Occurrence and removal of organic pollutants in sewages and landfill leachates

Sewages of different composition and the effluents of four sewage treatment plants (STPs), plus sewage sludges were analysed for sentivolatile organic priority pollutants. Furthermore, 11 landfill leachates were analysed to evaluate their contribution to sewage pollutants when co-treated. Bis(2-ethylhexyl) phthalate (DEHP) was the pollutant occurring at highest concentrations (up to 122 mug/1) and it was present in all sewages and leachates; concentrations of other phthalates were usually below 17 mug/1. Some polycyclic aromatic hydrocarbons (PAH) ( < 1 mug/1) and 2,6-dinitrotoluene ( less than or equal to 5.9 mug/1) were also present in many of the sewages and leachates. Phthalates were present in STP effluents in low concentrations (<8 mug/1), while PAHs were usually not present. DEHP concentrations were at the same level in the sewage consisting of household wastewater and stormwater runoff and the sewages also including industrial discharges and landfill leachates, while PAHs were present in sewages containing industrial discharges. Leachate contribution to the total pollutant load to the STP was less than 1%. Sorption of DEHP to different particle size fractions in sewage was studied by serial membrane filtration. Most of the DEHP (71-84%) was attached to the particles 0.1-41 mum in size, and approximately 10-27% of the DEHP was sorbed on particles larger than 41 mum. Less than 6% of the DEHP was in the fraction below 0.1 mum and readily available for microbial degradation. (C) 2002 Elsevier Science B.V. All rights reserved.