Variation in organic matter characteristics of landfill leachates in different stabilisation stages

Abstract

This study investigates the effect of landfill age on landfill leachate characteristics; two aspects are focused here. One is ultraviolet absorbance at 254 nm (UV₂₅₄) property, as the discharge of landfill leachates to publically owned treatment works can cause interference with UV₂₅₄ disinfection. The other is biorefractory organic nitrogen in leachates, as it can contribute to effluent nitrogen making it difficult to meet stringent effluent nitrogen regulations. To study variation in UV₂₅₄-absorbing organic carbon and organic nitrogen, leachate samples ranging from cells with ages 2 to 30 y from a large landfill in Kentucky, were collected and fractionated on a basis of their molecular weight and chemical nature into humic acids, fulvic acids and a hydrophilic fraction. The effectiveness of long term landfilling and membrane treatment for organic matter and organic nitrogen removal was examined. Humic materials, which were the major UV₂₅₄-absorbing substances, were mainly >1 kDa and they degraded significantly with landfill age. The hydrophilic organic fraction, which was the major contributor to organic nitrogen, was mainly <1 kDa and it became increasingly recalcitrant with landfill age. This study provides insight into the characteristics of the different leachate fractions with landfilling age that might aid the design of on-site leachate treatment techniques.