Steven Deshayes

Removal of a wide range of emerging pollutants from wastewater treatment plant discharges by micro-grain activated carbon in fluidized bed as tertiary treatment at large pilot scale

Among the solutions to reduce micropollutant discharges into the aquatic environment, activated carbon adsorption is a promising technique and a large scale pilot has been tested at the Seine Centre (240,000 m(3)/d - Paris, France) wastewater treatment plant (WWTP). While most of available works studied fixed bed or contact reactors with a separated separation step, this study assesses a new type of tertiary treatment based on a fluidized bed containing a high mass of activated carbon, continuously renewed. For the first time in the literature, micro-grain activated carbon (μGAC) was studied. The aims were (1) to determine the performances of fluidized bed operating with μCAG on both emerging micropollutants and conventional wastewater quality parameters, and (2) to compare its efficiency and applicability to wastewater to former results obtained with PAC. Thus, conventional wastewater quality parameters (n=11), pharmaceuticals and hormones (PPHs; n=62) and other emerging pollutants (n=57) have been monitored in μGAC configuration during 13 campaigns. A significant correlation has been established between dissolved organic carbon (DOC), PPHs and UV absorbance at 254 nm (UV-254) removals. This confirms that UV-254 could be used as a tertiary treatment performance indicator to monitor the process. This parameter allowed identifying that the removals of UV-254 and DOC reach a plateau from a μGAC retention time (SRT) of 90-100 days. The μGAC configuration substantially improves the overall quality of the WWTP discharges by reducing biological (38-45%) and chemical oxygen demands (21-48%), DOC (13-44%) and UV-254 (22-48%). In addition, total suspended solids (TSS) are retained by the μGAC bed and a biological activity (nitratation) leads to a total elimination of NO2(-). For micropollutants, PPHs have a good affinity for μGAC and high (>60%) or very high (>80%) removals are observed for most of the quantified compounds (n=22/32), i.e. atenolol (92-97%), carbamazepine (80-94%), ciprofloxacin (75-95%), diclofenac (71-97%), oxazepam (74-91%) or sulfamethoxazole (56-83%). In addition, alkylphenols, artificial sweeteners, benzotriazole, bisphenol A, personal care products (triclocarban and parabens) and pesticides have removals lying in the 50 ->90% range. Overall, the fluidized bed of μGAC allows obtaining performances comparable to PAC at the same activated carbon dose. Indeed, the average removal of the 13 PPHs found at a high occurrence (>75%) in WWTP discharges is similar at 20 g/m(3) of μGAC (78-89%) and PAC (85-93%). In addition, this recycled μGAC operation leads to several operational advantages (no FeCl3, reactivable, higher SRT, higher treated flow) and has a stronger impact on the overall wastewater quality compared to PAC.

Fate of emerging and priority micropollutants during the sewage sludge treatment: Case study of Paris conurbation. Part 1: Contamination of the different types of sewage sludge

This article provides data on the contamination of different kinds of sludge (raw, centrifuged, digested, thermally dried sludge and sludge cake) from Paris conurbation by 71 various pollutants including pharmaceutical products (PHPs), hormones, perfluorinated acids (PFAs), linear alkylbenzene sulfonate (LAS), alkylphenols (APs), phthalates (PAEs), polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs). Very high contents of LAS (0.1-10g/kg dry matter - DM) compared to other compounds were found in all types of sludge followed by DEHP (10-100mg/kg DM) and fluoroquinolones (1-100mg/kg DM). APs were measured at intermediary contents in Parisian sludge, lying in the 2-20mg/kg DM range. Finally, hormones, PAHs, PCBs, PAEs, PFAs and the remaining PHPs were all found at contents lower than 1mg/kg DM. For most compounds (PHPs, PFOS, DEHP, PAHs), no significant differences in the micropollutant contents were found for similar types of sludge from different WWTP in Paris, highlighting the homogeneity of sludge contamination in downstream Paris catchment. The variability of concentration is rather high (coefficient of variation >100%) for several PHPs, PFAs or PCBs while it is moderate (<100%) or low (<50%) for fluoroquinolones, hormones, PAHs, APs or LAS. In addition, digestion seems to have a buffer effect as variabilities are lower in digested sludge for PHPs, PFAs, APs and PCBs. During sludge treatment (centrifugation, digestion, thermal drying, sludge conditioning+press filtration), the hormones, LAS, APs, PAHs, DEHP and PCBs concentrations increased, while those of PHPs and PFAs decreased. In the case of digestion, the increase of content can be explained by no pollutant removal or a lower removal than DM removal (concentration phenomenon) whereas the decrease underlines that the compound is more removed than the DM. In any case, these concentration variations presuppose the mechanisms of dissipation that could be attributed to volatilization, biotic or abiotic transformation (complete or with metabolites production), bound residues formation. In addition, data on sludge liquors - centrifuged (CW) and condensed (TDW) waters - from respectively centrifugation and thermal drying were collected. Several hormones, PHPs, PFAs, LAS, PAEs, APs, PCBs and PAHs were quantified in CW and TDW, displaying a transfer through the water removal. The concentrations observed are rather comparable to those found in wastewater.