Transformation of phthalates in young landfill cells

Phthalic acid diesters are additives in a variety of materials that can end up in landfills. Leachates from a series of full-scale young landfill cells were analysed over time for dimethyl, diethyl, dibutyl, butylbenzyl, and di(2-ethylhexyl) phthalate (respectively designated DMP, DEP, DBP, BBP, and DEHP), and their corresponding monoesters monomethyl, monoethyl, monobutyl, monobenzyl, and mono(2-ethylhexyl) phthalate (MMP, MEP, MbutP, MbenzP, and MEHP, respectively), as well as o-phthalic acid (PA). One landfill cell was created in each of three consecutive years by deposition of the same type of waste in July and August. The pH, volatile fatty acids (VFAs), and total organic carbon (TOC) were measured to characterise development of the degradation phases in three landfill cells, which revealed early acidogenic to initial methanogenic stages. Analysis of the phthalate compounds showed that observed concentrations of the degradation products were below the detection limit in the acidogenic leachates but exceeded concentrations of their corresponding diesters in leachates from cells in the initial methanogenic phase. Maximum and average concentrations of phthalic acid were 50 and 23 mg/l, respectively, and the corresponding values for the other phthalates were 430 and 27 μg/l. The concentrations of all phthalates decreased during the establishment of stable methanogenic conditions.