Nitrate potentially has a major impact on the quality of groundwater for potable supply. Conventional treatment methods to control nitrate problems in abstracted groundwater are expensive, in terms of unit costs and environmental impact. Utilizing the natural denitrifying capacity of aquifers offers an alternative approach to nitrate management based on in-situ bioremediation, which may have a number of strategic advantages including financial benefits and environmental sustainability. This paper reviews a range of literature from different scientific disciplines, regarding the physical and biological factors controlling denitrification in fissured aquifers, to assess whether in-situ bioremediation of nitrate in Chalk groundwaters is technically feasible. The principal conclusion is that, despite the dual-porosity operating in this type of aquifer, nitrate removal by engineered, in-situ bioremediation is potentially a viable and practicable method for treating groundwater. Process optimization could be achieved by investment in a programme of fundamental research in a number of key areas. The review highlights the need for a combined experimental and modelling approach, to satisfy the data and predictive requirements for configuring in-situ bioremediation systems at the field-scale. It also provides the necessary conceptual basis for developing a combined macroscale hydrogeological and biochemical model of denitrification activity in Chalk aquifers.

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