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Evaluation of acute ecotoxicity removal from industrial wastewater using a battery of rapid bioassays Jan Dries, Dominique Daens, Luc Geuens and Ronny Blust
ABSTRACT The present study compares conventional wastewater treatment technologies (coagulation– flocculation and activated sludge) and powdered activated carbon (PAC) treatment for the removal of acute ecotoxicity from wastewater generated by tank truck cleaning (TTC) processes. Ecotoxicity was assessed with a battery of four commercially available rapid biological toxicity testing systems, verified by the US Environmental Protection Agency. Chemical coagulation–flocculation of raw TTC wastewater had no impact on the inhibition of the bioluminescence by Vibrio fischeri (BioTox assay). Subsequent biological treatment with activated sludge without PAC resulted in BioTox inhibition-free effluent (50%) (i) the bioluminescence by Photobacterium leiognathi (ToxScreen³ test kit), (ii) the photosynthesis by the green algae Chlorella vulgaris (LuminoTox SAPS test kit), and (iii) the particle ingestion by the crustacean Thamnocephalus platyurus (Rapidtoxkit test kit). The
Jan Dries (corresponding author) Dominique Daens Luc Geuens Research group BIT, Biochemical Engineering Technology, Faculty of Applied Engineering, University of Antwerp, Salesianenlaan 90, 2660 Antwerp, Belgium E-mail: [email protected] Ronny Blust Research group SPHERE, Systemic Physiological and Ecotoxicological Research, Department of Biology, Faculty of Science, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
lowest inhibition was measured after activated sludge treatment with the highest PAC dose (400 mg/L), demonstrating the effectiveness of PAC treatment for ecotoxicity removal from TTC wastewater. In conclusion, the combination of bioassays applied in the present study represents a promising test battery for rapid ecotoxicty assessment in wastewater treatment. Key words
| activated sludge, coagulation–flocculation, powdered activated carbon, tank truck cleaning, whole effluent toxicity
INTRODUCTION The tank truck cleaning (TTC) process involves cleaning of tank truck interiors. The wide range of transported cargo, ranging from food products to hazardous chemicals, results in a complex wastewater with variable composition and characteristics. The discharge limits for treated TTC effluents are currently mostly based on chemical parameters, such as chemical oxygen demand (COD). Several studies, however, indicate that results from both routine and advanced chemical analyses are unable to predict the potential ecological impact of complex effluents, emphasizing the need for whole effluent toxicity testing (WET) (Hernando et al. ; Rosa et al. ; Huybrechts et al. ). In previous studies with a particular TTC wastewater, we found that conventional treatment technologies such as chemical coagulation and activated sludge treatment did not suffice for complete detoxification, resulting in a significant residual ecotoxicity in the final effluent (De Schepper et al. ; Dries et al. ). An advanced treatment step, doi: 10.2166/wst.2014.459
such as powdered activated carbon treatment (PACT), is probably needed for complete removal of the toxicity in these cases (Eckenfelder et al. ). In the PACT process, powdered-activated carbon (PAC) is directly added to the activated sludge at influent doses of 20–500 mg/L (Çeçen & Aktas ). WET is commonly performed with green algae, daphnids, and fish as representatives of different trophic levels in the aquatic food chain (Escher & Leusch ). Major drawbacks of these tests, however, are the high cost, the need for trained personnel for the cultivation of the organisms and the large exposure times. To date, the bacterial bioluminescence inhibition test using Vibrio fischeri is the only standardized cost-effective and rapid toxicity assay that is widely applied for screening purposes in aquatic toxicity analysis (Parvez et al. ; Ma et al. ). The relative sensitivity of the assay using Vibrio fischeri in comparison with algae and daphnids varies according to the compound
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classes present in effluent samples (Girotti et al. ). These observations highlight the need to expand the array of rapid assays that can be combined for toxicity applications in wastewater treatment. The objectives of the present study were (i) to compare conventional wastewater treatment technologies with the PACT process for the removal of acute ecotoxicity from real TTC wastewater and (ii) to evaluate the response of a battery of four commercially available rapid bioassays, based on distinct inhibition principles.
METHODS Sampling The full-scale TTC wastewater treatment plant is located in the harbor region of Antwerp, and consists of the following steps: oil separation, primary coagulation–flocculation followed by dissolved air flotation, activated sludge treatment including sedimentation, and finally tertiary sand filtration (for the removal of suspended solids). At regular time intervals, we collected raw wastewater samples before coagulation–flocculation, and effluent samples after biological treatment. The grab samples were kept cool (at 4 C) and in the dark before use. W
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originating from the TTC company. The applied SBR cycle simulated the operation of the full-scale plant. Each 6 h cycle consisted of nine steps: initialization (1 min), two aerobic feed phases (28 min each) followed by two aerobic reaction phases (1 h 29 min each), post-anoxic mixing (30 min), refresh (5 min aeration), settling (45 min), and discharge (45 min). The starting mixed liquor volume in the SBRs was 10 L, and 620 mL of wastewater was added every cycle; 250 mL of the mixed liquor was wasted daily to obtain a sludge retention time of approximately 40 days. In aerated steps, the aeration was continuous, and dissolved oxygen was above 2 mg/L at all times. Pulsorb FG5 PAC (Chemviron Carbon) was added daily to SBR 2 (influent PAC dose of 80 mg/L) and SBR 3 (400 mg/L). No PAC was added to SBR 1. Chemical analyses Turbidity was measured using a portable turbidimeter (Hach model 2100P), and expressed as nephelometric turbidity units (NTU). COD and soluble COD (sCOD, i.e. COD analysis after filtration over a 0.45 μm glass fiber filter) were determined using micro-COD tubes (Hannah Instruments, Temse, Belgium). Mixed liquor suspended solids were measured gravimetrically after three consecutive centrifugation/washing cycles to remove the dissolved salts, and drying overnight at 105 C. W
Laboratory-scale treatment Rapid ecotoxicity tests The raw wastewater samples were treated by coagulation– flocculation in two phases. In a first phase, the coagulation was performed in 500 mL glass beakers using a range of coagulant doses. The coagulant was PAX-XL19, a water solution of polyaluminum chloride provided by the TTC company. Increasing concentrations of PAX from 0 to 100 mg/L were added while the samples were intensively mixed (200 rpm, using a Lovibond jar-tester). Subsequently, the mixing rate was lowered (to 40 rpm), the pH was adjusted to approximately 8.0–8.2, and a flocculant was added. The flocculant was anionic Optifloc 330 (Kemira Chemicals) provided by the TTC company, and the dose applied was about 0.8 mg/L. In the final step, the flocculated samples were allowed to settle for 30 min. In the second phase, we repeated the coagulation–flocculation for each wastewater sample on 20 L batches using only one PAX dose, based on the results from the first phase. The samples that were chemically treated in this second phase, were subsequently fed to three parallel sequencing batch reactors (SBR 1, 2, and 3) inoculated with activated sludge
A battery of four different commercially available acute toxicity tests was applied in the current study. Each assay was performed according to the instructions supplied by the test manufacturer, as described briefly below. The BioTox kit (Aboatox Oy, Finland) uses freeze-dried naturally luminescent Vibrio fischeri. The test protocol involved combining 500 μL of test samples (with adjusted salinity of 2% sodium chloride) with 500 μL of reconstituted bacteria. After a contact time of 30 min at 15 C, the decrease of light intensity was measured with a portable tube luminometer (Berthold Technologies Junior LB 9509). The inhibitory effect is compared to a negative control (2% sodium chloride) to give the percentage inhibition. The ToxScreen³ test kit (CheckLight Ltd, Israel) uses freeze-dried luminescent Photobacterium leiognathi and two proprietary assay buffers: one for detecting heavy metals (Pro-Metal Buffer) and the other for organic pollutants (pro-organic buffer). The test procedure involved combining 800 μL of test samples with 200 μL of assay W
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buffer and 10 μL of hydrated bacteria. The decrease of light intensity was measured after a contact time of 15 min at 30 C. The relative inhibitory effect for each sample is calculated by comparing the extent of luminescence change to a negative control (clean water with assay buffer). The LuminoTox SAPS test kit (Lab-Bell Inc., Canada) uses whole algae (Chlorella vulgaris) hereafter referred to as SAPS. The test is performed in the dark by exposing 100 μL of SAPS solution to 2 mL of test sample for 10 min (at ambient temperature). SAPS are then activated at a wavelength of 470 nm in a dedicated fluorometer. Some of the absorbed energy is emitted as fluorescence at wavelengths longer than 700 nm, which is the signal measured both in background water and effluent samples. Decreases in fluorescence as a result of toxic contamination are expressed as percent inhibition. Prior to analysis, SAPS were activated in room light for 90 min at ambient temperature. The Rapidtoxkit (MicroBioTests, Inc., Belgium) uses larvae of the anostracan crustacean Thamnocephalus platyurus. The bioassay was performed in test tubes using T. platyurus hatched from cysts (hatching was initiated 30–45 h prior to performing the test). The T. platyurus were exposed to samples for 1 h at 25 C, after which a suspension of red microspheres was added. The organisms ingest the microspheres, resulting in a deep red color in their digestive tracts. Stressed organisms either fail to take up particles or ingest at a much lower rate. The presence or the absence of colored microspheres in the digestive tract of the larval crustaceans was observed under a W
W
Table 1
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stereomicroscope. The total number of T. platyurus in the control (standard freshwater) wells and the number of T. platyurus that have taken up the red particles were counted. The fraction of larval crustaceans affected by the sample is defined as the percent inhibition. Statistical analyses Analysis of variance (ANOVA) and Tukey’s multiple comparisons of means were performed using the R software environment for statistical computing and graphics (http:// www.r-project.org). A paired t-test for comparison of means was performed using the Data Analysis tool in Microsoft Excel 2010.
RESULTS AND DISCUSSION Selection of the test battery From 1995 to 2013, the US EPA Environmental Technology Verification Program verified the performance of nearly 500 innovative environmental technologies (http://www.epa. gov/etv/vt-ams.html). Table 1 gives an overview of the 12 commercially available rapid biological toxicity testing systems that were included in the verification program. Exposure times between the test organisms and the test samples in these systems varies from 5 min to 2 h, which is significantly less than the conventional acute ecotoxicity assays using daphnids (48 h) or green algae (72 h).
Overview of commercially available biological rapid toxicity testing systems verified by the EPA Environmental Technology Verification Program
Type
Name
Organism
Inhibition
Bacterial
AbraTox
Vibrio fischeri
Bioluminescence
Plant Crustacean
BioTox
Vibrio fischeri
Bioluminescence
Deltatox
Vibrio fischeri
Bioluminescence
Microtox
Vibrio fischeri
Bioluminescence
ToxScreen³
Photobacterium leiognathi
Bioluminescence
Toxi-Chromotest
Escherichia coli
β-Galactosidase activity
ToxTrak
Different species
Resazurin reduction
PolyTox
Mixed culture
Respiration
LuminoTox PECs
Chloroplast membranes
Photosynthesis
LuminoTox SAPS
Chlorella vulgaris
Photosynthesis
IQ Toxicity Test
Daphnia magna
Enzyme activity
Rapidtoxkit
Thamnocephalus platyurus
Particle ingestion
The four toxicity tests in bold were applied in the current study.
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Most listed bioassays are based on a bacterial biosensor system such as the bioluminescent Vibrio fischeri. In contrast, only one test system, with two variants, is based on green plants (LuminoTox). In order to cover a wide range of ecological effects, we selected a test battery (highlighted in bold in Table 1) consisting of two distinct bacterial sensors, one algal assay and one crustacean-based system. With respect to the ToxScreen³ test, only results obtained with the proorganic buffer are reported. The assay using the pro-metal buffer yielded no significant inhibition in any of the samples, suggesting that metal toxicity was not an issue for this particular effluent (results not shown). Figure 2
Removal of Vibrio fischeri bioluminescence inhibition by conventional treatment technologies Over a period of about 4 months, we collected seven batches of raw TTC wastewater after oil separation in the full-scale treatment plant. The average total COD, sCOD, and turbidity of these raw wastewater samples were 1268 ± 328 mg/L, 1023 ± 334 mg/L and 163 ± 70 NTU, respectively. Treatment of raw wastewater by coagulation–flocculation in the laboratory removed 8–25% of the total COD (Figure 1; p < 0.001), yielding clear water with an average turbidity of 5 ± 1 NTU. In contrast, the average sCOD removal was not significant at about 5% (Figure 2; p > 0.05). The inhibition of the Vibrio fischeri bioluminescence by the raw wastewater, measured using the BioTox assay, varied strongly from 39 to 84% for the different samples, with an average of 58%. Coagulation–flocculation had no impact on the bioluminescence inhibition (Figure 2). In contrast, several authors report a significant reduction of bioluminescence inhibition from diverse industrial effluents, including TTC wastewater, after treatment with either ferric
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Removal of sCOD, and bioluminescence inhibition (% INH) measured with the BioTox assay, from raw TTC wastewater by coagulation–flocculation and subsequent activated sludge treatment without PAC addition; the data shown are averaged over a 4-month period (n ¼ 14; COD error bars represent 1 SD; % INH error bars not shown).
chloride or aluminum salts (e.g. Gotvajn et al. ; Dries et al. ). Our results can be explained by the fact that the measured bioluminescence inhibition was entirely associated with the filtered fraction of the raw wastewater (results not shown), which was not removed by the coagulation–flocculation step (Figure 2). Subsequent activated sludge treatment, without PAC addition, removed 93% of the remaining sCOD (Figure 2). Final sCOD concentrations were comparable to the values obtained after activated sludge treatment in the full-scale installation, and are well below the Flemish discharge limits for TTC effluents in surface water (i.e. 10-day average of 300 mg/L). Activated sludge treatment also removed 86% of the BioTox bioluminescence inhibition (Figure 2). In agreement with our results, a number of researchers report a significant decrease in bioluminescence inhibition after activated sludge treatment of both domestic and industrial wastewaters (Araújo et al. ; Katsoyiannis & Samara ; Rosa et al. ; Ma et al. ; Dries et al. ; Zhao et al. ). Response of the battery of rapid toxicity tests and evaluation of the PACT process
Figure 1
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COD removal from TTC wastewater by coagulation with 20 mg/L PAX and flocculation with 0.8 mg/L polyelectrolyte; the data shown are for unfiltered samples (duplicate measurements; error bars represent 1 SD).
Table 2 shows the effect of PAC treatment on the response of the battery of rapid bioassays for the three laboratoryscale SBR reactors and the full-scale plant. The response of the BioTox assay was well below 10% inhibition in all effluent samples, corresponding to an absence of toxicity. These results indicate that activated sludge treatment, without PAC addition, was sufficient for the removal of the Vibrio fischeri bioluminescence inhibition from this
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Average COD and average response of the rapid bioassays for effluent samples after activated sludge treatment in the full-scale treatment plant, and in laboratory-scale SBRs with or without PAC dosage (average ± SD) Full-scale
SBR1
SBR2
SBR3
Parameter
0 mg PAC/L
0 mg PAC/L
80 mg PAC/L
400 mg PAC/L
COD effluent (mg/L)
55 ± 9 (a)
64 ± 8 (a)
38 ± 6 (b)
17 ± 5 (c)
BioTox (% INH)
< 10
< 10
< 10
< 10
ToxScreen³ 41 ± 12 (a b) 57 ± 11 (a) 43 ± 16 (a b) 28 ± 12 (b) (% INH) SAPS (% INH)
74 ± 3 (a)
Rapidtoxkit 74 ± 9 (a) (% INH)
65 ± 6 (a)
33 ± 6 (b)
61 ± 14 (a) 73 ± 20 (a)
14 ± 9 (c) 58 ± 16 (a)
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the response of the ToxScreen³ test (p < 0.05). The Rapidtoxkit yielded inhibition values above 50% in all effluent samples, but the impact of PAC treatment was not statistically significant (p ¼ 0.25). The results of the pairwise comparison of means according to Tukey’s procedure, for the different parameters and reactors are summarized in Table 2. The highest COD and inhibition values were found in the laboratoryscale reactor without PAC, and in the effluent of the full-scale plant where PAC was not applied. Conversely, the lowest effluent COD and ecotoxicity were recorded in the laboratory-scale SBR treated with the highest PAC dose (400 mg/L). These results clearly demonstrate the effectiveness of PAC dosing on ecotoxicity removal from TTC wastewater, as observed in earlier studies for other types of wastewaters (Bundschuh et al. ; Margot et al. ).
Dissimilar letter codes in parenthesis indicate significant differences between treatment means (Tukey’s multiple comparison of means, p < 0.05). INH: inhibition.
CONCLUSIONS particular TTC wastewater (see also Figure 2). Similarly, Huybrechts et al. () only found a significant bioluminescence inhibition when TTC effluent samples were 10 times concentrated. In contrast, the response of the three other bioassays was significantly different from the non-toxic negative controls (Table 2). These results indicate (i) that ecotoxic effects were still present in the treated effluent and (ii) that the assays applied were more sensitive to TTC effluent toxicity than the Vibrio fischeri inhibition test. In agreement with our observations, Ulitzur et al. () reported the higher sensitivity of the ToxScreen test for a series of organic toxicants, in comparison with the Microtox test. Like the Vibrio fischeri inhibition test, the LuminoTox algal photosynthesis inhibition test aims at identifying general ecotoxic effects (Bellemare et al. ). Comparative responses of these two assays toward (industrial) effluents have not been reported before. The Rapidtoxkit, finally, uses the same test organism (Thamnocephalus platyurus) as the 24 h mortality Thamnotoxkit test which has been reported to have comparable sensitivity for wastewater as the Microtox test (Nalecz-Jawecki & Persoone ; Mendonça et al. ). Our results confirm that comparative sensitivities of different test organisms for environmental samples cannot be generalized, but should be investigated for each individual case (Ma et al. ). To the best of our knowledge, this is the first report on the application of a battery of EPA-verified rapid biological toxicity testing systems in wastewater treatment. ANOVA results (Table 2) indicate that PAC treatment had significant impact on the effluent COD (p < 0.001), on the response of the Lumintox SAPS test (p < 0.001) and on
In the present study, we found that primary coagulation– flocculation and activated sludge treatment did not suffice for the removal of ecotoxic effects from TTC wastewater. The PACT process on the other hand resulted in lower effluent COD values and significantly decreased the inhibition response of a battery of rapid ecotoxicity assays. The biological toxicity testing systems ToxScreen³, LuminoTox SAPS, and Rapidtoxkit were more sensitive to TTC effluent toxicity than the Vibrio fischeri-based BioTox inhibition test. The combination of rapid assay systems based on distinct inhibition principles and using a variety of biosensors holds great promise for time-efficient monitoring of wastewater treatment processes. In order to validate the test battery applied in the present study, future research should investigate the comparative sensitivity with the common WET battery using green algae, daphnids, and fish.
ACKNOWLEDGEMENT The authors would like to thank the University of Antwerp Research Fund (BOF) for funding this work.
REFERENCES Araújo, C. V. M., Nascimento, R. B., Oliveira, C. A., Strotmann, U. J. & da Silva, E. M. The use of Microtox to assess toxicity removal of industrial effluents from the industrial district of Camaçari (BA, Brazil). Chemosphere 58, 1277–1281.
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Bellemare, F., Rouette, M. E., Lorrain, L., Perron, E. & Boucher, N. Combined use of photosynthetic enzyme complexes and microalgal photosynthetic systems for rapid screening of wastewater toxicity. Environmental Toxicology 21, 445–449. Bundschuh, M., Zubrod, J. P., Seitz, F., Stang, C. & Schulz, R. Ecotoxicological evaluation of three tertiary wastewater treatment techniques via meta-analysis and feeding bioassays using Gammarus fossarum. Journal of Hazardous Materials 192, 772–778. Çeçen, F. & Aktas, Ö. Activated Carbon for Water and Wastewater Treatment. Integration of Adsorption and Biological Treatment. Wiley-VCH, Weinheim, Germany. De Schepper, W., Dries, J., Geuens, L. & Blust, R. Wastewater treatment plant modeling supported toxicity identification and evaluation of a tank truck cleaning effluent. Ecotoxicology and Environmental Safety 73, 702–709. Dries, J., De Schepper, W., Geuens, L. & Blust, R. Removal of ecotoxicity and COD from tank truck cleaning wastewater. Water Science and Technology 68, 2202–2207. Eckenfelder, W. W., Ford, D. L. & Englande, A. J. Industrial Water Quality. McGraw-Hill, New York, USA. Escher, B. & Leusch, F. Bioanalytical Tools in Water Quality Assessment. IWA Publishing, London, UK. Girotti, S., Ferri, E. N., Fumo, M. G. & Maiolini, E. Monitoring of environmental pollutants by bioluminescent bacteria. Analytica Chimica Acta 608, 2–29. Gotvajn, A. Z., Tisler, T. & Zagorc-Koncan, J. Comparison of different treatment strategies for industrial landfill leachate. Journal of Hazardous Materials 162, 1446–1456. Hernando, M. D., Fernàndez-Alba, A. R., Tauler, R. & Barceló, D. Toxicity assays applied to wastewater treatment. Talanta 65, 358–366. Huybrechts, D., Weltens, R., Jacobs, G., Borburgh, A., Smets, T., Hoebeke, L. & Polders, C. The relevance of physicochemical and biological parameters for setting emission limit values for plants treating complex wastewaters. Environmental Science and Pollution Research 21, 2805–2816. Katsoyiannis, A. & Samara, C. Ecotoxicological evaluation of the wastewater treatment process of the sewage treatment plant of Thessaloniki, Greece. Journal of Hazardous Materials 141, 1446–1456.
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Ma, X. Y., Wang, X. C. & Liu, Y. J. Study of the variation of ecotoxicity at different stages of domestic wastewater treatment using Vibrio-qinghaiensis sp.-Q67. Journal of Hazardous Materials 190, 100–105. Ma, X. Y., Wang, X. C., Ngo, H. H., Guo, W., Wu, M. N. & Wang, N. Bioassay based luminescent bacteria: interferences, improvements and applications. Science of the Total Environment 468–469, 1–11. Margot, J., Kienle, C., Magnet, A., Weil, M., Rossi, L., de Alencastro, L. F., Abegglen, C., Thonney, D., Chèvre, N., Schärer, M. & Barry, D. A. Treatment of micropollutants in municipal wastewater: ozone or powdered activated carbon? Science of the Total Environment 461–462, 480–498. Mendonça, E., Picado, A., Paixão, S. M., Silva, L., Cunha, M. A., Leitão, S., Moura, I., Cortez, C. & Brito, F. Ecotoxicity tests in the environmental analysis of wastewater treatment plants: case study in Portugal. Journal of Hazardous Materials 163, 665–670. Nalecz-Jawecki, G. & Persoone, G. Toxicity of selected pharmaceuticals to the anostracan crustacean Thamnocephalus platyurus – comparison of sublethal and lethal effect levels with the 1h Rapidtoxkit and the 24h Thamnotoxkit microbiotests. Environmental Science and Pollution Research 13, 22–27. Parvez, S., Venkataraman, C. & Mukherij, S. A review on advantages of implementing luminescence inhibition test (Vibrio fischeri) for acute toxicity prediction of chemicals. Environment International 32, 265–268. Rosa, R., Moreira-Santos, M., Lopes, I., Silva, L., Rebola, J., Mendoça, E., Picado, A. & Ribeiro, R. Comparison of a test battery for assessing the toxicity of a bleached-kraft pulp mill effluent before and after secondary treatment implementation. Environmental Monitoring and Assessment 161, 439–451. Ulitzur, S., Lahav, T. & Ulitzur, N. A novel and sensitive test for rapid determination of water toxicity. Environmental Toxicology 17, 291–296. Zhao, J. L., Jiang, Y. X., Yan, B., Wei, C., Zhang, L. J. & Ying, G. G. Multispecies acute toxicity evaluation of wastewaters from different treatment stages in a coking wastewater treatment plant. Environmental Toxicology and Chemistry 33, 1967–1975.
First received 23 July 2014; accepted in revised form 4 November 2014. Available online 15 November 2014
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© IWA Publishing 2014 Water Science & Technology
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70.12
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2014
Evaluation of acute ecotoxicity removal from industrial wastewater using a battery of rapid bioassays Jan Dries, Dominique Daens, Luc Geuens and Ronny Blust
ABSTRACT The present study compares conventional wastewater treatment technologies (coagulation– flocculation and activated sludge) and powdered activated carbon (PAC) treatment for the removal of acute ecotoxicity from wastewater generated by tank truck cleaning (TTC) processes. Ecotoxicity was assessed with a battery of four commercially available rapid biological toxicity testing systems, verified by the US Environmental Protection Agency. Chemical coagulation–flocculation of raw TTC wastewater had no impact on the inhibition of the bioluminescence by Vibrio fischeri (BioTox assay). Subsequent biological treatment with activated sludge without PAC resulted in BioTox inhibition-free effluent (50%) (i) the bioluminescence by Photobacterium leiognathi (ToxScreen³ test kit), (ii) the photosynthesis by the green algae Chlorella vulgaris (LuminoTox SAPS test kit), and (iii) the particle ingestion by the crustacean Thamnocephalus platyurus (Rapidtoxkit test kit). The
Jan Dries (corresponding author) Dominique Daens Luc Geuens Research group BIT, Biochemical Engineering Technology, Faculty of Applied Engineering, University of Antwerp, Salesianenlaan 90, 2660 Antwerp, Belgium E-mail: [email protected] Ronny Blust Research group SPHERE, Systemic Physiological and Ecotoxicological Research, Department of Biology, Faculty of Science, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
lowest inhibition was measured after activated sludge treatment with the highest PAC dose (400 mg/L), demonstrating the effectiveness of PAC treatment for ecotoxicity removal from TTC wastewater. In conclusion, the combination of bioassays applied in the present study represents a promising test battery for rapid ecotoxicty assessment in wastewater treatment. Key words
| activated sludge, coagulation–flocculation, powdered activated carbon, tank truck cleaning, whole effluent toxicity
INTRODUCTION The tank truck cleaning (TTC) process involves cleaning of tank truck interiors. The wide range of transported cargo, ranging from food products to hazardous chemicals, results in a complex wastewater with variable composition and characteristics. The discharge limits for treated TTC effluents are currently mostly based on chemical parameters, such as chemical oxygen demand (COD). Several studies, however, indicate that results from both routine and advanced chemical analyses are unable to predict the potential ecological impact of complex effluents, emphasizing the need for whole effluent toxicity testing (WET) (Hernando et al. ; Rosa et al. ; Huybrechts et al. ). In previous studies with a particular TTC wastewater, we found that conventional treatment technologies such as chemical coagulation and activated sludge treatment did not suffice for complete detoxification, resulting in a significant residual ecotoxicity in the final effluent (De Schepper et al. ; Dries et al. ). An advanced treatment step, doi: 10.2166/wst.2014.459
such as powdered activated carbon treatment (PACT), is probably needed for complete removal of the toxicity in these cases (Eckenfelder et al. ). In the PACT process, powdered-activated carbon (PAC) is directly added to the activated sludge at influent doses of 20–500 mg/L (Çeçen & Aktas ). WET is commonly performed with green algae, daphnids, and fish as representatives of different trophic levels in the aquatic food chain (Escher & Leusch ). Major drawbacks of these tests, however, are the high cost, the need for trained personnel for the cultivation of the organisms and the large exposure times. To date, the bacterial bioluminescence inhibition test using Vibrio fischeri is the only standardized cost-effective and rapid toxicity assay that is widely applied for screening purposes in aquatic toxicity analysis (Parvez et al. ; Ma et al. ). The relative sensitivity of the assay using Vibrio fischeri in comparison with algae and daphnids varies according to the compound
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classes present in effluent samples (Girotti et al. ). These observations highlight the need to expand the array of rapid assays that can be combined for toxicity applications in wastewater treatment. The objectives of the present study were (i) to compare conventional wastewater treatment technologies with the PACT process for the removal of acute ecotoxicity from real TTC wastewater and (ii) to evaluate the response of a battery of four commercially available rapid bioassays, based on distinct inhibition principles.
METHODS Sampling The full-scale TTC wastewater treatment plant is located in the harbor region of Antwerp, and consists of the following steps: oil separation, primary coagulation–flocculation followed by dissolved air flotation, activated sludge treatment including sedimentation, and finally tertiary sand filtration (for the removal of suspended solids). At regular time intervals, we collected raw wastewater samples before coagulation–flocculation, and effluent samples after biological treatment. The grab samples were kept cool (at 4 C) and in the dark before use. W
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originating from the TTC company. The applied SBR cycle simulated the operation of the full-scale plant. Each 6 h cycle consisted of nine steps: initialization (1 min), two aerobic feed phases (28 min each) followed by two aerobic reaction phases (1 h 29 min each), post-anoxic mixing (30 min), refresh (5 min aeration), settling (45 min), and discharge (45 min). The starting mixed liquor volume in the SBRs was 10 L, and 620 mL of wastewater was added every cycle; 250 mL of the mixed liquor was wasted daily to obtain a sludge retention time of approximately 40 days. In aerated steps, the aeration was continuous, and dissolved oxygen was above 2 mg/L at all times. Pulsorb FG5 PAC (Chemviron Carbon) was added daily to SBR 2 (influent PAC dose of 80 mg/L) and SBR 3 (400 mg/L). No PAC was added to SBR 1. Chemical analyses Turbidity was measured using a portable turbidimeter (Hach model 2100P), and expressed as nephelometric turbidity units (NTU). COD and soluble COD (sCOD, i.e. COD analysis after filtration over a 0.45 μm glass fiber filter) were determined using micro-COD tubes (Hannah Instruments, Temse, Belgium). Mixed liquor suspended solids were measured gravimetrically after three consecutive centrifugation/washing cycles to remove the dissolved salts, and drying overnight at 105 C. W
Laboratory-scale treatment Rapid ecotoxicity tests The raw wastewater samples were treated by coagulation– flocculation in two phases. In a first phase, the coagulation was performed in 500 mL glass beakers using a range of coagulant doses. The coagulant was PAX-XL19, a water solution of polyaluminum chloride provided by the TTC company. Increasing concentrations of PAX from 0 to 100 mg/L were added while the samples were intensively mixed (200 rpm, using a Lovibond jar-tester). Subsequently, the mixing rate was lowered (to 40 rpm), the pH was adjusted to approximately 8.0–8.2, and a flocculant was added. The flocculant was anionic Optifloc 330 (Kemira Chemicals) provided by the TTC company, and the dose applied was about 0.8 mg/L. In the final step, the flocculated samples were allowed to settle for 30 min. In the second phase, we repeated the coagulation–flocculation for each wastewater sample on 20 L batches using only one PAX dose, based on the results from the first phase. The samples that were chemically treated in this second phase, were subsequently fed to three parallel sequencing batch reactors (SBR 1, 2, and 3) inoculated with activated sludge
A battery of four different commercially available acute toxicity tests was applied in the current study. Each assay was performed according to the instructions supplied by the test manufacturer, as described briefly below. The BioTox kit (Aboatox Oy, Finland) uses freeze-dried naturally luminescent Vibrio fischeri. The test protocol involved combining 500 μL of test samples (with adjusted salinity of 2% sodium chloride) with 500 μL of reconstituted bacteria. After a contact time of 30 min at 15 C, the decrease of light intensity was measured with a portable tube luminometer (Berthold Technologies Junior LB 9509). The inhibitory effect is compared to a negative control (2% sodium chloride) to give the percentage inhibition. The ToxScreen³ test kit (CheckLight Ltd, Israel) uses freeze-dried luminescent Photobacterium leiognathi and two proprietary assay buffers: one for detecting heavy metals (Pro-Metal Buffer) and the other for organic pollutants (pro-organic buffer). The test procedure involved combining 800 μL of test samples with 200 μL of assay W
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buffer and 10 μL of hydrated bacteria. The decrease of light intensity was measured after a contact time of 15 min at 30 C. The relative inhibitory effect for each sample is calculated by comparing the extent of luminescence change to a negative control (clean water with assay buffer). The LuminoTox SAPS test kit (Lab-Bell Inc., Canada) uses whole algae (Chlorella vulgaris) hereafter referred to as SAPS. The test is performed in the dark by exposing 100 μL of SAPS solution to 2 mL of test sample for 10 min (at ambient temperature). SAPS are then activated at a wavelength of 470 nm in a dedicated fluorometer. Some of the absorbed energy is emitted as fluorescence at wavelengths longer than 700 nm, which is the signal measured both in background water and effluent samples. Decreases in fluorescence as a result of toxic contamination are expressed as percent inhibition. Prior to analysis, SAPS were activated in room light for 90 min at ambient temperature. The Rapidtoxkit (MicroBioTests, Inc., Belgium) uses larvae of the anostracan crustacean Thamnocephalus platyurus. The bioassay was performed in test tubes using T. platyurus hatched from cysts (hatching was initiated 30–45 h prior to performing the test). The T. platyurus were exposed to samples for 1 h at 25 C, after which a suspension of red microspheres was added. The organisms ingest the microspheres, resulting in a deep red color in their digestive tracts. Stressed organisms either fail to take up particles or ingest at a much lower rate. The presence or the absence of colored microspheres in the digestive tract of the larval crustaceans was observed under a W
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stereomicroscope. The total number of T. platyurus in the control (standard freshwater) wells and the number of T. platyurus that have taken up the red particles were counted. The fraction of larval crustaceans affected by the sample is defined as the percent inhibition. Statistical analyses Analysis of variance (ANOVA) and Tukey’s multiple comparisons of means were performed using the R software environment for statistical computing and graphics (http:// www.r-project.org). A paired t-test for comparison of means was performed using the Data Analysis tool in Microsoft Excel 2010.
RESULTS AND DISCUSSION Selection of the test battery From 1995 to 2013, the US EPA Environmental Technology Verification Program verified the performance of nearly 500 innovative environmental technologies (http://www.epa. gov/etv/vt-ams.html). Table 1 gives an overview of the 12 commercially available rapid biological toxicity testing systems that were included in the verification program. Exposure times between the test organisms and the test samples in these systems varies from 5 min to 2 h, which is significantly less than the conventional acute ecotoxicity assays using daphnids (48 h) or green algae (72 h).
Overview of commercially available biological rapid toxicity testing systems verified by the EPA Environmental Technology Verification Program
Type
Name
Organism
Inhibition
Bacterial
AbraTox
Vibrio fischeri
Bioluminescence
Plant Crustacean
BioTox
Vibrio fischeri
Bioluminescence
Deltatox
Vibrio fischeri
Bioluminescence
Microtox
Vibrio fischeri
Bioluminescence
ToxScreen³
Photobacterium leiognathi
Bioluminescence
Toxi-Chromotest
Escherichia coli
β-Galactosidase activity
ToxTrak
Different species
Resazurin reduction
PolyTox
Mixed culture
Respiration
LuminoTox PECs
Chloroplast membranes
Photosynthesis
LuminoTox SAPS
Chlorella vulgaris
Photosynthesis
IQ Toxicity Test
Daphnia magna
Enzyme activity
Rapidtoxkit
Thamnocephalus platyurus
Particle ingestion
The four toxicity tests in bold were applied in the current study.
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Most listed bioassays are based on a bacterial biosensor system such as the bioluminescent Vibrio fischeri. In contrast, only one test system, with two variants, is based on green plants (LuminoTox). In order to cover a wide range of ecological effects, we selected a test battery (highlighted in bold in Table 1) consisting of two distinct bacterial sensors, one algal assay and one crustacean-based system. With respect to the ToxScreen³ test, only results obtained with the proorganic buffer are reported. The assay using the pro-metal buffer yielded no significant inhibition in any of the samples, suggesting that metal toxicity was not an issue for this particular effluent (results not shown). Figure 2
Removal of Vibrio fischeri bioluminescence inhibition by conventional treatment technologies Over a period of about 4 months, we collected seven batches of raw TTC wastewater after oil separation in the full-scale treatment plant. The average total COD, sCOD, and turbidity of these raw wastewater samples were 1268 ± 328 mg/L, 1023 ± 334 mg/L and 163 ± 70 NTU, respectively. Treatment of raw wastewater by coagulation–flocculation in the laboratory removed 8–25% of the total COD (Figure 1; p < 0.001), yielding clear water with an average turbidity of 5 ± 1 NTU. In contrast, the average sCOD removal was not significant at about 5% (Figure 2; p > 0.05). The inhibition of the Vibrio fischeri bioluminescence by the raw wastewater, measured using the BioTox assay, varied strongly from 39 to 84% for the different samples, with an average of 58%. Coagulation–flocculation had no impact on the bioluminescence inhibition (Figure 2). In contrast, several authors report a significant reduction of bioluminescence inhibition from diverse industrial effluents, including TTC wastewater, after treatment with either ferric
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Removal of sCOD, and bioluminescence inhibition (% INH) measured with the BioTox assay, from raw TTC wastewater by coagulation–flocculation and subsequent activated sludge treatment without PAC addition; the data shown are averaged over a 4-month period (n ¼ 14; COD error bars represent 1 SD; % INH error bars not shown).
chloride or aluminum salts (e.g. Gotvajn et al. ; Dries et al. ). Our results can be explained by the fact that the measured bioluminescence inhibition was entirely associated with the filtered fraction of the raw wastewater (results not shown), which was not removed by the coagulation–flocculation step (Figure 2). Subsequent activated sludge treatment, without PAC addition, removed 93% of the remaining sCOD (Figure 2). Final sCOD concentrations were comparable to the values obtained after activated sludge treatment in the full-scale installation, and are well below the Flemish discharge limits for TTC effluents in surface water (i.e. 10-day average of 300 mg/L). Activated sludge treatment also removed 86% of the BioTox bioluminescence inhibition (Figure 2). In agreement with our results, a number of researchers report a significant decrease in bioluminescence inhibition after activated sludge treatment of both domestic and industrial wastewaters (Araújo et al. ; Katsoyiannis & Samara ; Rosa et al. ; Ma et al. ; Dries et al. ; Zhao et al. ). Response of the battery of rapid toxicity tests and evaluation of the PACT process
Figure 1
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COD removal from TTC wastewater by coagulation with 20 mg/L PAX and flocculation with 0.8 mg/L polyelectrolyte; the data shown are for unfiltered samples (duplicate measurements; error bars represent 1 SD).
Table 2 shows the effect of PAC treatment on the response of the battery of rapid bioassays for the three laboratoryscale SBR reactors and the full-scale plant. The response of the BioTox assay was well below 10% inhibition in all effluent samples, corresponding to an absence of toxicity. These results indicate that activated sludge treatment, without PAC addition, was sufficient for the removal of the Vibrio fischeri bioluminescence inhibition from this
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Average COD and average response of the rapid bioassays for effluent samples after activated sludge treatment in the full-scale treatment plant, and in laboratory-scale SBRs with or without PAC dosage (average ± SD) Full-scale
SBR1
SBR2
SBR3
Parameter
0 mg PAC/L
0 mg PAC/L
80 mg PAC/L
400 mg PAC/L
COD effluent (mg/L)
55 ± 9 (a)
64 ± 8 (a)
38 ± 6 (b)
17 ± 5 (c)
BioTox (% INH)
< 10
< 10
< 10
< 10
ToxScreen³ 41 ± 12 (a b) 57 ± 11 (a) 43 ± 16 (a b) 28 ± 12 (b) (% INH) SAPS (% INH)
74 ± 3 (a)
Rapidtoxkit 74 ± 9 (a) (% INH)
65 ± 6 (a)
33 ± 6 (b)
61 ± 14 (a) 73 ± 20 (a)
14 ± 9 (c) 58 ± 16 (a)
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the response of the ToxScreen³ test (p < 0.05). The Rapidtoxkit yielded inhibition values above 50% in all effluent samples, but the impact of PAC treatment was not statistically significant (p ¼ 0.25). The results of the pairwise comparison of means according to Tukey’s procedure, for the different parameters and reactors are summarized in Table 2. The highest COD and inhibition values were found in the laboratoryscale reactor without PAC, and in the effluent of the full-scale plant where PAC was not applied. Conversely, the lowest effluent COD and ecotoxicity were recorded in the laboratory-scale SBR treated with the highest PAC dose (400 mg/L). These results clearly demonstrate the effectiveness of PAC dosing on ecotoxicity removal from TTC wastewater, as observed in earlier studies for other types of wastewaters (Bundschuh et al. ; Margot et al. ).
Dissimilar letter codes in parenthesis indicate significant differences between treatment means (Tukey’s multiple comparison of means, p < 0.05). INH: inhibition.
CONCLUSIONS particular TTC wastewater (see also Figure 2). Similarly, Huybrechts et al. () only found a significant bioluminescence inhibition when TTC effluent samples were 10 times concentrated. In contrast, the response of the three other bioassays was significantly different from the non-toxic negative controls (Table 2). These results indicate (i) that ecotoxic effects were still present in the treated effluent and (ii) that the assays applied were more sensitive to TTC effluent toxicity than the Vibrio fischeri inhibition test. In agreement with our observations, Ulitzur et al. () reported the higher sensitivity of the ToxScreen test for a series of organic toxicants, in comparison with the Microtox test. Like the Vibrio fischeri inhibition test, the LuminoTox algal photosynthesis inhibition test aims at identifying general ecotoxic effects (Bellemare et al. ). Comparative responses of these two assays toward (industrial) effluents have not been reported before. The Rapidtoxkit, finally, uses the same test organism (Thamnocephalus platyurus) as the 24 h mortality Thamnotoxkit test which has been reported to have comparable sensitivity for wastewater as the Microtox test (Nalecz-Jawecki & Persoone ; Mendonça et al. ). Our results confirm that comparative sensitivities of different test organisms for environmental samples cannot be generalized, but should be investigated for each individual case (Ma et al. ). To the best of our knowledge, this is the first report on the application of a battery of EPA-verified rapid biological toxicity testing systems in wastewater treatment. ANOVA results (Table 2) indicate that PAC treatment had significant impact on the effluent COD (p < 0.001), on the response of the Lumintox SAPS test (p < 0.001) and on
In the present study, we found that primary coagulation– flocculation and activated sludge treatment did not suffice for the removal of ecotoxic effects from TTC wastewater. The PACT process on the other hand resulted in lower effluent COD values and significantly decreased the inhibition response of a battery of rapid ecotoxicity assays. The biological toxicity testing systems ToxScreen³, LuminoTox SAPS, and Rapidtoxkit were more sensitive to TTC effluent toxicity than the Vibrio fischeri-based BioTox inhibition test. The combination of rapid assay systems based on distinct inhibition principles and using a variety of biosensors holds great promise for time-efficient monitoring of wastewater treatment processes. In order to validate the test battery applied in the present study, future research should investigate the comparative sensitivity with the common WET battery using green algae, daphnids, and fish.
ACKNOWLEDGEMENT The authors would like to thank the University of Antwerp Research Fund (BOF) for funding this work.
REFERENCES Araújo, C. V. M., Nascimento, R. B., Oliveira, C. A., Strotmann, U. J. & da Silva, E. M. The use of Microtox to assess toxicity removal of industrial effluents from the industrial district of Camaçari (BA, Brazil). Chemosphere 58, 1277–1281.
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Bellemare, F., Rouette, M. E., Lorrain, L., Perron, E. & Boucher, N. Combined use of photosynthetic enzyme complexes and microalgal photosynthetic systems for rapid screening of wastewater toxicity. Environmental Toxicology 21, 445–449. Bundschuh, M., Zubrod, J. P., Seitz, F., Stang, C. & Schulz, R. Ecotoxicological evaluation of three tertiary wastewater treatment techniques via meta-analysis and feeding bioassays using Gammarus fossarum. Journal of Hazardous Materials 192, 772–778. Çeçen, F. & Aktas, Ö. Activated Carbon for Water and Wastewater Treatment. Integration of Adsorption and Biological Treatment. Wiley-VCH, Weinheim, Germany. De Schepper, W., Dries, J., Geuens, L. & Blust, R. Wastewater treatment plant modeling supported toxicity identification and evaluation of a tank truck cleaning effluent. Ecotoxicology and Environmental Safety 73, 702–709. Dries, J., De Schepper, W., Geuens, L. & Blust, R. Removal of ecotoxicity and COD from tank truck cleaning wastewater. Water Science and Technology 68, 2202–2207. Eckenfelder, W. W., Ford, D. L. & Englande, A. J. Industrial Water Quality. McGraw-Hill, New York, USA. Escher, B. & Leusch, F. Bioanalytical Tools in Water Quality Assessment. IWA Publishing, London, UK. Girotti, S., Ferri, E. N., Fumo, M. G. & Maiolini, E. Monitoring of environmental pollutants by bioluminescent bacteria. Analytica Chimica Acta 608, 2–29. Gotvajn, A. Z., Tisler, T. & Zagorc-Koncan, J. Comparison of different treatment strategies for industrial landfill leachate. Journal of Hazardous Materials 162, 1446–1456. Hernando, M. D., Fernàndez-Alba, A. R., Tauler, R. & Barceló, D. Toxicity assays applied to wastewater treatment. Talanta 65, 358–366. Huybrechts, D., Weltens, R., Jacobs, G., Borburgh, A., Smets, T., Hoebeke, L. & Polders, C. The relevance of physicochemical and biological parameters for setting emission limit values for plants treating complex wastewaters. Environmental Science and Pollution Research 21, 2805–2816. Katsoyiannis, A. & Samara, C. Ecotoxicological evaluation of the wastewater treatment process of the sewage treatment plant of Thessaloniki, Greece. Journal of Hazardous Materials 141, 1446–1456.
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Ma, X. Y., Wang, X. C. & Liu, Y. J. Study of the variation of ecotoxicity at different stages of domestic wastewater treatment using Vibrio-qinghaiensis sp.-Q67. Journal of Hazardous Materials 190, 100–105. Ma, X. Y., Wang, X. C., Ngo, H. H., Guo, W., Wu, M. N. & Wang, N. Bioassay based luminescent bacteria: interferences, improvements and applications. Science of the Total Environment 468–469, 1–11. Margot, J., Kienle, C., Magnet, A., Weil, M., Rossi, L., de Alencastro, L. F., Abegglen, C., Thonney, D., Chèvre, N., Schärer, M. & Barry, D. A. Treatment of micropollutants in municipal wastewater: ozone or powdered activated carbon? Science of the Total Environment 461–462, 480–498. Mendonça, E., Picado, A., Paixão, S. M., Silva, L., Cunha, M. A., Leitão, S., Moura, I., Cortez, C. & Brito, F. Ecotoxicity tests in the environmental analysis of wastewater treatment plants: case study in Portugal. Journal of Hazardous Materials 163, 665–670. Nalecz-Jawecki, G. & Persoone, G. Toxicity of selected pharmaceuticals to the anostracan crustacean Thamnocephalus platyurus – comparison of sublethal and lethal effect levels with the 1h Rapidtoxkit and the 24h Thamnotoxkit microbiotests. Environmental Science and Pollution Research 13, 22–27. Parvez, S., Venkataraman, C. & Mukherij, S. A review on advantages of implementing luminescence inhibition test (Vibrio fischeri) for acute toxicity prediction of chemicals. Environment International 32, 265–268. Rosa, R., Moreira-Santos, M., Lopes, I., Silva, L., Rebola, J., Mendoça, E., Picado, A. & Ribeiro, R. Comparison of a test battery for assessing the toxicity of a bleached-kraft pulp mill effluent before and after secondary treatment implementation. Environmental Monitoring and Assessment 161, 439–451. Ulitzur, S., Lahav, T. & Ulitzur, N. A novel and sensitive test for rapid determination of water toxicity. Environmental Toxicology 17, 291–296. Zhao, J. L., Jiang, Y. X., Yan, B., Wei, C., Zhang, L. J. & Ying, G. G. Multispecies acute toxicity evaluation of wastewaters from different treatment stages in a coking wastewater treatment plant. Environmental Toxicology and Chemistry 33, 1967–1975.
First received 23 July 2014; accepted in revised form 4 November 2014. Available online 15 November 2014
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