortality was correlated with the concentration of Chelex-labile Cd but not with that of Chelex-nonlabile Cd. Measurements of Cd²⁺-complexing capacity by the Chelex method indicated that toxicity was due, at least in part, to Cd²⁺. Values were less than those obtained by the ion-selective-electrode method; these indicated that toxicity was due only to complexed Cd. Values from both methods were uncorrelated with LC₅₀ values.     

Fish toxicity of jet fuels—I. The toxicity of the synthetic fuel JP-9 and its components

The toxicity of the jet fuel JP-9 and its components RJ-4, RJ-5 and MCH was assessed in static bioassays on the warm water fish, golden shiner (Notemigonus chrysoleucas). The 96-h LC₅₀ of emulsions was 2.0 mg 1⁻¹ for JP-9, 0.51 mg 1⁻¹ for RJ-4, 0.61 mg 1⁻¹ for RJ-5 and 72 mg 1⁻¹ for MCH. As determined by the 96-h LC₅₀ values unemulsified fuel (pools of fuel) JP-9 was 235 times less toxic, RJ-4 was 196 times less toxic, RJ-5 was 7700 times less toxic and MCH was 3.3 times less toxic than the corresponding emulsified materials.

In continuous flow bioassays with the water soluble fraction of the fuel and its components the effect on egg hatchability and fry development of flagfish (Jordanella floridae) and rainbow trout (Salmo gairdneri) was studied. The no effect of level on flagfish egg hatchability was 0.23 mg 1⁻¹ for JP-9 and 0.05 mg 1⁻¹ for RJ-5. Concentrations of 0.83 mg 1⁻¹ MCH and 0.2 mg 1⁻¹ RJ-4 did not affect egg hatchability. In rainbow trout studies 97-day LC₅₀ values for RJ-4 and RJ-5 were 0.045 mg 1⁻¹ and 0.072 mg 1⁻¹, respectively, and 23-day LC₅₀ values for JP-9 and MCH were 0.26 mg 1⁻¹ and 1.3 mg 1⁻¹, respectively.

The accumulation of fuels in fish bodies was studied and it was found that flagfish can tolerate a total body burden of 0.5 mg MCH g⁻¹ wet weight without lethality. It was also found that body burdens of 0.43 mg RJ-4 g⁻¹ and of 0.27 mg RJ-5 g⁻¹ on a wet weight basis will produce 50% mortality in rainbow trout.

Voiding of MCH from fish bodies occurs readily in fuel-free water, but RJ-4 and RJ-5 are retained in the tissues.     

Toxicity of chlorine to juvenile spot, Leiostomus Xanthurus

The sensitivity of juvenile spot, Leiostomus xanthurus, to total residual chlorine (TRC) in flowing sea-water was investigated. Incipient LC₅₀ bioassays, histopathology, avoidance tests and the combined effect of thermal stress and TRC were used to assess sensitivity.

Estimated incipient LC₅₀ values were 0.12 mg 1⁻¹ TRC at 10°C and 0.06 mg 1⁻¹ TRC at 15°C. Histological examination of spot used in the incipient LC₅₀ bioassay at 15°C and sacrificed while alive indicated pseudobranch and gill damage occurred in individuals exposed to a measured TRC concentration of 1.57 mg 1⁻¹. Spot exposed to lower concentrations of TRC, 0.02 0.06 mg 1⁻¹ at 15°C and sacrificed alive showed no consistent tissue damage.

Spot demonstrated temperature dependent avoidance responses to TRC. At 10°C, a concentration of 0.18 mg 1⁻¹ was required for significant (X²; P < 0.05) avoidance; at 15 and 20°C, spot showed significant avoidance of TRC concentrations as low as 0.05 mg 1⁻¹.

Simultaneous exposure of spot to thermal stress (5, 10 or 13°C above the acclimation temperature of 15°C) at measured TRC concentrations of 0.05 0.07 and 0.34–0.52 mg 1⁻¹ demonstrated a significant, (Z²) with Yates correction, P < 0.05) increase in sensitivity to TRC with increased temperature and exposure times for some of the groups tested.     

Effect of exposure time and copper concentration on reproduction of the fathead minnow (Pimephales Promelas)

Three concurrent studies were conducted to determine the chronic effect of prespawning exposure to various concentrations of copper on fathead minnow reproduction. Copper was introduced into the three exposure systems to give 6-, 3-, and 0-months exposure prior to spawning. Prespawning exposure time had no significant effect on reproduction. Number of eggs produced per female decreased, however, with increase in copper concentrations. Egg production at copper concentrations of 37μg 1⁻¹ and higher was significantly lower (P = 0.05) than in the control, but at concentrations of 24μg 1⁻¹ and lower it was not different. The maximum acceptable toxicant concentration (MATC) was estimated to be 32μg Cu 1⁻¹, which is 0.07 of the 96h LC₅₀. This application factor for copper is similar to those found in other studies.     

Hypolimnetic aeration and dissolved gas concentrations: Enclosure experiments

Two large circular enclosures, each containing approx. 550 m³ of water, 14 m deep, and open to the mud-water interface, were used to monitor the effects of hypolimnetic aeration. One enclosure was held as a control, the other aerated every 3 or 4 days for a period long enough (usually < 2 h) to maintain hypolimnetic O₂ levels at > 4 mg 1⁻¹. Nutrient additions (10 g of 90% H₃ PO₄ and 250 g NaNO₃ per week) to each enclosure were controlled from the commencement of the experiment (17 June 1980) until its completion (2 November 1981). Temperatures in both enclosures were identical. Hypolimnetic O₂ levels in the control fell to zero during both summers, but remained at > 4 mg 1⁻¹ in the aerated enclosure. Free N₂ concentrations in the hypolimnion of the aerated enclosure was higher than in the control. Concentrations of H₂S in the control hypolimnion increased to > 5 mg 1⁻¹ and concentrations of CH₄ increased to > 18 mg 1⁻¹. Both remained at or near zero in the aerated enclosure. Tests of aerator efficiency suggested that the full air-lift design that was employed had an average O₂ exchange efficiency of 42% which is higher than the values reported for most other designs.     

Effect of water hardness on the toxicity of cadmium to micro-organisms

A study was made of the effect of water hardness at different concentrations (viz. 0, 80, 120, 160, 240, 320, 400 and 480 mg l⁻¹ as CaCO₃) on the toxicity of cadmium metal (5 mg 1⁻¹) as sulphate to saprophytic and nitrifying bacteria, with respect to the rate constant (K) and ultimate biochemical oxygen demand (L) which were calculated from BOD data (15 days) using the Thomas Graphical Method. Glucose was used as a source of carbon for micro-organisms. It was observed that the toxicity of cadmium to micro-organisms (both saprophytic and nitrifying) decreased with increasing hardness and reached a maximum at 320 mg 1⁻¹ as CaCO₃ for nitrifying and 400 mg l⁻¹ as CaCO₃ for saprophytic bacteria. After these hardness levels, the ultimate BOD (L) and rate constant (K) showed a decrease. Nitrifying bacteria were found to be more sensitive to the metal as well as to its complexation with calcium or with other ions as they retained their normal activity at a lower hardness level as compared to saprophytic bacteria.     

Sorption of cadmium(II) and zinc(II) ions from aqueous solutions by cassava waste biomass (Manihot sculenta Cranz)

The sorption of two divalent metal ions, Cd(II) and Zn(II), onto untreated and differentially acid-treated cassava waste biomass over a wide range of reaction conditions was studied at 30°C. The metal ion removal from the spent biomass was also measured. The batch experiments show that pH 4.5–5.5 was the best range for the sorption of the metal ions for untreated and acid-treated biomass. Time-dependent experiments for the metal ions showed that for the two metals examined, binding to the cassava waste biomass was rapid and occurred within 30 min and completed within 1 h. High sorption capacities were observed for the two metals. The binding capacity experiments revealed the following amounts of metal ions bound per gram of biomass: 86.68 mg/g Cd, 55.82 mg/g Zn and 647.48 mg/g Cd, 559.74 mg/g Zn for untreated and acid-treated biomass, respectively. It was further found that the rate of sorption was particle-diffusion controlled, and the sorption rate coefficients were determined to be 2.30×10⁻¹ min⁻¹ (Cd²⁺), 4.0×10⁻³ min⁻¹ (Zn²⁺) and 1.09×10⁻¹ min⁻¹ (Cd²⁺), 3.67×10⁻² min⁻¹ (Zn²⁺) for 0.5 and 1.00 M differential acid treatment, respectively. Desorption studies showed that acid treatment inhibited effective recovery of metal ions already bound to the biomass as a result of stronger sulfhydryl-metal bonds formed. Less than 25% of both metals were desorbed as concentration of acid treating reagent increases. However, over 60% Cd and 40% Zn were recovered from untreated biomass during the desorption study. The results from these studies indicated that both untreated and acid-treated cassava waste biomass could be employed in the removal of toxic and valuable metals from industrial effluents.     

Examination of the applicability of cellulose ion exchangers for water and waste water treatment

Three cellulose ion exchangers were examined and it was found that they are able to remove proteins, azodyes, DBS, humic acid, chromate and heavy metal ions (here Cu²⁺). The selectivity of the ion exchangers for removal of these compounds is very high, which explains their ability to remove the examined compounds with high efficiency and capacity, although the three cellulose ion exchangers have only a small capacity expressed as eqv 1⁻². The mass transfer coefficient was found, and it was stated that only the internal mass transfer determines the uptake rate. Theoretical column calculations based upon the found mass transfer coefficient were confirmed by pilot plan experiments.     

Combined γ-ray irradiation-activated sludge treatment of humic acid solution from landfill leachate

Humic acid, which is a typical microbially refractory organic substance, was extracted from a landfill leachate. The humic acid solution (COD = 367 mg 1⁻¹; TOC = 293 mg 1⁻¹; BOD = 27 mg 1⁻¹) was applied to a batch scale activated sludge treatment after the modification of its biodegradability by γ-ray irradiation. The BOD increased to 64 mg 1⁻¹ by irradiation of 15 kGy (1.5 Mrad), while the COD and TOC decreased to 231 and 230 mg 1⁻¹, respectively. When the irradiated sample was treated with an activated sludge, the BOD decreased rapidly in 2–3 h to about 15 mg 1⁻¹ which was a similar value as the unirradiated sample was treated. The elimination efficiency of TOC by the sludge treatment was approximately equal to that obtained by irradiation of 15 kGy. These facts suggest a utility of applying microbial processes after radiation treatment of microbially refractory wastewaters.     

Microbial uptake of cadmium and its effects on the biochemical oxygen demand at various temperatures

Uptake of cadmium by microbes at different temperatures has been studied at pH 7. Glycine was used as a source of carbon for microorganisms in the BOD bottle at 20, 30, 40 and 50°C with varying concentrations of cadmium: control 0.0437, 0.437, 0.875 and 1.31 mg 1⁻¹ in each set. The influence of temperatures on the toxic effects of cadmium has been studied with respect to rate constant (k) and ultimate biochemical oxygen demand which were calculated from BOD data using Thomas Graphical method. Consumed cadmium mg 1⁻¹ was determined after eight days and it varied from 14.04 to 32.40% at four temperatures. Highest consumption of Cd was noted in the set at 30 and 40°C and lowest at 50°C.     

Denitrification rates in relation to stream sediment characteristics

Potential rates of nitrate removal were studied in sediments from three Ontario rivers that differed in texture, organic carbon contents and other characteristics. Intact 0–5 cm depth sediment cores from 22 sites on each river were overlain with aerated 5 mg 1⁻¹ NO₃⁻-N solution and incubated in the laboratory at 21°C for 48 h. Rates of nitrate-N loss from the overlying solutions varied from 37 to 412 mg m⁻² day⁻¹ for a 24 h incubation period. The acetylene blockage technique was used with nitrate amended sediments to evaluate the relative importance of denitrification and nitrate reduction to ammonium. Denitrification accounted for 80–100% of the nitrate loss in the majority of sediment samples tested. Rates of nitrate loss for the 24 h period exhibited a highly significant positive correlation (r = 0.82–0.89) with the water-soluble carbon content of the sediments in each river. Significant relationships were also observed between nitrate loss and organic carbon, total nitrogen and sediment ammonium. A decline in nitrate loss via denitrification and increased nitrate reduction to ammonium was correlated with the organic carbon and water-soluble carbon content of the stream sediments.     

Kinetics of alachlor transformation and identification of metabolites under anaerobic conditions

Alachlor is one of the two most commonly used herbicides in the United States. In the environment, little mineralization of this compound has been found to occur, and metabolites of alachlor may be formed and could accumulate. The objectives of this study were to determine the rate of alachlor biotransformation and to identify the transformation intermediates formed under aqueous denitrifying, methanogenic, and sulfate-reducing conditions. Second-order biotrasnformation coefficients for alachlor were determined to be 7.6 × 10⁻⁵ (±4.0 × 10⁻⁵), 2.9 × 10⁻³ (±1.6 × 10⁻³), and 1.5 × 10⁻² (±1.4 × 10⁻²) 1 mg VSS⁻¹ day⁻¹ under denitrifying, methanogenic, and sulfate-reducing conditions, respectively. Acetyl alachlor and diethyl aniline were positively identified as transformation products of alachlor under all conditions. In denitrifying reactors aniline was identified as a product of alachlor. When acetyl alachlor was fed as the parent compound, aniline was also identified as a transformation product under methanogenic conditions. This research showed that although alachlor is degraded under denitrifying, methanogenic, and sulfate-reducing conditions, significant concentrations of several metabolites are formed and are only slowly degraded.     

Formation equation of halogenated organic compounds when water is chlorinated

Various halogenated organic compounds are formed by chlorination of water. In this study, formation of organic compounds halogenated from a reagent humic acid and extract of a leaf mold were examined under various conditions. The following overall formation equation was obtained from empirical data under the practical wide range when free chlorine remained.

[TOX]=k_TOX[TOC][Cl₂]_ot^β.

Here, [TOX] is the concentration of total organic halogen after t h in units of mg chlorine per liter; [TOC] and [Cl₂]_o are concentrations of total organic carbon and dosed chlorine in units of mg per liter; k_TOX is the rate constant and and β are parameters. From the values of k_TOX, and β, the character of organic substances i.e. precursor of halogenated organic compounds, in water can be evaluated. The values k_TOX, and β for humic acid are 0.053, 0.28 and 0.13, and the values for extract of the leaf mold are 0.032, 0.36 and 0.15, respectively. The activation energies are 10 kJ mol⁻¹ and 11 kJ mol⁻¹ for the reactions of humic acid and leaf mold extract, respectively.     

Utilisation de l''algue oocystis sp. pour le traitement tertiaire des eaux usées—I. Culture en vrac de cellules préalablement conditionnées en cyclostat

With the aim of developing an efficient and economic method for the tertiary treatment of wastewater, a two-phased culture system of Oocystis alga is presented. During the first phase, a unialgal strain grows in a cyclostat supplied with secondary effluents diluted to a low concentration (50 μM NH₄⁺, i.e. 0.7 mg N 1⁻¹) of inorganic ions. Once the equilibrium is reached (i.e. the cell population is conditioned and the nutrient concentration is zero), in a second phase, the starved cells are mixed with a secondary effluent which has a higher nutrient content (200–400 μM NH₄⁺, i.e., 2.8–5.6 mg N 1⁻¹). Ion depletion (NH₄⁺, NO₃^-, NO₂^- and PO₄^3-) follows specific kinetics; successive identifiable stages related to photoperiod lead to a complete stripping of nutrients. In addition to ion concentrations, pH and cell population were determined every 2 h during the experiment. Results and conclusions are presented.     

Empirical rate equation for trihalomethane formation with chlorination of humic substances in water

Trihalomethane (THM) in drinking water is formed by chlorination of humic substances. In this study, the rates of THM formation in aqueous solution of humic acid were examined under various conditions. The following rate equation was obtained empirically. [THM] = k (pH − a)[TOC][Cl₂]₀^mtⁿ.

Here, [THM] is the concentration of total THM after t h, [TOC] and [Cl₂]₀ are the concentrations of total organic carbon and chlorine dose, k is the rate constant and a, m and n are parameters. The values of k, a, m and n for humic acid as reagent were obtained as 8.2 × 10⁻⁴ (l^mmg^−mh⁻ⁿ), 2.8, 0.25 and 0.36, respectively. The activation energy was obtained as 37 kJ mol⁻¹. Further, it was proved that the above equation could be applied to the rates of THM formation from precursors in actual river and lake waters.     

Characterization of copper complexation with natural dissolved organic matter (DOM)--link to acidic moieties of DOM and competition by Ca and Mg

We investigated Cu complexation by three dissolved organic matters (DOMs) collected by reverse osmosis (RO). Alkalimetric titration, pH-stat Cu and Ca titrations, pH edges of Cu–DOM complexation, and Ca/Mg–Cu exchange experiments were investigated at I=10⁻² M for DOM samples of 10 mg C/L. The proton and Cu binding characteristics indicated similarity for all three DOMs. All Cu titrations employed ion selective electrode measurement and indicated the presence of relatively small amounts of strong Cu-binding sites. Four distinct classes of Cu binding sites are required for FITEQL 4.0 to provide good fits to the entire curves. The estimated total Cu binding site density is 4.55 mmol/g C, much less than the total acidity but very close to the phenolic site content. Cu–DOM complexation increases approximately 10-fold per pH unit, even at relatively high pH (>8). We suggest that sites characterized as phenolic based on alkalimetric titration, not carboxyl sites, account for the majority of Cu complexation under natural water conditions, and Cu–DOM complexation is principally through the replacement of H⁺ by Cu²⁺ at the phenolic binding sites. The Cu–H exchange ratio is 1:1 for the first three sites and about 1:2 for the 4th site. This 4-site model describes well the pH dependency of Cu–DOM complexation and provides good estimates of free Cu concentrations throughout wide total copper (Cu_T) and pH ranges. Comparison between Ca–DOM and Cu–DOM complexation demonstrated that (i) Ca–DOM complexation increases much less than an order of magnitude per pH unit and decreases at higher Ca concentration, different from that of Cu–DOM complexation; and (ii) Cu–DOM complexation is highly non-linear, in contrast to the much reduced extent of non-linearity of Ca–DOM complexation. Ca/Mg–Cu exchange experiments showed small competition effect, less than expected by a simple competition model, and the competition tended to reduce with increasing Ca or Mg concentrations. The extent of the competition by Mg and Ca are essentially comparable. Put all together, it suggests that Ca and Mg are preferably bound by carboxyl sites, especially at relatively high concentrations, resulting in a weakened apparent competition effect.     

Adsorption of trace metals on aluminium oxide: A simulation of processes in freshwater systems by close approximation to natural conditions

The interaction of the trace metals Cu, Co, Zn, Ni, Pb and Cd with aluminium hydroxide precipitated in-situ from homogeneous solution was studied. Using total concentrations of 10⁻⁴ M Al, 10⁻⁷ M Zn, Cu, Co, Ni and 10⁻⁸ M Pb and Cd a removal of Zn, Cu, Pb, Cd from solution occurred together with Al, while Co and Ni concentrations in solution remained unchanged. The binding of Cu, Pb and Zn, Cd is in agreement with the effect predicted by using published (resp. evaluated for Zn and Cd), values for stability constants of surface complexes on preformed Al₂O₃-suspension. The different behaviour of these elements and of Co and Ni is expected from the hydrolysis and adsorption tendencies. The experimental conditions correspond to natural conditions in lake waters, where due to the pH-dependent solubility of aluminium hydroxide, in-situ precipitation may occur and cause the scavenging of trace elements.     

Plant-scale phosphate removal experiments at the Balatonfüred sewage treatment plant

Operational parameters at the Balatonfüred sewage treatment plant and the technology of chemical phosphate removal on a plant-scale have been examined in a 3-week series of experiments. Aluminium sulphate and iron(II) sulphate have been used as precipitating agents. It was found that the addition of 30 mg 1⁻¹ aluminium gave 90 per cent removal of total phosphorus. The addition of 60 mg 1⁻¹ iron(II) gave 89 per cent removal of total phosphorus. The costs of these chemicals are 0·93 Ft m⁻³ for aluminium and 0·11 Ft m⁻³ for iron precipitants, resp. Thus the iron is significantly less expensive as a phosphorus precipitant.     

Histological and toxicological responses of the mummichog, Fundulus Heteroclitus (L.) to combinations of levels of cadmium and dissolved oxygen in a freshwater

Impact of dissolved oxygen concentration (D.O.) on toxicity of cadmium to mummichogs in a freshwater medium and histological changes associated with exposure were determined. Levels of mortality were related to duration of exposure, cadmium concentration, and levels of dissolved oxygen. Median tolerance concentrations, at 96h, ranged upward from 1.3 to about 3.0 mg Cd 1⁻¹ at 2.3 and 8.5 mg DO 1⁻¹, respectively. Statistical analyses of mortality data showed factors examined were interdependent and that Cd × DO and Cd × time interactions were significant (P < 0.01). No histopathology was evident at 3 mg Cd 1⁻¹, although histopathology was evident in gills from fish exposed to 28 mg Cd 1⁻¹ for 6 1/2 h.

Responses of mummichogs to cadmium in freshwater are compared with results of a previous study involving exposure of the species to cadmium in seawater and with responses of freshwater fishes subjected to various heavy metals. Differences and similarities in patterns of response are discussed in terms of water balance.     

The bioavailability of copper in wastewater to Lemna minor with biological and electrochemical measures of complexation

Lemna minor (duckweed) was grown in treated domestic wastewater containing added Cu to study the relationship between complexation and bioavailability. Growth was not inhibited until total Cu exceeded 0.079–0.119 mg/l or internal Cu exceeded 81 to 235 μ/g. Cu²⁺ was detectable in the wastewater when total Cu measured ≥ 0.378 mg/l. There was a significant (P < 0.05) relationship between Cu bioconcentration and total Cu in wastewater that was attributed, in part, to heterotrophy of duckweed. Results indicated that, in addition to the bioavailable Cu²⁺ species, some complexes of Cu formed with ligands in wastewater may also be bioavailable. Measurement of the Cu Complexing Capacity (CC) of the wastewater by Ion-Selective Electrode (ISE) gave values of 0.26 to 0.29 mg/l and indicated the presence of ligands with a continuum of binding strengths which eliminated two of three commonly used methods for calculating CC. The biologically-measured CuCC based on growth was 0.077–0.125 mg/l when calculated by two out of three measures of Effective Concentration (EC) and was two to three times more sensitive than the ISE method for measurement of CC. ECs based on tissue concentration of Cu rather than solution concentration were 81–471 μ/g and have been proposed as an alternative for work in complex solutions like wastewater.