TRACE ORGANIC COMPOUNDS BROUGHT IN BY THE LAND APPLICATION OF WASTEWATER TREATMENT PLANT SLUDGES

The risk of incorporation of trace organic compounds (TOCs) from biosolids land application to the food chain is being assessed at present by the European Union. The present study aims at evaluating the transfer potential of TOCs from biosolids to crops. The behaviour of three characteristic groups of trace organic compounds (Phtalates, Nonyl Phenol Ethoxylates and Chlorophenols) in a vegetative system has been carried out. With the aim of reclaiming biosolids for agriculture, the transfer potential has been studied in hydroponically grown tomato plants (Lycopersicon esculentum var. Rondello), where transfer should be optimal for hydrophilic compounds. Plant containers inside a temperature and humidity controlled plant house were used.There were two types of experiments. The first involved addition of Trace organic compounds as pure substances to the plant growth solution. A second experiment was carried out under the same conditions, but using filtrate from wastewater treatment plant biosolids as an addition to the plant growth solution. Plants were cultivated over a period of time while being exposed to TOCs, and were later analysed to characterize TOC uptake.The results clearly show a difference in behaviour of the trace organic compounds according to the part of the plant and method of introduction. Generally speaking, for the experiments using pure substances, the roots absorb higher quantities of trace organic compounds and block more or less their transfer to the above ground parts of the tomato plant. However, with the biosolids filtrate, the Di-ethylhexyl phtalate and the Nonyl ethoxylate phenol can be traced all over the plant.