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-–N) or nitrate nitrogen (NO3-–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.