Microorganisms control the fluxes of geochemical cycles, and new anaerobic microbial processes are new. Only 20 years ago, the anaerobic oxidation processes of both ammonia and methane were discovered. Anammox bacteria discovered in 1999, became a successful application for ammonia removal in full-scale wastewater after 10 years of fundamental physiological studies in controlled bioreactors. Anaerobic processes integrated in oxygen-limited systems, offer significant engineering, financial and environmental advantages. 9 years ago, microorganisms that oxidize methane using nitrate and/or nitrite were discovered; these “anaerobic methane oxidizers” have the potential to revolutionize the current challenges in greenhouse gas (GHG) emissions in wastewater transport and sewage treatment. For that to happen, the understanding of the intricate microbial ecophysiology in full-scale engineered sewage systems is of extreme importance. Physiology and microbial ecology studies have yielded limited results in the last 5 years, and studies such as this proposal, are relevant to advance sustainable wastewater management. In this project, we apply state-of-the-art omics, modern bio-reactor technology, and use current real treatment systems as models; to unravel further their potential. The candidate Dr. Guerrero, has extensive knowledge in their physiology and enrichment crucial to expand the knowledge gap in this field needed to truly develop new applications. The supervisor Dr. Pijuan, has the experience and knowledge in applied engineering in sewage treatment and this proposal can enhance the leadership role of female mentors. ICRA as host institution, has a multidisciplinary team and extensive facilities to host the research and maximize its impact in the field. This proposal will focus on connecting research to an applied context by engaging leaders in water management, and developing international relationships, and forming new innovation human resource.