Limitation of the concentration of organic pollutants in sewage sludge for agricultural purposes: A case study in South Spain

In 2000, the EU published the third draft of a future sludge directive entitled “Working document on sludge” where limit values for some organic compounds, including di-(2-ethyhexyl)phthalate (DEHP), sum of nonylphenol (NP), nonyphenol mono-(NP1EO) and diethoxylates (NP2EO), seven polychlorinated biphenyl congeners (PCB), polycyclic aromatic hydrocarbons (PAH) and linear alkylbenzene sulphonates (LAS), are fixed. In the present work, the monitoring of these organic compounds in sludge samples from four wastewater treatment plants (WWTPs) is reported. All WWTPs use anaerobic biological stabilization of sludge. The highest concentration levels were found for LAS, NPE and DEHP, in this order, with, in general, anaerobically-digested dehydrated sludge and compost samples being the most contaminated samples. DEHP, NPE, LAS and PAH were found at concentration levels above the limit values fixed in the third draft of the future EU sludge directive in the 44%, 88%, 13% and 6% of the analyzed anaerobically-digested dehydrated sludge and compost samples.