G. Ferraiolo

Fermentation of hardwood hemicellulose hydrolysate byPachysolen tannophilus, candida shehatae andPichia stipitis

SummaryHardwood hemicellulose hydrolysate has been utilized as a substrate for ethanol production. Among the three different yeasts tested, the best performances have been obtained, in decreasing order, usingPachysolen tannophilus, Candida shehatae andPichia stipitis. Several pretreatments of this raw material have been studied to improve ethanol yields; in one such pretreatment a strain ofP. tannophilus produced ethanol with a yield of 0.29 gethanol/gsugars (gP/gS); which is only 15% less than the values observed with synthetic media. Neither aeration nor acetone addition improved the fermentation of this substrate; in fact, only a marked stimulation of biomass growth has been observed at the expense of both ethanol and xylitol production.

Hydrogenolysis of organochlorinated pollutants: Kinetics and thermodynamics

Abstract Hydrogenolysis is one of the most promising innovating technologies because it allows the toxic organic chlorides to change quickly into their correspo

Influence of nutrient concentration in new operating criteria for biological removal of phosphorus from wastewaters

Abstract The actual practicability of biological treatment of effluents heavily polluted by phosphoric compounds is evaluated in this paper. Preliminary batch tests have shown that high COD levels inhibit phosphorus release during anaerobic conditions but allow, at the same time, a more efficacious removal during the subsequent aerobic stage. Removal yields exceeding 60% have been calculated for an influent COD level of about 840 mg/l. The A/O process, suitably modified so as to alternate aerobic and anaerobic phases in the same reactor, has been tested for the biological removal of phosphorus in synthetic wastewaters with high phosphate concentrations. The start-up phase, carried out with a synthetic solution having a starting phosphorus concentration of 10 mg/l, showed average phosphate and COD removals of 78 and 90%, respectively. The results obtained after reaching steady-state conditions, by feeding P concentrations up to 100 mg/l, seem to indicate this process as an excellent means of reducing phosphorus emissions into the environment and therefore may contribute to the solution of eutrophication-related problems. Removals higher than 90% have been assured for wastewaters containing phosphate levels up to 70 mg/l; at higher concentrations, the system proved capable of tolerating phosphate overloading for no more than 10 days; yield then rapidly fell to zero.

The fluidized bed reactor in the anaerobic treatment of wine wastewater

The aim of the present work is the performance evaluation of a fluidized bed reactor in the anaerobic treatment of a wastewater deriving from the washing operations of the wine industry. The results are in agreement with the ones obtained using a mixture of municipal and food processing wastewaters containing high organic contents. A comparison with other liquid wastes shows that no subtrate inhibition phenomenon occurs with the above substrates. A saturation kinetic model is also presented for describing the dependence of the COD removal rate on the organic loading rate.

Influence of organic loading rate on the anaerobic treatment of high strength semisynthetic waste waters in a biological fluidized bed

Abstract The results of anaerobic digestion in a fluidized bed reactor fed with municipal waste waters enriched with glucose are presented. Several process conditions have been tested by varying the influent chemical oxygen demand (COD) from 4 to 13 kg m −3 and the residence time from 5.0 to 68.2 h. The degradation efficiency and methane production rate are substantially affected by an increase in organic loading rate from 4 to 24 kgCOD i m −3 day −1 , suggesting a maximum operational value for this parameter. Using a Monod-type kinetic model, a maximum theoretical specific degradation rate of 1.76 kgCOD r kgVSS −1 day −1 has been calculated, which is very similar to values calculated for other effluents from food industry activities.

Fly ash as adsorbent material for toluene vapours

Abstract Experiments were carried out to find new uses for fly ash, such as the treatment of polluted organic gases and vapours. In particular, the adsorption of toluene vapours on fly ash has been studied in an effort to assess the role of some geometric, physical and chemical parameters of fly ash particles on toluene recovery. The effect of particle aggregation and chemical activation on the total porosity, the specific surface area of the adsorbent and the adsorption phenomenon were investigated. Preliminary results show the possibility of obtaining fly ash products with a satisfactory adsorption performance.

In-situ ethanol recovery and substrate recycling during continuous alcohol fermentation

In order to reduce the inhibiting effect of product on ethanol fermentation and to exploit at best the sugar substrate, a system continuously recycling the unfermented sugars and recovering produced ethanol is proposed in this paper. Unacceptable increases of unfermentable polysaccharides and ions in the broth up to inhibiting levels have been evidenced after about 40 d of continuous recycling. The accumulation of these substances has been overcome by installing in the production cycle two subsequent separated stages for polysaccharide enzymatic hydrolysis and ion bioaccumulation, respectively.

Influence of process variables on the modelling and design of a rotating biological surface

Abstract An investigation of the Rotating Biological Surface (RBS) process variables to determine the efficiency of BOD 5 removal from wastewater is presented. Operating parameters including influent substrate concentration, liquid retention time, stage temperature, flow rate, disk surface area, hydraulic loading, disk rotational speed, disk sizes, number of disks, fractional submergence, were evaluated. The process parameters were obtained from a pilot scale RBS plant constructed and applied to the treatment of municipal and industrial wastewater and from the literature. The data were employed to determine a kinetic equation of general application, whch tends to the well-known Michaelis-Menten equation for municipal wastewater and easily degradable substrates. The study shows that influent BOD 5 concentration, the type of substrate, hydraulic loading, stage number and wastewater temperature are the most significant variables predicting the RBS system performance. The model presently developed was verified by field data concerned with the treatment of domestic and low strength industrial wastewater. The obtained model for urban wastewater cannot be applied to high strength industrial wastewaters where poorly biodegradables substrates are present together with easily degradable substrates. The situation has been verified by treating straw paper and tannery wastewaters. For those substrates a more complex equation has been obtained that becomes the Michaelis-Menten type equation at high values of a BOD fraction in the effluent.

The effects of mixing on bioprocesses. Concentration distributions and mechanical shear stress

The effects of mixing on batch alcohol fermentation of diluted solutions of starch hydrolysate is studied. The results of a limited number of samples simultaneously drawn at different locations in the reactor and after different reaction times have been used in a simple mathematical model to provide a picture of the concentration distributions within the reaction environment. The optimal mixing conditions for the fermentation are met at rotation speeds between 1.7 and 5.0 s−1, while the broth homogeneity obviously increases indefinitely with increasing this parameter. This suggests the existence of a shear stress for the biomass, whose effect increases with the application time and seems to affect the process mainly at the end of the fermentation.

Simultaneous hydrolysis of tri- and tetrasaccharides by industrial mixtures of glucoamylase and α-amylase : kinetics and thermodynamics

The present paper deals with the study of the kinetics and thermodynamics of batch enzymic hydrolysis of multisubstrate media in the presence of more than one glucanase. A kinetic model, similar to the one proposed for competitive inhibition, is presented to describe the competition between two substrates, tri- and tetrasaccharides, for the same enzyme, glucoamylase. A literature research on the most recurrent values of the Michaelis-Menten constant also shows a linear relationship between this parameter and the molecular weight of the sugar substrate for a given glucanase.