Removal of emerging micropollutants from wastewater discharges by powdered and micro-grain activated carbon - Progress of the CarboPlus® project

International audienceThe implementation of a tertiary treatment in conventional wastewater treatment plants is more and more considered by managers to reduce the emerging contaminant discharges into the aquatic environment. In this context, a collaboration between the public sanitation service of Paris conurbation and the Water Environment and Urban Systems laboratory has been initiated since 2013 to study at large scale a pilot (CarboPlus® - SAUR/STEREAU) based on a high concentration fluidized bed activated carbon reactor (>100 kg/m3) with continuous fresh activated carbon injection. The objectives of this project are to i) characterize the efficiency of the process for emerging pollutants for powdered (PAC) and micro-grain (µGAC) activated carbons, ii) characterize the parameters influencing the sorption mechanism (organic matter, operating parameters, activated carbon structure and properties, etc.) and iii) identify the eventual improvements of the conventional quality parameters.In addition to the 14 campaigns already performed in 2013 in PAC configuration, 14 campaigns have been planed in 2014 (8 already performed) to study the fate of 131 micropollutants, including 61 pharmaceuticals and hormones and 70 other emerging pollutants, in addition to conventional wastewater parameters. This presentation aims at displaying the pilot efficiency in µGAC configuration and comparing it to the PAC configuration. The use of µGAC instead of PAC has several operational and economical advantages, but this new type of carbon was never tested with wastewater. Based on the first 8 campaigns, the results tend to indicate that the pilot is as efficient with µGAC than with PAC. In particular, ketoprofen, paracetamol, ibuprofen, ofloxacin, ciprofloxacin, trimethoprim, roxithromycin, atenolol, propranolol, carbamazepine, oxazepam, lorazepam and estrone have removals higher than 80% in average. In addition, first results on the other emerging micropollutants show high or very high removals for pesticides (60-95%), bisphenol A (60-90%), alkylphenols (60-95%), PFOS (75-95%) and X-ray contrast agents (50-70%). Moreover, the high solid retention time (60-90 days) of the µGAC leads to a biological activity within the reactor, as displayed by NO2- (65-99%) and NH4+ (20-70%) removals. However, the results are still partial at this stage of the project, another µGAC dose is currently tested on the pilot and complementary lab-scale tests are still performed to better understand the sorption mechanism