RESUMEN
High salinity in sewage sludge can affect not only the operation of wastewater treatment plants (WWTPs) but also the quality of treated water generated, thereby limiting its downstream reuse. Using data on geochemical parameters, both for the central WWTP in Abu Dhabi, UAE, and literature values for potential regional saline water sources (e.g., shallow groundwater and regional Arabian Gulf seawater), a variety of chemical fingerprinting diagnostic ratios were calculated and plotted in order to determine the source of salinity in the municipal sewage. Data were compared with data from a regional WWTP that was not impacted by salinity. Monitoring data demonstrated persistently elevated levels of salinity in the municipal wastewater arriving at the central WWTP from the city. Dilution/concentration analysis using a conductivity vs. chloride plot showed both potential sources, i.e. Arabian Gulf seawater and coastal hypersaline groundwater, as feasible sources of wastewater salinization. Further diagnostic analysis using a Panno Plot indicated that coastal groundwater was the only likely source of salinization of municipal sewage. Additional confirmation of the identity of the source and the extent of mixing using different lines of evidence like stable isotope ratios is recommended for future study.
Asunto(s)
Monitoreo del Ambiente , Agua Subterránea/química , Salinidad , Agua de Mar/química , Aguas del Alcantarillado/química , Ciudades , Isótopos/análisis , Emiratos Árabes Unidos , Purificación del AguaRESUMEN
In this study, multi-walled carbon nanotubes (MWNTs) were employed to remove benzene, toluene, ethylbenzene, and xylenes (BTEX) from low and high salinity water pre-equilibrated with crude oil. The treatment endpoint of crude oil-contaminated water is often controlled by BTEX compounds owing to their higher aqueous solubility and human-health toxicity compared to other hydrocarbons. The MWNT sorbent was extensively characterized and the depletion of the organic sorbate from the produced water was monitored by gas chromatography-mass spectrometry (GC-MS) and total organic carbon (TOC) analyses. The equilibrium sorptive removal of BTEX followed the order: ethylbenzene/o-xylene > m-xylene > toluene > benzene in the presence of other competing organics in produced water. Sorption mechanisms were explored through the application of a variety of kinetics and equilibrium models. Pseudo 2(nd) order kinetics and Freundlich equilibrium models were the best at describing BTEX removal from produced water. Hydrophobic interactions between the MWNTs and BTEX, as well as the physical characteristics of the sorbate molecules, were regarded as primary factors responsible for regulating competitive adsorption. Salinity played a critical role in limiting sorptive removal, with BTEX and total organic carbon (TOC) removal falling by 27% and 25%, respectively, upon the introduction of saline conditions. Results suggest that MWNTs are effective in removing risk-driving BTEX compounds from low-salinity oilfield produced water.