Microbusters, an integrated approach for the treatment of micropollutants: the key role of suitable analytical tools

The “Microbusters” project, funded by Compagnia di San Paolo and University of Torino, aims to develop an innovative integrated tertiary water treatment for the removal of micropollutants (MPs) such as pharmaceuticals, personal care products, etc…., from natural as well as treated waters. Wastewater treatment plants are not specifically designed nor optimized for MPs abatement at trace concentrations (from few ng/L to several μg/L). Thus, many of these MPs are still present at the end of wastewater treatment processes and can re-enter the water cycle. The presence of MPs in natural waters has been associated with many negative effects, such as short- and long- term toxicity, endocrine-disrupting effects, antibiotic resistance of microorganisms. Microbusters deals with the development of novel materials for optimizing four complementary technologies that have shown promising results in the treatment of MPs, namely membranes, adsorption, biocatalysis and photocatalysis. Moreover, based on the preliminary results, the present research has the ambitious goal of creating a consortium of academic and industrial partners for preparing a proposal under H2020, including the Life Cycle Assessment of new materials and the design of a prototype for MPs abatement in real waters at pilot plant scale. To face these aspects, beside additional expertise in the field of biology, engineering, economics, environmental and soil chemistry, the development of suitable analytical tools for MPs analysis at sub-trace level is mandatory. A list of 16 MPs, chosen on the basis of their presence in surface waters and toxicological interest, has been considered for the development of fast and sensitive UHPLC-MS/MS methods. Since the physical-chemical properties of the chosen analytes range from the high polarity of glyphosate and its degradation product AMPA to the more lipophilic alpha-cypermetrin and nonylphenol, three different analytical methods have been developed. Glyphosate and AMPA have been separated by an HILIC-MS/MS method, whereas the other two methods consist in the separation on an Eclipse XDB-C18 column (4.6x50 mm 1.8 m, Agilent) of eight basic species (caffeine, carbamazepine, tricyclazole, diclofenac, acetaminophen, terbuthylazine, tetracycline, amoxicillin) that ionize in positive ion mode, and of five acidic species (nonylphenol, bisphenol A, butylparaben, triclosan, clofibric acid) that easily ionize in negative ion mode. All the UHPLC-MS/MS methods have been directly interfaced with on-line SPE, not only to purify the water samples, but also to pre-concentrate the MPs on the SPE HLB cartridge (2.1x20 mm, 25 m, Waters) that is able to retain all the analytes thanks to its versatility. The analytes have been loaded on the SPE cartridge for 2 minutes at flow-rate of 2.0 mL/min in order to achieve LOD and LOQ values of the order of few ng/L. All the methods have been validated according to the UNI CEI EN ISO/IEC 17025, evaluating LODs, LOQs, linearity range, sensitivity, reproducibility, selectivity, accuracy, recovery, and matrix effect. The obtained recovery values are greater than 94%, whereas the absence of matrix effect is the result of the optimized washing step of SPE sorbent, which employs a washing volume of about 30-folds the column volume. These analytical procedures will be applied to different water samples (surface river waters, groundwater, samples taken at different stages in a water treatment plant) before and after spiking with a known amount of the 16 MPs, in order i) to perform a screening of their presence and concentration level; ii) assess the matrix effect on their determination. Afterwards the analytical procedures will be applied to evaluate the efficiency of the above-mentioned tertiary water treatments for MPs removal.