Nitrogen removal from recycled landfill leachate by ex situ nitrification and in situ denitrification

A three-compartment system, comprising a landfill column with fresh municipal solid waste, a column with a well-decomposed refuse layer as methane producer, and a sequential batch reactor as ex situ nitrifying reactor, was employed to remove nitrogen from municipal solid waste leachate. Since food waste comprised a major portion of refuse collected in Shanghai, an intense hydrolysis reaction occurred and caused the rapid accumulation of ammonia nitrogen (NH₃-N) and total organic carbon in the leachate. This paper discusses the role of the three mentioned units and the design and operation of the proposed system. With most NH₃-N being converted to nitrite nitrogen (NO₂^- s(-) N) or nitrate nitrogen (NO₃^- s(-) N) by the nitrifying reactor, and with the well-decomposed refuse layer transforming most dissolved organic compounds to CO₂, carbonates and methane, it was found that the fresh refuse column could efficiently denitrify the hydrolyzed nitrogen to N₂ gas. The role of the three mentioned units and comments on the design and operation of the proposed system are also discussed. © 2005 Elsevier Ltd. All rights reserved.