Control of microbial contamination in drinking water from microfiltering dispensers by dialysis ultrafilters
Luca BOLELLI, Elida Nora FERRI, Stefano GIROTTI » Abstract » Download full version
Abstract. – Tap water filtering devices are widely employed to improve odor and taste of tap water, or to obtain refrigerated or sparkling drinking water. The presence of disinfectants-resistant bacteria in tap water is responsible of the biofilm formation inside tubes and tanks. The consequent contamination of dispensed water is a well-known hygiene problem because of the quite constant presence of potentially pathogenic bacteria likes P. aeruginosa. In this study, we tested the technical feasibility and effectiveness of the addition to different commercial devices of a packaged polysulphone fibers filter. We aimed to find a simple solution to implement the quality of the delivered water. Water contamination levels were determined in a wide selection of microfiltered water dispensers and we selected among them a representative group of 10 devices, new or in use. The packaged ultrafilter was introduced in about half of them, to monitor, when possible, in parallel the contamination levels and flow rate of a couple of identical units, with and without the filter. The placement of the dialysis filters resulted feasible at different positions along the water circuits of the variously designed filtration units. Delivered water resulted completely free from bacteria when the filter was placed exactly at, or very close to, the outlet in spite of the inner surfaces contamination. This performance was not obtained in presence of a more or less long tract of water circuits downstream the ultrafilter: a significant but not complete reduction of the plate count numbers was observed. The filters worked in continue over the whole study period, ten months, showing exactly the same efficiency. Moreover, the flow rate in presence of the filter was quite unaffected. The addition of this kind of filter to already in use water dispensers was technically easy, and its use can be recommended in all cases a simple but reliable water sanitization is requested.
Keywords: water microfiltration devices; drinking water quality; sterile dialysis filters; P. aeruginosa.
Nadia B. BARILE, Mariaspina SCOPA, Sara RECCHI, Eliana NERONE » Abstract » Download full version
Abstract. – The overall objective of this study was to develop a biological early warning system (Mosselmonitor®) on offshore platform to detect critical environmental situations. The experiment was conducted on oil off-shore platform called Rospo Mare B. This structure is located in the area in front of Molise coast line (Italy, Adriatic Sea), characterized by a depth of about 77 m and a bathymetry between 65 and 80 m. The Mosselmonitor® works with eight mussels connected via specific sensors to PC for recording opening values of valves. A probe was installed inside the instrument to daily control of water pH, dissolved oxygen, salinity and temperature. Water samples are weekly analyzed for heavy metals, organochlorine pesticide and suspended matter. During the entire observation period, closure alarms were predominantly detected (99.9%) and a decrease of 65% in alarms maximum duration was recorded from the fifth week. During the first month, none changes in water physicochemical parameters were observed so that affect the bivalves behavior. The only chemical parameter steadily detected in water was copper; its average concentrations were of 10 ppb. Detected alarms were not comparable to those recorded in the first month: this observation could be explained considering that mussels will be adapted to copper constant presence.
Keywords: Mosselmonitor®, biomonitoring, biosensor, mussel, anthropogenic areas, offshore platform.
Szeged Matrix Property Indices as Descriptors to Characterize Fullerenes
Lorentz JÄNTSCHI, and Sorana D. BOLBOACĂ » Abstract » Download full version » Supplementary material
Abstract. Fullerenes are class of allotropes of carbon organized as closed cages or tubes of carbon atoms. The fullerenes with small number of atoms were not frequently investigated. This paper presents a detailed treatment of total strain energy as function of structural feature extracted from isomers of C40 fullerene using Szeged Matrix Property Indices (SMPI). The paper has a two-fold structure. First, the total strain energy of C40 fullerene isomers (40 structures) was linked with SMPI descriptors under two scenarios, one which incorporate just the SMPI descriptors and the other one which contains also five calculated properties (dipole moment, scf-binding-energy, scf-core-energy, scf-electronic-energy, and heat of formation). Second, the performing models identified on C40 fullerene family or the descriptors of these models were used to predict the total strain energy on C42 fullerene isomers. The obtained results show that the inclusion of properties in the pool of descriptors led to the reduction of accurate linear models. One property, namely scf-binding-energy proved a significant contribution to total strain energy of C40 fullerene isomers. However, the top-three most performing models contain just SMPI descriptors. A model with four descriptors proved most accurate model and show fair abilities in prediction of the same property on C42 fullerene isomers when the approach considered the descriptors identified on C40 as the predicting descriptors for C42 fullerene isomers.
Keywords: nano structure-property relationship; C40 fullerene; C42 fullerene; Szeged Matrix Property Indices (SMPI).