Mathematical model of aerobic stabilization of old landfills

A short-term aerobic stabilization of digested waste in the final methane phase was studied. The effect of aeration rate on the reduction of leachate parameters and on the rate of CO₂ production and O₂ assimilation was investigated. Experimental simulation of aerobic landfill stabilization was carried out using lysimeters. When testing the effect of aeration rate on the reduction of leachate indices (BOD₅, COD, N-NH₄⁺), it was reported that the most significant reduction was obtained at the highest rate of aeration and the smallest reduction of leachate indices was attained not at the lowest but at medium aeration rates. Both the rate of CO₂ production and the O₂ assimilation reached their highest values in the lysimeters aerated at a high rate of aeration. The proposed mathematical model which consists of a system of five differential equations describing CO₂ production, O₂ assimilation and the changes of organic carbon content in the leachate correspond well with the experimental data.     

Decomposition of meta- and para-phenylphenol during ozonation process

The decomposition of meta-phenylphenol (m-PP) and para-phenylphenol (p-PP) in a heterogeneous gas-liquid system using ozone was investigated. The influence of different reaction parameters such as ozone and PP isomers concentration as well as pH and temperature of the reaction mixture on the PP decay rate was determined. The second-order rate constants for the direct reaction of molecular ozone, determined in a homogeneous system, were (5.85 ± 0.35) × 10² M^?1 s^?1 and (8.90 ± 0.33) × 10² M^?1 s^?1 for m-PP and p-PP, respectively. The rate constants for the reaction of m-PP and p-PP with ozone increased with increasing pH. The reaction rate constants with ozone were found to be (1.75 ± 0.02) × 10⁹ M^?1 s^?1 and (1.86 ± 0.02) × 10⁹ M^?1 s^?1 for m-PP and p-PP anions, respectively.     

Alkaline hydrogen peroxide pretreatment of energy crops for biogas production

In this study, the influence of alkaline hydrogen peroxide (H₂O₂) pretreatment of the three different plant sources: Miscanthus giganteus, Sorghum Moench, and Sida hermaphrodita, for biogas production was investigated. The influence of temperature, reaction time, and H₂O₂ concentration on the efficiency of biomass degradation and on the further methanogenic fermentation were studied. The results obtained after chemical pretreatment indicate that using H₂O₂ at alkaline conditions leads to the decomposition of three major structures: lignin, hemicellulose, and cellulose. The best results were achieved for the process performed at 25°C for 24 h with the use of a 5 mass % H₂O₂ solution. Although the degradation level was very high for all three plant sources, the biogas production from the energy crops pretreated chemically was strongly inhibited by byproducts and the residual oxygen formed after H₂O₂ decomposition. This fact indicates that alkaline H₂O₂ pretreatment is a very promising method for plant material degradation for further biogas production, but pretreated biomass must be separated from supernatant before the fermentation process because of the high concentration of inhibitors in the hydrolysates. The best results were obtained for Sida with biogas and methane production of 2.29 Ndm³ and 1.06 Ndm³, respectively.     

Co-digestion of agricultural and industrial wastes

The efficiency of anaerobic digestion process is dependent on the type and composition of the material to be digested. This work examines the co-digestion of corn silage, beet pulp silage, carrot residues, and cheese whey in different configurations together with a glycerin fraction — the waste product of transestrification of oils (biodiesel production) in a 25 L bioreactor operated mesophically in a quasi-continuous mode. Co-digestion of corn silage with carrot residues appeared to be more effective than that with cheese whey resulting in the gas production rate equal to 5.9 L L⁻¹ d⁻¹ and 1.4 L L⁻¹ d⁻¹, respectively. The performed experiments showed that a combination of three substrates: corn silage, cheese whey, and glycerin fraction resulted in the highest methane content equal to 61 % and the biogas production rate of 1.8 L L⁻¹ d⁻¹.     

Kinetics of benzene photochlorination

An empirical approach to the kinetic investigations of photo-initiated liquid-phase chlorination of benzene is presented. Reaction order and the reaction constants for chlorine consumption and for the production of hexachlorocyclohexane isomers were evaluated from experimental data.     

CO2 gasification of char from spent mushroom substrate in TG-MS system

Journal of Thermal Analysis and Calorimetry - Gasification of the char obtained from the spent substrate after mushroom cultivation was carried out in a thermobalance connected to a mass...     

Application of anoxic fixed film and aerobic CSTR bioreactor in treatment of nanofiltration concentrate of real textile wastewater

An anoxic fixed film bioreactor (FFB) with biomass immobilized on activated carbon and an aerobic continuous stirred tank bioreactor with overflow were applied to degrade concentrate from nanofiltration of real textile effluents containing Reactive Red 120 (RR-120). The efficiency of color removal was 99 % irrespective of the fraction of nanofiltration concentrate in the feed. An approximate dye balance based on the assessed adsorption capacity of RR-120 by activated carbon indicated that the dye was removed by means of adsorption as well as of biological processes. Aromatic amine released from a dye molecule was fully adsorbed by activated carbon. COD level in the outflow of the system was above that imposed by legislation. Despite an adjustment of the feed pH to 7 this was constantly increasing up to the value above 9 in both reactors. Neither the nanofiltration concentrate nor the effluents from the bioreactors affected the growth of Pseudomonas putida used as toxicity indicator.     

Prediction of Henry''s constants by the UNIFAC-FV model for hydrocarbon gases and vapors in high-boiling hydrocarbon solvents

The design of absorption processes and gas liquid reactors requires the knowledge of gas solubility data. It is shown that a modified UNIFAC-FV model can be applied to predict Henry's constants for hydrocarbon gases and vapors in high-boiling hydrocarbon solvents. Very good agreement with experimental data has been achieved.     

Continuous laccase concentration in an aqueous two-phase system

An approach to describe continuous partitioning of Cerrena unicolor laccase in a PEG 6000—phosphate aqueous two-phase system was proposed. The laccase was separated from crude supernatant of C. unicolor-submerged culture, and all the experiments were carried out in 25 °C and pH 7 conditions. Masses of both phases and their compositions at phase equilibrium, as well as laccase activity concentrations at different mixing points, were measured in batch experiments. An empirical short-cut method was developed which allows for calculation of mass and volume fractions of the phases, laccase concentration factors, and laccase recoveries. Theoretical predictions were verified by several experiments carried out in a special mixer-settler unit with automatic substrate feed and continuous collection of separated phases. Required concentration of the laccase was possible to achieve in a one-step extraction process in the mixer-settler unit. The predictions of the short-cut method were compared to the results of experimental measurements of phase compositions, phase volume fractions, concentration factors and enzymatic yields at steady-state operation of the extraction unit. The values of experimental results lay well within the 10% error range of the predicted values.     

Alkali pre-treatment of Sorghum Moench for biogas production

This work studies the influence of the alkali pre-treatment of Sorghum Moench — a representative of energy crops used in biogas production. Solutions containing various concentrations of sodium hydroxide were used to achieve the highest degradation of lignocellulosic structures. The results obtained after chemical pre-treatment indicate that the use of NaOH leads to the removal of almost all lignin (over 99 % in the case of 5 mass % NaOH) from the biomass, which is a prerequisite for efficient anaerobic digestion. Several parameters, such as chemical oxygen demand, total organic carbon, total phenolic content, volatile fatty acids, and general nitrogen were determined in the hydrolysates thus obtained in order to define the most favourable conditions. The best results were obtained for the Sorghum treated with 5 mass % NaOH at 121°C for 30 min The hydrolysate thus achieved consisted of high total phenolic compounds concentration (ca. 4.7 g L^?1) and chemical oxygen demand value (ca. 45 g L^?1). Although single alkali hydrolysis causes total degradation of glucose, a combined chemical and enzymatic pre-treatment of Sorghum leads to the release of large amounts of this monosaccharide into the supernatant. This indicates that alkali pre-treatment does not lead to complete cellulose destruction. The high degradation of lignin structure in the first step of the pre-treatment rendered the remainder of the biomass available for enzymatic action. A comparison of the efficiency of biogas production from untreated Sorghum and Sorghum treated with the use of NaOH and enzymes shows that chemical hydrolysis improves the anaerobic digestion effectiveness and the combined pre-treatment could have great potential for methane generation.