Removal of ammoniacal nitrogen from landfill leachate by irrigation onto vegetated treatment planes

Leachate is a contaminated liquor resulting from the disposal of solid and liquid wastes at landfill sites that must be treated before discharge. Vege tated leachate treatment planes have been used at landfill sites in the UK but have received little scientific attention. This paper describes studies of model leachate, treatment planes with a focus on the removal of ammonia cal nitrogen (NH3-N). Small-scale and field-scale experimental treatment pl anes were constructed, filled with clay loam soil and vegetated with grass (Agrostis stolonifera). Landfill leachate was applied at hydraulic loading rates ranging from 17-2171/m(2)/d. An exponential relationship was used to characterise the pattern of NH3-N removal. No relationship was observed bet ween the hydraulic loading rate and the NH3-N removal rate constants (R-2 = 0.0039). The daily specific NH3-N mass removal rate was found to be linear ly related to the NH3-N concentration at the start of that day of treatment (R-2 = 0.35). Possible causes of variation in the rate of NH3-N removal be tween experiments are discussed. A simple inorganic nitrogen balance indica ted that the mass of NH3-N and NO2-N removed was not accounted for by NO3-N production. Explanations for this apparent nitrogen deficit are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.