Demonstration of a Multifunctional Permeable Reactive Barrier for the Treatment of Landfill Leachate Contamination

摘要

A pilot-scale multifunctional permeable reactive barrier (multibarrier) was designed and demonstrated at the Belgian landfill site Hooge Maey for semipassive treatment of landfill leachate containing 190-250 mg L-1 ammonium, 460-690 μg Cl L-1 adsorbable organic halogens (AOX) and 340-543 mg L-1 of chemical oxygen demand (COD). Earlier, the effectiveness of this sequential multibarrier concept, combining different reactive materials and contaminant removal processes, was proven via laboratoryscale column tests performed at a representative groundwater temperature (12 °C). In a second phase, the concept was performed at a pilot-scale level in a 9 m long steel container, comprising different compartments. AOX and COD were efficiently removed by a compartment filled with active carbon, to levels below the regulatory discharge limits of the landfill wastewater treatment system. Nitrification compartments, equipped with diffusive oxygen emitters, were included to convert ammonium microbially to nitrite and nitrite, which at their turn should be converted to N2 in a downgradient denitrification compartment, supplied with an external carbon source. Despite an efficient diffusive oxygen supply, ammonium was insufficiently removed in the nitrification compartments due to exceptionally low winter temperatures inhibiting microbial activity. Nitrificationdenitrification processes are believed to restore with increasing temperatures in Spring. Remaining ammonium concentrations were largely removed by ion-exchange in a compartment filled with clinoptilolite, until saturation of the material occurred. Potential insitu bioregeneration of the saturated clinoptilolite material is currently investigated in laboratory-scale tests.