Nitrogen contamination and bioremediation in groundwater and the environment: A review

Nitrogen contamination of groundwater and the environment is an increasing problem in today's society. Since the invention of the Haber-Bosh process in 1913, the impacts of N on human health and the environment have become increasingly widespread due to the industrial scale production of reactive N (Nr). As a result, government organisations and the scientific community continue to make advances towards tackling this ongoing problem. The inherent difficulties of accessing, observing and monitoring groundwater, combined with the complexity of interactions between groundwater chemistry, hydrogeology and ecology have resulted in gaps in fundamental knowledge, specifically regarding the understanding and remediation of N contaminated groundwater. As these knowledge gaps are addressed with ongoing research, current and future remediation targets are being consistently updated; this has resulted in past remediation strategies that may no longer be consistent in meeting new regulatory guidelines for water quality. As such, the search for more technically and economically feasible remediation strategies continues. Recent advances in bioremediation technologies have opened up promising avenues for research in the remediation of N contaminated groundwater. This literature review outlines the past, present and future of Nr-contamination and remediation in Nr -contaminated groundwater within the broader context of the larger environment. The literature cited in this review is critically evaluated to determine significant knowledge gaps.