Zsuzsanna László

Investigation of the photodecomposition of phenol in near-UV-irradiated aqueous TiO2 suspensions. I: Effect of charge-trapping species on the degradation kinetics

Abstract The effects of charge-trapping species on the kinetics of phenol decomposition were studied in near-UV-irradiated aqueous TiO 2 (anatase) suspensions in a batch photoreactor. The influence of catalyst loading, initial phenol concentration, dissolved O 2 concentration, Ag + content and H 2 O 2 concentration on the rate of phenol degradation is reported. The observed heterogeneous degradation of phenol followed apparently zero-order kinetics up to ca. 70% conversion. The Langmuir–Hinshelwood kinetic model successfully described the influence of the initial phenol concentration and dissolved O 2 concentration on the rate of heterogeneous photooxidation of phenol. The data obtained by applying the Langmuir–Hinshelwood treatment are consistent with the available kinetic parameters. The results of the experiments in the presence of Ag + indicated that the phototransformation of phenol can proceed via direct electron transfer, neither dissolved O 2 nor its reduction forms playing a significant role in the degradation mechanism.

Comparison of the effects of microwave irradiation with different intensities on the biodegradability of sludge from the dairy- and meat-industry

Microwave (MW) irradiation is a relatively new possibility of conditioning and pretreating for wastewater sludge. Following its application in the telecommunications and food-industries, the environmental use of this technique has come into the limelight in recent years, and has become increasingly popular. Various publications have dealt with the examination of the effects of MW irradiation in municipal sludge-handling processes. We focused on the effects of MW irradiation at different power levels on solubilization (sCOD/tCOD), biodegradation and anaerobic digestion of sludge from the food-industry. For evaluating the efficiency of MW pre-treatment, the changes in the soluble fraction of the organic matter, the VS/TS ratio, the biogas yield, the methane content in the biogas, and the rate of batch mesophilic digestion were used as control parameters. Additionally, the energetic efficiency of MW pre-treatment was also examined. The results were compared with those of conventional heat (CH) treatments of the same sludge. The MW treatment proved to increase both the sCOD/tCOD and the VS/TS ratio. Furthermore, the biogas and methane yields increased during the digestion of the MW-pretreated food-industry sludge. A higher MW power level generally enhanced the biogas and methane production. Energetically, the most economic pre-treatment of sludge from dairy and meat processing was at a power level of 1.5 Wg(-1) and 2.5 Wg(-1) MW respectively; the surplus energy content of the enhanced biogas product could not compensate the extra energy demand of the stronger MW pre-treatments.

Biogas Production of Ozone and/or Microwave-Pretreated Canned Maize Production Sludge

The production of canned maize is accompanied by formation of large volumes of waste water, with high contents of starch, and high chemical- and biochemical oxygen demand. In our work the effects of acidic, microwave and ozone pretreatment on the biogas production and aerobic biodegradability of canned maize production sludge were examined and the energy balance of the processes were determined when different sludge pretreatments were used. It was found that ozone treatment decreased the chemical oxygen demand, while the biochemical oxygen demand and the aerobic biodegradability increased. The combination of microwave and ozone treatment increased the biodegradability relative to ozone treatment alone.

Dairy Waste Water Treatment by Combining Ozonation and Nanofiltration

Abstract The aim of this investigation was to examine the applicability of the membrane technique and the effect of preozonation in dairy waste water treatment technology. The best degree of surfactant removal from model anionic surfactant solution by nanofiltration was achieved at 20°C and 40 bar. Investigations on the effects of ozone treatment of the waste water indicated that preozonation decreased the flux and increased the chemical oxygen demand and surfactant removal efficiency. Ozone treatment enhanced the biodegradability of the retentate from 68.8% to 96.4%.

Comparison of ozone-based and other (VUV and TiO2/UV) radical generation methods in phenol decomposition

Abstract The degradation reaction kinetics and chemical mechanism of phenol decomposition by ozonation, TiO2-photocatalysis and vacuum ultraviolet (VUV) photolysis were investigated. The concentration dependences of the aromatic and aliphatic intermediates and the TOC content were compared as a function of the phenol conversion. The concentration profiles and the TOC curves obtained with each method were very similar. The results suggest a similar chemical mechanism for the transformation of phenol irrespective of the starting active component (a positive hole on the surface of the catalysts, a VUV photon, ozone or the hydroxyl radical).

Comparison of the Effects of Ozone, UV and Combined Ozone/UV Treatment on the Color and Microbial Counts of Wheat Flour

The effects of direct ozone treatment, UV treatment and combined ozone/UV treatment on the color and microbiological count of milled wheat flour were compared. The changes in color and microbiological properties during a 19-week storage period were also examined. Each of the treatments significantly reduced the microbial count of the flour and resulted in whiter flour. The results showed that only the combined treatment furnished flour suitable for consumption. The effect of the combined treatment was similar to, but more pronounced than that of ozone treatment. Changes in the quality of the dough were observable, similar by as in response to other oxidizing agents.

Treatment of oily wastewater by combining ozonation and microfiltration

AbstractIn process industries, a large amount of wastewater is generated in the form of oil-in-water emulsions, which cannot be treated effectively using traditional physical methods. The aim of our investigation was to examine the applicability of the membrane technique and the effect of pre-ozonation in oily wastewater treatment. Pre-ozonation followed by microfiltration (MF) was investigated to determine the main effects of ozonation on the oily water and the filtration parameters such as permeate flux, organic content retention and membrane fouling. Experiments were carried out with a laboratory-scale batch-stirred filtration device, using polyethersulphone MF membranes with a pore size 0.2 μm. The model oily wastewater that was used in these experiments contained petroleum. The results demonstrated that the chemical oxygen demand could be eliminated more effectively through the combination of ozone pre-treatment and membrane filtration, compared to membrane filtration alone.

Investigation of parameters affecting the ultrafiltration of oil-in-water emulsion wastewater

Abstract The ultrafiltration (UF) of model oily wastewater containing an emulsifier was investigated in order to determine the main parameters affecting the flux, retention and membrane fouling. The experiments were carried out with a laboratory UF device, using regenerated cellulose UF membranes. The finding that the fall in flux with time correlated best with the cake formation model is in accordance with the result that increasing resistance during filtration is caused predominantly by the concentration polarization, while the participation of membrane fouling in the total resistance is negligible. Analysis of the parameters affecting the UF of oily wastewater demonstrated that the flux is mainly influenced by temperature and concentration (besides the membrane pore size), while the concentration and the stirring speed are the parameters affecting the resistance. The retention increased slightly with concentration, but this was mainly determined by the membrane pore size.

Enzyme recovery and fouling mitigation by ultrasound-enhanced ultrafiltration

Abstract The development of second-generation biofuels from cellulosic/lignocellulosic biomass has advantages from energy and environmental aspects, but the overall cost of the process is mainly dependent on the cost of the enzymes. Enzyme recovery and recycling is one of the most important and effective means of increasing the efficiency of enzymatic hydrolysis processes by lowering the enzyme costs. The primary objective of this study was to investigate the possibilities of enzyme recovery by membrane separation. Ultrafiltration (UF) membranes with various cut-off values and materials were used to recycle cellulase and cellobiase in model solutions and cellulosic hydrolysates. The membrane separation process was followed by determination of the flux, and its efficiency of it was measured via sugar and protein retention, and the resistances were also calculated. A polyether–sulfone membrane with a cut-off value of 5 kDa, (PES5) operated at 26.8 L m−2 h−1 with 87.3% protein rejection while a thin-film mem...

Treatment of model oily produced water by combined pre-ozonation–microfiltration process

Oily wastewaters are one of the major environmental pollutants in aquatic systems. This is due to the emission of a variety of industrial oily wastewaters from sources such as crude oil mining (production), refineries, petrochemical plants and transportation. The aims of this work were to investigate the treatment of oil-contaminated wastewaters with a pre-ozonation/microfiltration combined system and the effect of pre-ozonation on the microfiltration parameters. The results demonstrated that ozone pre-treatment modified the chemical nature (pH and conductivity) of oil-in-water emulsion, resulting in higher wettability of the polyethersulphone membrane. In case of salt-containing model emulsions compared to pure oil emulsions, ozone treatment was found to be more effective for membrane resistance reduction and in chemical oxygen demand retention.