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Ferric (Fe3+) salt dosing is an efficient sulfide control strategy in the sewer network, with potential for multiple benefits including phosphorus removal in the biological reactors and sulfide emission control in the anaerobic digesters of wastewater treatment plant (WWTP). This paper extends the knowledge on the benefit of iron dosing by exploring its impact on the fate of organic micropollutants (MPs) in the wastewater using sewer reactors simulating a rising main sewer pipe. The sulfide produced by the sewer biofilms reacted with Fe3+ forming black colored iron sulfide (FeS). Among the selected MPs, morphine, methadone, and atenolol had >90% initial rapid removal within 5 min of ferric dosing in the sewer reactor. The ultimate removal after 6 h of retention time in the reactor reached 93-97%. Other compounds, ketamine, codeine, carbamazepine, and acesulfame had 30-70% concentration decrease. The ultimate removal varied between 35 and 70% depending on the biodegradability of those MPs. In contrast, paracetamol had no initial removal. The rapid removal of MPs was likely due to adsorption to the FeS surface, which is further confirmed by batch tests with different FeS concentrations. The results showed a direct relationship between the removal of MPs and FeS concentration. The transformation kinetics of these compounds in the reactor without Fe3+ dosing is in good agreement with biodegradation associated with the sewer biofilms in the reactor. This study revealed a significant additional benefit of dosing ferric salts in sewers, that is, the removal of MPs before the sewage enters the WWTP.

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The chemical, structural, and elemental composition of any adsorbents plays undoubtedly crucial role and has paramount significance in adsorption process. The present study of chemical, structural, and elemental characterization of powdered Pinus densiflora pine cones, lignite and coconut shell-based activated carbon fiber (ACF), and powdered oyster shell prior employed for anionic surfactant sodium dodecyl sulfate (SDS) adsorption was undertaken using field emission scanning electron microscope (FE-SEM), scanning electron microscope coupled with energy dispersive x-ray (SEM-EDX), X-ray diffraction/X-ray powder diffraction (XRD/XRPD), and multiple internal reflectance (MIR) or attenuated transform reflectance -fourier transform infrared spectroscopy (ATR-FTIR) techniques. The FE-SEM imaging observed at three different magnifications depicted the change in surface texture of aforementioned biosorbents before and after SDS adsorption. SEM-EDX analysis indicated alteration in the concentration and distribution of different compositional elements. The XRD analysis suggested the amorphous character in lignite and coconut shell-based ACF and powdered Pinus densiflora cones, whilst indicating the sample of powdered oyster shell to be crystalline in nature and entirely composed of CaCO 3 with the very trivial amount of impurities. Further, infrared (IR) spectroscopy demonstrated variation in IR spectra of the samples prior to and after surfactant adsorption and also further suggested occurrence of complexing or (complexation) process between ionizable functional groups and DS -or Na + ions of SDS. In addition, iodine number of the lignite and coconut shell-based ACF, powdered Pinus densiflora cones, and powdered oyster shell were found to be 285.86 mg/g, 25.01 mg/g, and 28.48 mg/g, respectively.