Biomedical subjects

P Pavan

Publications and source records attributed to P Pavan.

At least 19 recordsLinked to original sources

PubMed2006

Observation of 54Ni: cross-conjugate symmetry in f7/2 mirror energy differences.

Gamma decays from excited states up to Jpi=6+ in the N=Z-2 nucleus 54Ni have been identified for the first time. Level energies are compared with those of the isobars 54Co and 54Fe and of the cross-conjugate nuclei of mass A=42. The good but puzzling f7/ cross-conjugate symmetry in mirror and triplet energy differences is analyzed. Shell model calculations reproduce the new data but the necessary nuclear charge-dependent phenomenology is not fully explained by modern nucleon-nucleon potentials.

Journal Article↗

PubMed2006

Dry anaerobic digestion of differently sorted organic municipal solid waste: a full-scale experience.

This paper presents a comparison of dry anaerobic digestion reactors fed with differently sorted municipal organic solid wastes. One reactor was fed with source sorted organic wastes and a second reactor was fed with mixed organic wastes consisting of grey wastes, mechanically selected municipal solid wastes and sludge. The two reactors utilised the same process (Valorga) and operational conditions at full scale. The results of the study emphasise the influence of the kind of treated material on the process performances, especially in terms of biogas and methane production, thus, energy reclamation. The reactor treating the source sorted organic waste and the reactor treating the mixed organic wastes generated some 200 m3 and 60 m3 of biogas per ton of waste treated, respectively, while the specific methane production was some 0.40 and 0.13 m3CH4/kgTVS, respectively. The mass balance and the final fate of the digested material from the two reactors were also clearly different. As for the costs, these were some 29 Euro per ton of treated waste (50% for personnel) and 53 Euro/ton for disposing of the rejected materials. Incomes were some 100 Euro/ton (on average) and an other 15 Euro/ton came from green certificates. The initial investment was 16 million Euros.

Anaerobiosis↗

PubMed2006

Application of a membrane bioreactor for the treatment of low loaded domestic wastewater for water re-use.

This paper describes the demonstrative scale application of a membrane biological reactor (MBR) for low loaded domestic wastewater with low attitude to biological treatment (carbon/nitrogen approximately 5). The biological process was managed by the automatically controlled alternate cycles allowing for re-use purposes with a remarkable reduction of the operational costs. The global process evaluation revealed the system capability of obtaining high nitrogen removal (effective nitrogen removal of 69%) thanks to its high flexibility related to the hourly loading fluctuation. Moreover, high removal of heavy metals and polycyclic aromatic hydrocarbons (PAH) was obtained due to the perfect retention capability of the membranes. In-depth studies were conducted to determine the process behaviour for activated sludge over aeration and with addition of exogenous carbon. Limitation of sludge over aeration and energy savings were observed with a gradient air supplying method. The addition of exogenous carbon (acetic acid up to carbon/nitrogen approximately 9) led to complete nitrogen removal (Ed = 96%) and permitted biological phosphorus uptake. In conclusion, it was been found that the coupled process alternated cycles-MBR had the capacity to remove COD, BOD, N, P and suspended solids, as well as heavy metals and organic micropollutants, resulting in high quality effluent suitable for re-use purposes.

Biomass↗

PubMed2006

Anaerobic co-digestion of sludge with other organic wastes and phosphorus reclamation in wastewater treatment plants for biological nutrients removal.

This paper deals with the performances obtained in full scale anaerobic digesters co-digesting waste activated sludge from biological nutrients removal wastewater treatment plants, together with different types of organic wastes (solid and liquid). Results showed that the biogas production can be increased from 4000 to some 18,000 m3 per month when treating some 3-5 tons per day of organic municipal solid waste together with waste activated sludge. On the other hand, the specific biogas production was improved, passing from 0.3 to 0.5 m3 per kgVS fed the reactor, when treating liquid effluents from cheese factories. The addition of the co-substrates gave minimal increases in the organic loading rate while the hydraulic retention time remained constant. Further, the potentiality of the struvite crystallisation process for treating anaerobic supernatant rich in nitrogen and phosphorus was studied: 80% removal of phosphorus was observed in all the tested conditions. In conclusion, a possible layout is proposed for designing or upgrading wastewater treatment plants for biological nutrients removal process.

Anaerobiosis↗

PubMed2005

Auto-nucleation and crystal growth of struvite in a demonstrative fluidized bed reactor (FBR).

The experience of P removal by auto-nucleation and crystal growth of struvite (MAP) in a demonstrative plant is proposed. The demonstrative plant is located in a municipal wastewater treatment plant in northern Italy. The trials are a consequence of previous experimentation carried out using silica sand as seed material. Working in metastable conditions the auto-nucleation process is performed, and allows the control of the precipitation and the growth of MAP inside the FBR reactor. No scaling problems are observed in the collecting pipes. After the treatment of 650m3 of anaerobic supernatants, 0.28 tons of granulated crystalline MAP are produced. The chemical analysis shows its possible use in agriculture as fertilizer. Operative costs analysis confirms the SCP as a cheap way to remove and recover P from anaerobic supernatants.

Anaerobiosis↗

PubMed2004

Viscoelastic response of the periodontal ligament: an experimental-numerical analysis.

A viscoelastic constitutive model for the periodontal ligament (PDL) capable of accounting for large strains, anisotropy, and inelastic time-dependent effects was developed. Anisotropy characteristics are determined by the composite nature of the tissue and, in particular, by the distribution of collagen fibres. Time-dependent viscous phenomena are due to microstructural modifications during loading, such as fluid fluxes moving through the solid matrix and the internal rearrangement of fibers and constitutive adaptation. The viscoelastic model presented here was implemented in a general purpose finite element code. In vitro experimental tests were carried out on the PDL specimens of adult pigs to obtain stress-relaxation and cyclic stress-strain curves. The comparison of experimental and numerical results revealed good correspondence and confirmed the capability of the formulation assumed to properly interpret the viscoelastic behavior of the PDL.

Animals↗

PubMed2003

Semi-dry thermophilic anaerobic digestion of the organic fraction of municipal solid waste: focusing on the start-up phase.

The paper concerns the results of a pilot-scale study of the simulation of the start-up phase of the thermophilic semi-dry anaerobic digestion of the organic fraction of municipal solid wastes. The aim of the study was to aid and shorten the start-up phase of the full-scale plant (500 t/d) in Verona--Ca' del Bue, where the semi-dry anaerobic digestion process is being used. The substrate used in the experimentation was the mechanically sorted organic fraction of municipal solid waste (MS-OFMSW) enriched with the putrescent fraction from the source sorted OFMSW in order to simulate the substrate which is dealt with in the Verona plant. The results of the pilot scale study agreed with literature data and previous work of the authors: it showed a specific gas production of 0.23 m3/kg TVSfeed and a gas production rate of 2.1 m3/m3 d when operating at a specific organic loading rate of 0.135 kgTVSfeed/kgTVSreacter d. No problems regarding process stability were encountered in the gradual acclimation of the biomass. The design organic loading rate of 9 kg TVSfeed/m3reactor d was reached in about 30 days, during which the total solids content in the feedwas increased. Only a partial comparison with the full scale start-up, which is now in progress, is possible: this shows an initial general concordance with the results found in previous work.

Bacteria, Anaerobic↗

PubMed2003

The under sink garbage grinder: a friendly technology for the environment.

The use of garbage grinders is not a usual practice in Europe, but it is in other countries around the world (e.g., North America, Japan and Australia). Sometimes, garbage grinders are accused of producing problems in sewers and wastewater treatment plants and are prohibited by environmental protection laws. In this study, the different impacts determined by the use of this technology were considered to show the positive impacts of its use. In particular, it was shown that garbage grinders enable the disposal of household organic wastes with advantages for the wastewater treatment processes because of an increase in the carbon/nutrients ratio in the wastewater. This is particularly important for biological nutrients removal processes. Daily specific contributions for person equivalent (PE) due to organic waste disposal through garbage grinders were found to be equal to 75 gCODPE(-1) d(-1) for carbon (as COD), 2.5 gNPE(-1) d(-1) for nitrogen and 0.25 gPPE(-1) d(-1) for phosphorous, respectively. Those determined a value of 30 for the COD/N ratio. Moreover, no problems with solids settling in sewers were noted. These results were extensively compared with literature data. The economical balance showed that the use of garbage grinders allowed a global saving of some 17 Euro year(-1) for a three people family. Important benefits are also gained from an environmental point of view (e.g, organic wastes disposal nutrients removal in wastewater treatment and increase in biogas production with energy reclamation).

Conservation of Natural Resources↗

PubMed2002

The monitoring of a two step aerobic-anoxic process with separate biomass to enhance performance in the treatment of liquid industrial wastes.

The paper presents the results of a one-year study of the performance of a full scale plant for the treatment of industrial liquid wastes adopting the alternate cycle process. The carbon and nitrogen removal performances were discussed according to the experimental measurements of maximum nitrification and denitrification rates. It was demonstrated that the nitrification process was the limiting step: it worked with a rate in the range 0.002 - 0.02 KgNH4-N kg(-1)VSS d(-) at 20 degrees C. This was because of inhibition phenomena due to the presence of both complex organic compounds and heavy metals which were not removed by the chemical-physical pre-treatment step. The denitrification process was characterized by a maximum rate ranging from 0.015 to 0.056 Kg NO3-N kg(-1)VSS d(-1) at 20 degrees C, according to the available amount of readily biodegradable COD in the treated wastes. The reliability of the aerobic-anoxic process was determined on the basis of the percentage of successful cycles compared with the performed ones. It was shown that the actual cycles ranged from 50 to 100% of the expected ones, while effective cycles were up to 84% in the first step and up to 60% in the second one. These were related to the carbon to nitrogen ratio. Even if at times the nitrogen and carbon removal yields were not satisfactory, the two step aerobic-anoxic process operated in the alternate cycle mode seems a successful solution for the treatment of liquid industrial wastes.

Bacteria, Aerobic↗

PubMed2002

The AF-BNR-SCP process as a way to reduce global sludge production: comparison with classical approaches on a full scale basis.

The paper presents a comparison between the performances of two full scale wastewater treatment plants operating in Italy, considering the mass balances including P treatments, and results coming from an analysis of 16 similar plants in Europe and USA, in order to evaluate sludge overproduction due to chemical P removal adoption. Specific production of 9.5 and 12.5 kgTS/P.E.y were found for a BNR and denitrification plant scheme respectively. These results were compared, on a mass balance basis, with the performances coming from the adoption of the integrated waste/wastewater cycles, in which OFMSW fermentation is used as C source to promote BNR performances and P removal from anaerobic supernatants as struvite crystals. ASM2 simulations are used to verify the advantages coming from this approach in terms of sludge reduction. A complete mass balance of the process is carried out, and it is shown that this last process allows us to achieve the lowest sludge production among the processes considered, coupling this with the economic benefits coming from OFMSW disposal and struvite crystallisation.

Bacteria, Anaerobic↗

PubMed2001

Phosphorus removal from a real anaerobic supernatant by struvite crystallization.

In this paper the phosphorus removal from a real anaerobic supernatant through the crystallization of struvite and or hydroxyapatite was investigated. A comparison between experimental results on phosphorus crystallization carried out in a fluidized-bed reactor (FBR) on a bench-scale and on a half-scale plant is presented, together with a double saturational model able to describe all experimental results, independent of the different geometry of the reactors, the distinct contact times and the unlike products obtained. Experimental results show that removal efficiencies are very satisfactory, and the maximum phosphorus removal is of 80%.

Anaerobiosis↗

PubMed2001

Denitrification potential enhancement by addition of anaerobic fermentation products from the organic fraction of municipal solid waste.

The aim of this study is to demonstrate the denitrification potential enhancement determined by the addition of the anaerobic fermentation products from the organic fraction of municipal solid waste in BNR wastewater treatment plants. The denitrification potential rose from 6 to 17 mgNO3-N/l thanks to the good performances showed by the fermentation products in the denitrification step: a typical maximum denitrification rate of about 5 mgN/gVSS d was observed. This value is similar to those obtained by using pure organic substrates. The denitrification capacity increase is determined by a significant increase of S8 and Xs availability in the influent due to the anaerobic fermentation products addition which leads to an influent COD increase equal to 68% of the total load: this value is significantly higher than the one obtained by fermentation of primary and/or waste activated sludge (3-5%).

Bacteria, Anaerobic↗

PubMed2000

Acidogenic fermentation of source separated mixtures of vegetables and fruits wasted from supermarkets.

A pilot scale mesophilic anaerobic acidogenic fermenter was fed with mixtures of vegetables and fruits shredded by a hammer mill and mixed in a stock tank, in order to produce a liquid phase suitable as RBCOD source in denitrification and EBPR processes. Different operative conditions were studied working with a HRT in the range 1-12 days. The effluent coming from the fermenter was screw pressed, and the solid phase was recycled adopting different ratios to the fermenter, in order to define its effect on the final liquid phase composition. The variations of the VFA, lactate, methyl and ethyl alcohol concentrations, TCOD, SCOD and pH during more than one year were analysed and discussed both with reference to the fresh feed, and to the content of the fermenter. It was found that almost all the organic matter in the liquid phase inside the fermenter was represented by VFA (mainly acetate), lactate (in particular) and methyl and ethyl alcohols when HRT was longer than 6 days.

Acids↗

PubMed2000

Two-phase anaerobic digestion of source sorted OFMSW (organic fraction of municipal solid waste): performance and kinetic study.

The results of a two-phase system operated in different conditions, treating the source-sorted organic fraction of municipal solid waste (SS-OFMSW), coming mainly from fruit and vegetable markets, are presented. Hydraulic retention time (HRT) in the hydrolytic reactor and in the methanogenic reactor and also the temperature in the hydrolytic reactor (mesophilic and thermophilic conditions) are varied in order to evaluate the effect of these factors. The methanogenic reactor is always operated within the thermophilic range. Optimum operating conditions are found to be around 12 days (total system) using the mesophilic range of temperature in the first reactor. Specific gas production (SGP) in these conditions is around 0.6 m3/kg TVS. A kinetic study is also carried out, using the first and the step diffusional models. The latter gives much better results, with fitted constants comparable to other studies. Finally, a comparison with a one-phase system is carried out, showing that a two-phase system is much more appropriate for the digestion of this kind of highly biodegradable substrate in thermophilic conditions.

Bacteria, Anaerobic↗

PubMed2000

Rheology of sludge from double phase anaerobic digestion of organic fraction of municipal solid waste.

In this paper experimental results on the anaerobic digestion of sewage sludge and organic fraction of municipal solid waste (OFMSW) by using a double phase process are reported. The long-term experiment has been carried out on a pilot scale plant, performed in different sets of operative conditions, during which granulometric distributions of particles in sludges and rheological properties of sludges were monitored. A significant fluidification of sludge was evidenced in the meso-thermo process, especially taking into account the variation in sludge behaviour from the first to the second phase. In the thermo-thermo process a fluidification higher than that shown in meso-thermo conditions is not observed, this suggesting that better results in terms of sludge conditioning can be obtained in a long time spent in thermophilic anaerobic digestion. Total volatile solids (TVS) and total fixed solids (TFS) become the most important parameters when mathematical modelling is applied to these processes. In the acidogenic phase, hydraulic retention time (HRT) and temperature are used to determine rigidity coefficient (RC), while only temperature is needed for yield stress (YC). Organic loading rate (OLR) and specific gas production (SGP) exert an important role in methanogenic phase description.

Bacteria, Anaerobic↗

PubMed2000

Performance of thermophilic semi-dry anaerobic digestion process changing the feed biodegradability.

The study concerns the application of the semi-dry single phase thermophilic anaerobic digestion process to the organic fraction of municipal solid waste. The experiments were carried out using 3 m3 and 1 m3 CSTR pilot scale reactors. The process performance in terms of biogas yields, digester stability and kinetic aspects was studied, considering a progressive increase in the feed biodegradability, in order to evaluate the process behaviour changing from an undifferentiated collection of waste to a separate collection. This was carried out using blends of two different kinds of substrates: mechanically sorted organic fraction of municipal solid wastes (MS-OFMSW) and source sorted organic fraction of municipal solid wastes (SS-OFMSW). The study shows that OLR up to 6 kg TVS/m3d can be applicable for the medium selected fraction (TVS/TS < or = 0.7), while for the MS-OFMSW alone this limit can be doubled. The results obtained with SS-OFMSW alone suggest the use of the double phase process to give more stable conditions.

Bacteria, Anaerobic↗

PubMed1999

Effect of different times of administration of a single ethanol dose on insulin action, insulin secretion and redox state.

AIMS: Ethanol (EtOH) can affect glucose metabolism by altering the redox state, insulin-mediated glucose uptake and insulin secretion. We sought to determine the effects of an acute oral EtOH load on insulin secretion and glucose tolerance and the importance of a different timing of administration relative to a glucose load. METHODS: Eleven subjects underwent a frequently sampled intravenous glucose tolerance test (FSIGT) on three occasions in random order. In one, EtOH was given 50 min 'before' the FSIGT; on the second, the same amount was administered 6 min after the glucose pulse ('during' study); on the third no EtOH was given. RESULTS: Blood EtOH peaked at 4.43+/-0.24 mmol/l (mean +/- SD) in the 'during' and 4.16+/-0.31 mmol/l in the 'before' study. No differences were noticed in S(I), the index of insulin sensitivity, or in S(G), the glucose effectiveness, between the 'before', 'during' and control studies. There were no differences in the first-phase insulin secretion between the three studies but a significant increase in the sensitivity to glucose of second-phase dynamic insulin response, phi2, in the 'before' (0.062+/-0.036 pmol x min(-2) x (mg(-1) x dl(-1))(-1)) and 'during' (0.063+/-0.059) studies, compared to the control study (0.017+/-0.010, P<0.05) was observed. No differences were observed in the hepatic extraction of insulin. In the 'before' study, there was a significant decline in NEFA (non-esterified fatty acid) concentration from the baseline (mean 602+/-51 micromol/l) to the O min value (mean 353+/-37, P<0.01). During the FSIGT, the mean plasma NEFA concentration was significantly lower in the 'before' and in the 'during' than in the control study. CONCLUSION: An acute oral EtOH load does not impair glucose metabolism, at least in part because of an increased second-phase insulin secretion. Since this effect is observed irrespective of whether EtOH is consumed either before or during the glucose load, the existence of a priming effect is questioned.

Adult↗

PubMed1997

Long-term effects of octreotide on markers of bone metabolism in acromegaly: evidence of increased serum parathormone concentrations.

The effects of octreotide on biochemical markers of bone turnover were evaluated in patients with active acromegaly. Serum GH, IGF-I and serum and urinary markers of bone metabolism were measured before and after 4 months of treatment in 27 patients (short-term treatment) and after 12 and 24 months of treatment in 15 patients (long-term treatment). In the short-term, octreotide significantly decreased the levels of serum GH, IGF-I, calcium, osteocalcin, carboxyterminal propeptide of type I collagen and alkaline phosphatase plus urinary excretion of calcium. Short-term treatment significantly increased serum parathormone levels (before treatment 30.1 +/- 9.57 and at 4 months 46.1 +/- 24.98 ng/L, p < 0.001) and urinary excretion of phosphate; urinary excretion of hydroxyproline was unchanged. The same results were observed during long-term treatment, except that there was no significant difference of serum calcium and alkaline phosphatase levels before and after treatment. Parathormone concentrations were still higher at 24 months compared with those prior to treatment (before treatment 31.9 +/- 9.74 and at 24 months 44.9 +/- 21.18 ng/L, p < 0.05). The changes of most bone markers during octreotide therapy can be explained by the decrease of serum GH and IGF-I concentrations. On the other hand, the rise of parathormone concentrations suggests that octreotide has ulterior and long-standing actions on calcium homeostasis: intestinal malabsorption of calcium due to the octreotide could contribute to this secondary hyperparathyroidism. The clinical consequences of these alterations of bone metabolism need to be further clarified.

Acromegaly↗