Innovative techniques for the removal of organic micropollutants from wastewaters

Personal care products are a heterogeneous group of chemicals that include Polycyclic Musk Fragrances (PMFs) as Galaxolide (HHCB), Tonalide (AHTN), Celestolide (ADBI) and Phantolide (AHDI). PMFs are widely spread substances employed in perfumes, detergents and house-cleaning products. The massive use leads to PMF release into the environment mainly through Wastewater Treatment Plants (WWTPs) discharges. Even if Italy is the European country with the highest use of PMFs, only a few data are available about these products’ occurrence in Italian water and about PMF fate in conventional WWTPs. In this, PhD was firstly focused on developing protocols for PMF determination in wastewater and in activated sludge. PMFs in water samples were determined by SPE extraction and analysis in GC-MS with a triple-quadrupole while for the analysis of activated sludge an ultrasonic bath and a GC-Ion trap were employed. Detection limits of selected compounds were considerably lower than sample concentrations. These methods allow the analysis of many samples in short times employing simple instrumentation and limiting the solvent volumes used. After that, PMFs inside an Italian conventional WWTPs was monitored. HHCB and its main by-product, Galaxolidone (HHCB-lactone), were found in concentrations of µg/L, one order of magnitude greater than AHTN, AHDI was always lower than LOD while ADBI was measured only at trace levels. No seasonal variability was recorded in PMF input onto WWTP. In the water phase, HHCB and AHTN evidenced a modest reduction during treatments (20% and 50%, respectively) mainly due to adsorption processes during the biological treatment as suggested by the high stable PMF concentrations in activated sludges. HHCB-lactone registered an increase up to 70% during treatments caused by HHCB biotransformation during biological treatment. This study revealed that current technologies are not enough efficient in removing PMFs from wastewaters which are discharged into the environment. Additional treatments are therefore necessary inside WWTPs. In this, the efficiency of ozonation and adsorption on activated carbon in removing PMFs from wastewaters was assessed. Treatments were tested through two pilot plants installed after the biological treatment in two WWTPs located in Northern Italy. Different conditions were tested to achieve the best compromise between removal efficiencies and management costs. Regarding ozonation, a medium-low dosage of O3 was applied. HHCB was efficiently removed at low O3 dosages and short hydraulic retention times while AHTN and HHCB-lactone were less reactive to oxidation. HHCB-lactone registered insufficient removals even with the highest O3 dosage and hydraulic retention time. Ozonation was effective in removing PMFs from wastewater but high gas dosages may be required to avoid the formation of oxidation by-products. Adsorption on powdered activated carbon (PAC) was tested in a pilot plant consisting on a series of tanks in which PAC is added to the wastewater together with coagulant, microsand and flocculant and can be further recirculated. By operating on water flow, quantity of virgin PAC added to the system and concentration of PAC inside the pilot plant, different setups were studied and satisfactory removals were achieved for all studied compounds even at low concentrations of the two PACs. A dependence between PMF removal efficiency and PAC concentration, quantity of virgin PAC and hydraulic flow rate was highlighted. In our pilot plant, lower dosages of carbon can be further tested in order to obtain high removals together with lower management costs. By comparing two different PACs, the importance of associating the PAC type with the class of compound to remove was highlighted. Overall, both technologies were effective in removing PMFs from wastewaters even if adjustment of operational parameters is needed to obtain great performances with low operating costs.