Frantisek Kastanek

In-field experimental verification of cultivation of microalgae Chlorella sp. using the flue gas from a cogeneration unit as a source of carbon dioxide

A complex treatment of agricultural waste including the following major steps: anaerobic fermentation of suitable waste, cogeneration of the obtained biogas and growth of microalgae consuming the CO2 from biogas and flue gas was verified under field conditions in a pilot-scale photobioreactor. The growth kinetics of microalgae Chlorella sp. consuming mixture of air and carbon dioxide (2% (v/v) of CO2), or flue gas (8—10% (v/v) of CO2) was investigated. The results obtained in the pilot photobioreactor were compared with results previously measured in laboratory photobioreactors. The field tests were performed in a pilot-scale outdoor solar-bubbled photobioreactor located at a biogas station. The pilot-scale photobioreactor was in the shape of a flat and narrow vertical prism with a volume of 300 L. The microalgae growth rates were correlated with empirical formulas. Laboratory analyses of the produced microalgae confirmed that it meets the strict EU criteria for relevant contaminants level in foodstuffs. Utilization of flue gases from cogeneration therefore was not found to be detrimental to the quality of microalgal biomass, and may be used in these types of bioreactors.

Biodegradation of polychlorinated biphenyls and volatile chlorinated hydrocarbons in contaminated soils and ground water in field condition

Three sites with a long history of contamination with polychlorinated biphenyls (PCBs) or chlorinated ethenes (CIUs) were investigated to evaluate the natural attenuation process. Data showed that both the rates and mechanisms of biodegradation differed and that the occurrence of aerobic and anaerobic microorganisms differed qualitatively and quantitatively. Criteria for feasibility of spontaneous degradation of CIUs and PCBs in ground water and soil are formulated. (a) Congener analysis was applied to evaluate the long-term exposure of individual congeners of PCBs in the environment. In the course of approximately 20 years the small changes in congener composition could be probably due to slow biodegradation of light congeners in the relatively good oxygenated superficial layers of soil. (b) Enhanced reductive dehalogenation of PCBs was accomplished by the solid-state fermentation in reactors of 15 cubic metres of volume. Efficiency of biodegradation of individual congeners was evaluated and limits of the method were determined. (c) Different reaction rates of CIU degradation in ground water have been ascribed to the presence and/or activity of anaerobic bacteria in field conditions.

Combination of Advanced Oxidation and/or Reductive Dehalogenation and Biodegradation for the Decontamination of Waters Contaminated with Chlorinated Organic Compounds

Abstract The method of decomposition of chlorinated organic substances in contaminated water based upon successive steps of chemical pretreatment of organic compound with a) active radicals (Fenton reaction) and/or with b) reductive dehalogenation on metallic Pd in the presence of zero‐valent iron, followed by aerobic biodegradation using bacteria strain Pandoraea sp. was studied. 4‐chlorophenol was chosen as a model compound. Generally, chlorophenols show limited biodegradability. The average efficiency of biodegradability of 4‐chlorophenol with both free and immobilized cells does not exceed 70% after 42 days of biodegradation, but their intermediates obtained by partial oxidation (products of hydrolytic‐hydroxylation) and/or a product of their partial reductive dechlorination (phenol) show increased biodegradability. To test the efficiency of the method, water exposed to this contaminant was treated in the laboratory in batch conditions. Because the products of partial oxidation and partial reductive dehalogenation of 4‐chlorophenol essentially differ, the main factor studied was the efficiency of biodegradation of 4‐chlorophenol after oxidative or reductive pre‐treatment steps. In comparison with the rate of biodegradation using free cells without application of the pre‐treatment step, the rate of degradation of 4‐chlorophenol by the application of consecutive combination of Fenton reagent and biotreatment was two‐fold. As for the combination of reductive dechlorination pre‐treatment step with consecutive biodegradation, the rate of decontamination of the 4‐chlorophenol was a little bit higher here in comparison with the rate of biotreatment after the pre‐oxidizing step: the remaining concentration of 4‐chlorophenol corresponding to the sampling in 7, 28, and 56 days after the inoculation were 70 mg/L, 12 mg/L, and 1.1 mg/L, respectively, in samples containing the average initial concentration of 126 mg/L of 4‐chlorophenol. Positive results may probably be due to the co‐substrate effect of phenol presented in the samples after the pre‐traetment reductive step. We have shown that both procedures followed with aerobic biodegradation can be considered suitable for removing hazardous chlorinated compounds from contaminated waters. The rate of biodegradation after the application of pre‐treatment procedures was slightly enhanced in comparison with the rate of biodegradation without the application of the pre‐treatment steps. It is evident that the choice of the decontamination pre‐treatment procedure cannot be generalized and will essentially depend upon the type and concentration of target contaminants and on process costs.

Microwave-Enhanced Thermal Desorption of Polyhalogenated Biphenyls from Contaminated Soil

The effect of microwave (MW) field on the rate of thermal desorption of polychlorinated biphenyls (PCBs) from long-term contaminated soil was examined in the laboratory environment. For these purposes a modified MW oven was used, with a uniformly extended MW field and a power consumption of 200–600 W. The weight of the soil samples was 100 g, the sum of concentrations of seven indicative congeners of PCB Nos. 28, 52, 101, 118, 153, 138, and 180 was, on average, 264 mg/kg of dry matter. It was experimentally proven that the efficiencies of PCB desorptions were high, over 99.9%. The maximal desorption temperature of 600°C was reached within 15–17 min. It came to light that the presence of alkaline additives in the soil (such as carbonates and alkaline metal hydroxides) did not have an apparent effect on the desorption of PCBs under those conditions. The results concerning the efficiency of PCB separations are in agreement with our previous findings regarding the efficiency of thermal desorption without usin...

Elimination of heavy metals from microbial cultures by chemical and biological leaching under decreased values of pH

Abstract The article compares experimental results of the effectiveness of the extraction of heavy metals contained in mixed microbial cultures forming activated sediments from communal sewage disposal plants. The methods used were elimination of the metals from the sediments based on their extraction with strong inorganic acids under pH 1, extraction with the aid of acid ion exchangers and simultaneous oxidation of the sludge with chlorine and ozone in the pH area 2.7 - pH 3 and a method of biological leaching through the effect of the micro-organism Thiobacil lus ferrooxidans under pH 2. Relatively the most effective method appears to be extraction with acids under pH l when, with the exception of copper and lead, the other metals are extracted with great efficiency. Chrome is also well extracted with these low pH, in contrast, for instance, with the ion exchanger method. But this second case is good for the extraction of copper. Ni and Cd are well extracted by both methods. Biological leaching is shown to be the most suitable for the extraction of zinc, but it can also be used as an auxiliary method for disrupting the strong bonds even of sulphides of other heavy metals with their receptors on the surface of cell membranes. It seems from our results that the majority of metals are mainly bound just on the surface of the cells, with the exception of copper, which evidently penetrates into the volume of the cells, from which it can be partially washed out only after disrupting the cell walls through the effect of strong oxidative agents. It is stated, on the basis of evaluation of the experiments that successive application of all three methods could be practically utilizable as an effective way of extracting heavy metals from sludge from sewage treatment plants.

Erratum to: Selective bioaccumulation of rubidium by microalgae from industrial wastewater containing rubidium and lithium

Bioaccumulation of rubidium (Rb+) and lithium (Li+) from alkaline wastewater containing 480 mg L−1 Rb+ and 540 mg L−1 Li+, a by-product of zinnwaldite processing, was studied at laboratory scale using growing freshwater microalgae (Chlorella vulgaris, Desmodesmus quadricauda and Scenedesmus obliquus). Bioaccumulation of Li+ was very low, while the bioaccumulation of Rb+ was significant by all tested strains. The best result was found for C. vulgaris, which accumulated 54% of the original amount of rubidium in growth media (48 mg L−1) within 4 days. In addition, the wastewater did not affect the growth rate of C. vulgaris. The effect of potassiun (K+) concentration on total bioaccumulation of alkali metal ions and its selectivity by C. vulgaris was also tested. The highest K+ concetration (334 mg L−1) resulted in bioaccumulation of 4.3 mg Rb+ per gram of biomass with Rb+:Li+ uptake ratio of 26.9. By decreasing the K+ concetration in medium (56 mg L−1), the total bioaccumulation improved (4.70 Li+ per gram of biomass, 5.93 Rb+ per gram of biomass) but at the cost of lower selectivity (Rb+:Li+ uptake ratio 1.3). These findings have a potential of practical utilization, as both Rb+ and Li+can be recovered from biomass by incineration and subsequent chemical separation.

Microalgae for bioenergy: key technology nodes.

Microalgae have increasingly gained research interest as a source of lipids for biodiesel production. The wet way processing of harvested microalgae was suggested and evaluated with respect to the possible environmental impacts and production costs. This study is focused on the three key steps of the suggested process: flocculation, water recycling, and extraction of lipids. Microalgae strains with high content of lipids were chosen for cultivation and subsequent treatment process. Ammonium hydroxide was tested as the flocculation agent and its efficiency was compared with chitosan. Determined optimal flocculation conditions for ammonium hydroxide enable the water recycling for the recurring microalgae growth, which was verified for the use of 30, 50, and 80% recycled water. For extraction of the wet microalgae hexane, hexane/ethanol and comparative chloroform/methanol systems were applied. The efficiency of hexane/ethanol extraction system was found as comparable with chloroform/methanol system and it seems to be promising owing to its low volatility and toxicity and mainly the low cost.

Solid waste decontamination by thermal desorption and catalytic oxidation methods

Combined thermal desorption and catalytic oxidation for soil decontamination was studied at the pilot plant scale. Gasoline, xylene, and 2-methylnaphthalene were used as model contaminants in the concentrations from 2 g to 10 g per kg of soil. To guarantee the flow of the exhaust gas from the thermal desorption unit into the catalytic oxidation unit, a Venturi pump was used. Based on the laboratory scale catalytic tests, the commercial catalyst EnviCat® VOC-1544 was employed in the catalytic oxidation. Residual concentrations of hydrocarbons in soil after the thermal desorption were below the detection limits of the applied analytical method (GC-MS). Although the contaminant concentrations at the inlet of the catalytic reactor significantly varied during the experiments, the efficiency of catalytic oxidation was higher than 90 % in all cases.

Biodegradation of Petroleum Hydrocarbons After the Departure of the Soviet Army

The contamination of soils and groundwater caused by the operation of army vehicles by the former Soviet Army (SA) can be considered a typical example of wide-spread, multiple point-source pollution. It has been shown that mixed populations of autochthonous microbes are particularly suited for the remediation of soil and groundwater. In fact, petroleum contaminant levels in groundwater were found to have been reduced to permissible levels within approximately 6 months, though it is necessary to continue monitoring contaminant levels after treatment. Soils are treatable in this fashion as well. Concentration of contaminants have been reduced from tens of thousands of mg kg-1 to approximately 250 mg kg-1 within a three month summer season in favorable soils (i.e., sand, sandy loam, metamorphosed clays, gravel).

The role of titania layers in decomposition of endocrine disruptors under UV Light

AbstractDegradation of three different endocrine disruptors (EDs) was thoroughly studied on prepared durable thin layers of titanium dioxide with an anatase crystalline structure. Specially constructed laboratory reactors bringing information on all individual processes (photolysis, photocatalysis, sorption) involved in decomposition of the studied EDs (17α-ethynylestradiol, bisphenol A and 4-nonylphenol) were applied. It was found that photolytic removal of EDs is the fastest degradation process; nevertheless, this method may be less effective regarding all indicators including toxicity. It was verified that individual degradation processes (photolysis and photocatalysis) showed a significantly different influence on toxicity of resulting solutions. During the photolytic process, EDs degradation caused increasing toxicity contrary to the photocatalytic process. Obtained results were corroborated by a mathematical model, which showed that a limitation step for photocatalysis is a sorption and for photolysis a toxicity of resulting products.