Water Transformation in the Media of Biofilters Controlled by Rhodococcus fascians in Treating an Ethyl Acetate-Contaminated Airstream

Abstract

Biofilters do not provide much water for bacteria to grow. To use them efficiently and properly, it is essential to understand the kinetics of water transformation and to control moisture levels. This study aims to clarify whether the metabolism of microorganisms will improve the water-holding capacity of media or will intensify drying. This experiment was conducted in duplicate, that is, both with and without bacterial inoculation. Both the constant water content mode and the declining water content mode show that microbial growth in a log phase will enhance drying. In contrast, the bacteria growing in a logarithmic decline phase will improve water-holding capacity. Basically, water evaporation can result from the latent heat obtained from microbial respiration or from the physical temperature difference between the unsaturated air and the wet media. Two ways that biofilters can gain water are from water incorporated into bacteria cells and from water obtained from the oxidation of volatile organic compounds (VOCs).     

Assessment of characteristic distribution of PCDD/Fs and BFRs in sludge generated at municipal and industrial wastewater treatment plants

The presence of polychlorinated dibenzo-p-dioxins and furan (PCDD/Fs) and brominated flame retardants (BFRs) in sludge generated at municipal wastewater treatment plants (MWTPs) and industrial wastewater treatment plants (IWTPs) was investigated. The concentrations of these pollutants were in the following ranges: 5.38-7947 ng kg⁻¹ dw (0.02-49.9 ng WHO-TEQ kg⁻¹ dw) for 17 PCDD/Fs, 17.5-66 761 μg kg⁻¹ dw for 27 polybrominated diphenyl ethers (PBDEs), 1.55-29 604 μg kg⁻¹ dw for hexabromocyclododecanes (HBCDs) (α-, β-, and γ-diastereomers), and 4.01-618 μg kg⁻¹ dw for tetrabromobisphenol A (TBBPA). Generally, the levels of each compound in the sewage-sludge samples were higher than those in the industrial-sludge samples with some exceptions. The characteristic distribution profiles of target compounds were observed for different types of sludge and different sources of wastewater. High-chlorinated PCDD/Fs were dominant in all samples except those from the textile industry. The distribution of the BFRs in industrial-sludge samples varied, whereas that of the BFRs in sewage-sludge samples was consistent. The proportion of penta-BDEs in sewage sludge was higher than that in industrial sludge, even though BDE-209 was the most dominant congener in all the samples. For HBCDs, the distribution of diastereomers (α-, β-, and γ-HBCD) was similar across sludge samples that had the same source of wastewater and treatment processes.     

Pretreatment of automobile shredder residue (ASR) for fuel utilization

Automobile shredder residue (ASR) was pretreated to improve its quality for fuel utilization. Composition analysis revealed that ASR components could be classified into four groups: (1) urethane and textile-light fraction and combustibles containing low levels of ash and Cl; (2) plastics and rubber-light or heavy fraction and combustibles containing high levels of Cl; (3) metals and electrical wire-heavy fraction and incombustibles, and (4) particles smaller than 5.6mm with high ash contents. Based on these results, we successively performed sieving to remove particles smaller than 5.6mm, float and sink separations to reject the heavy fraction and plastics and rubber containing Cl, thermal treatment under an inert atmosphere to remove Cl derived from PVC, and char washing to remove soluble chlorides. This series of pretreatments enabled the removal of 78% of the ash and 91% of the Cl from ASR. Sieving using a 5.6-mm mesh removed a considerable amount of ash. Product quality was markedly improved after the float and sink method. Specifically, the sink process using a 1.1 g cm(-3) medium fluid rejected almost all rubber containing Cl and a large amount of PVC. The remaining Cl in char, after heating at 300 degrees C under an inert atmosphere and washing, was considered to be present as insoluble chlorides that volatilized at temperatures above 300 degrees C. Based on a tradeoff relationship between product quality and treatment cost, ASR may be utilized as a form of refuse plastic fuel or char.     

Combustion characteristics of simulated gas fuel in a 30 kg/h scale pyrolysis-melting incinerator

Combustion characteristics of gas fuel in a pyrolysis-melting incinerator having a 30kg/h capacity were investigated. Pyrolyzed gas from waste was simulated by propane that was injected in the combustion chamber, and burnt through multi-staged combustion by distributing the combustion air to primary, secondary, and tertiary air nozzles. Temperatures and the concentrations of gas components in the combustion chamber were measured. Combustion performance was evaluated with respect to the temperature distribution and combustion gas concentrations of O(2), CO and NO(x). Using secondary air and/or tertiary air, the combustion performance was improved, and, in particular, NO(x) concentration decreased significantly following the tertiary air injection.     

Polymorphism in the brown alga<Emphasis Type="Italic"> Dictyota dichotoma</Emphasis> (Dictyotales,Phaeophyceae) from Korea

Two morphotypes of Dictyota dichotoma of uncertain taxonomic status have been identified in Korea. The broad thallus type is common on the south and east coasts of Korea, and is similar to European D. dichotoma in gross morphology. The slender thallus type is only found on the west coast. Morphological differences between the two plant types are evident in their thallus width, their terminal bifurcations, the shapes of apices, and their thallus thickness. The differences in the size and shape of the tetrasporangia and tetraspores are also notable. Plants from the east coast exhibit a dominant asexual annual life-cycle involving sporophytes but not gametophytes, and maintain their population by the production of in-situ germlings. In the slender plants from the west coast, a sexual life-cycle dominates. The rbcL, rbcS, psaA and psbA gene sequence differences between the two morphotypes were congruent with morphological, anatomical and phenological characteristics. In spite of these differences, there is no known inbreeding barrier between these two morphotypes. The L_m/L_c values of the second internodes from two types are also within the range of the species criterion specified by Hörnig et al. These results suggest that the two types of D. dichotoma from Korea should be classified as a single species and that they may be in the process of speciation due to geographical isolation (allopatric speciation).Communicated by O. Kinne, Oldendorf/Luhe     

Distribution of 90Sr in coastal seawater, sediments and organisms off two atomic power stations in Korea

We have measured 90Sr activities in the marine environment (seawater, sediments and organisms) off the two Korean atomic power stations at Gori and Weolseong. The marine sampling sites were chosen in the vicinity of the power stations to investigate the dispersion of any local 90Sr sources. The 90Sr activities in seawater ranged from 1.3 to 1.9 mBq/l (mean: 1.4, n = 16) and 0.9 to 1.5 mBq/l (mean: 1.3, n = 29) at the Gori and Weolseong sites, respectively. These activities are comparable with those reported for the remote open ocean, suggesting that the 90Sr at these sites originated primarily from global fallout, which occurred during the 1960s, rather than from any local sources. The 90Sr activities in marine sediments ranged from 116 to 1,277 mBq/kg (mean: 565, n = 12) and from 304 to 1,799 mBq/kg (mean 933, n = 6) at the Gori and Weolseong sites, respectively. The horizontal distribution of 90Sr in surface sediments appears to be affected by grain size as well as local sedimentation rate. The enrichment of 90Sr in fish (5.5 +/- 2.6 mBq/kg, n = 5) and shellfish (7.1 +/- 1.2 mBq/kg, n = 2) was much lower than that in seaweed (57 +/- 33 mBq/kg, n = 5).     

Effects on nano zero-valent iron reactivity of interactions between hardness, alkalinity, and natural organic matter in reverse osmosis concentrate

Nanoscale zero-valent iron （NZVI） is considered to have potential to reduce nitrate in the concentrate generated by high pressure membrane processes aimed at water reuse. However, it is necessary to verify the effect of the matrix components in the concentrates on NZVI reactivity. In this study, the influence of hardness, alkalinity, and organic matter on NZVI reactivity was evaluated by the response surface method （RSM）. Hardness （Ca/＋） had a positive effect on NZVI reactivity by accelerating iron corrosion. In contrast, alkalinity （bicarbonate; HCO3） and organic matter （humic acid; HA） had negative effects on NZVI reactivity due to morphological change to carbonate green rust, and to competitive adsorption of HA, respectively. The validity of the statistical prediction model derived from RSM was confirmed by an additional confirmation experiment, and the experimental result was within the 95% confidential interval. Therefore, it can be indicated that the RSM model produced results that were statistically significant.