COMBINED NITRITATION AND CHEMICAL DENITRIFICATION - A NEW TREATMENT SYSTEM FOR NITROGEN REMOVAL FROM LANDFILL LEACHATES / Kombinerad nitritation och kemisk denitrifikation - ett nytt behandlingssystem for att avlägsna kväve ur lakvatten från deponier
Liquids obtained during handling of solid wastes may contain a high concentration of nitrogen (ten times higher than the nitrogen concentration in municipal wastewater). At the same time these liquids contain too low concentration of biodegradable organic material for nitrogen to be removed by conventional denitrification. This paper proposes a new treatment system for leachates that uses chemical denitrification of ammonium rich wastewater. Furthermore, the proposed system consists of two main parts: the first part is a biological step with a SHARON-type reactor, where biological nitritation happens (oxidation of ammonium to nitrite). The second part is chemical denitrification where ammonium or urea is oxidized with nitrite to nitrogen gas and water. Natural chemical denitrification has been investigated earlier and proved to happen in frozen soils, in the drying process of dew and in the dried human urine. It was stated that concentrating of nitrite and ammonium or nitrite and urea plays the most important part for the chemical denitrification. Therefore, the second part of the proposed treatment system begins with the concentrating step. Different proposals for the concentrating step are discussed.