Luigi Falletti

Polyfluorinated Organic Micropollutants Removal from Water by Ion Exchange and Adsorption

Polyfluorinated organic micropollutants have been recently found in ground water in some industrialized areas of Veneto Region (north-east Italy). Very recent studies evidenced their presence also in River Lambro near Milan (Castiglioni et al, 2015). These compounds can be removed by adsorption on activated carbon with high efficiency, but frequent regeneration is requested especially because of polyfluorobutylic acid (PFBA) and polyfluorobutyl sulfonate (PFBS) that saturate activated carbon much more quickly than heavier molecules as polyfluoro-octanoic acid (PFOA) and polyfluoroctyl sulfonate (PFOS). In this research work an alternative solution based on ion exchange resins and/or polystyirenic adsorbents was tested both in laboratory with batch tests and on pilot-scale with a continuously fed plant. Experimental work is still in progress and is focused on five different materials supplied by Purolite® Italia and called respectively A600E, PAD500, PAD428, A520E and MN102. Laboratory batch experiments were (and are) performed in order to study both sorption kinetics and spent resin regeneration; four materials have been tested until now: A600E, PAD500, A520E and MN102. Sorption isotherms showed a progressively decreasing adsorption capacity following the order PFOS>PFOA>PFBS> PFBA indicating a dependence of sorption phenomena both on the length of the perfluorinated tail and the pKa of the polyfluorinated acid. Further, batch experiments showed that for A600E the best regenerating solution was a 2 % NH4Cl and 1 % NaCl aqueous solution. Pilot-scale experiments were (and are) conducted in cooperation with the water service company Centro Veneto Servizi of Monselice (PD, Italy) nearby a drinking water treatment plant. The pilot plant was and is made of four parallel columns filled with different materials, each one with a volume of 350 mL and fed with 35 mL/min (2.1 L/h ) microfiltered water; so residence time is 10 min and surface hydraulic load is 3.0 m3/m2h. Four materials have been tested until now: A600E, PAD500, PAD428 and MN102. Results of first 800 h working (that correspond to a total treated water volume which is ca. 4,500 times the volume of material in each column) were excellent for PFOA and PFOS removal, but a rapid decrease in PFBA and PFBS removal efficiency was encountered with PAD500 and PAD428. Further experiments are scheduled to test A520E on pilot-scale. Moreover, it would be interesting to test more hydrophobic resins which may display an increased affinity for super hydrophobic PFAS anions reducing competitive action of anions such as nitrates and sulfates.

Small wastewater treatment plants in Italy: situation and case studies of upgrading with advanced technologies

ABSTRACT The choice between centralization and decentralization of wastewater treatment depends on many factors and requires a case-specific approach. In Italy, 92% of plants have a potentiality of less than 10,000 p.e., but altogether they treat 31% of total pollutant load. They must comply with different local regulations and they have higher specific costs than larger plants. This paper reports some examples of upgrading small overloaded plants with advanced technologies such as lamellar settlers, dissolved air flotation (DAF), moving bed biofilm reactors (MBBRs), and membrane biological reactors (MBRs). In plant nr. 1, nitrification was improved by converting part of the aerated tanks into hybrid MBBRs. Plant nr. 2 was upgraded by converting an out-of-use tank into a tertiary MBBR. Plant nr. 3 was upgraded by introducing lamellae into the settler and converting a thickener into a tertiary MBBR. In plant nr. 4, a DAF unit was installed as a primary treatment to remove Total Suspended Solids and part of...

Identification and quantification of linear and branched isomers of perfluorooctanoic and perfluorooctane sulfonic acids in contaminated groundwater in the veneto region

Perfluoroalkylated acids (PFAAs) are ubiquitous xenobiotic substances characterized by high persistency, bioaccumulation potential and toxicity. They have generated global concern because of their widespread presence both in water and biota compartments. In the past four years, alarming levels of these pollutants have been found in both surface and groundwater collected in an area covering more than 150 square kilometers in the south-western part of the province of Vicenza (Veneto region, Italy). One of the sources of the contamination recognized by local authorities is a fluorochemicals production plant that produced PFAAs since late sixties by electrochemical fluorination involving the obtainment of a complex mixture of linear and branched isomers. Branched isomers account for a significant part of total long chain homologues (22%-35%). Because of the potential threat to public health and the absence of specific limits set for these pollutants by Directive 98/83/EC, local authorities have established the following performance limits for drinking water: 90 ng L-1 for PFOA + PFOS, (reduced to 40 ng L-1 in the most contaminated municipalities), 30 ng L-1 for PFOS and 300 ng L-1 for the sum of all other PFAAs. Given the non-negligible incidence of branched isomers, it appears very important to correctly identify and quantify their contribution to total PFAAs. A liquid chromatography-electrospray ionization tandem spectrometry LC-MS/MS method, coupled with solid phase extraction, was developed to identify and quantify 25 PFAAs including six branched isomers of PFOS and four branched isomers of PFOA. Expanded uncertainty, recovery and precision were determined and found to agree with the reference EPA method 537:2009. The quantification limit is comprised in the 1-5 ng L-1 range.