Adoph Muleja
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PhD, 2016, Chemical Engineering, Wits University, Johannesburg, South Africa

Qiujin Xu
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Joint Doctoral Student, Civil and Environmental Engineering
B.S.,2021, Environmental Engineering, Zhejiang University

I currently work on the biodegradation of PFAS compounds via reductive defluorination.

Publications

Alvarez started his academic career in 1993 at the University of Iowa, where he also served as Associate Director for the Center for Bioprocessing and Biocatalysis.  During his tenure at Iowa, he pioneered research on the groundwater quality impacts associated with ethanol-blend releases. He discovered that the preferential degradation of ethanol and the accelerated depletion of nutrients and electron acceptors hinders hydrocarbon degradation and results in longer hydrocarbon plumes that pose a greater risk of exposure. He also characterized potential aesthetic impacts such as taste and odor produced by butyric acid and other byproducts of ethanol fermentation. His more recent finding that ethanol preferentialy migrates through the capillary fringe and undergoes phase separation (leaving behind a hydrocarbon non-aqueous phase) has important implications for site assessment and remediation of fuel ethanol releases.  Alvarez’s research on the potential groundwater impacts of fuel ethanol earned him the Malcom Pirnie-AEESP Frontiers in Research Award in 2008, and provided guidelines for many states (e.g., California, Iowa and Maine) and the EPA on the remediation and natural attenuation of groundwater impacted by leaking underground storage tanks.

After moving to Rice University in 2003, Alvarez continued to contribute to the practice and pedagogy of hazardous waste remediation. He wrote two bioremediation textbooks (including the only one written in Spanish and one published by Wiley & Sons). In collaboration with Herb Ward and Joe Hughes in a pilot-scale study, Alvarez’s students demonstrated that chlorinated solvent DNAPLs commonly present in source zones can be effectively treated by bioaugmentation with dehalorespiring bacteria.  This approach can significantly cut down remediation cost, and is being increasingly used by remediation companies at sites impacted by chlorinated solvents. This project received the WEF McKee Medal for Groundwater Restoration or Sustainable Use. Recently, Alvarez developed catabolic gene biomarkers to quantify the presence and expression of anaerobic degradation of monoaromatic hydrocarbons.  This contribution has significant potential to support site-specific decisions to select or reject natural attenuation as a remedial approach, and to enhance the performance assessment and forensic analysis of bioremediation. For instance, it can help to reliably estimate biodegradation rates (and cleanup time) at a small fraction of the cost of traditional flux transects or mass balance approaches.

Alvarez has led various international collaborative field studies. With Henry Corseuil at the Universidade Federal de Santa Catarina, Brazil, they conducted a comprehensive long-term (10-year) study of an ethanol blend release, and showed that the transient accumulation of acetate (a common anaerobic metabolite) thermodynamically inhibitis anaerobic benzene biodegradation. Thus, some state agencies and the EPA are beginning to request acetate analysis as part of the regular site characterization process for ethanol blend releases. In collaboration with Nankai University, Alvarez directed a 100-mile survey of the Haihe River and showed that antibiotic resistance genes draining from animal farms are an emerging class of pollutants, and discerned environmental factors that contribute to their environmental amplification or attenuation.

Alvarez has applied his expertise in environmental microbiology to advance our understanding of the microbial response, adaptation, and impact due to nanomaterials exposure.  This is an important subject because microorganisms are the basis of all known ecosystems, serving as primary agents of biogeochemical cycling and supporting food webs.  Recent discoveries include that (a) buckminsterfullerene stable water suspensions (nC₆₀) are strongly bactericidal and their mode of action involves oxidation of cell membrane proteins and interruption of energy transduction upon direct contact; (b) nC₆₀ is also teratogenic and delays zebrafish embryo and larva development and causes pericardial edema, which can be mitigated by antioxidants (this was the first developmental toxicity study of any type of nanomaterial and showed the importance of mitigating oxidative stress); (c) C₆₀ bioaccumulates in earthworms to a much lower extent than predicted by its hydrophobicity (which showed that traditional fugacity models do not apply to nanoparticles); (d) the antibacterial mechanism of silver nanoparticles is exclusively due to silver ion release, whose bioavailability and toxicity can be significantly mitigated by common ligands in water; and (e) quantum dots are easily weathered and release toxic metals that, at sublethal concentrations, can stimulate nitrogen cycling.  These findings are important not only to understand and mitigate potential impacts to microbial ecosystem services, but also to develop greener disinfection, anti-fouling and anti-corrosion applications based on nanotechnology.  Contributions to such applications include findings that (f) aminofullerene photocatalysts exhibit high efficiency for viral disinfection and detoxification of pharmaceuticals under solar irradiation (thus obviating the need for electricity), and (g) water filtration membranes that incorporate antimicrobial nanoparticles exhibit superior biofouling resistance.

Alvarez has also made several international contributions to water resources protection and associated policy. When he was a Ph.D. student, acting as an independent consultant, he helped formulate policies for the sustainable development of water resources in the Commonwealth of Dominica, and designed and implemented the groundwater monitoring plan for the City of Ann Arbor landfill.  Later as a professor, he served as advisor to two Presidents of Nicaragua (Violeta Chamorro and Enrique Bolaños) on matters ranging from the remediation of Lake Nicaragua to hydroelectric power development. As a member of the board of directors of the Nicaraguan National Agency for Water Supply and Wastewater Treatment (ENACAL), he oversaw the design concept and bidding process for a $30-million wastewater treatment plant (the first one) in Managua.  He also helped formulate groundwater remediation policy for the Mexican Petroleum Institute (IMP) as a scientific advisory board member.  More recently, he increased public awareness about the large water footprint of fuel ethanol (e.g., driving one mile on ethanol is the equivalent of consuming 50 gallons of water – a drink or drive issue) with the help of the Leopold Leadership Foundation. Alvarez was also a Founding Member of the Nicaraguan Academy of Sciences in 2008, and promoted the adoption of sustainable water management as a core value.