Influence of dilution water on the toxicity of kraft pulp and paper mill effluent, including mechanisms of effect

Ten natural freshwater samples differing widely in pH and other characteristics were collected and examined for their influence as dilution waters on the acute lethality (24-h LC50 values) of a sample of bleached kraft whole mill effluent. When bioassays were conducted at the pH of each dilution water, LC50 values varied by 3.5-fold. These differences were largely accounted for by adjustment of the pH of each test solution to a common value (6.5). The remaining minor differences in LC50 values were attributed to the ionizable inorganic constituents of the dilution waters.A separate study examined the effects of test pH and the involvement of aging of solutions prior to bioassays or of pH overshoots during pH adjustment on the toxicity of a second sample of pulp mill effluent: using a single dilution water. The LC50 values obtained for bioassays conducted at pH 9.5 were significantly higher than those for tests performed at pH 6.5. Neither the adjustment of test solutions to pH 9.5 with immediate readjustment to pH 6.5, nor the prior aging of solutions at pH 9.5 or 6.5 with minimal or no aeration for 6 h, altered the differences due to test pH.The pH-toxicity relationship of the resin acid dehydroabietate and a third sample of bleached kraft whole mill effluent was similar throughout the pH range 5.0–10.5, with test solutions least toxic at pH 9.0–9.5. This pH-toxicity relationship for pulpmill effluents and the influence of dilution water pH on effluent toxicity were attributed mainly to the ionization equilibria of the effluents' resin acid constituents.     

An appraisal of the effect of biological treatment on the environmental quality of high-yield mechanical pulping effluents

Before biological treatment, the effluents from one CTMP (chemi-thermomechanical pulping) and three TMP (thermomechanical pulping) mills were acutely lethal to fathead minnows (Pimephales promelas) and the water flea Ceriodaphnia with 48-h LC₅₀ values of 2.2 to > 50%. The effluents also caused chronic effects at concentrations of 0.01–5.3%. After biological treatment, effluents from the three TMP mills were not acutely lethal to either test species. Biotreated effluents from the CTMP mill were also not acutely lethal to minnows but were lethal to Ceriodaphnia (48-h LC₅₀: 54–80%). The chronic effects of biotreated effluents occurred at concentrations of 47 to > 100% for fathead minnows and at 5–37% for Ceriodaphnia. Biological treatment also reduced the levels of BOD (>80%), COD (>60%) and wood extractives (>99%).     

Disruption of precopulatory behavior in the amphipod Anisogammarus pugettensis upon exposure to bleached kraft pulpmill effluent

Marine amphipods in precopula, Anisogammarus pugettensis (Dana), were used in static 117 h bioassays with neutralized, filtered, bleached kraft pulp mill effluent (BKME) and daily solution replacement. The effluent interfered with precopula behavior; high concentrations (40% of full strength BKME) resulted in rapid release of paired amphipods. A concentration-related time to 50% release of paired individuals was observed. For one batch of BKME, the behavioral threshold concentration (EC₅₀) was estimated at 10–15% of full strength BKME. The estimated 96 h LC₅₀ for underyearling coho salmon (Oncorhynchus kisutch) for the same effluent tested in freshwater was 36% BKME—illustrating a greater sensitivity of the amphipod behavioral bioassay in comparison to the salmonid acute lethal toxicity test. The amphipod precopula bioassay for toxicity testing has some merit in that it is moderately quantitative under given test conditions and does not require elaborate equipment.     

The residual oxygen bioassay: A rapid procedure to predict effluent toxicity to rainbow trout

A rapid bioassay procedure is described which for the toxic effluents tested, is sensitive to concentrations in the 96-h lc₅₀ range. The procedure requires less than eight hours to complete and is based on the consumption of available oxygen by fish in sealed containers.The procedure was evaluated using sodium pentachlorophenate, 3 kraft pulp mill bleach plant effluents and a chloralkali plant waste. The threshold concentrations obtained from the rapid procedure were directly comparable to 96-h lc₅₀ values obtained by standard methods. For replicate tests with sodium pentachlorophenate, no significant difference (p < 0.05) between means of data obtained by the two bioassay procedures could be demonstrated, using the Student “t”-test.     

Hepatic metallothionein level and mixed function oxidase activity in fingerling rainbow trout (Oncorhynchus mykiss) after acute exposure to pulp and paper mill effluents

Hepatic metallothionein (MT) levels and mixed function oxidase (MFO) activity (7-ethoxyresorufin-o-deethylase or EROD) were measured in fingerling rainbow trout (Oncorhynchus mykiss) exposed to sublethal concentrations of 12 pulp and paper effluents, after completion of 96 h static acute lethality assays. Barring one primary-treated effluent where MFO levels were significantly depressed and two secondary-treated effluents where no significant MFO induction were observed, all other effluents triggered significant induction of MT and EROD, regardless of mill process/treatment or of effluent lethality and chemical characteristics. MT and EROD inductions were significant, however, at higher concentrations for secondary-treated effluents than for primary-treated ones. Lethal (96 h LC₅₀s) to sublethal (MT and EROD lowest observable effect concentrations) ratios were variable and indicated that significant biochemical effects were present at effluent concentrations that were roughly 4–33 (MT) and 3–59 (EROD) times lower than the LC₃₀. Enzyme induction ranged from 1.3 to 2.5-fold for MT and from 1.3 to 9.4-fold for EROD compared to controls. Limited chemical data available suggest that there were indeed classes of compounds present capable of inducing MT or EROD. Observed patterns of MT/MFO responses also suggest that contaminant interactions may have interfered with induction for some of the effluents studied. Refinements of this combined (sub)lethal bioassay procedure are envisaged to determine whether it can provide an efficient means of detecting hazardous chemicals in industrial wastewaters.     

Effects of pH increases and sodium chloride additions on the acute toxicity of 2,4-dichlorophenol to the fathead minnow

The observable toxic effects produced by short-term exposure of fathead minnows (Pimephales promelas) to 2,4-dichlorophenol were reduced when the pH of the test water was increased by the addition of NaOH. After exposure for 192 h to 7.43 mg 2,4-dichlorophenol l^-1, the average survival of fathead minnows ranged from 28% at pH 7.57 to 100% at pH 9.08. Normal schooling behaviour was completely disrupted, and the equilibrium of most fish was affected after a 24-h exposure to 7.43 mg 2,4-dichlorophenol 1^-1 at pH 7.57, but neither schooling nor equilibrium were affected even after 192 h at pH 8.68 and 9.08. Schooling and swimming behaviour of fathead minnows exposed to 12.33 mg 2,4-dichlorophenol l^-1 were affected at all pH levels. Survival of these fish after 24 h ranged from 0% at pH 7.84–46% at pH 8.81. Sodium chloride in concentrations ranging from 0 to 13.9 mg l^-1 had no observable effects on the acute toxicity of 2,4-dichlorophenol to fathead minnows.     

Toxic effects of aliphatic chlorinated by-products from vinyl chloride production on marine animals

The acute toxic effects of chlorinated aliphatic hydrocarbons, formed as by-products from one Swedish and one Norwegian plastic production factory, were examined by experiments with cod (Gadus morhua), shrimp (Crangon crangon) and a polychaete (Ophyryotrocha labronica). The toxicity of 1,2-dichloroethane—a dominating compound of the by-products—and a distillate with heavier compounds were also estimated. The toxicity (48 h, LC50) ratio between the concentrations of a Swedish by-product, a Norwegian by-product, and dichloroethane was 1:9:34. The effects of 1,2-dichloroethane, 1,1,2-trichloroethane and 1,1,2-trichloroethene on the reproductivity, and on the survival of adults of Ophryotrocha were studied. The reproductivity was affected by these components in far lower concentrations than those having acute toxic effects on adult specimens. In one experiment series Ophryotrocha was exposed suddenly to the test solutions and in a second series the first presentation was made by a successive increase of the concentration during one hour. The estimated 96-h LC50-values for the test with successive increase were 1·8–3·1 times higher than those found for the test with sudden exposure. It is suggested that a physiological shock in the start of bioassay experiments might have reduced the LC50-values in many previous tests.     

The acute toxicity of vanadium and copper to eyed eggs of rainbow trout (Salmo gairdneri)

The effects of vanadium (25–595 mg l⁻¹) and of copper (0.03–4.78 mg l⁻¹) on embryonic survival and hatching of eyed eggs of rainbow trout, Salmo gairdneri, were investigated. Copper was approx. 300-fold more toxic than vanadium (96-h LC₅₀ = 0.4 and 118 mg l⁻¹, respectively) but had little effect on the timing of hatch. Vanadium induced premature hatching of eyed eggs at concentrations from 44 to 595 mg l⁻¹. Concentrations of copper required to produce lethality in eyed eggs were similar to concentrations required to produce mortality in juveniles. Vanadium concentrations approx. 15 times higher were required to produce mortality in eyed eggs than in juveniles. Therefore, acute exposure of eyed rainbow trout eggs to vanadium is not a sensitive toxicity test for use in establishing water quality criteria or maximum acceptable toxicant concentrations.     

Effects of aluminum and pH on the early life stages of smallmouth bass (Micropterus dolomieui)

The sensitivity of smallmouth bass Micropterus dolomieui to acidified conditions was examined by exposing recently-hatched fish to pH levels ranging from 5.1 to 7.5 and aluminum concentrations ranging from 32 to 1000 μg l⁻¹. The range of pH and aluminum concentrations included those found in the northern part of the species' range. Acute bioassays (96 h) conducted at a pH of 5.1 and aluminum concentrations 180 μgl⁻¹ resulted in total mortality. The LC₅₀ calculated for this species was 130 μg l⁻¹. At pH values of 6.1 and 7.5, mortality was low ( 20%) regardless of aluminum concentrations. A 30-day chronic toxicity test was conducted at three pH levels (low 5.1, intermediate 5.5–5.7 and high 7.3), each with two aluminum concentrations (approx. 0 and 200 μg l⁻¹). Survival was significantly lower in the test at pH 5.1 with aluminum, and at pH 5.7 with aluminum treatments than in the other treatments. Fish in the pH 5.1 without aluminum treatment had intermediate survival, while fish exposed to pH 5.7 without aluminum, pH 7.3 without aluminum and pH 7.3 with aluminum had high, and similar, survival. Sublethal effects on fish exposed to low pH and aluminum included deformities, reduced activity and abnormal swimming behavior. We conclude that the sensitivity of smallmouth bass to low pH and aluminum concentrations corroborates field investigations linking acidification and aluminum mobilization with depletion of smallmouth bass populations.     

On the measurement of particulate association of americium in freshwater

A laboratory investigation tested various filtration methods to study the particulate-water fractionation of ²⁴¹Am added to filtered freshwater (Monaco tap water) adjusted to different pH's. By using a system of washed Nuclepore polycarbonate filters, the particulate association (>0.2 or >1 μm) was found to increase hyperbolically with pH and with time, so that less than 1% of the Am was filterable (i.e. retained by a filter) at pH 4.2 and about 5% was filterable at pH 8.2 after 1 day; light had no apparent effect on the filterability of the Am. These values are somewhat greater than those for particle association of Am in seawater but substantially lower than previous estimates of Am particulate association in filtered freshwater. Filter adsorption problems are identified for other filtration systems commonly employed to assess metal particulate association. The results suggest that Am in freshwater is unlikely to form particles to an appreciable extent at pH's ?8.     

Flameless atomic absorption analyses of mercury in model aquatic systems

Chemical models of freshwater and seawater (34‰ S) have been used to examine the effect of humic material on the analysis of mercury by flameless atomic absorption spectrometry. Solutions containing mercuric chloride (1 μg Hg 1⁻¹) and various concentrations of humic material were allowed to attain equilibrium under carefully controlled conditions. In both media, association between the inorganic and organic entities took place within 90 min at pH ≥ 7 and the organically bound mercury was not detected by an analytical method designed for inorganic mercury. The amount of detectable mercury was related to the quantity of humic material added to the solutions.In experiments involving changes of pH the model solutions showed three characteristics: (1) a flat response in the neutral and alkaline pH range, where the humates are apparently stable; (2) a minima in the pH range 2–4 where the formation of an acid flocculent appears to remove additional mercury from solution: (3) at pH = 1, some release of mercury occurs from the organic precipitate.Photolysis studies using the model freshwater solutions showed that total mercury measurements could be made after 2 h irradiation at pH = 1. Using the same technique methylmercury chloride and diphenylmercury decomposed within 1 h. These results are relevant to routine and analyses of total mercury in natural waters.     

Acute toxicity of unbleached kraft mill effluent (UKME) to the opossum shrimp, Neomysis americana smith

Ninety-six hour TL₅₀ values of unbleached kraft mill effluent (UKME) for Neomysis americana were found to range from concentrations of 3.29–6.85 per cent at 26–28°C and 3.90–7.30 per cent at 16–18°C. Differences between batches of effluent proved insignificant in experiments at each temperature regime. Furthermore, UKME did not lose its toxicity when stored for 5–7 days at 4°C. A concentration of 20 per cent effluent killed 100 per cent of the organisms in 8 of the 12 bioassays. Slope functions and confidence limits of TL₅₀ were calculated. Toxicity did not appear to be correlated with the Biochemical Oxygen Demand (BOD) of individual batches of raw effluent.     

A comparison of the characteristics of soluble organic nitrogen in untreated and activated sludge treated wastewaters

Soluble organic materials containing nitrogen (SON) are present in effluents from activated sludge treatment of domestic wastewater, but little is known about the sources and characteristics of these materials. The objective of this research was to evaluate the characteristics of SON in untreated wastewaters and activated sludge effluents. Characterization techniques used included low microbial seed biodegradability, molecular weight distribution using gel filtration chromatography, removal by activated carbon and ion exchange, and analysis for free and combined amino acids. Activated sludge effluent SON was more refractory (40–50%; first-order decay rates for the remainder were about 0.014 day⁻¹ than SON in untreated wastewater (18–38%; decay rates for the remainder were 0.08–0.16 day⁻¹). SON produced biologically during treatment had decay rates (about 0.028 day⁻¹) similar to SON in municipal activated sludge effluents, and was from 20 to 100% refractory. Less than 10% of the SON in municipal activated sludge effluent consisted of free or combined amino acids. Approximately 15–30% appeared to nucleic acid degradation products. Fifty to 60% of the SON and SCOD had apparent molecular weights of less than 1800. Apparent molecular weight distributions of treated and untreated wastewaters were similar; however, the excess SON produced during activated sludge start-up contained considerably more SON with molecular weights greater than 1800. The 165–340 molecular weight fraction had a significantly higher SON to SCOD ratio than any other fraction for all wastewaters examined. Activated carbon adsorption efficiently removed SON (72 ± 9%) and SCOD (78 ± 6%) from treated and untreated wastewaters, and from biologically produced organics. Significantly more SON was removed by cationic exchange at pH 2.0 (33–56%) than by anionic exchange at pH 9.5 (10–24%) for all wastewaters tested. Cationic exchange at pH 2.0 selectively removed more biologically produced SON relative to SCOD.     

A comparison of toxicity tests conducted in the laboratory and in experimental ponds using cadmium and the fathead minnow (Pimephales promelas)

Acute toxicity tests were conducted in the laboratory with fathead minnows (Pimephales promelas) to determine the 96-h LC₅₀ of cadmium under three conditions: (1) in laboratory water, (2) in water from experimental ponds, and (3) in pond water underlain by sediment. Cadmium was then applied at doses equivalent to the estimated LC₅₀ values to 0.07-ha ponds containing caged fathead minnows. A cadmium ion selective electrode, ultrafiltration, and equilibrium calculations were used to determine cadmium speciation, and several water quality characteristics were measured to correlate differences in mortality between test systems (laboratory and field) with observed differences in water quality. The LC₅₀ estimates (mg l⁻¹) for the bioassays were 4.39 for the laboratory water, 3.52 for the pond water with sediment, and 2.91 for the pond water. Concentrations of Cd²⁺ decreased and those of cadmium in the particulate (> 1.2 μm) and 300,000 mol. wt (0.018–1.2 μm) fractions increased over the 96-h; cadmium in these fractions was believed to consist of colloidal sized CdCO₃ precipitates. Concentrations of Cd²⁺ decreased at different rates between test systems, regulated by the degree of CdCO₃(s) supersaturation which in turn depended on pH and total metal concentrations. Differences in toxicity in the laboratory tests were attributed to differences in water hardness and Cd²⁺ concentrations. Mortality of fathead minnows was low (0–10%) during the 96-h test period in the ponds due to the higher pH, which produced supersaturated conditions resulting in the rapid formation of nontoxic CdCO₃ precipitates and a more rapid decrease in Cd²⁺ concentrations as compared to the laboratory bioassays.     

Complexation and toxicity of copper and the free metal bioassay technique

The concentrations of free and total copper toxic to Daphnia and guppies were determined in inorganic media with and without addition of various concentrations of β-alanine, glycine, glutamic acid or Tris. Free copper concentrations were determined using a cupric ion electrode. Stability constants calculated for each of the detected complexes compared favourably with previously published values, with the possible exception of the Cu(OH)₂ complex. Free copper concentrations in solutions equally toxic to Daphnia were observed to vary greatly, primarily because of the toxicity of copper amino acid complexes to this organism. The copper/amino acid complexes were, nevertheless, less toxic than the free copper ions. The copper/β-alanine complex was observed to be less toxic to guppies than to Daphnia, indicating a difference in sensitivity to different copper complexes in different organisms. Copper/Tris complexes were found to be only slightly toxic to both Daphnia and guppies. A bioassay technique for determining free copper concentrations by comparing copper toxicity before and after addition of Tris was tested and verified. Although free metal concentrations can be determined from properly conducted bioassays, the variation in free metal concentration in equally toxic solutions demonstrates that free metal concentrations cannot be calculated by simply comparing metal toxicity in a test solution with toxicity of the same metal in a standard solution with known free metal concentration, unless it is known that no complexes are present in the test solution which can form toxic complexes with the metal.     

The role of pH on the acute toxicity of sulfite in water

The toxicity of sulfite to fish decreases with increasing pH value, because the HSO⁻₃ ion is more toxic than the SO²⁻₃ ion. An effective sulfite concentration S_eff which is proportional to the toxicity on fish, is expressed by the following equation: S_eff=[HSO⁻₃]+ƒ[SO²⁻₃]where ƒ is a coefficient which expresses the change of toxicity of sulfite depending on the pH of the water, and varies for each species of fish. For goldfish, owing to the very small toxic contribution of SO²⁻₃ ion (ƒ = 0·07), the pH dependence of the toxicity of sulfite on pH was so strong that sulfite seemed almost non-toxic in basic solution. However, ƒ for guppy is somewhat larger (ƒ = 0·20) so that the toxicity of sulfite weakly depends on the pH value of water.     

Selective removal of resin and fatty acids from mechanical pulp effluents by ozone

Fresh chemithermomechanical (CTMP) mill primary clarifier (combined) effluents were treated using a system capable of accurately applying small measured charges of ozone. It was shown that the efficiency of ozone transfer into effluent was much better than into water, and that there was no residual dissolved ozone. Small ozone charges destroyed high proportions of the total resin and fatty acids (RFAs) and juvabiones (JBs) present in the effluents. This effect diminished with increasing ozone charges. Likewise, effluent toxicity, as measured in the Microtox assay, decreased rapidly with the low ozone charges. The low charges of ozone were also shown to be effective in destroying both soluble and particulate RFAs. It was shown that there was a strong positive correlation between the RFA content and the acute toxicity of an effluent sample, and that all the acute toxicity was extractable with methyl-t-butyl ether. Both Microtox and Daphnia magna acute toxicity assays correlated with effluent RFA content, but the Microtox was somewhat more sensitive. Thus, ozone may be a useful economical treatment agent for selectively removing RFAs and toxicity from mill effluent streams.     

Algae and crustaceans as indicators of bioactivity of industrial wastes

Freshwater (Selenastrum capricornutum) and marine (Skeletonema costatum) algae were exposed to liquid wastes from 10 industrial sites in laboratory bioassays. All wastes affected algal growth, either by stimulation only or by stimulation at low concentrations and inhibition at high concentrations. Generally, S. capricornutum and Sk. costatum responded similarly to each waste: SC20's (concentration that stimulated growth by 20%) were between 0.01 and 20.0% waste; EC50's (concentration that inhibited growth by 50%), between 5.1 and 85.5% waste. Since toxicity to S. capricornutum was usually lost by the sixth or seventh day of exposure in all wastes except one, it is recommended that algal tests be carried out for 4 days. Both algal species were more sensitive to the wastes than were Daphnia magna (freshwater) and Mysidopsis bahia (marine). Only three wastes were toxic to D. magna and two were toxic to M. bahia. SC20 and EC50 values are used to calculate the 7-day, 10-year flow rate of the receiving stream required for dilution of effluents to non-toxic concentrations.     

Toxicity of lipid-soluble copper(II) complexes to the marine diatom Nitzschia closterium: Amelioration by humic substances

Algal assays, using the marine diatom Nitzschia closterium, have established that humic acid (5 mg kg⁻¹) can ameliorate the toxicity of the lipophilic complex Cu(oxine)₂ (3 × 10⁻⁸ mol l⁻¹ in unsupplemented seawater). The toxicity of Cu(PAN)₂ is not ameliorated [PAN = 1-(2-pyridylazo)-2-napthol]. In conjunction with previous visible absorption spectrophotometry and polarographic measurements it was established that humic acid sequesters copper(II) from the hydrophobic complexes, releasing a ligand molecule. The copper(II) toxicity may be ameliorated provided the ligand itself is not toxic.Fulvic acid was significantly less effective in ameliorating toxicity. Because of the significant competition from Ca(II) and Mg(II) in seawater, it is inferred that humic substances may be more effective in ameliorating toxicity of hydrophobic copper complexes in fresh water.     

Reduction of aquatic toxicity of linear alkylbenzene sulfonate (LAS) by biodegradation

Partial biodegradation of LAS is shown to significantly reduce the specific toxicity (i.e. per unit weight) of the remaining LAS to Daphnia magna (water fleas) and Pimephales promelas (fathead minnows). This results from the fact that the longer homologs and more terminal isomers, which are the more toxic, are also the more rapidly degraded under bacterial action. The acute aquatic LC₅₀ of LAS may range from 0.5 to 50 mg/l depending mainly upon the chain length of the particular homolog. A high molecular weight commercial type LAS with LC₅₀ around 2 mg/l before biodegradation may show Daphnia LC₅₀'s of 30–40 mg/l. for the LAS remaining after 80–85% degradation.A further contribution to this toxicity reduction may occur if the methylene blue analytical method is used to determine the amount of LAS remaining, since some of the biodegradation intermediates show methylene blue activity but no significant toxicity. For example, sulfophenylundecanoate, a model of early intermediates, shows Daphnia and fathead lc₅₀'s 200 and 75 mg/l., respectively. Sulfophenylbutyrate, modeling somewhat later intermediates, gives lc₅₀ values around 5000–10,000 mg/l. Dialkyl tetralin/indane sulfonates (the major non-linear components in commercial LAS) exhibit 1/2–1/10 the toxicity of the corresponding LAS homologs.These results re-emphasize that analysis simply for methylene blue active substances (MBAS) gives no basis for predicting the aquatic toxicity of an environmental sample. And furthermore, that meaningful water quality criteria and standards cannot be established in terms of MBAS content while based on toxicity studies on intact, undegraded LAS.