Nitrate concentrations in surface water and especially in ground water have increased in Canada, the United States, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that ion exchange and biological denitrification are more acceptable for nitrate removal than reverse osmosis. Ion exchange is more viable for ground water while biological denitrification is the preferred alternative for surface water. This paper reviews the developments in the field of nitrate removal processes.

Nitrate Removal From Drinking Water—Review

New methods of nitrate removal from water.

Biological nitrate removal from water and wastewater by solid-phase denitrification process.

Imbalances in the nitrogen cycle caused by human activities (combustion, fertiliser-intensive agriculture) have resulted in alarmingly increased levels of nitrate in groundwater and other water bodies, with potentially health-threatening consequences. The electrocatalytic removal of nitrate from polluted water is a promising alternative to bacterial denitrification, provided that full selectivity to harmless N2, which can be returned to the atmosphere, is achieved. This perspective article discusses the state-of-the-art of research on electrocatalytic denitrification, critically evaluating the obstacles still hampering large-scale application of this technique. The milestones of fundamental research focussing on the cathode reaction will first be dealt with, followed by their translation into electrochemical reactors of practical interest. Finally, a short foray into the novel field of bioelectrochemical reactors will close the article. Challenges and opportunities pertaining to these three topics will be analysed.

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Powering denitrification: the perspectives of electrocatalytic nitrate reduction

Effects of macrophytes and external carbon sources on nitrate removal from groundwater in constructed wetlands.

Biological water denitrification—A review

The continuous denitrification of drinking water was performed by microorganisms from activated sludge chemically immobilized in a water-soluble polymer. The influence of temperature, pH, input nitrate and dissolved oxygen concentrations on the process rate was studied. Nitrates were reduced on average from 25.8 to 6.8 mg dm -3 NO 3 - -N over a 100-day operation

Water denitrification by an immobilized biocatalyst

Soil-dwelling annelids of the genus Enchytraeus are used in ecotoxicology for testing of chemicals mixed in artificial soil or for testing of wastes and soils of unknown quality. ISO 16387 describes a method for determining the effects of substances or contaminated soils on survival and reproduction of Enchytraeus albidus or of the smaller species Enchytraeus buchholzi or Enchy-traeus crypticus. After the total test duration of 6 (or 4) weeks, the juveniles hatched in the meantime are counted. There are several possible extraction techniques, which are always followed by counting the juveniles by hand, but none of them seems easy to handle. We proposed a new modification of the worm extraction method using flotation of fixed and stained juveniles followed by taking a photograph. The digital image of the juveniles is evaluated by computer processing. It makes the counting of juveniles much easier and less labor intensive.

Vít Matějů

Papers

Biological water denitrification—A review

Water denitrification by an immobilized biocatalyst

The reproduction of Enchytraeus sp.--technical improvement for the counting of juveniles.