English abstract
Contaminants of emerging concern (CECs) is a term used to describe unregulated chemicals, including pharmaceuticals and personal care products (PPCPs), present in environmental matrices (mainly water) at very low concentrations. However, they have potential to cause unknown or suspected ecological and public health effects. Recently, they have been considered as issue for many scientific studies due to its frequent detection in various natural waters and wastewaters. They are not regulated by legislation and not included in routine monitoring programs. Here, wastewater samples from three sewage treatment plants (STPs) (old Al Ansab, new Al Ansab and A'Seeb) in Muscat Governorate, Sultanate of Oman were obtained and analyzed for occurrence and levels of diclofenac, caffeine, paracetamol, tetracycline, triclosan, ibuprofen, and sulfamethoxazole using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). In addition, correlation between the detected CECs and physicochemical parameters of wastewater samples (conductivity, pH, total organic carbon or TOC and turbidity) were examined. Prior to actual analyses, the solid phase extraction (SPE) using C18 cartridge was assessed using two spiking concentrations (0.1 ppb and 0.5 ppb) of the standard mixture solution containing all the selected CECs. The result showed recoveries for the investigated CECs ranging from 82 to 100%. In wastewater samples from the 3 STPs, all compounds were detected except ibuprofen and sulfametoxazole with detection of sample percentages ranging from 15% (for triclosan) to 65% (for diclofenac). The wide variability in concentrations reported here for the selected CECs were found mainly in wastewater samples obtained before aeration tanks dominantly in old Al Ansab STP, a conventional STP still receiving raw wastewater via tankers. Generally, the detection of the CECs may be influenced by various factors including low levels in wastewater samples, effectiveness of STPs in removal of such contaminants and likely the delayed elution of the compounds retained in the C18 cartridge. While all detected CECs exhibited significant correlations with turbidity, diclofenac and paracetamol were also significantly related to pH and TOC of the wastewater samples. Overall, the study provided quantitative data on presence and levels of typical aforementioned CECs for wastewater samples from Oman.
