title: Sorption and desorption of diverse contaminants of varying polarity in wastewater sludge with and without alum.
abstract: Sewage sludge sorption and desorption measurements were conducted for nine diverse contaminants of varying polarity: caffeine, sulfamethoxazole, carbamazepine, atrazine, estradiol, ethinylestradiol, diclofenac, and, for the first time desethylatrazine and norethindrone. Two types of sorption behaviour were observed. Compounds with a log octanol-water partition coefficient, log Kow, below 3 showed little or no sorption over 48 hours of shaking, while compounds with log Kow over 3 showed 30 to 90% sorption within the first few minutes. After 6 hours of shaking, mass loss through suspected biotransformation became evident for some compounds. At the pH range considered (5.7-6.7), diclofenac (pKa 4.0, log Kow 4.5) was the only compound in which pH dependent sorption could be quantified. The log sewage sludge-water distribution coefficients, log Kd, ranged from 0.2 to 2.9, and, as expected, increased with increasing log Kow of the compound and organic carbon (OC) content of the sewage sludge. A sewage sludge precipitated with alum had a substantially lower Kd values, as well as lower OC content, compared to alum-free sludge. Desorption was studied by sequentially replacing supernatant water. With each water replacement, log Kd values tended to either remain similar (following a linear isotherm) or in some cases increase (following a Freundlich-type isotherm). The length of time required to restore equilibrium increased with each rinsing step. A literature review of reported Kd values compared well with the alum-free sludge data, but not the alum-sludge data. Sewage sludge Kd across the literature appear more consistent with increasing Kow.
authors: Department of Chemistry, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montreal, QC H3C 3J7, Canada. sebastien.sauve@umontreal.ca.
authors: M-F
authors: MF
authors: Morissette
authors: S
authors: S
authors: Vo Duy
authors: H P H
authors: HP
authors: Arp
authors: S
authors: S
authors: Sauvé
mesh_terms: D000327:Adsorption; D000534:Alum Compounds / Q000032:analysis / Q000737:chemistry*; D008956:Models, Chemical; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D000534:Alum Compounds; D062065:Wastewater; D014874:Water Pollutants, Chemical; C041524:aluminum sulfate