Abstract
This study evaluates the occurrence of flame retardants (FR) in five wastewater treatment plants (WWTPs) located close to Barcelona (NE Spain), an area with high urban and industrial pressures. Compounds studied include eight polybromodiphenyl ethers (PBDEs) and eight New Brominated Flame Retardants (NBFRs), for which little information regarding their presence, partitioning and fate within the WWTPs is available. In unfiltered influent samples, PBDEs were not detected and bis(2-ethyl-1-hexyl)tetrabromophthalate was the only NBFR detected, and all WWTPs were efficient in eliminating this compound as no residues were found in the effluents. However, primary sludge contained from 279 to 2299 ng/g dry weight of ΣFR and the concentration increased in secondary (biological) sludge. NBFRs accounted for the main FR detected in sludge, representing a 63-97% of the total load, and among PBDEs, BDE-209 was the most ubiquitous congener. Considering the amount of sludge generated in each WWTP, it was estimated that 0.34-17.2 kg of FR are released annually through the sludge, which can have negative environmental and health implications if sludge is used as biosolid in agriculture. Overall, this study provides a sampling design and analytical protocol to be used to determine the evolution of FR in WWTPs and compares the levels detected, considering that PBDEs are being phased out to be substituted by other compounds which also have high accumulative and recalcitrant properties.
Highlights
Population growth and the expansion of industrial activities has lead to the generation of large amounts of wastewaters which are commonly treated in Wastewater Treatment Plants (WWTPs) prior to discharge to avoid contamination of receiving waters
This study evaluates the occurrence of flame retardants (FR) in five wastewater treatment plants (WWTPs) located close to Barcelona (NE Spain), an area with high urban and industrial pressures
polybromodiphenyl ethers (PBDEs) and New Brominated Flame Retardants (NBFRs) were determined in influent, effluent and sludge of five WWTPs situated close to Barcelona, an area receiving urban and industrial pressures
Summary
Population growth and the expansion of industrial activities has lead to the generation of large amounts of wastewaters which are commonly treated in Wastewater Treatment Plants (WWTPs) prior to discharge to avoid contamination of receiving waters. Within a conventional activated sludge WWTP, primary sedimentation and biological treatment are combined sequentially to remove the initial wastewater organic matter. Whilst this treatment is efficient to eliminate many organic contaminants from water, it produces the accumulation of apolar compounds in the sludge which is in many cases used as organic fertilizer. NBFRs are used in thermoplastic, elastomeric and thermoset polymer systems, unsaturated polyesters, adhesives, coatings, and textiles, in wire and cable insulation, film and sheeting, in polyurethane foam or styrene polymers [12] Both PBDEs and NBFRs have low water solubilities and a high organic carbon partitioning factors (koc), which imply that they will rapidly sorb to organic and particulate matter. Sixteen compounds were determined in influent and effluent waters and in primary and secondary (biological) sludge
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