Strategies to Overcome Intermediate Accumulation During in situ Nitrate Remediation in Groundwater by Hydrogenotrophic Denitrification

Abstract

Bioremediation of polluted groundwater is one of the most difficult actions in environmental science. Nonetheless, the clean-up of nitrate polluted groundwater may become increasingly important as nitrate concentrations frequently exceed the EU drinking water limit of 50 mg L–1, largely due to intensification of agriculture and food production. Denitrifiers are natural catalysts that can reduce increasing nitrogen loading of aquatic ecosystems. Porous aquifers with high nitrate loading are largely electron donor limited and additionally, high dissolved oxygen concentrations are known to reduce the efficiency of denitrification. Therefore, denitrification lag times (time prior to commencement of microbial nitrate reduction) up to decades were determined for such groundwater systems. The stimulation of autotrophic denitrifiers by the injection of hydrogen into nitrate polluted regional groundwater systems may represent a promising remediation strategy for such environments. However, besides high costs other drawbacks, such as the transient or lasting accumulation of the cytotoxic intermediate nitrite or the formation of the potent greenhouse gas nitrous oxide, have been described. In this article, we detect causes of incomplete denitrification, which include environmental factors and physiological characteristics of the underlying bacteria and provide possible mitigation approaches.

The key factor in High Pressure Hydrogenotrophic Denitrification: Hydrogen partial pressure

“…accumulation [40]. Combining biological denitrification with ironbased abiotic nitrite reduction (the addition of Fe(II)-containing minerals) was also suggested to counteract nitrite accumulation and foster complete hydrogenotrophic denitrification [41].…”

Organic matter composition and inorganic nitrogen response to Hurricane Harvey’s negative storm surge in Corpus Christi Bay, Texas

“…Previous studies within the Nueces Estuary have found SGD contributions to be significant (Douglas et al, 2020;Murgulet et al, 2022), with important fluxes of nutrients and DOM that could impact ecosystem health (Douglas et al, 2021a;Douglas et al, 2021b). Though groundwater is generally rich in NO 3 − (Kennedy et al, 2009;Duffner et al, 2021), transport from aquifers to estuaries facilitates conversion to, and accumulation of, NH 4 + in saline and anoxic porewaters (Santos et al, 2009;Lopez et al, 2020;Wong et al, 2020;Douglas et al, 2021b). From the long-term analyses, surface water NH 4 + is negatively correlated with water level (p-value = 0.03) and positively with creek discharge (p-value = 0.02).…”

Development of Bio-Electrochemical Reactor for Groundwater Denitrification: Effect of Electric Current and Water Hardness

“…Nocadia was defined as hydrogen-oxidizing bacteria, and is able to utilize H 2 as the electron donor and O 2 as the electron accepter [27]. Pseudomonas and Thermonas were known as typical active denitrifiers when organic carbon was available; however, these genera were suggested in the main hydrogenotrophic denitrifiers community [28]. Hydrogenophaga was commonly found in the denitrification system, and, after carrying out hydrogenotrophic denitrification, was higher in the BER-10 (2.7%) than that in the BER-20 (1.9%).…”