G. Di Giacomo

Kinetic analysis of Kluyveromyces lactis fermentation on whey: batch and fed-batch operations

A kinetic analysis of Kluyveromyces lactis fermentation on whey is reported. Batch and fed-batch operations have been considered in 10, 100 and 1000 l fermentors. A simple kinetic model for cell growth during batch and fed-batch operation was used. As expected, the specific growth rate was well represented by the Monod equation. Parameters have been estimated by fitting the model to experimental results achieved in the batch step. Results obtained in the fed-batch operation showed the ability of the model to predict K. lactis fermentation courses on whey in different scales.

RO treatment of waste waters from dairy industry

Abstract An important problem in the dairy industry is posed by the disposal of very polluting wastes like milk whey (COD 60,000+70,000 mg/l) and washing waters. Reverse osmosis can be used to concentrate milk whey (C.F. 2.5+3) in the dairy industry thus obtaining a water stream that can be re-used for the process needs and a concentrated milk whey stream that can be sent to large treatment plants, reducing the transportation costs. The concentration of milk whey has been tested at pilot plant scale, using a 600 1/hr RO unit. Figures 1 and 2 show the flow rates of feed and permeate for the milk whey concentration and retentate and permeate volumes respectively.

Integrated approach in the biotreatment of starch wastes by Rhizopus oligosporus: kinetic analysis

A biotreatment process of starch-contaminated wastes coming from potato manufacturing plants was studied and developed with an integrated approach. The reduction of starch content in the waste, and of the relative COD, is obtained in a mechanical stirred bioreactor under aerobic conditions, producing a suitable biomass potentially useful as additive in animal feeding. In this manner the COD reduction of the waste may be obtained with the production of a useful biomass with a market value. At the same time the microorganism produces glucoamylase, an extracellular enzyme, that may be recovered from the fermentation broth. The kinetics of microbial growth was monitored in synthetic media to evaluate the effect of starch concentration, pH, and stirring condition during the biotreatment process in shaken flasks and bioreactor tests. The biomass was recovered by filtration, washed by water and finally lyophilized. A kinetic model useful to describe the kinetics of microbial growth was developed: substrate consumption, microbial growth and enzyme production can be followed by the model. Considering the obtained experimental results the potential technical feasibility of the process was demonstrated.

Milk whey treatment with recovery of valuable products

This paper deals with the environmentally acceptable disposal of the polluting water solutions resulting from the manufacturing of cheese and other similar milk derived products. The proposed treatment, which allows one to recover the most valuable compounds of the milk whey, is based on the integration of a simple purification process with various independent manufacturing processes at different levels. The purification process was obtained by a proper connection of ultrafiltration (UF) treatment with a reverse osmosis (RO) treatment. As a consequence, it is characterized by a significant lower energy consumption in comparison to traditional evaporative processes which allow to produce a much less valuable mixture of both whey proteins and lactose. The process was tested at pilot plant scale by using a previously described multipurpose pilot plant (MPP) equipped with all the automatically controlled units required for this study.

Evaporation of olive oil mill vegetation waters

Abstract The evaporation of olive oil mill vegetation waters permits to pull down the polluting load to an extent superior to the 90% in terms of COD. This operation can be easily done by using the industrial evaporators now existing, and it can be optimized up to a level whose value depends on the nature and age of the vegetation water in question. The concentrated solution which comes out from the evaporator can be thermally decomposed by a two stage pyrolytic process which allows to previously divide the inorganic salts, avoiding, in this way, to encrust the boiler during the combustion of the polluting organic substances. Since the thermal decomposition process of the concentrated solution is strongly exothermic, the exceeding heat can be used to ulteriorly lower the COD of the treated water to values compatible with the environmental regulations.

High pressure phase equilibria of the system phenol-m-cresol-carbon dioxide

Abstract The ternary system composed of phenol, m-cresol and supercritical carbon dioxide is characterized by unusual phase behaviour. In fact the ternary diagram shows five distinct regions: a three phase region of solid-liquid-gas, two two phase regions liquid-solid and liquid-gas, and two single phase regions liquid and gas. In addition when pressure was increased and temperatures were below the temperature of fusion of phenol, it was observed that the carbon dioxide causes recrystallization of phenol from the liquid phase. To understand and to describe all these phenomena, several experimental measurements were performed and are reported in this paper. Finally, using all the available data for the pure compounds as well as for the three binary sub-systems, a modified Peng-Robinson Equation of State was parametrized and then used to describe, at least qualitatively, the multicomponent multiphase behaviour in the whole range of composition under different values of pressure and temperature.

High temperature distillation process with sea water feed decalcification pretreatment

Abstract The performance ratio of a desalination plant can be increased to reach 16–18 by coupling it with a decalcification pretreatment by ion exchange of the sea-water make-up, so making MSF comparable with RO from energetic point of view. A new strong cationic resin DECAL has been tailored; its main features are high selectivity towards the calcium ion and low concentration of the regenerating brine. These characteristics make it compatible with the normal operating range of multiflash plants and very suitable for the above service, when compared with other resins. The optimum coupling conditions of the whole plant, as has been pointed out, lie between 140°C and 150 °C for the top brine temperature and 2 to 2.5 for the brine concentration factor. In these conditions it is possible to operate with sea water-resin bed ratio higher than 20.

Biological Treatment of Agro‐Industrial Wastewater for the Production of Glucoamylase and Rhizopus Biomass

Abstract The present work concerns the biological treatment of a starch wastewater, coupled with the production of microbial biomass and glucoamylase. Every unit operation of the process was tested in a laboratory scale, in order to perform a feasibility analysis. Fermentation tests confirmed that a stirring rate of 300 rpm was the optimum (in the investigated range) as concerns biomass growth and enzyme activity. Ultrafiltration tests showed that the best operating conditions in the investigated range for enzyme recovery were: temperature 25°C, transmembrane pressure 100 kPa, membrane cut off 30 kDa. Diafiltration tests evidenced that an effective enzyme washing (about 85% reduction of chemical oxygen demand) was achieved with 3 volumes of water per volume of feed and no significant enzyme deactivation was observed.

Solubility of boric acid in aqueous solutions of sulfate salts

Abstract Solubility of boric acid in aqueous solutions of sodium sulfate, potassium sulfate and of both sodium and potassium sulfates and solubility of sulfate salts in aqueous solutions of boric acid were measured in a wide range of salt concentrations at temperatures from 303–373 K. The experimental data have been correlated by a thermodynamic model which uses the Wilson equation along with contributions from Debye-Huckel and a Born term in order to express the activity coefficients. The predictive capability of this model, which contains only binary interaction parameters, has been verified on multicomponent systems in the whole range of the process operating conditions.

Magnesium oxide production from concentrated brines

Abstract Magnesium oxide production from concentrated brines wasted in sea water desalting plants has been investigated. Unlike traditional Mg recovery plants from sea water, it is necessary to undertake purification of the precipitated magnesium hydroxide by means of a carbonation-decarbonation section in order to remove calcium sulphate impurities. Such an operation gives flexibility to the whole plant and allows a high purity product to be obtained. This note illustrates all the stages of the proposed process together with the relevant operating conditions. In comparison with the traditional Mg recovery plants from sea water, it has been also found that the capital and operating costs related to the carbonation-decarbonation section are substantially balanced by the elimination of the sea water intake and of the feed pretreatments, as well as by the reduction of the flow rates to be handled in the first plant section.