Comparative acute toxicity of glyphosate-based herbicide (GBH) to Daphnia magna, Tisbe longicornis, and Emerita analoga.

The aim of this work was to know the differential composition of the dissolved fraction of a glyphosate-based herbicide (GBH), commercialized as GLIFOPAC, when reaches different aquatic environments and its ecotoxicological effects on crustaceans species living in them. Daphnia magna, Tisbe longicornis, and Emerita analoga were exposed to glyphosate herbicide called GLIFOPAC (480 g L-1 of active ingredient or a.i.) at concentrations between 0.5 and 4.8 g a.i. L-1. Acute toxicity in D. magna (48 h-LC50), E. analoga (48 h-LC50), and T. longicornis (96 h-LC50) was studied. Chromatographic analysis of the GBH composition used and water (freshwater/sea water) polluted with GLIFOPAC were evaluated. Results reported acute toxicity (48-96 h-LC50) values for D. magna, E. analoga and T. longicornis of 27.4 mg L-1, 806.4 mg L-1, and 19.4 mg L-1, respectively. Chromatographic evaluation described around 45 substances of the GLIFOPAC composition, such as from the surfactant structures (aliphatic chain with esther/ether group), metabolites (AMPA), and other substances (glucofuranose, glucopyranoside, galactopyranose). This study evidenced differences in the GLIFOPAC composition in freshwater and marine water, which may differentiate the toxic response at the crustacean-level in each aquatic environment.

Removal of stigmasterol from Kraft mill effluent by aerobic biological treatment with steroidal metabolite detection.

Stigmasterol is a phytosterol contained in Kraft mill effluent that is able to increase over 100% after aerobic biological treatment. This compound can act as an endocrine disrupter as its structure is similar to that of cholesterol. The aim of this study was to evaluate the removal of stigmasterol from Kraft mill effluents treated by a moving bed biofilm reactor (MBBR) with steroidal metabolite detection. The MBBR was operated for 145 days, with a hydraulic retention time of 2 days. Stigmasterol and steroidal metabolites were detected by gas chromatography with a flame ionization detector during MBBR operation. The results show that the MBBR removed 87.4% of biological oxygen demand (BOD5), 61.5% of chemical oxygen demand (COD), 24.5% of phenol and 31.5% of lignin, expressed in average values. The MBBR system successfully removed 100% of the stigmasterol contained in the influent (33 µg L(-1)) after 5 weeks of operation. In that case, the organic load rate was 0.343 kg COD m(-3) d(-1). Furthermore, different steroidal compounds (e.g., testosterone propionate, stigmast-4-en-3-one, 5α-pregnan-12-one-20α-hydroxy, 5α-pregnane-3,11,20-trione and 3α-hydroxy-5α-androstane-11,17-dione were detected in the Kraft mill effluent as potential products of phytosterol biotransformation.

Sublethal Effects of Chlorine-Free Kraft Mill Effluents on Daphnia magna.

The implementation of elemental chlorine-free (ECF) bleaching methods has drastically reduced the aquatic toxicity of Kraft mill effluents during the last decade. However, the residual toxicity of Kraft mill effluents is still a potential concern for the environment, even when subjected to secondary wastewater treatment. The aim of this study is characterize potential sublethal effects of ECF Kraft mill effluents using Daphnia magna as model species. D. magna exposed towards increasing concentration of ECF Kraft mill effluent showed a significant, dose-dependent reduction in feeding. Conversely, post-feeding assay, life history, and allometric growth analyses showed stimulatory, rather than inhibitory effects in exposed animals at low concentrations, while high concentrations of ECF Kraft mill effluents reduced their reproductive output. These results suggest a hormetic effect in which moderate concentrations of the effluent had a stimulatory effect with higher concentrations causing inhibition in some variables.

Analysis of aryl hydrocarbon receptor ligands in kraft mill effluents by a combination of yeast bioassays and CG-MS chemical determinations.

Aryl Hydrocarbon Receptor (AhR) ligands also known as dioxin-like compounds, constitute a substantial part of the total toxicity from many pollution sources, including pulp mill effluents. The aim of this article was to evaluate dioxin-like activity in different kraft mill effluents by a combination of yeast bioassays and gas chromatography-mass spectrometry (GC-MS) chemical analysis. The study includes kraft mill effluents from three sources of raw material: Pinus radiata, Eucalyptus globulus and a combination of both (50% each). The Recombinant Yeast Assay (RYA) showed an effective concentration of AhR ligands more than 30-fold higher in Eucalyptus globulus than in Pinus radiata effluents. Our results suggest that specific ligands, rather than the total amount of extractive material, determined the observed activity. Analysis of extract composition by GC-MS indicated that moderately hydrophobic aromatic compounds were likely responsible for the observed dioxin-like activity. In particular, benzaldehyde derivatives appeared as candidates for eliciting the observed dioxin-like activity in pulp mill effluents, giving their structural properties and their high concentration in AhR ligand-rich samples.

Stigmasterol Removal by an Aerobic Treatment System.

Stigmasterol is a phytosterol contained in kraft mill effluent that is able to increase over 100% after aerobic biological treatment. This compound can act as an endocrine disrupter as its structure is similar to that of cholesterol. Furthermore, stigmasterol contained in kraft mill effluent shows high toxicity (25-fold more than ß-sitosterol) to aquatic organisms such as Daphnia magna. However, the operation of the aerobic treatment and biomass adaptation could be affecting their removal. The performances of activated sludge (AS), aerated lagoon (AL), and moving bed biofilm reactors (MBBR) are compared to remove the stigmasterol contained in kraft mill effluent. The AL operates at a hydraulic retention time of 6 h and removes up to 90% of phytosterols. So, a 96% of stigmasterol is removed by AL when the sterol retention load is 0.6 mg/L · d. However, stigmasterol concentrations increase from 29% to 37% at a low stigmasterol load rate (0.2 mg/L · d). On the other hand, the stigmasterol is removed between 65% and 87% by an AS under a hydraulic retention time of 3 h. Moreover, a 100% of stigmasterol can be removed by the MBBR when the hydraulic retention time is 2 days.

Selection of Biodegrading Phytosterol Strains.

The phytosterol-biotransforming strains can be selected from Mycobacterium sp. using a high concentration of ß-sitosterol. The selection is made by culturing the strains in a medium enriched with 14 g/L of ß-sitosterol as the unique source of carbon. During 2 months, the bacterial cultures are transferred successively. The extraction of the biotransformation products is made with methanol and ethyl acetate. The qualitative and quantitative analyses are made by means of thin-layer chromatography, gas-liquid chromatography (GLC), and GLC-mass spectrometry. Under these conditions, it is observed that after seven transfers, the strains Mycobacterium sp. MB-3683 and Mycobacterium fortuitum B-11045 increase their biotransformation capacity from 20% to 64% and from 34% to 55%, respectively. The products in the highest proportion identified for each trial are androstenedione and androstadienedione. The results suggest that the high substrate concentration could be a selective mechanism to obtain strains more efficient in the biotransformation of ß-sitosterol into steroidal bases.

Selection of Biodegrading Phytosterol Strains.

The phytosterol-biotransforming strains were selected from Mycobacterium sp., using a high concentration of ß-sitosterol. The selection was made by culturing the strains in a medium enriched with 14 g ß-sitosterol/L as the unique source of carbon. During 2 months, the bacterial cultures were transferred successively. The extraction of the biotransformation products was made with methanol and ethyl acetate. The qualitative and quantitative analysis was made by means of thin-layer chromatography, gas-liquid chromatography (GLC), and GLC-mass spectrometry. Under these conditions, it was observed that after seven transfers, the strains Mycobacterium sp. MB-3683 and the Mycobacterium fortuitum B-11045 increased their biotransformation capacity from 20% to 64% and from 34% to 55%, respectively. The products in the highest proportion identified for each trial were androstenedione and androstadienedione. The results suggest that the high substrate concentration could be a selective mechanism to obtain strains more efficient in the biotransformation of ß-sitosterol into steroidal bases.

Stigmasterol Removal by an Aerobic Treatment System.

Stigmasterol is a phytosterol contained in Kraft mill effluent that is able to increase over 100% after aerobic biological treatment. This compound can act as an endocrine disrupter as its structure is similar to that of cholesterol. Furthermore, stigmasterol contained in Kraft mill effluent shows high toxicity (25-fold that of ß-sitosterol) to aquatic organisms such as Daphnia magna (24-48 h). However, the operation of the aerobic treatment and biomass adaptation could be affecting their removal. The performances of activated sludge (AS), aerated lagoon (AL), and moving bed biofilm reactors (MBBR) are compared for removing stigmasterol contained in Kraft mill effluent. The AL operates at a hydraulic retention time of 6 h and removes up to 90% of phytosterols. So, a 96% of stigmasterol is removed by AL when the sterol retention load is 0.6 mg/L/day. However, stigmasterol concentrations increase from 29% to 37% at a low stigmasterol load rate (0.2 mg/L/day). On the other hand, the stigmasterol is removed between 65% and 87% by an AS under a hydraulic retention time of 3 h. Moreover, a 100% of stigmasterol can be removed by the MBBR when the hydraulic retention time is 2 days.

Aerobic removal of stigmasterol contained in kraft mill effluents

Kraft mill effluent, due to its organic matter content and acute toxicity, must be treated. A primary treatment followed by a secondary treatment is the most common system. Aerated lagoon is also considered an effective biological treatment, although this technology has some drawbacks related with operation parameters and land extension space. Moreover, the recovery efficiency for micropollutants contained in kraft mill effluent is questioned due to the anoxic zone in the system. The goal of this work is to evaluate the performance of the aerated lagoon to remove stigmasterol contained in kraft mill effluents. Kraft mill effluent was treated by an aerated lagoon (AL), which was operated with three different stigmasterol load rates (SLR = 0.2, 0.6 and 1.1 mg/L x d) and a hydraulic retention time of 1 day. The AL’s maximum Chemical Oxygen Demand (COD) removal was 65 percent, whereas the Biological Oxygen Demand (BOD5) was around 95 percent. The removal efficiency of stigmasterol removal was 96 percent when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR.