Effect of ultra-high-density polyethylene microplastic on the sorption and biodegradation of organic micropollutants.

Microplastics and organic micropollutants are two emerging contaminants that interact with each other in environmental and engineered systems. Sorption of organic micropollutants, such as pharmaceuticals, pesticides and industrial compounds, to microplastics can modify their bioavailability and biodegradation. The present study investigated the capacity of ultra-high density polyethylene particles (125 µm in diameter), before and after aging, to sorb 21 organic micropollutants at different environmentally relevant concentration. Furthermore, the biodegradation of these organic micropollutants by a biofilm microbial community growing on the microplastic surface was compared with the biodegradation by a microbial community originating from activated sludge. Among all tested organic micropollutants, propranolol (70%), trimethoprim (25%) and sotalol (15%) were sorbed in the presence of polyethylene particles. Growth of a biofilm on the polyethylene particles had a beneficial effect on the sorption of bromoxynil, caffeine and chloridazon and on the biodegradation of irbesartan, atenolol and benzotriazole. On the other hand, the biofilm limited the sorption of trimethoprim, propranolol, sotalol and benzotriazole and the biodegradation of 2,4-D. These results showed that ultra-high density polyethylene particles can affect both in a positive and negative way for the abiotic and biotic removal of organic micropollutants in wastewater. This project highlights the need for further investigation regarding the interaction between microplastics and organic micropollutants in the aquatic environment.

Impact of mixed microalgal and bacterial species on organic micropollutants removal in photobioreactors under natural light.

Single microalgae species are effective at the removal of various organic micropollutants (OMPs), however increased species diversity might enhance this removal. Sixteen OMPs were added to 2 continuous photobioreactors, one inoculated with Chlorella sorokiniana and the other with a microalgal-bacterial community, for 112 d under natural light. Three media were sequentially used in 3 Periods: I) synthetic sewage (d 0-28), II) 10x diluted anaerobically digested black water (AnBW) (d 28-94) and III) 5x diluted AnBW (d 94-112). Twelve OMPs were removed > 30 %, while 4 were < 10 % removed. Removal efficiencies were similar for 9 OMPs, yet the mixed community showed a 2-3 times higher removal capacity (µg OMP/g dry weight) than C. sorokiniana during Period II pseudo steady state. The removal decreased drastically in Period III due to overgrowth of filamentous green algae. This study shows for the first time how microbial community composition and abundance are key for OMPs removal.

Key constructed wetland design features for maximized micropollutant removal from treated municipal wastewater: A literature study based on 16 indicator micropollutants.

The removal of micropollutants from wastewater by constructed wetlands (CWs) has been extensively studied and reviewed over the past years. However, most studies do not specifically focus on the removal of micropollutants from the effluent of conventional wastewater treatment plants (WWTP) that still contains micropollutants, but on the removal of micropollutants from raw wastewater. Raw wastewater has a significantly different composition compared to WWTP effluent, which positively or negatively affects micropollutant removal mechanisms. To determine the optimal CW design for post-treatment of WWTP effluent to achieve additional micropollutant removal, this review analyzes the removal of 16 Dutch indicator micropollutants for post-treatment technology evaluation from WWTP effluent by different types of CWs. It was concluded that CW systems with organic enhanced adsorption substrates reach the highest micropollutant removal efficiency as a result of adsorption, but that the longevity of the enhanced adsorption effect is not known in the systems studied until now. Aerobic biodegradation and photodegradation are other relevant removal mechanisms for the studied micropollutants. However, a current knowledge gap is whether active aeration to stimulate the aerobic micropollutant biodegradation results in an increased micropollutant removal from WWTP effluent. Further knowledge gaps that impede the wider application of CW systems for micropollutant removal from WWTP effluent and allow a fair comparison with other post-treatment technologies for enhanced micropollutant removal, such as ozonation and activated carbon adsorption, relate to i) saturation of enhanced adsorption substrate; ii) the analysis of transformation products and biological effects; iii) insights in the relationship between microbial community composition and micropollutant biodegradation; iv) plant uptake and in-plant degradation of micropollutants; v) establishing design rules for appropriate hydraulic loading rates and/or hydraulic retention times for CWs dedicated to micropollutant removal from WWTP effluent; and vi) the energy- and carbon footprint of different CW systems. This review finishes with detailed suggestions for future research directions that provide answers to these knowledge gaps.

Impact of wastewater characteristics on the removal of organic micropollutants by Chlorella sorokiniana.

Microalgae-based technologies can be used for the removal of organic micropollutants (OMPs) from different types of wastewater. However, the effect of wastewater characteristics on the removal is still poorly understood. In this study, the removal of sixteen OMPs by Chlorella sorokiniana, cultivated in three types of wastewater (anaerobically digested black water (AnBW), municipal wastewater (MW), and secondary clarified effluent (SCE)), were assessed. During batch operational mode, eleven OMPs were removed from AnBW and MW. When switching from batch to continuous mode (0.8 d HRT), the removal of most OMPs from AnBW and MW decreased, suggesting that a longer retention time enhances the removal of some OMPs. Most OMPs were not removed from SCE since poor nutrient availability limited C. sorokiniana growth. Further correlation analyses between wastewater characteristics, biomass and OMPs removal indicated that the wastewater soluble COD and biomass concentration predominantly affected the removal of OMPs. Lastly, carbon uptake rate had a higher effect on the removal of OMPs than nitrogen and phosphate uptake rate. These data will give an insight on the implementation of microalgae-based technologies for the removal of OMPs in wastewater with varying strengths and nutrient availability.

Phytoremediation of micropollutants by Phragmites australis, Typha angustifolia, and Juncus effuses.

Micropollutants (MPs) include organic chemicals, for example, pharmaceuticals and personal care products. MPs have been detected in the aquatic environment at low concentrations (ng/L-µg/L), which may lead to negative impacts on the ecosystem and humans. Phytoremediation is a green clean-up technology, which utilizes plants and their associated rhizosphere microorganisms to remove pollutants. The selection of plant species is important for the effectiveness of the phytoremediation of MPs. The plant species Phragmites australis, Typha angustifolia, and Juncus effuses are often used for MP removal. In this study, batch experiments were conducted to select plant species with an optimal ability to remove MPs, study the effect of temperature on MP removal in plants and the phytotoxicity of MPs. This study also explored the degradation of a persistent MP propranolol in plants in more detail. Data show that all three investigated plant species removed most MPs efficiently (close to 100 %) at both 10 and 21.5 °C. The tested plant species showed a different ability to translocate and accumulate propranolol in plant tissues. Typha angustifolia and Juncus effuses had a higher tolerance to the tested MPs than Phragmites australis. Typha angustifolia and Juncus effuses are recommended to be applied for phytoremediation of MPs.Novelty statement The novelty of this study is the selection of Typha angustifolia and Juncus effuses as proper plant species for phytoremediation of micropollutants (MPs). These two plant species were selected due to their good ability to remove MPs, tolerate low temperature, and resist the toxicity of MPs. The outcomes from this study can also be applied for constructed wetlands in removing MPs from wastewater. This study demonstrates the uptake and degradation processes of persistent MP propranolol in plants in more detail. Understanding the degradation mechanisms of a MP in plants is significant not only for the application of phytoremediation on MP removal but also for the development of constructed wetland studies.

The removal of micropollutants from treated effluent by batch-operated pilot-scale constructed wetlands.

Micropollutants (MPs), such as pharmaceuticals and antibiotics, are present in the environment at low concentrations (ng/L-µg/L). A constructed wetland (CW) is a nature-based wastewater treatment technology, which can be used to remove MPs from wastewater treatment plant effluent. This study aimed to improve MP removal of CWs by optimizing the design of batch-operated CW. Three pilot-scale CWs were built to study the effect of two design-features: the use of a support matrix (a mixture of bark and biochar) and continuous aeration. The use of bark-biochar as support matrix increased the removal of 11 of 12 studied MPs compared to the CW filled with conventional material sand. The highest improved removal by the addition of bark-biochar was more than 40% (median) for irbesartan, carbamazepine, hydrochlorothiazide and benzotriazole. Aerating the bed of the bark-biochar CW did not change MP removal. Besides, the presence of bark-biochar also enhanced the removal of total nitrogen during 10 months of operation, but no improvement was observed on the total organic carbon and total phosphorus removal. Considering the application in a batch-operated CW, MP removal can be greatly enhanced by replacing sand with bark-biochar that will act as MP adsorbing matrix.

Removal processes of individual and a mixture of organic micropollutants in the presence of Scenedesmus obliquus.

Organic micropollutants (OMPs) need to be removed from wastewater as they can negatively affect aquatic organisms. It has been demonstrated that microalgae-based technologies are efficient in removing OMPs from wastewater. In this study, the removal processes and kinetics of six persistent OMPs (diclofenac, clarithromycin, benzotriazole, metoprolol, carbamazepine and mecoprop) were studied during cultivation of Scenedesmus obliquus in batch mode. These OMPs were added as individual compounds and in a mixture. Short experiments (8 days) were performed to avoid masking of OMP removal processes by light and nutrient limitation. The results show that diclofenac, clarithromycin, and benzotriazole were mainly removed by photodegradation (diclofenac), biodegradation (benzotriazole), or a combination of these two processes (clarithromycin). Peroxidase was involved in intracellular and extracellular biodegradation when benzotriazole was present as individual compound. Carbamazepine, metoprolol and mecoprop showed no biodegradation or photodegradation, and neglectable removal (<5%) by bioadsorption and bioaccumulation. Using an OMP mixture had an adverse effect on the photodegradation of clarithromycin and diclofenac, with reduced first-order kinetic constants compared to the individual compounds. Benzotriazole biodegradation was inhibited by the presence of the OMP mixture. This indicates that the presence of OMPs inhibits the photodegradation and biodegradation of some individual OMPs. These results will improve our understanding of removal processes of individual and mixtures of OMPs by microalgae-based technologies for wastewater treatment.

Mesocosm constructed wetlands to remove micropollutants from wastewater treatment plant effluent: Effect of matrices and pre-treatments.

The contamination of the aquatic environment by micropollutants (MPs) brings risks for the ecosystem and human health. Constructed wetlands (CWs) were an eco-friendly technology to remove MPs from wastewater treatment plant effluent. In this study, the removal of MPs was evaluated in seven vertical flow mesocosm CWs with different configurations, including different support matrices (sand and a combination of bark-biochar), light pre-treatments (UVC and sunlight) or bioaugmentation in support matrices (activated sludge). The CWs with bark-biochar as support matrix significantly enhanced the removal of irbesartan and carbamazepine (>40 %), compared to the CW filled with the conventional support matrix sand. UVC irradiation as pre-treatment was more efficient in removing MPs than sunlight irradiation. After UVC pre-treatment, less MPs accumulated in the plants in the subsequent CW unit compared to the CW unit without any pre-treatment. Moreover, in the UVC combined CW system, less sulfamethoxazole, furosemide, mecoprop and diclofenac were accumulated in the plants (<0.5 µg) than other MPs (>3 µg). The addition of 0.5 % activated sludge combined with the aeration of influent did not improve MP removal in the CW. Considering the application, a bark-biochar based CW combined with UVC pre-treatment will result in more MP removal than a conventional sand CW.

Prolonged lifetime of biological activated carbon filters through enhanced biodegradation of melamine.

Micropollutants can be removed in Biological Activated Carbon (BAC) filters through biodegradation, besides adsorption, when the conditions are favorable. In the present study, we build upon previous work on melamine biodegradation and activated carbon regeneration in batch experiments and assess the efficiency of this process in continuous flow lab-scale BAC filters. Melamine is frequently detected at low concentrations in surface water and is used here as a model micropollutant. BAC filters were inoculated with melamine degrading biomass and the contribution of biodegradation to melamine removal was assessed. Furthermore, we tested the effect of an additional carbon source (methanol) and the effect of contact time on melamine removal efficiency. We demonstrate that inoculation of activated carbon filters with melamine degrading biomass increases melamine removal efficiency by at least 25%. When an additional carbon source (methanol) is supplied, melamine removal is almost complete (up to 99%). Finally, through a nitrogen mass balance, we demonstrate that around 60% of the previously adsorbed melamine desorbs from the BAC surface when biodegradation rates in the liquid phase increase. Melamine desorption resulted in a partial recovery of the adsorption capacity.

Sorption of micropollutants on selected constructed wetland support matrices.

Micropollutants (MPs) are organic chemicals that are present in the environment at low concentrations (ng/L-µg/L), for example pharmaceuticals. A constructed wetland (CW) is a promising post-treatment technique to remove MPs from wastewater effluent. Selecting a suitable material for support matrix is important when designing such a CW. Nine materials were studied as potential support matrices: Light Expanded Clay Aggregates (LECA), compost, bark, granulated activated carbon (GAC), biochar, granulated cork, lava rock, sand and gravel. Batch experiments were conducted to study MP removal by nine materials in phosphate buffer with 5 or 50 µg/L MPs, or wastewater effluent with 50 µg/L of MPs. GAC and biochar removed almost all MPs in both phosphate buffer and wastewater effluent, followed by bark, compost, granulated cork. Sand, gravel, LECA and lava rock removed less than 30% of most MPs in both matrixes. Based on set criteria (e.g. removal efficiency), biochar, bark, compost, LECA and sand were selected, and used in combinations in column studies to test their overall performance. A combination of bark and biochar performed the best on MP removal, as 4 MPs were highly (70%-100%) removed, 4 MPs were moderately (30%-70%) removed while only 3 MPs were hardly removed. The main flow regime of this combination was both plug flow and dispersive flow. Moreover, we hypothesized to apply bark and biochar in a CW. Based on the assumptions and calculations, some benefits are expected, such as increasing MP removal and extending operation time.

2,4-Dichlorophenoxyacetic acid degradation in methanogenic mixed cultures obtained from Brazilian Amazonian soil samples.

2,4-Dichlorophenoxyacetic acid (2,4-D) is the third most applied pesticide in Brazil to control broadleaf weeds in crop cultivation and pastures. Due to 2,4-D's high mobility and long half-life under anoxic conditions, this herbicide has high probability for groundwater contamination. Bioremediation is an attractive solution for 2,4-D contaminated anoxic environments, but there is limited understanding of anaerobic 2,4-D biodegradation. In this study, methanogenic enrichment cultures were obtained from Amazonian top soil (0-40 cm) and deep soil (50 -80 cm below ground) that biotransform 2,4-D (5 µM) to 4-chlorophenol and phenol. When these cultures were transferred (10% v/v) to fresh medium containing 40 µM or 160 µM 2,4-D, the rate of 2,4-D degradation decreased, and biotransformation did not proceed beyond 4-chlorophenol and 2,4-dichlorophenol in the top and deep soil cultures, respectively. 16S rRNA gene sequencing and qPCR of a selection of microbes revealed no significant enrichment of known organohalide-respiring bacteria. Furthermore, a member of the genus Cryptanaerobacter was identified as possibly responsible for phenol conversion to benzoate in the top soil inoculated culture. Overall, these results demonstrate the effect of 2,4-D concentration on biodegradation and microbial community composition, which are both important factors when developing pesticide bioremediation technologies.

Melamine degradation to bioregenerate granular activated carbon.

The industrial chemical melamine is often detected in surface water used for drinking water production, due to its wide application and insufficient removal in conventional wastewater treatment plants. Melamine can be removed from water by adsorption onto granular activated carbon (GAC), nevertheless, GAC needs periodic reactivation in costly and energy intense processes. As an alternative method, GAC can also be regenerated using biomass capable of degrading melamine in a process called bioregeneration. We assessed melamine biodegradation in batch experiments in fully oxic and anoxic, as well as in alternating oxic and anoxic conditions. Additionally, we studied the effect of an additional carbon source on the biodegradation. The most favourable conditions for melamine biodegradation were applied to bioregenerate GAC loaded with melamine. We demonstrate that melamine can be biodegraded in either oxic or anoxic conditions and that melamine degrading biomass can restore at least 28% of the original GAC adsorption capacity. Furthermore, our results indicate that bioregeneration occurs mainly in the largest pore fraction of GAC, impacting adsorption kinetics. Overall, we show that bioregeneration has a large potential for restoring GAC adsorption capacity in industrial wastewater.

Experimental infrastructure requirements for quantitative research on microbial communities.

Natural microbial communities are composed of a large diversity of interacting microorganisms, each with a specific role in the functional properties of the ecosystem. The objectives in microbial ecology research are related to identifying, understanding and exploring the role of these different microorganisms. Because of the rapidly increasing power of DNA sequencing and the rapid increase of genomic data, main attention of microbial ecology research shifted from cultivation-oriented studies towards metagenomic studies. Despite these efforts, the direct link between the molecular properties and the measurable changes in the functional performance of the ecosystem is often poorly documented. A quantitative understanding of functional properties in relation to the molecular changes requires effective integration, standardization, and parallelization of experiments. High-resolution functional characterization is a prerequisite for interpretation of changes in metagenomic properties, and will improve our understanding of microbial communities and facilitate their exploration for health and circular economy related objectives.

Effects of salinity on the treatment of synthetic petroleum-industry wastewater in pilot vertical flow constructed wetlands under simulated hot arid climatic conditions.

Petroleum-industry wastewater (PI-WW) is a potential source of water that can be reused in areas suffering from water stress. This water contains various fractions that need to be removed before reuse, such as light hydrocarbons, heavy metals and conditioning chemicals. Constructed wetlands (CWs) can remove these fractions, but the range of PI-WW salinities that can be treated in CWs and the influence of an increasing salinity on the CW removal efficiency for abovementioned fractions is unknown. Therefore, the impact of an increasing salinity on the removal of conditioning chemicals benzotriazole, aromatic hydrocarbon benzoic acid, and heavy metal zinc in lab-scale unplanted and Phragmites australis and Typha latifolia planted vertical-flow CWs was tested in the present study. P. australis was less sensitive than T. latifolia to increasing salinities and survived with a NaCl concentration of 12 g/L. The decay of T. latifolia was accompanied by a decrease in the removal efficiency for benzotriazole and benzoic acid, indicating that living vegetation enhanced the removal of these chemicals. Increased salinities resulted in the leaching of zinc from the planted CWs, probably as a result of active plant defence mechanisms against salt shocks that solubilized zinc. Plant growth also resulted in substantial evapotranspiration, leading to an increased salinity of the CW treated effluent. A too high salinity limits the reuse of the CW treated water. Therefore, CW treatment should be followed by desalination technologies to obtain salinities suitable for reuse. In this technology train, CWs enhance the efficiency of physicochemical desalination technologies by removing organics that induce membrane fouling. Hence, P. australis planted CWs are a suitable option for the treatment of water with a salinity below 12 g/L before further treatment or direct reuse in water scarce areas worldwide, where CWs may also boost the local biodiversity. Graphical abstract.

Improving removal of antibiotics in constructed wetland treatment systems based on key design and operational parameters: A review.

While removal of antibiotics in constructed wetland treatment systems (CWTS) has been described previously, few studies examined the synergistic effect of multiple design and operational parameters for improving antibiotic removal. This review describes the removal of 35 widely used antibiotics in CWTS covering the most common design parameters (flow configuration, substrate, plants) and operational parameters (hydraulic retention time/hydraulic loading rates, feeding mode, aeration, influent quality), and discusses how to tailor those parameters for improving antibiotic removal based on complex removal mechanisms. To achieve an overall efficient removal of antibiotics in CWTS, our principal component analysis indicated that optimization of flow configuration, selection of plant species, and compensation for low microbial activity at low temperature is the priority strategy. For instance, a hybrid-CWTS that integrates the advantages of horizontal and vertical subsurface flow CWTS may provide a sufficient removal performance at reasonable cost and footprint. To target removal of specific antibiotics, future research should focus on elucidating key mechanisms for their removal to guide optimization of the design and operational parameters. More efficient experimental designs (e.g., the Box-Behnken design) are recommended to determine the settings of the key parameters. These improvements would promote development of this environmentally friendly and cost-efficient technology for antibiotic removal.

Development of a simple method to quantify fipronil and its intermediates in soil.

A simple and reproducible method was developed and validated for simultaneous quantification of the pesticide fipronil and its intermediates fipronil desulfinyl, fipronil sulfone and fipronil sulfide, in soil. The analytes were extracted by ultrasonic bath and the ratio of solvents (hexane/acetone), number and time of cycles were optimized by Box-Behnken design with a triplicate central point. The optimal extraction conditions were achieved through a response surface analysis. The clean-up step was conducted by cartridges of solid phase extraction (SPE) containing silica (Florisil®) and aluminum oxide. Gas chromatography with electron capture detection (GC-ECD) was employed for separating fipronil and its intermediates with a suitable resolution and runtime of 20 minutes. The best quantification was achieved with 1 : 1 (v/v) acetone/hexane and 2 ultrasound cycles of 15 minutes each. The recovery values were between 81 to 108%, with relative standard deviation (RSD) lower than 6%, with no effect of the used matrix. Analytical curves presented regression coefficients values above 0.9908 for a concentration range from 0.005 to 0.6 µg g-1. Limits of detection (LOD) from 0.002 to 0.006 µg g-1 and limits of quantification (LOQ) from 0.006 to 0.020 µg g-1 were reached for all analytes. This method can be used to monitor and quantify fipronil and its intermediates in soil.

Pilot-scale hybrid constructed wetlands for the treatment of cooling tower water prior to its desalination and reuse.

Cooling towers are responsible for a large part of the industrial fresh water withdrawal, and the reuse of cooling tower water (CTW) effluents can strongly lower industrial fresh water footprints. CTW requires desalination prior to being reused, but various CTW components, such as total organic carbon (TOC), conditioning chemicals and total suspended solids (TSS) hamper physico-chemical desalination technologies and need to be removed from the CTW. A cost-efficient and robust pre-treatment is thus required, which can be provided by constructed wetlands (CWs). The present study is the first study that determined the CTW pre-treatment efficiency of hybrid-CWs and the impact of winter season and biocides in the CTW on the pre-treatment efficiency. The most efficient CW flow type and dominant removal mechanisms for CW components hampering physico-chemical desalination were determined. Subsurface flow CWs removed PO43-, TSS and TOC as a result of adsorption and filtration. Vertical subsurface flow CWs (VSSF-CW) excelled in the removal of benzotriazole as a result of aerobic biodegradation. Horizontal subsurface flow CWs (HSSF-CW) allowed the denitrification of NO3- due to their anaerobic conditions. Open water CWs (OW-CWs) did not contribute to the removal of components that hamper physico-chemical desalination technologies, but do provide water storage options and habitat. The biological removal processes in the different CW flow types were negatively impacted by the winter season, but were not impacted by concentrations of the biocides glutaraldehyde and DBNPA that are relevant in practice. For optimal pre-treatment, a hybrid-CW, consisting of an initial VSSF-CW followed by an OW-CW and HSSF-CW is recommended. Future research should focus on integrating the hybrid-CW with a desalination technology, e.g. reverse osmosis, electrodialysis or capacitive ionization, to produce water that meets the requirements for use as cooling water and allow the reuse of CTW in the cooling tower itself.

Biodegradation and adsorption of micropollutants by biological activated carbon from a drinking water production plant.

The presence of micropollutants in surface water is a potential threat for the production of high quality and safe drinking water. Adsorption of micropollutants onto granular activated carbon (GAC) in fixed-bed filters is often applied as a polishing step in the production of drinking water. Activated carbon can act as a carrier material for biofilm, hence biodegradation can be an additional removal mechanism for micropollutants in GAC filters. To assess the potential of biofilm to biodegrade micropollutants, it is necessary to distinguish adsorption from biodegradation as a removal mechanism. We performed experiments at 5 °C and 20 °C with biologically active and autoclaved GAC to assess the biodegradation of micropollutants by the biofilm grown on the GAC surface. Ten micropollutants were selected as model compounds. Three of them, iopromide, iopamidol and metformin, were biodegraded by the GAC biofilm. Additionally, we observed that temperature can increase or decrease adsorption, depending on the micropollutant studied. Finally, we compared the adsorption capacity of GAC used for more than 100,000 bed volumes and fresh GAC. We demonstrated that used GAC shows a higher adsorption capacity for guanylurea, metformin and hexamethylenetetramine and only a limited reduction in adsorption capacity for diclofenac and benzotriazole compared to fresh GAC.

Anaerobic biodegradation of pharmaceutical compounds coupled to dissimilatory manganese (IV) or iron (III) reduction.

Pharmaceuticals in water have adverse effects on aquatic environment. Anaerobic pharmaceutical biodegradation coupled to dissimilatory manganese(Mn) (IV)- or iron(Fe) (III)-oxides reduction is potentially efficient but unexplored. In this study, batch experiments were performed using different Mn(IV) and Fe(III) species with a microbial inoculum pre-cultivated with 15 mM chemically-synthesized Mn(IV) and 10 mg L-1 metoprolol. Results show 26% caffeine and 52% naproxen are degraded with Mn(IV) as terminal electron acceptor and insignificant biodegradation for other pharmaceuticals tested. Reduction of Mn(IV) from drinking water treatment is coupled to anaerobic biodegradation of metoprolol and propranolol, resulting in removal efficiencies of 96% and 31%, respectively. The results indicate that adsorption contributes to the pharmaceutical removal during the first 10 days of incubation, while biodegradation is the main removal mechanism in the whole period. Fe(III) can also be used as electron acceptor in anaerobic pharmaceutical biodegradation. Over half of the added metoprolol is degraded with both chemically-synthesized Fe(III) and Fe(III)-citrate as terminal electron acceptors. However, this process did not occur when using Fe(III) from drinking water treatment or Fe(III)-based sorbents. This study indicates that anaerobic pharmaceutical biodegradation coupled to dissimilatory Mn(IV) or Fe(III) reduction is possible, and promising for application to cleaning wastewater treatment plant effluents.

Benzotriazole removal mechanisms in pilot-scale constructed wetlands treating cooling tower water.

The reuse of discharged cooling tower water (CTW) in the cooling tower itself could reduce fresh water intake and help mitigating fresh water scarcity problems. However, this requires desalination prior to its reuse, and hindering fractions, such as conditioning chemicals, should be removed before desalination to obtain a higher desalination efficiency. Constructed wetlands (CWs) can provide such a pre-treatment. In this study, the mechanisms underlying the removal of conditioning chemical benzotriazole (BTA) in CWs was studied using an innovative approach of differently designed pilot-scale CWs combined with batch removal experiments with substrate from these CWs. By performing these combined experiments, it was possible to determine the optimal CW design for BTA removal and the most relevant BTA removal processes in CWs. Adsorption yielded the highest contribution, and the difference in removal between different CW types was linked to their capability to aerobically biodegrade BTA. This knowledge on the main removal mechanisms for BTA allows for a CW design tailored for BTA removal. In addition, the outcomes of this research show that performing batch experiments with CW substrate allows one to determine the relevant removal mechanisms for a given compound which results in a better understanding of CW removal processes.