Micropollutants Research Papers

Wastewater, a Wasted Resource

The Oxford English Dictionary defines wastewater as superfluous water, or water that has served its purpose. This definition of wastewater is ingrained in our perception and attitude. Yet, this definition would appear to be outdated in light of the emerging view that wastewater represents an unutilized water resource and not a waste product to be discarded. Furthermore, promoting such use of wastewater is neither new nor radical. Virtually all urban societies already make use of water sources laden with wastewater, albeit in varying amounts. For example, consider the Mississippi, the longest river in North America, which serves as both a water source and wastewater receptor for the numerous towns and cities located along its path. As the river meanders downstream, water increasingly enriched by upstream discharges of wastewater serves as a source of potable water for downstream communities. Such observations support the view that wastewater is better defined as a potential water resource that is currently wasted. A third of the world's population lives in water-stressed countries and this proportion is expected to rise to two thirds by 2025 (Service, 2006). Finding alternate water sources is critical to the survival of these water stressed societies. Although wastewater has been overlooked as a potential water resource, it could become an option if appropriate treatment technologies can be developed.

While biological treatment processes are significantly cheaper to build and operate, current designs are not capable of delivering high quality water suitable for a variety of purposes. Despite several advances since the inception of biological wastewater treatment processes, with an initial focus on removing organic carbon through to subsequent extension to include nitrogen and phosphorous removal, these systems continue to only be able to effectively degrade substances present at mg/L concentrations.

Over the past decade the rapid increase in instrument sensitivity has led to wide detection of ng/L levels of biologically active contaminants, referred to as emerging pollutants or organic micropollutants, in the environment. These contaminants include pharmaceuticals, personal care products, steroid hormones, industrial chemicals, and pesticides (Galloway et al., 2010; Oulton et al., 2010; Vandenberg et al., 2013; Richardson and Ternes, 2014; Petrie et al., 2015; Richardson and Kimura, 2016). Discharges from wastewater treatment plants are acknowledged as a major source of these contaminants in receiving environments (Spongberg and Witter, 2008; Bartelt-Hunt et al., 2009; Loganathan et al., 2009). Various studies have highlighted the need to remove the ng/L levels of these contaminants from the treated wastewater discharge due to their negative effect on human and animal health and ecotoxicology effects (Escher et al., 2011)—for example, a recent critical review concluded that doses of bisphenol A up to 4 orders of magnitude lower than the currently prescribed lowest observed adverse effect level of 50 mg/kg/day reliably produced effects in animals (Vandenberg et al., 2013) and another study reported changes in sex hormones associated with exposure to bisphenol A in men (Galloway et al., 2010). The cost of treating impacted environments can be large. London's drinking water is reported to be tainted with synthetic estrogens from excreted contraceptive pill residues in the Thames that have resulted from the water having gone through the equivalent of six people before reaching London. The cost of cleaning up Britain's contaminated waterways is estimated to exceed £30bn (McKie, 2012). Development of appropriate technologies is needed to convert wastewater into a water resource, potentially even for meeting potable needs. This paper aims to stimulate a discussion on ways to enhance the performance of biological treatment systems to achieve this vision.

Current Wastewater Treatment Approaches

The biological treatment approach, specifically the activated sludge process, is the most commonly used wastewater treatment technology. While it was originally designed to only remove organic carbon, it was subsequently extended to remove nitrogen and phosphorous. Transitioning between aerobic, anoxic, and anaerobic conditions is key to achieving biological nutrient removal. Doing so triggers the utilization of different electron acceptors and donors, therefore promoting the transformation of C, N, and P compounds. This strategy has continued to be exploited with the development of new system configurations, such as the Anammox (Lackner et al., 2014), SHARON (Hellinga et al., 1998; van Dongen et al., 2001), and Nareda (van der Roest et al., 2011) processes. Different redox environments influence organic micropollutant removal in different ways. Various studies have reported that organic micropollutant removal occurs to varying extent in biological treatment systems via a combination of biosorption and biodegradation. Maximum achievable removal for micropollutant such estrogens, nonylphenolics and metals was recorded at the highest sludge retention times (SRT) and hydraulic retention time (HRT) studied (Petrie et al., 2014). This micropollutant removal is related to the concomitant reduction in food: microorganism ratio. Nevertheless, studies have concluded that micropollutant degradation is insensitive to different SRTs (Falås et al., 2016). Other aspects influencing micropollutant removal in biological treatment processes are heterotrophic activity (Majewsky et al., 2010), pH (Gulde et al., 2014), and suspended/attached growth configuration (Falås et al., 2013). Although the heterogeneity of micropollutants in wastewaters makes removal difficult to predict since their chemistry is so diverse. For instance micropollutants can be broadly classified as easily, moderate and poorly degradable. The reality is that the biological processes are not designed to remove these pollutants, resulting in their incomplete removal and detection in final effluents and receiving surface waters (Joss et al., 2006; Racz and Goel, 2010). No specific strategies appear to have been successfully developed to enhance micropollutant removal by biological systems. Instead, organic micropollutant removal is typically achieved using physicochemical processes. These processes include adsorption in to organic matrices, passive effluent treatment in wetlands and aquifers, advanced oxidation processes (e.g., ozonation, UV treatment, photocatalysis, and Fenton oxidation), membrane filtration (nanofiltration and reverse osmosis membranes), and membrane biological reactor (Bolong et al., 2009; Rossner et al., 2009; Oulton et al., 2010; Luo et al., 2014). The shortcomings of these treatment systems are high investment and maintenance costs, generation of toxic residuals, and complex treatment procedures (Grassi et al., 2012). Operational difficulties of these physicochemical processes also need to be considered. For instance, wetlands and aquifers require large surface areas and large HRTs, which significantly complicates its implementation in urban areas. Similarly, advanced oxidation processes require chemicals not easily available (e.g., O3, , H2O2) and the non-selective nature of these reactions can result in formation of daughter products that are more toxic than the parent micropollutant (Rosal et al., 2009). Other concerns may also need consideration: energy and chemical inputs of ozonation processes are substantial (Cañizares et al., 2009); the Fenton process requires rigorous pH control (Chong et al., 2012); specially configured reactors are needed to maximize light exposure by UV and photocatalysis based water treatment, or water turbidity could significantly influence treatment efficiency (Chong et al., 2012); and membrane filtration and membrane biological reactors treatments routinely suffer from membrane fouling and biofilm formation (Guo et al., 2012).

Enhancing Biological Wastewater Treatment

Exploiting Microbial Diversity

Complex microbial consortia composed by bacteria-bacteria, bacteria-archea and bacteria-fungi can be developed to enhance biological degradation of micropollutants. Oxidase enzymes have great potential as biocatalysts for micropollutant and organic waste breakdown. Two of such class of enzymes are the oxygenase Cytochromes P450 (CYPs or Cyt P450), a highly efficient group of monooxygenases responsible for the destruction of drugs and toxins in organisms, and the laccases (EC, a class of copper-containing oxidase enzymes used by microorganisms to break down lignin) (Riva, 2006; Kumar, 2010). Both enzymes have been shown to efficiently degrade a vast array of organic micropollutants in pure enzyme assays (Harms et al., 2011; Lah et al., 2011). Despite the demonstrated effectiveness of these enzymes, their use in wastewater treatment is just starting to be investigated and has not been implemented in pilot or full scale (Lah et al., 2011). Current biological systems are reliant on using prokaryotic bacteria, which can rapidly oxidize organic carbon but generally do not express Cyt P450. Additionally, no applications of bacterial laccases have yet been realized due to their limited characterization (Werck-Reichhart and Feyereisen, 2000). In comparison, many fungi produce Cyt P450 (Lah et al., 2008; Kelly and Kelly, 2013) and only fungal laccases are used currently in biotechnological applications (Sharma et al., 2007; Harms et al., 2011). A system integrating suspended phase bacteria with activated fungi to transform conventional and emerging categories of pollutants can potentially take advantage of both organisms. Fungi can be activated by inducing the production of high levels of oxidase enzymes and at the same time stimulating enzyme activity (e.g., by providing H2O2 as cofactor for bacterial Cyt P450). By controlling the carbon source and electron acceptor regimens, it is possible to induct biocatalyst expression and activation (Price et al., 2013; Chubukov et al., 2014). As whole-cell catalyzed reactions are reportedly 10- to 100-fold slower than reactions catalyzed by free enzymes (Sotirova et al., 2008), cell membranes can be permeabilized to enhance extracellular laccase secretion and promote cellular influx of pollutants to membrane bound Cyt P450. In addition, gel encapsulated of fungi or bacterial cells can be implemented for improved performance. Alternatively, iterating between different redox conditions can promote the growth of different microbial populations to improve micropollutant biodegradation (Falås et al., 2016).

Exploiting Metabolic Diversity

New bioprocesses to treat wastewater can be developed by exploiting the diverse metabolic capabilities of microbes. Traditionally, only metabolic capabilities in relation to aerobic heterotrophy, aerobic nitrification and anoxic denitrification, and phosphate accumulation have been used in biological wastewater treatment systems. Exploiting alternative metabolic capabilities such as heterotrophic sulfate-reduction (Zhang and Wang, 2014), autotrophic sulfur-oxidizing denitrification (Hao et al., 2014; Pokorna and Zabranska, 2015), anaerobic methane-oxidation denitrification (Raghoebarsing et al., 2006), partial nitrite reduction to nitrous oxide for energy generation (Scherson et al., 2013) and electron shuttle redox biotransformation (Van der Zee and Cervantes, 2009) could improve micropollutant removal from wastewaters. These metabolic capabilities can also be exploited to remove inorganic micropollutants (e.g., heavy metals and radioactive elements) in which redox transformations can alter the solubility and precipitate the contaminants (Groudev et al., 1999; Gadd, 2010).

Exploiting Biocatalyst Diversity

Many enzymes are “promiscuous” biocatalysts capable of transforming a variety of substrates that share structural similarity with their primary substrate. These promiscuous or generalized enzymes: (i) are frequently not essential, (ii) maintain low metabolic fluxes, and (iii) require less regulation of enzyme activity to control metabolic flux in dynamic environments than do specialized enzymes (Nam et al., 2012). This non-specificity makes them promising biocatalysts for organic micropollutant degradation. Bacteria are constantly developing new catabolic pathways in order to either access sources of carbon, energy and nutrients or simply to detoxify new compounds. However, unraveling these degradation processes in nature is made difficult by the large number of chemicals, their occurrence at mostly low concentrations, and the number of unknown chemicals resulting from bacterial transformation and biodegradation. Genomics has revealed that many microorganisms have far greater potential to produce specialized enzymes and metabolites than was thought from classic bioactivity screens; however, realizing their degradation potential has been hampered by the fact that many specialized metabolite biosynthetic gene clusters are not expressed in laboratory cultures (Keller et al., 2005; Miller et al., 2010; Mora-Pale et al., 2014; Rutledge and Challis, 2015). Theoretically bacteria can utilize the full space of catabolic biochemical reaction types and initiate several pathways to degrade micropollutants (Kolvenbach et al., 2014). For example, multiple biodegradation mechanisms have been discovered for bisphenol A (BPA), an industrial chemical found in a variety of plastics and epoxies and a putative endocrine disrupting compound. Similarly, enzymatic biodegradation pathways may be discoverable for other compounds using biocatalyst and daughter products screening techniques such as metagenomics (Fernández-Arrojo et al., 2010), metaproteomics, and metabolomics (Villas-Bôas and Bruheim, 2007; Helbling et al., 2010, 2012).


Current designs focus on removing conventional pollutants (organic and inorganic substances present) that are present at much larger concentrations than micropollutants to be metabolized as a source of carbon and energy. The low concentrations of organic micropollutants suggests that these substances are more likely to be cometabolized. Hence, system design will need to focus on ways of stimulating the production of enzymes that could degrade the micropollutants. Current wastewater treatment system designs contain the basic ingredients required to formulate new processes for efficiently degrading micropollutants using the strategies discussed in the sections above. Biological treatment systems contain a wide variety of active microorganisms, and employ different redox environments are used to stimulate a wider range of chemical transformations. Rapid degradation of micropollutants could be achieved by stimulating the production of enzymes (e.g., oxidoreductases and laccases) by using hard-to-degrade substrates or by employing other environmental stresses. Liquids from anaerobic digestate could serve as carbon source that promotes such activity. The performance of such systems could be further enhanced by employing operational strategies that avert a lowering of enzyme production resulting from adaptation of microbial consortium to the imposed stress. Two plant configurations could potentially be developed using these approaches: (i) main stream micropollutant removal (i.e., modification of existing bioprocesses) or (ii) add-on reactors for micropollutant removal (i.e., dedicated tanks to remove micropollutants in the effluent of treatment plant).


Numerous organic micropollutants are present in wastewater. To convert wastewater into high quality water will require their removal. Current wastewater treatment systems are not designed to degrade organic micropollutants. Physicochemical treatment systems are effective but expensive while biological approaches cheap but ineffective and inconsistent. The next stage in the evolution of biological wastewater treatment processes could be based on discovering and employing novel metabolic traits of unconventional microbes (e.g., sulfur or iron oxidizing bacteria), or inducing the synthesis of enzymes capable of degrading micropollutants. Implementation of these new bioprocesses will involve the use of different waste streams used as substrate and new process operation strategies such as dynamic substrates control.

Author Contributions

NS developed the overall concept. NS and OP equally contributed to the writing of the article.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Bartelt-Hunt, S. L., Snow, D. D., Damon, T., Shockley, J., and Hoagland, K. (2009). The occurrence of illicit and therapeutic pharmaceuticals in wastewater effluent and surface waters in Nebraska. Environ. Pollut. 157, 786–791. doi: 10.1016/j.envpol.2008.11.025

PubMed Abstract | CrossRef Full Text | Google Scholar

Bolong, N., Ismail, A. F., Salim, M. R., and Matsuura, T. (2009). A review of the effects of emerging contaminants in wastewater and options for their removal. Desalination 239, 229–246. doi: 10.1016/j.desal.2008.03.020

CrossRef Full Text | Google Scholar

Cañizares, P., Paz, R., Sáez, C., and Rodrigo, M. A. (2009). Costs of the electrochemical oxidation of wastewaters: a comparison with ozonation and Fenton oxidation processes. J. Environ. Manag. 90, 410–420. doi: 10.1016/j.jenvman.2007.10.010

PubMed Abstract | CrossRef Full Text | Google Scholar

Chong, M. N., Sharma, A. K., Burn, S., and Saint, C. P. (2012). Feasibility study on the application of advanced oxidation technologies for decentralised wastewater treatment. J. Cleaner Prod. 35, 230–238. doi: 10.1016/j.jclepro.2012.06.003

CrossRef Full Text | Google Scholar

Escher, B. I., Baumgartner, R., Koller, M., Treyer, K., Lienert, J., and McArdell, C. S. (2011). Environmental toxicology and risk assessment of pharmaceuticals from hospital wastewater. Water Res. 45, 75–92. doi: 10.1016/j.watres.2010.08.019

PubMed Abstract | CrossRef Full Text | Google Scholar

Falås, P., Longrée, P., la Cour Jansen, J., Siegrist, H., Hollender, J., and Joss, A. (2013). Micropollutant removal by attached and suspended growth in a hybrid biofilm-activated sludge process. Water Res. 47, 4498–4506. doi: 10.1016/j.watres.2013.05.010

PubMed Abstract | CrossRef Full Text | Google Scholar

Falås, P., Wick, A., Castronovo, S., Habermacher, J., Ternes, T. A., and Joss, A. (2016). Tracing the limits of organic micropollutant removal in biological wastewater treatment. Water Res. 95, 240–249. doi: 10.1016/j.watres.2016.03.009

PubMed Abstract | CrossRef Full Text | Google Scholar

Fernández-Arrojo, L., Guazzaroni, M. E., López-Cortés, N., Beloqui, A., and Ferrer, M. (2010). Metagenomic era for biocatalyst identification. Curr. Opin. Biotechnol. 21, 725–733. doi: 10.1016/j.copbio.2010.09.006

PubMed Abstract | CrossRef Full Text | Google Scholar

Galloway, T., Cipelli, R., Guralnick, J., Ferrucci, L., Bandinelli, S., Corsi, A. M., et al. (2010). Daily bisphenol a excretion and associations with sex hormone concentrations: results from the inchianti adult population study. Environ. Health Perspect. 118, 1603–1608. doi: 10.1289/ehp.1002367

PubMed Abstract | CrossRef Full Text | Google Scholar

Grassi, M., Belgiorno, V., and Lofrano, G. (2012). “Removal of emerging contaminants from water and wastewater by adsorption process,” in Emerging Compounds Removal from Wastewater, ed Lofrano G. (New York, NY: Springer), p15–p37.

Groudev, S. N., Bratcova, S. G., and Komnitsas, K. (1999). Treatment of waters polluted with radioactive elements and heavy metals by means of a laboratory passive system. Minerals Eng. 12, 261–270. doi: 10.1016/S0892-6875(99)00004-7

CrossRef Full Text | Google Scholar

Gulde, R., Helbling, D. E., Scheidegger, A., and Fenner, K. (2014). pH-dependent biotransformation of ionizable organic micropollutants in activated sludge. Environ. Sci. Technol. 48, 13760–13768. doi: 10.1021/es5037139

PubMed Abstract | CrossRef Full Text | Google Scholar

Hao, T.-W., Xiang, P., Mackey, H. R., Chi, K., Lu, H., Chui, H., et al. (2014). A review of biological sulfate conversions in wastewater treatment. Water Res. 65, 1–21. doi: 10.1016/j.watres.2014.06.043

PubMed Abstract | CrossRef Full Text | Google Scholar

Harms, H., Schlosser, D., and Wick, L. Y. (2011). Untapped potential: exploiting fungi in bioremediation of hazardous chemicals. Nat. Rev. Microbiol. 9, 177–192. doi: 10.1038/nrmicro2519

PubMed Abstract | CrossRef Full Text | Google Scholar

Helbling, D. E., Hollender, J., Kohler, H.-E., Singer, H., and Fenner, K. (2010). High-throughput identification of microbial transformation products of organic micropollutants. Environ. Sci. Technol. 44, 6621–6627. doi: 10.1021/es100970m

PubMed Abstract | CrossRef Full Text | Google Scholar

Helbling, D. E., Johnson, D. R., Honti, M., and Fenner, K. (2012). Micropollutant biotransformation kinetics associate with WWTP process parameters and microbial community characteristics. Environ. Sci. Technol. 46, 10579–10588. doi: 10.1021/es3019012

PubMed Abstract | CrossRef Full Text | Google Scholar

Hellinga, C., Schellen, A. A. J. C., Mulder, J. W., van Loosdrecht, M. C. M., and Heijnen, J. J. (1998). The sharon process: an innovative method for nitrogen removal from ammonium-rich waste water. Water Sci. Technol. 37, 135–142. doi: 10.1016/S0273-1223(98)00281-9

CrossRef Full Text | Google Scholar

Joss, A., Zabczynski, S., Göbel, A., Hoffmann, B., Löffler, D., McArdell, C. S., et al. (2006). Biological degradation of pharmaceuticals in municipal wastewater treatment: proposing a classification scheme. Water Res. 40, 1686–1696. doi: 10.1016/j.watres.2006.02.014

PubMed Abstract | CrossRef Full Text | Google Scholar

Kelly, S. L., and Kelly, D. E. (2013). Microbial cytochromes P450: biodiversity and biotechnology. Where do cytochromes P450 come from, what do they do and what can they do for us? Philos. Trans. R. Soc. B 368, 20120476. doi: 10.1098/rstb.2012.0476

PubMed Abstract | CrossRef Full Text | Google Scholar

Kolvenbach, B. A., Helbling, D. E., Kohler, H.-P. E., and Corvini, P. F.-X. (2014). Emerging chemicals and the evolution of biodegradation capacities and pathways in bacteria. Curr.Opin. Biotechnol. 27, 8–14. doi: 10.1016/j.copbio.2013.08.017

PubMed Abstract | CrossRef Full Text | Google Scholar

Kumar, S. (2010). Engineering cytochrome P450 biocatalysts for biotechnology, medicine and bioremediation. Expert Opin. Drug Metab. Toxicol. 6, 115–131. doi: 10.1517/17425250903431040

PubMed Abstract | CrossRef Full Text | Google Scholar

Lackner, S., Gilbert, E. M., Vlaeminck, S. E., Joss, A., Horn, H., and van Loosdrecht, M. C. M. (2014). Full-scale partial nitritation/anammox experiences – an application survey. Water Res. 55, 292–303. doi: 10.1016/j.watres.2014.02.032

PubMed Abstract | CrossRef Full Text | Google Scholar

Lah, L., Kraševec, N., Trontelj, P., and Komel, R. (2008). High diversity and complex evolution of fungal cytochrome P450 reductase: cytochrome P450 systems. Fungal Genet. Biol. 45, 446–458. doi: 10.1016/j.fgb.2007.10.004

PubMed Abstract | CrossRef Full Text | Google Scholar

Lah, L., Podobnik, B., Novak, M., Korošec, B., Berne, S., Vogelsang, M., et al. (2011). The versatility of the fungal cytochrome P450 monooxygenase system is instrumental in xenobiotic detoxification. Mol. Microbiol. 81, 1374–1389. doi: 10.1111/j.1365-2958.2011.07772.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Loganathan, B., Phillips, M., Mowery, H., and Jones-Lepp, T. L. (2009). Contamination profiles and mass loadings of macrolide antibiotics and illicit drugs from a small urban wastewater treatment plant. Chemosphere 75, 70–77. doi: 10.1016/j.chemosphere.2008.11.047

PubMed Abstract | CrossRef Full Text | Google Scholar

Luo, Y., Guo, W., Ngo, H. H., Nghiem, L. D., Hai, F. I., Zhang, J., et al. (2014). A review on the occurrence of micropollutants in the aquatic environment and their fate and removal during wastewater treatment. Sci. Total Environ. 473–474, 619–641. doi: 10.1016/j.scitotenv.2013.12.065

CrossRef Full Text | Google Scholar

Majewsky, M., Gallé, T., Zwank, L., and Fischer, K. (2010). Influence of microbial activity on polar xenobiotic degradation in activated sludge systems. Water Sci. Technol. 62, 701–707. doi: 10.2166/wst.2010.925

PubMed Abstract | CrossRef Full Text | Google Scholar

Miller, L. D., Mosher, J. J., Venkateswaran, A., Yang, Z. K., Palumbo, A. V., Phelps, T. J., et al. (2010). Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments. BMC Microbiol. 10:149. doi: 10.1186/1471-2180-10-149

PubMed Abstract | CrossRef Full Text | Google Scholar

Mora-Pale, M., Sanchez-Rodriguez, S. P., Linhardt, R. J., Dordick, J. S., and Koffas, M. A. G. (2014). Biochemical strategies for enhancing the in vivo production of natural products with pharmaceutical potential. Curr. Opin. Biotechnol. 25, 86–94. doi: 10.1016/j.copbio.2013.09.009

PubMed Abstract | CrossRef Full Text | Google Scholar

Nam, H., Lewis, N. E., Lerman, J. A., Lee, D., Chang, R. L., Kim, D., et al. (2012). Network context and selection in the evolution to enzyme specificity. Science 337, 1101–1104. doi: 10.1126/science.1216861

PubMed Abstract | CrossRef Full Text | Google Scholar

Oulton, R. L., Kohn, T., and Cwiertny, D. M. (2010). Pharmaceuticals and personal care products in effluent matrices: a survey of transformation and removal during wastewater treatment and implications for wastewater management. J. Environ. Monit. 12, 1956–1978. doi: 10.1039/c0em00068j

PubMed Abstract | CrossRef Full Text | Google Scholar

Petrie, B., Barden, R., and Kasprzyk-Hordern, B. (2015). A review on emerging contaminants in wastewaters and the environment: current knowledge, understudied areas and recommendations for future monitoring. Water Res. 72, 3–27. doi: 10.1016/j.watres.2014.08.053

Pioneering Wetsus researcher tackles micropollutants and antibiotic resistance

Published: 15 juni 2016

Working at Wetsus since 2005, Dr. Lucía Hernández Leal has played a fundamental role in Wetsus’ growth over the past decade. During this time, she has seen Wetsus evolve from its origins as a first-of-its-kind presence in the northern Netherlands to a research institute that connects scientists from around the world.

“I first came to Wetsus via Wageningen University, where I directly contacted Grietje Zeeman [Professor of Environmental Technology] with whom I wanted to work,” Hernández Leal said. “She told me about a position at the then-not-so-well-known Wetsus.”

Today, Hernández Leal is the scientific project coordinator of the Wetsus theme “Source-Separated Sanitation.” Her research focuses on micropollutants in wastewater that come from pesticides, medication, and household products, among other sources.

Since this research has such far-reaching implications, it often involves collaborating with researchers on a global scale. Recently, Hernández Leal has been working with scientists from Imperial College London, including supervising the work of PhD student Sofia Semitsoglou-Tsiapou.

Their work focuses on developing water treatment processes to remove toxic, non-biodegradable pesticides from the water supply that are not effectively removed by current water treatment processes. This treatment is vital for safe drinking water: one of these pesticides, metaldehyde, which is a molluscide used for controlling slugs and snails, was responsible for one-third of the water quality failures in the UK in 2009, according to the UK Drinking Water Inspectorate Annual Reports.

In a recent paper published in Water Research, the scientists investigated the safety of a new treatment method, UV-H2O2, which can effectively degrade metaldehyde and other difficult-to-remove pesticides. 

“The question was if this process would result in products of concern, such as carcinogens or estrogenic compounds,” Hernández Leal said. “This study focused on three pesticides, and for these compounds no dangerous products were detected. Further, fundamental information regarding kinetics was generated, which can be applied regardless of the type of water that is treated.”

A related area that Hernández Leal is working on is the possibility that antibiotics in wastewater are providing a breeding ground for antibiotic-resistant bacteria.

“As it turns out, low concentrations of antibiotics in water can act as a trigger for bacteria to share and spread antibiotic-resistant traits,” she said. “Wastewater treatment plants have been in the spotlight as hotspots for spreading antibiotic resistance. Literature in the topic is still mixed and not all the time thorough. So we aim at understanding if that is indeed the case, how it happens (under which conditions like temperature, oxygen concentration, heavy metals, antibiotics, etc.) and getting a better idea of how to prevent it.”

Working toward these goals, Hernández Leal and other researchers at Wetsus are currently building a research program that covers the different aspects of the environmental problem of antibiotic resistance.

The program involves several participating institutions aligned with four PhD projects: implications for the health sector (with the University Medical Center Groningen); gene transfer at wastewater treatment plants (with TU Delft); the impact of livestock production on the water cycle (with the Institute for Risk Assessment Sciences of Utrecht University [IRAS] and the Central Veterinary Institute); and the development of a treatment technology to specifically target and destroy bacteria (with Wageningen University).

“The problem of antibiotic resistance is huge; much must be done in the way antibiotics are administrated both to humans and animals,” Hernández Leal said. “Since we know that the environment plays a role in the spread and evolution of resistance, at Wetsus we want to take our stake and do our part to contain antibiotic resistance.”

As part of Wetsus’ responsibility, Hernández Leal emphasizes the importance of bringing together the top experts in these areas, who come from many different institutions. Sometimes this level of collaboration can be challenging, since it requires convincing university supervisors of the benefits of researchers working together at Wetsus, and not solely at their home universities.

“Wetsus is strong in joining different parties to a common goal, both from different universities and companies of all sizes,” Hernández Leal said. “I expect that this role will continue to grow.”

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