Georgia Gatidou

Removal of selected endocrine disrupters in activated sludge systems: Effect of sludge retention time on their sorption and biodegradation

The fate of three endocrine-disrupting compounds (EDCs), namely 4-n-nonylphenol (4-n-NP), triclosan (TCS) and bisphenol A (BPA), was studied in activated sludge process. The effect of sludge retention time (SRT) on their sorption and biodegradation was also investigated. Three continuous-flow activated sludge systems were used, operating at SRT of 3, 10 and 20 days, respectively. Batch experiments with biomass originated from the aforementioned systems showed that 4-n-NP and TCS are significantly sorbed on the suspended solids, while BPA to a lesser extent. The sorption affinity of target compounds did not seem to be affected by SRT, with the exception of 4-n-NP for which higher values of sorption coefficients were calculated at SRT of 3 days. The operation of continuous-flow systems in the presence of 10-40 microgL(-1) of EDCs indicated that more than 90%, 94% and 97% of BPA, TCS and 4-n-NP, respectively, can be removed during the activated sludge process in systems operating at SRT of 3-20 days. Determination of EDCs in the dissolved and particulate phase and calculation of their mass flux revealed that biodegradation was the principal removal mechanism of EDCs. For SRT values used in this study, this parameter does not seem to affect significantly percentage biodegradation of BPA. On the other hand, biodegradation of 4-n-NP and TCS was enhanced at SRT of 20 days. Calculation of biotransformation rates showed that the highest values for all EDCs were calculated at SRT of 3 days.

Bioconcentration of selected endocrine disrupting compounds in the Mediterranean mussel, Mytilus galloprovincialis.

The occurrence of three endocrine disrupting compounds, 4-n-nonylphenol, triclosan and bisphenol A, was investigated in different bivalves originating from the Aegean Sea (Greece). The bioconcentration potential of these compounds was studied using the Mediterranean mussel (Mytilus galloprovincialis). Tissue samples were extracted by sonication. Analysis was performed by gas chromatography-mass spectrometry. According to the field survey results, the average concentrations of 4-n-nonylphenol, triclosan and bisphenol A, were 158, 461 and 404 ng g(-1) (dry weight), respectively. During 28 days of exposure at 300 ng L(-1), the tissue concentrations of compounds were constantly increased. Steady state was not observed up to the end of the experiment. Kinetic bioconcentration factors varied from 1.7 (4-n-nonylphenol and triclosan) to 4.5 L g(-1) (bisphenol A). Following exposure, mussels were relocated to clean water for 28 days. This experiment revealed that depuration rates for all of the target compounds were lower than uptake rates. The biological half-lives of each compound ranged between 12 days (triclosan) and 26 days (bisphenol A).

Inhibitory effect of triclosan and nonylphenol on respiration rates and ammonia removal in activated sludge systems

The toxic effects of triclosan (TCS) and nonylphenol (4-n-NP) on activated sludge heterotrophic and autotrophic microorganisms were evaluated. Toxicity experiments with specific oxygen uptake rate (SOUR) and ammonia uptake rate (AUR) revealed that TCS was much more toxic to heterotrophic and autotrophic microorganisms than 4-n-NP. In experiments with heterotrophic biomass, increase of sludge age (theta(c)) from 5 to 15 days resulted in a decrease of median effective concentrations (EC(50)) of TCS from 38.2 to 9.97 mg l(-1) and in an increase of EC(50) values of 4-n-NP from 441 to 649 mg l(-1). In experiments with autotrophic biomass and sludge age of 15 days, significantly lower EC(50) values were obtained for both compounds, indicating the higher sensitivity of nitrifiers to TCS and 4-n-NP. To compare toxicity of TCS and 4-n-NP towards single species and mixed wastewater cultures, experiments were performed using marine bacterium Vibrio fischeri. EC(50) values of 0.22 and 3.51 mg l(-1) were estimated for TCS and 4-n-NP, respectively, indicating the higher sensitivity of this bioassay to toxicants. According to the levels of tested compounds commonly found in influent wastewater and the results of this study, there is a possible risk for deterioration of nitrification in activated sludge systems due to the presence of TCS.

Diuron biodegradation in activated sludge batch reactors under aerobic and anoxic conditions

Diuron biodegradation was studied in activated sludge reactors and the impacts of aerobic and anoxic conditions, presence of supplemental substrate and biomass acclimatization on its removal were investigated. Diuron and three known metabolites, namely DCPMU (1-(3,4-dichlorophenyl)-3-methylurea), DCPU (1-3,4-dichlorophenylurea) and DCA (3,4-dichloroaniline), were extracted by solid-phase extraction (dissolved phase) or sonication (particulate phase) and determined using High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD). During the experiments only a minor part of these compounds was associated with the suspended solids. Under aerobic conditions, almost 60% of Diuron was biodegraded, while its major metabolite was DCA. The existence of anoxic conditions increased Diuron biodegradation to more than 95%, while the major metabolite was DCPU. Mass balance calculation showed that a significant fraction of Diuron is mineralized or biotransformed to other unknown metabolites. The presence of low concentrations of supplemental substrate did not affect Diuron biodegradation, whereas the acclimatization of biomass slightly accelerated its elimination under anoxic conditions. Calculation of half-lives showed that under aerobic conditions DCPMU, DCPU and DCA are biodegraded much faster than the parent compound. In the future, the sequential use of anoxic and aerobic conditions could provide sufficient removal of Diuron and its metabolites from runoff waters.

Determination of two antifouling booster biocides and their degradation products in marine sediments by high performance liquid chromatography-diode array detection

A method for the simultaneous determination of two antifouling booster biocides, diuron [1-(3,4-dichlorophenyl)-3,3-dimethylurea] and irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) and their degradation products, DCPMU [1-(3,4-dichlorophenyl)3-methylurea], DCPU [1-(3,4-dichlorophenyl) urea], DCA [3,4-dichloroaniline] and M1 (2-methylthio-4-tert-butylamino-s-triazine), in marine sediments by high performance liquid chromatography–diode array detection (HPLC–DAD) was developed. The extraction of these compounds from sediment was achieved by means of methanolic ultrasonic extraction. The optimization of the extraction procedure included the variation of the volume of the extraction solvent, the amount of the extracted sediment, the duration and the temperature of sonication. C18 solid phase extraction (SPE) cartridges were used for the cleaning of the extracts. The relative standard deviations (R.S.Ds) of the developed procedure was <10% for all the tested compounds, except for DCA, where R.S.Ds up to 15% were obtained. Satisfactory recoveries were obtained (higher than 80% for all substances), except for DCA, which gave a recovery in the range of 35–50%. The limits of detection (LODs) of the substances varied between 1.7 (DCPU) and 4.0 (DCPMU) ng g −1 of dry sediment.

Assessing single and joint toxicity of three phenylurea herbicides using Lemna minor and Vibrio fischeri bioassays

Single and joint toxicity of three substituted urea herbicides, namely monolinuron [3-(4-chlorophenyl)-1-methoxy-1-methylurea], linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and diuron [1-(3,4 dichlorophenyl)-3,3 dimethyl urea], were studied. The duckweed Lemna minor and the luminescent bacterium Vibrio fischeri were used for the toxicity assessment and they were exposed to various concentrations of the herbicides, individually and in binary mixtures. The exposure time was 7d for the duckweed and 30 min for the bacterium. Estimation of EC50 values was performed by frond counting and reduction in light output for Lemna minor and Vibrio fischeri, respectively. Lemna minor was found to be much more sensitive than Vibrio fischeri to target compounds. The toxicity of the three herbicides applied solely was estimated to be in decreasing order: diuron (EC50=28.3 μg L(-1))≈linuron (EC50=30.5 μg L(-1))>monolinuron (EC50=300 μg L(-1)) for the duckweed and linuron (EC50=8.2 mg L(-1))>diuron (EC50=9.2 mg L(-1))>monolinuron (EC50=11.2 mg L(-1)) for the bacterium. Based on the environmental concentrations reported in the literature and EC50 values obtained from Lemna minor experiments, Risk Quotients (RQ) much higher than 1 were calculated for diuron and linuron. In Lemna minor experiments, combination of target compounds resulted to additive effects due to their same mode of phenylurea action on photosynthetic organisms. Regarding Vibrio fischeri, synergistic, additive and antagonistic effects were observed, which varied according to the concentrations of target compounds.

Determination of selected non-steroidal anti-inflammatory drugs in wastewater by gas chromatography-mass spectrometry.

An analytical method for the simultaneous determination of the four most detected non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater, namely ibuprofen (IBF), naproxen (NPX), diclofenac (DFC) and ketoprofen (KFN), was developed based on gas chromatography–mass spectrometry (GC-MS). Extraction from wastewater samples was performed by solid-phase extraction (SPE) with C18 cartridges, while meclofenamic acid (MFC) was used as surrogate. The optimisation of SPE procedure included the type of the extraction solvent used for the elution and the pH of the loading solution (acidic or neutral). The developed extraction procedure resulted in good repeatability and reproducibility with relative standard deviations (RSDs) less than 10% for all the compounds. Moreover, satisfactory recoveries (>98%) were obtained. Chromatographic analysis was achieved after derivatisation with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% trimethyl chlorosilane (TMCS) in the presence of pyridine, a derivatisation mixture used for the first time for these compounds. The limits of detection (LODs) of the method varied from 0.37 (KFN) to 3.1 ng L−1 (NPX). The analytical method was successfully applied for the determination of these compounds in the raw and treated wastewater of two different wastewater treatment plants (WWTPs) of the city of Mytilene in Lesvos, Greece. The maximum concentrations were detected in raw wastewater originated from a hospital and they were 574 ng L−1 and 704 ng L−1 for IBF and KFN, respectively.

Monitoring of triazine and phenylurea herbicides in the surface waters of Greece.

A large-scale study was implemented to monitor triazine and phenylurea herbicides in the main surface water bodies of continental Greece from October 1998 to September 1999. Samples from 10 rivers and 7 lakes were analyzed for the presence of five triazine (atrazine, cyanazine, prometryne, simazine, terbuthylazine) and five phenylurea (chlorotoluron, diuron, linuron, metobromuron, monolinuron) herbicides. The samples were extracted with C18 cartridges and analyzed by high-performance liquid chromatography–diode array detection (HPLC-DAD). The most frequently detected herbicides were atrazine, followed by prometryne, cyanazine, and simazine. The concentrations of the compounds were generally low (< 0.78 μ g/L) and are not considered harmful for the freshwater ecosystem. Most of the positive samples were taken from the water bodies of northern Greece where agricultural activity is more intense.

Sorption and biodegradation of selected benzotriazoles and hydroxybenzothiazole in activated sludge and estimation of their fate during wastewater treatment

Biodegradation of benzotriazole (BTR), 5-chlorobenzotriazole (CBTR), xylytriazole (XTR), 4-methyl-1H-benzotriazole (4TTR), 5-methy-1H-lbenzotriazole (5TTR) and 2-hydroxybenzothiazole (OHBTH) was studied in activated sludge batch experiments under aerobic and anoxic conditions, presence of organic substrate and different sludge residence times (SRTs). Their sludge-water distribution coefficients were also calculated in sorption experiments and ranged between 87 and 220 L kg(-1). Significant biodegradation of BTR, CBTR, XTR and OHBTH was observed in all biotic experiments. Half-life values ranged between 23 and 45 h (BTR), 18 and 47 h (CBTR), 14 and 26 h (XTR), 6.5 and 24 h (OHBTH). The addition of substrate did not suppress biodegradation kinetics; whereas in some cases accelerated biodegradation of microcontaminants. Except for CBTR, no effect of SRT on biodegradation constants was observed. Prediction of micropollutants removal in Sewage Treatment Plants (STPs) indicated that they will be partially removed, mainly due to aerobic biodegradation. Higher removal is expected at STPs operating at higher SRT and higher suspended solids concentrations.

Drugs of abuse and alcohol consumption among different groups of population on the Greek Island of Lesvos through sewage-based epidemiology.

The occurrence of 22 drugs of abuse, their metabolites, and the alcohol metabolite ethyl sulphate was investigated in raw sewage samples collected during the non-touristic season from three sewage treatment plants (STPs), which serve different sizes and types of population in the Greek island of Lesvos. Using the sewage-based epidemiology approach, the consumption of these substances was estimated. Five target analytes, cocaine (COC), benzoylecgonine (BE), 3,4-methylenedioxymethamphetamine (MDMA), 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH) and ethyl sulphate (EtS) were detected at concentrations above their limit of quantification, whereas the rest eighteen target compounds were not detected. THC-COOH was detected in most of the samples with concentrations ranging between <20 and 90ngL(-1), followed by EtS (range <1700-12,243ngL(-1)). COC, BE, and MDMA were present only in the STP that serves Mytilene (the main city of the island), at mean concentrations of 3.9ngL(-1) for COC (95% CI: 1.7-6.1), 9.4ngL(-1) for BE (95% CI: -1.6-23) and 3.2ngL(-1) for MDMA (95% CI: 1.2-5.1). Back-calculations to an amount of used substance indicated more intense use of drugs among city population than rural and University population with average values of 9.5 and 1.2mgday(-1) per 1000 inhabitants for COC (95% CI: -1.43-20.4) and MDMA (95% CI: 0.52-1.85), respectively, and 2.8gday(-1) per 1000 inhabitants for tetrahydrocannabinol (THC) (95% CI: 2.4-3.1), the active ingredient of cannabis. Alcohol consumption was observed to be higher in the city population (5.4mL pure alcohol per day per inhabitant) than in the rural population (3.4mL pure alcohol per day per inhabitant), but the difference was not statistically significant. Consumption of THC differed significantly among the three STPs.