Electrochemical removal of nitrates from drinking water and effluents
A process has been developed for the removal of nitrates from drinking water and effluents based on the cathodic reaction NO(3)(-) + 10H(+) + 8e(-) -> NH(4)(+) + 3H(2)O. In this process, the products formed in the cathodic compartment are subsequently transported to the anodic compartment, where they are oxidised anodically to nitrogen; 2NH(4)(+) + 8OH(-) -> N(2) + 8H(2)O + 6e(-). The balance of the current between the cathodic and anodic compartment goes to the formation of oxygen. The process was demonstrated by small scale experiments in simple laboratory cells with a 10 cm2 copper cathode, followed by studies in larger cells up to 500 cm2 electrode area. A significant number of experiments has been carried out, where the current density, the reagent concentrations and the pumping rates were varied. It was found that the nitrate reduction proceeds approximately as a first order reaction, which is an indication that the process is (at least partly) mass transfer controlled. The experimentally found reaction rate constant is about 3.5 x 1.0 E-6 m/s. The nitrate concentration could be reduced to values below 30 mg/l and the ammonia concentration of the liquid leaving the anodic compartment is reduced to much less than 1 mg/l. It has thus been demonstrated that the method for the electrochemical decomposition of nitrates is suitable for the treatment of effluent waters with a high nitrate concentration, as well as for the preparation of drinking water from surface waters with excessive nitrate content (above 50 mg/l).
Bibliographic Reference: Paper presented: Conference : Electrochemical Processing - A Clean Alternative, Toulouse (FR), April 24-27, 1995
Availability: Available from (1) as Paper EN 38914 ORA
Record Number: 199510649 / Last updated on: 1995-07-07
Original language: en
Available languages: en