The small Mediterranean country of Malta, an island located between Italy and North Africa, has been facing and will continue to face water stress and scarcity in the coming years, receiving the designation as the most water stressed country in Europe. In the past, Malta’s water challenges were centered around water quantity concerns, but in more recent years, the severity of their water stress has been strengthened by the deterioration of the groundwater quality and quantity. Through the over-extraction of their groundwater, saltwater intrusion has steadily occurred into their freshwater aquifer systems, worsening their groundwater quality for both domestic and agricultural purposes. The objective of this paper is to conduct an extensive review on the history of Malta’s water problems and how Malta is working to combat its water scarcity concerns. Additionally, this paper investigates the impact of Malta’s water scarcity on its food and energy security challenges. Our study concludes that while Malta has obstacles to overcome in their pursuit of water security and sustainable development, the future remains hopeful, with several alternatives still available. Some of the alternatives explored in this review include wastewater reuse, increased awareness, use of alternative energy sources, rainwater harvesting, and implementation of nation-wide strategic water policies.

Denitrifying woodchip bioreactors are a best management practice to reduce nitrate–nitrogen (NO₃–N) loading to surface waters from agricultural subsurface drainage. Their effectiveness has been proven in many studies, although variable results with respect to performance indicators have been observed. This paper serves the purpose of synthesizing the current state of the science in terms of the microbial community, its impact on the consistency of bioreactor performance, and its role in the production of potential harmful by‐products including greenhouse gases, sulfate reduction, and methylmercury. Microbial processes other than denitrification have been observed in these bioreactor systems, including dissimilatory nitrate reduction to ammonia (DNRA) and anaerobic ammonium oxidation (anammox). Specific gene targets for denitrification, DNRA, anammox, and the production of harmful by‐products are identified from bioreactor studies and other environmentally relevant systems for application in bioreactor studies. Lastly, cellulose depletion has been observed over time via increasing ligno‐cellulose indices, therefore, the microbial metabolism of cellulose is an important function for bioreactor performance and management. Future work should draw from the knowledge of soil and wetland ecology to inform the study of bioreactor microbiomes.

Denitrification bioreactors are an edge‐of‐field conservation practice being implemented to reduce nonpoint nitrogen pollution to downstream waterbodies. In the Midwestern region of the United States, these bioreactors are commonly used for the treatment of nitrate‐laden subsurface drainage systems. Innovative strategies will be needed to reach the nutrient reduction goals established; here, a typical denitrification bioreactor was retrofitted with a supplemental surface water pumping system to enhance the bioreactor use and performance. Potential benefits of the pumped bioreactor system include extended treatment beyond the typical drainage season, increased nitrate mass removal, extended bioreactor lifespan, and extended applications of the bioreactor such as treatment of surface waters. Current challenges associated with pumped bioreactors exist with the timing of the pumping and water source identification. Considerations include the water availability and the potential need to obtain a permit for the water extraction, and nitrate concentration, temperature, and carbon content of the source to be pumped from. Conditions that would promote complete nitrate removal should be avoided. Additional potential applications for these pumped bioreactors have been identified and include, but are not limited to, the treatment of additional surface water sources, irrigation waters, drainage ditches, and groundwater.