Evidences of non-reactive mercury-selenium compounds generated from cultures of Pseudomonas fluorescens

This work was designed to determine chemically inert mercury-selenium (Hg-Se) compounds formed in a culture of Pseudomonas fluorescens exposed to Hg²⁺ and Se^IV (selenite). To isolate these compounds, different digestion methods were studied and sodium dodecyl sulfate (SDS) lysis was selected. The Hg⁰ and non-reactive Hg were determined in two series of cultures containing 0.0-6.00 μg L⁻¹ Se^IV (0.0-76.0 μmol L⁻¹) in combination with low 5.00 μg L⁻¹ (0.025 μmol L⁻¹) or high 100 μg L⁻¹ (0.500 μmol L⁻¹) Hg²⁺. It was found that Hg⁰ formed in the culture decreased with the increase of initial Se^IV, while the non-reactive Hg increased with the Se^IV. In cultures with low initial [Hg²⁺], a median Se^IV (2.0 μg L⁻¹ or 25.3 μmol L⁻¹) resulted in about 70% of the added Hg²⁺ sequestered as non-reactive Hg, and in culture with high initial Hg²⁺, about 40% was sequestered. P. fluorescens was proved to be indispensible for the formation of the non-reactive Hg-Se compounds. The Hg:Se molar ratio in the non-reactive Hg-Se compounds was close to 1, suggesting the existence of mercuric selenide in cells. Mechanisms for the formation of the non-reactive Hg-Se compounds are proposed.     

Spatial isolation favours the divergence in microcystin net production by Microcystis in Ugandan freshwater lakes

It is generally agreed that the hepatotoxic microcystins (MCs) are the most abundant toxins produced by cyanobacteria in freshwater. In various freshwater lakes in East Africa MC-producing Microcystis has been reported to dominate the phytoplankton, however the regulation of MC production is poorly understood. From May 2007 to April 2008 the Microcystis abundance, the absolute and relative abundance of the mcyB genotype indicative of MC production and the MC concentrations were recorded monthly in five freshwater lakes in Uganda: (1) in a crater lake (Lake Saka), (2) in three shallow lakes (Lake Mburo, George, Edward), (3) in Lake Victoria (Murchison Bay, Napoleon Gulf). During the whole study period Microcystis was abundant or dominated the phytoplankton. In all samples mcyB-containing cells of Microcystis were found and on average comprised 20 ± 2% (SE) of the total population. The proportion of the mcyB genotype differed significantly between the sampling sites, and while the highest mcyB proportions were recorded in Lake Saka (37 ± 3%), the lowest proportion was recorded in Lake George (1.4 ± 0.2%). Consequently Microcystis from Lake George had the lowest MC cell quotas (0.03-1.24 fg MC cell⁻¹) and resulted in the lowest MC concentrations (0-0.5 μg L⁻¹) while Microcystis from Lake Saka consistently showed maximum MC cell quotas (14-144 fg cell⁻¹) and the highest MC concentrations (0.5-10.2 μg L⁻¹). Over the whole study period the average MC content per Microcystis cell depended linearly on the proportion of the mcyB genotype of Microcystis. It is concluded that Microcystis populations differ consistently and independently of the season in mcyB genotype proportion between lakes resulting in population-specific differences in the average MC content per cell.     

Sublethal toxicity of commercial insecticide formulations and their active ingredients to larval fathead minnow (Pimephales promelas)

Toxic effect concentrations of insecticides are generally determined using the technical grade or pure active ingredient. Commercial insecticide formulations, however, contain a significant proportion (> 90%) of so-called inert ingredients, which may alter the toxicity of the active ingredient(s). This study compares the sublethal toxicity of two insecticides, the pyrethroid bifenthrin, and the phenylpyrazole fipronil, to their commercial formulations, Talstar® and Termidor®. Both insecticides are used for landscape treatment and structural pest control, and can be transported into surface water bodies via stormwater and irrigation runoff. We used larval fathead minnow (Pimephales promelas), to determine effects on growth and swimming performance after short-term (24 h) exposure to sublethal concentrations of pure insecticides and the respective formulations. Significantly enhanced 7 d growth was observed at 10% of the 24 h LC₁₀ (53 μg L⁻¹) fipronil. Swimming performance was significantly impaired at 20% of the 24 h LC₁₀ (0.14 μg L⁻¹) of bifenthrin and 10% of the 24 h LC₁₀ of Talstar® (0.03 μg L⁻¹). Fipronil and Termidor® led to a significant impairment of swimming performance at 142 μg L⁻¹ and 148 μg L⁻¹ respectively, with more pronounced effects for the formulation. Our data shows that based on dissolved concentrations both formulations were more toxic than the pure active ingredients, suggesting that increased toxicity due to inert ingredients should be considered in risk assessments and regulation of insecticides.     

Water, vegetation and sediment gradients in submerged aquatic vegetation mesocosms used for low-level phosphorus removal

Gradients in phosphorus (P) removal and storage were investigated over 6 years using mesocosms (each consisting of three tanks in series) containing submerged aquatic vegetation (SAV) grown on muck and limerock (LR) substrates. Mean inflow total P concentrations (TP) of 32 μg L⁻¹ were reduced to 15 and 17 μg L⁻¹ in the muck and LR mesocosms, respectively. Mesocosm P loading rates (mean = 1.75 g m⁻² year⁻¹) varied widely during the study and were not correlated with outflow TP, which instead varied seasonally with lowest monthly mean values in December and January.The mesocosms initially were stocked with Najas guadalupensis, Ceratophyllum demersum, and Chara zeylanica, but became dominated by C. zeylanica. At the end of the study, highest vegetative biomass (1.1 and 1.4 kg m⁻² for muck and LR substrates) and tissue P content (1775 and 1160 mg kg⁻¹) occurred in the first tank in series, and lowest biomass (1.0 and 0.2 kg m⁻²) and tissue P (147 and 120 mg kg⁻¹) in the third tank. Sediment accretion rates (2.5, 1.9 and 0.9 cm yr⁻¹ on muck substrates), accrued sediment TP (378, 309 and 272 mg kg⁻¹), and porewater soluble reactive P (SRP) concentrations (40, 6 and 4 μg L⁻¹) in the first, second and third tanks, respectively, exhibited a similar decreasing spatial trend. Plant tissue calcium (Ca) near mesocosm inflow (19-30% dry weight) and outflow (23-26%) were not significantly different, and sediment Ca was also similar (range of 24 to 28%) among sequential tanks.Well-defined vegetation and sediment enrichment gradients developed in SAV wetlands operated under low TP conditions. While the mesocosm data did not reflect deterioration in treatment performance over 6 years, accumulation of P-enriched sediments near the inflow could eventually compromise hydraulic storage and P removal effectiveness of these shallow systems.     

Measurement and source identification of polycyclic aromatic hydrocarbons (PAHs) in the aerosol in Xi'an, China, by using automated column chromatography and applying positive matrix factorization (PMF)

In this study, we measured polycyclic aromatic hydrocarbons (PAHs) in aerosols in Xi'an, China from 2005 to 2007, by using a modified Soxhlet extraction followed by a clean-up procedure using automated column chromatography followed by HPLC/fluorescence detection. The sources of PAHs were apportioned by using the positive matrix factorization (PMF) method. The PM₁₀ concentration in winter (161.1 ± 66.4 μg m^− 3, n = 242) was 1.5 times higher than that in summer (110.9 ± 34.7 μg m^− 3, n = 248). ΣPAH concentrations, which are the sum of the concentrations of all detected PAHs, in winter (344.2 ± 149.7 ng m^− 3, n = 45) was 2.5 times higher than that in summer (136.7 ± 56.7 ng m^− 3, n = 24) in this study. These strong seasonal variations in atmospheric PAH concentration are possibly due to coal combustion for residential heating. According to the source apportionment with PMF method in this study, the major sources of PAHs in Xi'an are categorized as (1) mobile sources such as vehicle exhaust that constantly contribute to PAH pollution, and (2) stationary sources such as coal combustion that have a large contribution to PAH pollution in winter.     

Antimony, arsenic and mercury in the aquatic environment and fish in a large antimony mining area in Hunan, China

Antimony (Sb) has received increasing attention recently due to its toxicity and potential human carcinogenicity. In the present work, drinking water, fish and algae samples were collected from the Xikuangshan (XKS) Sb mine area in Hunan, China. Results show that serious Sb and moderate arsenic (As) contamination is present in the aquatic environment. The average Sb concentrations in water and fish were 53.6 ± 46.7 μg L^− 1 and 218 ± 113 μg kg^− 1 dry weight, respectively. The Sb concentration in drinking water exceeded both Chinese and WHO drinking water guidelines by 13 and 3 times, respectively. Antimony and As concentrations in water varied with seasons. Fish gills exhibited the highest Sb concentrations but the extent of accumulation varied with habitat. Antimony enrichment in fish was significantly lower than that of As and Hg.     

Manganese and lead in children's blood and airborne particulate matter in Durban, South Africa

Despite the toxicity and widespread use of manganese (Mn) and lead (Pb) as additives to motor fuels and for other purposes, information regarding human exposure in Africa is very limited. This study investigates the environmental exposures of Mn and Pb in Durban, South Africa, a region that has utilized both metals in gasoline. Airborne metals were sampled as PM_2.5 and PM₁₀ at three sites, and blood samples were obtained from a population-based sample of 408 school children attending seven schools. In PM_2.5, Mn and Pb concentrations averaged 17 ± 27 ng m^− 3 and 77 ± 91 ng m^− 3, respectively; Mn concentrations in PM₁₀ were higher (49 ± 44 ng m^− 3). In blood, Mn concentrations averaged 10.1 ± 3.4 μg L^− 1 and 8% of children exceeded 15 μg L^− 1, the normal range. Mn concentrations fit a lognormal distribution. Heavier and Indian children had elevated levels. Pb in blood averaged 5.3 ± 2.1 μg dL^− 1, and 3.4% of children exceeded 10 μg dL^− 1, the guideline level. Pb levels were best fit by a mixed (extreme value) distribution, and boys and children living in industrialized areas of Durban had elevated levels. Although airborne Mn and Pb concentrations were correlated, blood levels were not. A trend analysis shows dramatic decreases of Pb levels in air and children's blood in South Africa, although a sizable fraction of children still exceeds guideline levels. The study's findings suggest that while vehicle exhaust may contribute to exposures of both metals, other sources currently dominate Pb exposures.     

Degradation of diclofenac by TiO2 photocatalysis: UV absorbance kinetics and process evaluation through a set of toxicity bioassays

In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO₂ photocatalysis were investigated in terms of UV absorbance and COD measurements for a wide range of initial DCF concentrations (5-80 mg L⁻¹) and photocatalyst loadings (0.2-1.6 g TiO₂ L⁻¹) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the potential detoxification of DCF. A pseudo-first-order kinetic model was found to fit well most of the experimental data, while at high initial DCF concentrations (40 and 80 mg L⁻¹) and at 1.6 g TiO₂ L⁻¹ photocatalyst loading a second-order kinetic model was found to fit the data better. The toxicity of the treated DCF samples on D. magna and P. subcapitata varied during the oxidation, probably due to the formation of some intermediate products more toxic than DCF. Unicellular freshwater algae was found to be very sensitive to the treated samples as well as the results from D. magna test were consistent to those of algae tests. A. salina was not found to be sensitive under the investigated conditions. Finally, UV absorbance analysis were found to be an useful tool for a fast and easy to perform measurement to get preliminary information on the organic intermediates that are formed during oxidation and also on their disappearance rate.     

Citizen monitoring: Testing hypotheses about the interactive influences of eutrophication and mussel invasion on a cyanobacterial toxin in lakes

An existing volunteer monitoring network in the state of Michigan was exploited to conduct a statewide survey of the cyanobacterial toxin, microcystin, and to test hypotheses about the interactive influences of eutrophication and dreissenid mussel invasion. A total of 77 lakes were sampled by citizen volunteers for microcystin, total phosphorus (TP) and chlorophyll a. Microcystin was measured in depth-integrated samples collected from the euphotic zone as well as in surface-water samples collected along the shoreline. Average microcystin in samples collected by volunteers was not different from samples collected side-by-side by professionals. Euphotic-zone microcystin was positively related to TP in lakes without dreissenids (uninvaded) but not in lakes with dreissenids (invaded). Regression-tree analysis indicated that euphotic-zone microcystin was eight times higher in the presence of dreissenids for lakes with TP between 5 and 10 μg L⁻¹. In contrast, euphotic-zone microcystin was almost identical in invaded and uninvaded lakes with TP between 10 and 26 μg L⁻¹. Across all lakes, microcystin concentrations at the surface were on average more than double, and in some cases an order-of-magnitude greater than, concentrations in the euphotic-zone. Given these results, it seems prudent to include dreissenid invasion status in forecasting models for microcystin, and to include shoreline sampling in monitoring programs aimed at assessing recreational exposure to cyanobacterial toxins.     

Degradation of fifteen emerging contaminants at μg L initial concentrations by mild solar photo-Fenton in MWTP effluents

The degradation of 15 emerging contaminants (ECs) at low concentrations in simulated and real effluent of municipal wastewater treatment plant with photo-Fenton at unchanged pH and Fe = 5 mg L⁻¹ in a pilot-scale solar CPC reactor was studied. The degradation of those 15 compounds (Acetaminophen, Antipyrine, Atrazine, Caffeine, Carbamazepine, Diclofenac, Flumequine, Hydroxybiphenyl, Ibuprofen, Isoproturon, Ketorolac, Ofloxacin, Progesterone, Sulfamethoxazole and Triclosan), each with an initial concentration of 100 μg L⁻¹, was found to depend on the presence of CO₃²⁻ and HCO₃⁻ (hydroxyl radicals scavengers) and on the type of water (simulated water, simulated effluent wastewater and real effluent wastewater), but is relatively independent of pH, the type of acid used for release of hydroxyl radicals scavengers and the initial H₂O₂ concentration used. Toxicity tests with Vibrio fisheri showed that degradation of the compounds in real effluent wastewater led to toxicity increase.     

Kinetics and mechanism for degradation of dichlorvos by permanganate in drinking water treatment

The degradation kinetics and mechanism of dichlorvos by permanganate during drinking water treatment were investigated. The reaction of dichlorvos with permanganate was of second-order overall with negligible pH dependence and an activation energy of 29.5 kJ·mol⁻¹. At pH 7.0 and 25 °C, the rate constant was 25.2 ± 0.4 M⁻¹ s⁻¹. Dichlorvos was first degraded to trimethyl phosphate (TMP) and dimethyl phosphate (DMP) simultaneously which approximately accounted for <5% and ≥95% with respect to phosphorus mass, respectively. Further oxidation of DMP generated a final byproduct, monomethyl phosphate (MMP). MMP was for the first time identified as a major byproduct in chemical oxidation of dichlorvos. The kinetic model based on degradation mechanism and determined reaction rate constants allowed us to predict the evolution of dichlorvos and its byproduct concentrations during permanganate pre-oxidation process at water treatment plants. These results suggest that even though the dichlorvos concentration in surface water complies with the surface water quality standards of China (50 μg L⁻¹), its concentration after conventional water treatment will most probably exceed the drinking water quality standards (1 μg L⁻¹). Moreover, luminescent bacteria test shows that the acute toxicity of dichlorvos solution evidently increased after permanganate oxidation.     

Speciation and distribution of vanadium in drinking water iron pipe corrosion by-products

Vanadium (V) when ingested from drinking water in high concentrations (> 15 μg L^− 1) is a potential health risk and is on track to becoming a regulated contaminant. High concentrations of V have been documented in lead corrosion by-products as Pb₅(V⁵⁺O₄)₃Cl (vanadinite) which, in natural deposits is associated with iron oxides/oxyhydroxides, phases common in iron pipe corrosion by-products. The extent of potential reservoirs of V in iron corrosion by-products, its speciation, and mechanism of inclusion however are unknown. The aim of this study is to assess these parameters in iron corrosion by-products, implementing synchrotron-based μ-XRF mapping and μ-XANES along with traditional physiochemical characterization. The morphologies, mineralogies, and chemistry of the samples studied are superficially similar to typical iron corrosion by-products. However, we found V present as discrete grains of Pb₅(V⁵⁺O₄)₃Cl likely embedded in the surface regions of the iron corrosion by-products. Concentrations of V observed in bulk XRF analysis ranged from 35 to 899 mg kg^− 1. We calculate that even in pipes with iron corrosion by-products with low V concentration, 100 mg kg^− 1, as little as 0.0027% of a 0.1-cm thick X 100-cm long section of that corrosion by-product needs to be disturbed to increase V concentrations in the drinking water at the tap to levels well above the 15 μg L^− 1 notification level set by the State of California and could adversely impact human health. In addition, it is likely that large reservoirs of V are associated with iron corrosion by-products in unlined cast iron mains and service branches in numerous drinking water distribution systems.     

Biomonitoring of Cd, Cr, Hg and Pb in the Baluarte River basin associated to a mining area (NW Mexico)

With the purpose of knowing seasonal variations of Cd, Cr, Hg and Pb in a river basin with past and present mining activities, elemental concentrations were measured in six fish species and four crustacean species in Baluarte River, from some of the mining sites to the mouth of the river in the Pacific Ocean between May 2005 and March 2006. In fish, highest levels of Cd (0.06 μg g^− 1 dry weight) and Cr (0.01 μg g^− 1) were detected during the dry season in Gobiesox fluviatilis and Agonostomus monticola, respectively; the highest levels of Hg (0.56 μg g^− 1) were detected during the dry season in Guavina guavina and Mugil curema. In relation to Pb, the highest level (1.65 μg g^− 1) was detected in A. monticola during the dry season. In crustaceans, highest levels of Cd (0.05 μg g^− 1) occurred in Macrobrachium occidentale during both seasons; highest concentration of Cr (0.09 μg g^− 1) was also detected in M. occidentale during the dry season. With respect to Hg, highest level (0.20 μg g^− 1) was detected during the rainy season in Macrobrachium americanum; for Pb, the highest concentration (2.4 μg g^− 1) corresponded to Macrobrachium digueti collected in the dry season. Considering average concentrations of trace metals in surficial sediments from all sites, Cd (p < 0.025), Cr (p < 0.10) and Hg (p < 0.15) were significantly higher during the rainy season. Biota sediment accumulation factors above unity were detected mostly in the case of Hg in fish during both seasons. On the basis of the metal levels in fish and crustacean and the provisional tolerable weekly intake of studied elements, people can eat up to 13.99, 0.79 and 2.34 kg of fish in relation to Cd, Hg and Pb, respectively; regarding crustaceans, maximum amounts were 11.33, 2.49 and 2.68 kg of prawns relative to levels of Cd, Hg and Pb, respectively.     

Performance of a passive treatment system for net-acidic coal mine drainage over five years of operation

A full-scale passive treatment system (PTS) was commissioned in 2003 to treat two net-acidic coal mine water discharges in the Durham coalfield, UK. The principal aim of the PTS was to decrease concentrations of iron (< 177 mg L⁻¹) and aluminium (< 85 mg L⁻¹) and to increase pH (> 3.2) and alkalinity (≥ 0 mg L⁻¹ CaCO₃ eq). Secondary objectives were to decrease zinc (< 2.8 mg L⁻¹), manganese (< 20.5 mg L⁻¹) and sulfate (< 2120 mg L⁻¹). Upon treatment, water qualities were improved by 84% in the case of Fe, 87% Al, 83% acidity, 51% Zn, 23% Mn and 29% SO₄²⁻. Alkalinity (74%) and pH (95% as H⁺) were increased. Area adjusted removal rates (Fe = 1.49 ± 0.66 g d⁻¹ m⁻²; acidity = 6.7 ± 4.9 g d⁻¹ m⁻²) were low compared to design criteria, mainly due to load limitation. Disregarding seasonality effects, acidity removal and effluent pH were stable over time. A substantial temporal decrease in calcium and alkalinity generation suggests that limestone is increasingly armoured. Once pH is no longer buffered by the carbonate system, metals could be remobilized, putting treatment efficiency at risk.     

The impact of alum based advanced nutrient removal processes on phosphorus bioavailability

Because eutrophication is a widespread consequence of wastewater discharges, there is a strong impetus to develop new approaches to remove phosphorus (P) from wastewater treatment plant (WWTP) effluents. We examined the effluents from a pilot plant that is testing various alum based processes for achieving > 99% P removal, however, it is not known how these advanced P removal technologies affect the bioavailability of P (BAP). We tested how the percent BAP (%BAP) varied with different P removal levels using an algal growth bioassay methodology. This facility reduced total P concentrations from ≈ 500 μg L⁻¹ in the pilot plant influent to 19 ± 4 (±SD) μg L⁻¹ in the final effluent, and our results showed that as the level of P removal increased, the %BAP of the product declined sharply, r² = 0.98. Prior to alum treatment, the influent had an average %BAP of 79 ± 13%, and after three steps of alum-based removal the %BAP averaged 7 ± 4%. Thus, this alum based P removal process was very effective at sequestering the P forms that most readily stimulate algal growth. Further, our results show the final BAP of the effluent was only ≈ 50% of the “reactive” P concentration. These results have important implications for nutrient management and trading schemes.     

Occurrence and fate of organophosphorus flame retardants and plasticizers in urban and remote surface waters in Germany

Within this study, concentration levels and distribution of the organophosphates tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-1-methylethyl) phosphate (TCPP), tris(2-butoxyethyl) phosphate (TBEP), tri-iso-butyl phosphate (TiBP), and tri-n-butyl phosphate (TnBP) were investigated at nine lentic surface waters under different anthropogenic impact between June 2007 and October 2009. Furthermore, the possibility of in-lake photochemical degradation of the analytes was studied in laboratory experiments using spiked ultrapure water and lake water samples incubated in Teflon bottles (which transmit sunlight). TBEP, TiBP, and TnBP were photochemically degraded in spiked lake water samples upon exposure to sunlight. Organophosphate concentrations in the more remote lakes were often below or close to the limits of quantification (LOQ). TCPP was the substance with the highest median concentration in rural volcanic lakes (7-18 ng L⁻¹) indicating an atmospheric transport of the compound. At urban lakes their median concentrations were in the range of 23-61 ng L⁻¹ (TCEP), 85-126 ng L⁻¹ (TCPP), <LOQ-53 ng L⁻¹ (TBEP), 8-10 ng L⁻¹ (TiBP), and 17-32 ng L⁻¹ (TnBP). High variability but no significant seasonal trends were observed for all five organophosphates in urban lake water samples.     

Determination of arsenic leaching from glazed and non-glazed Turkish traditional earthenware

Glazed and non-glazed earthenware is traditionally and widely used in Turkey and most of the Mediterranean and the Middle East countries for cooking and conservation of foodstuff. Acid-leaching tests have been carried out to determine whether the use of glazed and non-glazed earthenware may constitute a human health hazard risk to the consumers. Earthenware was leached with 4% acetic acid and 1% citric acid solutions, and arsenic in the leachates was measured using hydride generation atomic absorption spectrometry. Arsenic concentrations in the leach solution of non-glazed potteries varied from 30.9 to 800 μg L^− 1, while the glazed potteries varied generally from below the limit of detection (0.5 μg L^− 1) to 30.6 μg L^− 1, but in one poorly glazed series it reached to 110 μg L^− 1. Therefore, the risk of arsenic poisoning by poorly glazed and non-glazed potteries is high enough to be of concern. It appears that this is the first study reporting arsenic release from earthenware into food.     

Ultrasonic treatment of water contaminated with ibuprofen

The application of ultrasound (US) waves for remediation of wastewater is an area of increasing interest and promising results. The aim of this paper is to evaluate the influence of several parameters of the US process on the degradation of ibuprofen (IBP), a widely used non-steroidal anti-inflammatory recalcitrant drug found in water. Applied US power, dissolved gas, pH and initial concentration of IBP were the parameters investigated under sonication (300 kHz).Ultrasound increased the degradation of IBP from 30 to 98% in 30 min. Initial rate of IBP degradation was evaluated in the range of 1.35 and 6.1 μmol L⁻¹ min⁻¹ for initial concentrations of 2 to 21 mg L⁻¹ or 9.7 μmol L⁻¹ to 101 μmol L⁻¹, respectively. Under air and oxygen the degradation rate of IBP was 4 μmol L⁻¹ min⁻¹ being higher than that when argon was used. The most favorable degradation pH was acidic media. Complete removal of IBP was achieved but some dissolved organic carbon (DOC) remained in solution showing that long-lived intermediates were recalcitrant to the US irradiation. However, chemical and biological oxygen demands (COD and BOD₅) indicated that the process oxidize the ibuprofen compound to biodegradable substances removable in a subsequent biological step.     

Influence of pharmaceutical residues on the structure of activated sludge bacterial communities in wastewater treatment bioreactors

Concern is growing over contamination of the environment with pharmaceuticals because of their widespread use and incomplete removal during wastewater treatment, where microorganisms drive the key processes. The influence of pharmaceuticals on bacterial community structure in activated sludge was assessed in small-scale wastewater treatment bioreactors containing different concentrations (5, 50, 200 and 500 μg L⁻¹) of several commonly used pharmaceuticals (ibuprofen, naproxen, ketoprofen, diclofenac and clofibric acid). T-RFLP analyses of the bacterial 16S rRNA genes indicated a minor but consistent shift in the bacterial community structure in the bioreactor R50 supplied with pharmaceuticals at a concentration of 50 μg L⁻¹, compared to the control reactor R0, which was operated without addition of pharmaceuticals. In the reactors operated with higher concentrations of pharmaceuticals, a greater structural divergence was observed. Bacterial community composition was further investigated by preparation of two clone libraries of bacterial 16S rRNA genes from reactors R0 and R50. Most clones in both libraries belonged to the Betaproteobacteria, among which Thauera, Sphaerotilus, Ideonella and Acidovorax-related spp. dominated. Nitrite-oxidizing bacteria of the genus Nitrospira sp., which are key organisms for the second stage of nitrification in wastewater treatment plants, were found only in the clone library of the reactor without pharmaceuticals. In addition, diversity indices were calculated for the two clone libraries, indicating a reduced diversity of activated sludge bacterial community in the reactor supplied with 50 μg L⁻¹ of each of selected pharmaceuticals.     

Degradation of carbamazepine by Trametes versicolor in an air pulsed fluidized bed bioreactor and identification of intermediates

The paper describes the aerobic degradation of carbamazepine (CBZ), an anti-epileptic drug widely found in aquatic environment, from Erlenmeyer flask to bioreactor by the white-rot fungus Trametes versicolor. In Erlenmeyer flask, CBZ at approximately 9 mg L⁻¹ was almost completely eliminated (94%) after 6 d, while at near environmentally relevant concentrations of 50 μg L⁻¹, 61% of the contaminant was degraded in 7 d. Acridone, acridine, 10,11-dihydro-10,11-dihydroxy-CBZ, and 10, 11-epoxy-CBZ were identified as major metabolites, confirming the degradation of CBZ. The degradation process was then carried out in an air pulsed fluidized bioreactor operated in batch and continuous mode. Around 96% of CBZ was removed after 2 days in batch mode operation, and 10,11-dihydro-10,11-epoxycarbamazepine was found as unique metabolite. In bioreactor operated in continuous mode with a hydraulic retention time of 3 d, 54% of the inflow concentration (approx. 200 μg L⁻¹) was reduced at the steady state (25 d) with a CBZ degradation rate of 11.9 μg CBZ g⁻¹ dry weight d⁻¹. No metabolite was detected in the culture broth. Acute toxicity tests (Microtox) indicated that the final culture broth in both batch and continuous mode operation were non toxic, with 15 min EC50 values of 24% and 77%, respectively.