The relationship between whole effluent toxicity (WET) and chemical-based effluent quality assessment in Vojvodina (Serbia)

Assessment of oil refinery wastewater and effluent integrating bioassays, mechanistic modelling and bioavailability evaluation

Water is used in petroleum oil refineries in significant volumes for cooling, steam generation and processing of raw materials. Effective water management is required at refineries to ensure their efficient and responsible operation with respect to the water environment. However, ascertaining the potential environmental risks associated with discharge of refinery effluents to receiving waters is challenging because of their compositional complexity. Recent European research and regulatory initiatives propose a more holistic approach including biological effect methods to assess complex effluents and surface water quality. The study presented here investigated potential effects of effluent composition, particularly hydrocarbons, on aquatic toxicity and was a component of a larger study assessing contaminant removal during refinery wastewater treatment (Hjort et al 2021). The evaluation of effects utilised a novel combination of mechanistic toxicity modelling based on the exposure composition, measured bioavailable hydrocarbons using biomimetic solid phase microextraction (BE-SPME), and bioassays. The results indicate that in the refinery effluent assessments measured bioavailable hydrocarbons using BE-SPME was correlated with the responses in standard bioassays. It confirms that bioassays are providing relevant data and that BE-SPME measurement, combined with knowledge of other known non-hydrocarbon toxic constituents, provide key tools for toxicity identification. Overall, the results indicate that oil refinery effluents treated in accordance to the EU Industrial Emissions Directive requirements have low to negligible toxicity to aquatic organisms and their receiving environments. Low-cost, animal-free BE-SPME represents a compelling tool for rapid effluent characterization.

Investigating the relationship between toxicity and organic sum-parameters in kraft mill effluents

Elaborate toxicity diagnostics, such as toxicity identification evaluation (TIE) and effects-directed analysis (EDA) have helped in identifying the causative agents of effluent wastewater toxicity. However, simpler means of relating ecotoxicological effects to effluent composition could be useful for effluent management practices when there is no scope for more complex procedures. The aim of this work was to investigate and isolate the relationship between biological responses and commonly measured organic sum-parameters, such as chemical- and biochemical oxygen demand (COD and BOD, respectively) in kraft mill effluents. In a top-down approach, the whole effluent toxicity (WET) of effluent samples was first determined from Pseudokirchneriella subcapitata and Ceriodaphnia dubia bioassays. The theoretical toxicity that could be attributed to the metal content was then estimated, via a combination of equilibrium chemical speciation- and metal toxicity modelling. By assuming concentration addition, the metal toxicity was subtracted from the WET, isolating the toxicity thought to be caused by the organics. Strong and significant correlations between the 'corrected' toxicity and organic sum-parameters were found for both species. The growth of P. subcapitata was negatively associated with increasing COD concentrations, whereas reproduction of C. dubia was negatively associated with increasing BOD concentrations. The linear relationships, along with robust estimations of their uncertainty bounds, can provide valuable, albeit rough, guidance for kraft mill effluent management practices.

The relevance of physicochemical and biological parameters for setting emission limit values for plants treating complex industrial wastewaters

The influents of plants treating complex industrial wastewaters from third parties may contain a large variety of often unknown or unidentified potentially harmful substances. The conventional approach of assessing and regulating the effluents of these plants is to set emission limit values for a limited set of physicochemical parameters, such as heavy metals, biological oxygen demand, chemical oxygen demand and adsorbable organic halogen compounds. The objective of this study was to evaluate the relevance of physicochemical parameters for setting emission limit values for such plants based on a comparison of effluent analyses by physicochemical and biological assessment tools. The results show that physicochemical parameters alone are not sufficient to evaluate the effectiveness of the water treatment plants for removing hazardous compounds and to protect the environment. The introduction of toxicity limits and limits for the total bioaccumulation potential should be considered to supplement generic parameters such as chemical oxygen demand and adsorbable organic halogens. A recommendation is made to include toxicity screening as a technique to consider in the determination of best available techniques (BAT) during the upcoming revision of the BAT reference document for the waste treatment industries to provide a more rational basis in decisions on additional treatment steps.

Cytotoxicity and genotoxicity of sewage treatment plant effluents in rainbow trout cells (RTG-2)

The cytotoxicity and genotoxicity of 11 organic fractions from sewage treatment plant (STP) effluents were tested using the RTG-2 rainbow trout permanent cell line. An automated in vitro micronucleus assay developed for RTG-2 cells was used to test the genotoxicity, whereas neutral red uptake, kenacid blue protein assay and ATP content were used to evaluate cytotoxicity. The induction of micronuclei (MN) and alterations in the cell cycle were analysed in these cells by flow cytometry after exposure to the organic fractions for 72 h. More than half of the organic extracts tested demonstrated a significant increase in the MN frequency, thus indicating that most of them can be considered to be genotoxic. The extracts were analysed chemically by GC/MS. Although the most frequently detected compounds in the effluents were bisphenol A (BPA), octylphenol (OP), di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP), as well as other possible mutagens, the concentrations cannot explain the genotoxicity of the individual chemicals, thereby suggesting a mixture effect. The results obtained support the need to apply effect-based tests to monitor complex mixtures as the most accurate means of assessing the genotoxicity of environmental samples.

Ecological risk assessment of on-site soil washing with iron(III) chloride in cadmium-contaminated paddy field

On-site soil washing with iron(III) chloride reduces Cd levels in soil, and thus the human health risks caused by Cd in food. However, it may threaten aquatic organisms when soil washing effluent is discharged to open aquatic systems. Therefore, we conducted trial-scale on-site soil washing and ecological risk assessment in Nagano and Niigata prefectures, Japan. The ecological effect of effluent water was investigated by two methods. The first was bioassay using standard aquatic test organisms. Twice-diluted effluent water from the Nagano site and the original effluent water from the Niigata site had no significant effects on green algae, water flea, caddisfly, and fish. The safe dilution rates were estimated as 20 times and 10 times for the Nagano and Niigata sites, respectively, considering an assessment factor of 10. The second method was probabilistic effect analysis using chemical analysis and the species sensitivity distribution concept. The mixture effects of CaCl(2), Al, Zn, and Mn were considered by applying a response additive model. The safe dilution rates, assessed for a potentially affected fraction of species of 5%, were 7.1 times and 23.6 times for the Nagano and Niigata sites, respectively. The actual dilution rates of effluent water by river water at the Nagano and Niigata sites were 2200-67,000 times and 1300-110,000 times, respectively. These are much larger than the safe dilution rates derived from the two approaches. Consequently, the ecological risk to aquatic organisms of soil washing is evaluated as being below the concern level.

Assessment of hormonal activities and genotoxicity of industrial effluents using in vitro bioassays combined with chemical analysis

Wastewaters from various industries are a main source of the contaminants in aquatic environments. The authors evaluated the hormonal activities (estrogenic/anti-estrogenic activities, androgenic/anti-androgenic activities) and genotoxicity of various effluents from textile and dyeing plants, electronic and electroplate factories, pulp and paper mills, fine chemical factories, and municipal wastewater treatment plants in the Pearl River Delta region by using in vitro bioassays (yeast estrogen screen [YES]; yeast androgen screen [YAS]; and genotoxicity assay [umu/SOS]) combined with chemical analysis. The results demonstrated the presence of estrogenic, anti-estrogenic, and anti-androgenic activity in most industrial effluents, whereas no androgenic activities were detected in all of the effluents. The measured estrogenic activities expressed as estradiol equivalent concentrations (EEQs) ranged from below detection (3 of 26 samples) to 40.7 ng/L, with a mean of 7.33 ng/L in all effluents. A good linear relationship was found between the EEQs measured by YES bioassay and the EEQs calculated from chemical concentrations. These detected estrogenic compounds, such as 4-nonylphenol and estrone, were responsible for the estrogenic activities in the effluents. The genotoxic effects expressed as benzo[a]pyrene equivalent concentrations (BaP EQs) varied between below detection and 88.2 µg/L, with a mean of 8.76 µg/L in all effluents. The target polycyclic aromatic hydrocarbons were minor contributors to the genotoxicity in the effluents, and some nontarget compounds in the effluents were responsible for the measured genotoxicity. In terms of estrogenic activities and genotoxicity, discharge of these effluents could pose high risks to aquatic organisms in the receiving environments.

Use of TIE techniques to characterize industrial effluents in the Pearl River Delta region

We investigated the acute toxicity of various industrial effluents in the Pearl River Delta region using lux bacteria, duckweed, green algae, crustaceans and zebrafish. The potential toxicants in the industrial effluents were identified and evaluated by lux bacteria bioassay and chemical analysis. The results show that green algae (Pseudokirchneriella subcapitata) and crustacean (Ceriodaphnia dubia) were more sensitive to the effluents from electronic and electroplate factories than other test species, while lux bacteria were more sensitive to all the other effluents. The toxicities of effluents from electronic and electroplate factories to the six test organisms were significantly higher than those of the other industrial effluents, and mainly caused by metals. Noticeably, organic pollutants were the main contributing factor to the toxicity of effluents from textile and dyeing plants, pulp and paper mills, fine chemical factories and municipal wastewater treatment plants.

Wastewater canal Vojlovica, industrial complex Pancevo, Serbia: Preliminary ecotoxicological assessment of contaminated sediment

Effluents collected from the industrial complex of Pancevo, Serbia (oil refinery, petrochemical plant, and fertilizer factory) are discharged into a wastewater canal entering the Danube River. In this study, which was focused on sediment assessment, a complex triad approach consisting of chemical analysis, sediment toxicity tests and macrozoobenthos community analysis was applied. In toxicity tests on sediment elutriates, the following responses were registered - stimulatory effect in algal bioassay, no effect in acute test with Daphnia magna, and low to moderate toxicity in the conventional Vibrio fischeri test. Moderate to high toxicities were recorded in solid phase tests on Myriophyllum aquaticum and V. fischeri. High content of Hg, certain PAHs and noncharacterised sediment contaminants accumulated over years contribute not only to the registered toxicity, but also to the complete absence of macrozoobenthos. The obtained results proved that regularly measured conventional and priority pollutants are hardly ever the only toxic contaminants present in sediments. Toxicity tests, in particular the contact test, might guide towards a better selection of parameters to be regularly or occasionally monitored. In addition, complete sediment toxicity tests proved to be an appropriate method for assessing the bioavailability of the chemically detected contaminants. The analysis of the macrozoobenthos composition and structure as inevitable part of sediment risk assessment procedures integrates the effects of multiple stressors and gives a realistic insight into not only sediment contamination by toxic pollutants, but also the sediment status in general.

Sensitivity of bacterial vs. acute Daphnia magna toxicity tests to metals

The objectives of this study were to evaluate the sensitivity of two bacterial tests commonly used in metal toxicity screening — the Vibrio fischeri bioluminescence inhibition test and the Pseudomonas putida growth inhibition test — in comparison to the standard acute Daphnia magna test, and to estimate applicability of the selected methods to the toxicity testing of environmental samples. The D. magna acute test proved to be more sensitive to cadmium (Cd), zinc (Zn) and manganese (Mn) than the two bacterial assays, whereas P. putida seems to be the most sensitive species to lead (Pb). Manganese appears to be slightly toxic to D. magna and non-toxic to the two selected bacteria. This leads to the conclusion that even in regions with high background concentrations, manganese would not act as a confounding factor. Low sensitivity of V. fischeri to heavy metals questions its applicability as the first screening method in assessing various environmental samples. Therefore, it is not advisable to replace D. magna with bacterial species for metal screening tests. P. putida, V. fischeri and/or other bacterial tests should rather be applied in a complex battery of ecotoxicological tests, as their tolerance to heavy metals can unravel other potentially present toxic substances and mixtures, undetectable by metal-sensitive species.

Ecotoxicological research and related legislation in Serbia

INTRODUCTION

Several hot spots of severe freshwater pollution and sediment contamination (mostly heavy metals, polyaromatic hydrocarbons and polychlorinated biphenyls) have been identified in Serbia as the consequence of outdated environmental legislation, negligible amounts of properly treated waste waters and accidental spills.

DISCUSSION

Since ecotoxicological methods have never been incorporated into risk assessment procedures, mandatory effluent discharge or ambient water monitoring programmes, ecotoxicological research, based on bioaccumulation studies, conventional ecotoxicological tests and, recently, biomarkers of exposure and effect have been restricted to independent small- to medium-scale studies, conducted, basically, to confirm, underline or oppose the results of chemical-based monitoring and to lament on inadequate environmental regulations/policy and management practice. Although hot and unresolved ecotoxicological problems still remain beyond the reach of ecotoxicological research currently conducted in Serbia, or are tackled only sporadically, it is to be expected that on-going research and institutional capacity building should, hopefully, increase the competence and competitiveness of scientific community and speed up the process of harmonisation of national environmental legislation and policy with European Union.