Wastewater treatment nitrate removal

Electrochemical wastewater treatment — may involve (a) -> electrolysis with the purpose of heavy metal ion removal, (b) electrochemical transformation of anions, e.g., perchlorate, nitrate, (c) oxidation of organic pollutants, (d) - electrodialysis, or (e) - capacitive deionization. 

Cellulose acetate (CA) is still considered the preeminent membrane for wastewater treatment because it is capable of producing the highest flux per unit surface area at specified levels of solute rejection. The rejection performance of RO using a 90% sodium chloride rejection CA membrane was studied. Phosphorous removal was greater than 95% in all cases. Ammonia removals were generally in excess of 90%, and nitrite and nitrate removals generally ranged from 84% to 97% (32). 

Even a combination of primary and secondary wastewater treatment systems will not remove dissolved inoi anic materials such as toxic metal ions, nutrients such as nitrate ions (NO ) or ammonium ions (NH ), or non-biodegradable organic compounds such as chlorinated hydrocarbons. These materials can be removed by a variety of tertiary wastewater treatment methods that are selectively introduced where the nature of the wastewater requires them. One obstacle to tertiary treatment is the initial expense of modifying sewage treatment plants and the ongoing expense of additional treatment. 

Nitrification has been extensively investigated as a very useful process in the first step of nitrogen removal in biological wastewater treatment. The oxidation of ammonia and nitrite by nitrifying processes generates nitrate for denitrifying processes where nitrate is converted to molecular nitrogen. 

Tertiary sewage treatment is essentially a chemical treatment that removes the fine particles, nitrates, and phosphates in wastewater. The basic procedure is adjusted for the specific substance to be removed. Activated charcoal filtration, for example, is used to remove most of the dissolved organic compounds. And alum (Al2(S04)3) is used to precipitate phosphate ions by dissolving and freeing the aluminum cation. 

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