REVIEW OF NATURAL AND ARTIFICIAL DENITRIFICATION OF GROUNDWATER

An approach to securing low nitrate supplies is to take advantage of the bacterially mediated process of denitrification. This paper reviews the factors controlling denitrification and describes the evidence for denitrification in the groundwater environment. It is found that natural denitrification, although not extensive, does occur in a variety of aquifers where there is a sufficient source of oxidizable organic carbon. However, natural processes cannot be expected to remove the large quantity of nitrate now present in many aquifers. Water treatment processes that stimulate artificial denitrification by the injection of the required nutrients are under development, and may offer a simple and inexpensive method of nitrate removal. This paper reviews the various above-ground and underground techniques to determine the advantages and disadvantages of this approach compared with other nitrate removal technology. It is concluded that artificial denitrification as an above-ground process affords the best nitrate removal rates and process control. Compared with alternative technology, namely ion exchange, above-ground biological treatment does not generate large quantities of waste product, but is more difficult to automate. Underground processes have been developed, but their long-term success will depend on restricting blocking of the aquifer matrix with accumulated biological matter.