The relationship between anammox and denitrification in the sediment of an inland river

This study measured the microbial processes of anaerobic ammonium oxidation (anammox) and denitrification in sediment sampled from two sites in the estuary of an inland river (Koisegawa River, Ibaragi prefecture, Japan) using a nitrogen isotope pairing technique (IPT). The responses of anammox and denitrification activities to temperature and nitrate concentration were also evaluated. Further, to elucidate the correlation between anammox and denitrification processes, an inhibition experiment was conducted, using chlorate to inhibit the first step of denitrification. Denitrification activity was much higher than anammox activity, and it reached a maximum at the surface layer in February 2012. Denitrification activity decreased as sediment depth increased, and a similar phenomenon was observed for anammox activity in the sediment of site A, where aquatic plants were absent from the surroundings. The activities of both denitrification and anammox were temperature-dependent, but they responded differently to changes in incubation temperature. Compared to a linear increase in denitrification as temperature rose to 35 °C, the optimal temperature for anammox was 25 °C, after which the activity decreased sharply. At the same time, both anammox and denitrification activities increased with NO3(-) concentration. The Michaelis-Menten kinetic constants (Vmax and Km) of denitrification were significantly higher than those of the anammox process. Furthermore, anammox activity decreased accordingly when the first step of denitrification was inhibited, which probably reduced the amount of the intermediate NO2(-). Our study provides the first direct exploration of the denitrification-dependent correlation of anammox activity in the sediment of inland river.

Degradation of 1,4-dioxane in water with heat- and Fe(2+)-activated persulfate oxidation

This research investigated the 1,4-dioxane (1,4-D) degradation efficiency and rate during persulfate oxidation at different temperatures, with and without Fe(2+) addition, also considering the effect of pH and persulfate concentration on the oxidation of 1,4-D. Degradation pathways for 1,4-D have also been proposed based on the decomposition intermediates and by-products. The results indicate that 1,4-D was completely degraded with heat-activated persulfate oxidation within 3-80 h. The kinetics of the 1,4-D degradation process fitted well to a pseudo-first-order reaction model. Temperature was identified as the most important factor influencing the 1,4-D degradation rate during the oxidation process. As the temperature increased from 40 to 60 °C, the degradation rate improved significantly. At 40 °C, the addition of Fe(2+) also increased the 1,4-D degradation rate. Interestingly, at 50 and 60 °C, the 1,4-D degradation rate decreased slightly with the addition of Fe(2+). This reduced degradation rate may be attributed to the rapid conversion of Fe(2+) to Fe(3+) and the production of an Fe(OH)3 precipitate which limited the ultimate oxidizing capability of persulfate with Fe(2+) under higher temperatures. Higher persulfate concentrations led to higher 1,4-D degradation rates, but pH adjustment had no significant effect on the 1,4-D degradation rate. The identification of intermediates and by-products in the aqueous and gas phases showed that acetaldehyde, acetic acid, glycolaldehyde, glycolic acid, carbon dioxide, and hydrogen ion were generated during the persulfate oxidation process. A carbon balance analysis showed that 96 and 93% of the carbon from the 1,4-D degradation were recovered as by-products with and without Fe(2+) addition, respectively. Overall, persulfate oxidation of 1,4-D is promising as an economical and highly efficient technology for treatment of 1,4-D-contaminated water.

Stimulation of nitrogen removal in the rhizosphere of aquatic duckweed by root exudate components

Plants can stimulate bacterial nitrogen (N) removal by secretion of root exudates that may serve as carbon sources as well as non-nutrient signals for denitrification. However, there is a lack of knowledge about the specific non-nutrient compounds involved in this stimulation. Here, we use a continuous root exudate-trapping system in two common aquatic duckweed species, Spirodela polyrrhiza (HZ1) and Lemna minor (WX3), under natural and aseptic conditions. An activity-guided bioassay using denitrifying bacterium Pseudomonas fluorescens showed that crude root exudates of the two species strongly enhanced the nitrogen-removal efficiency (NRE) of P. fluorescens (P < 0.05) under both conditions. Water-insoluble fractions (F) obtained under natural conditions stimulated NRE to a significant extent, promoting rates by about 30%. Among acidic, neutral and basic fractions, a pronounced stimulatory effect was also observed for the neutral fractions from HZ1 and WX3 under both conditions, whereas the acidic fractions from WX3 displayed an inhibitory effect. Analysis of the active fractions using gas chromatography/mass spectrometry (GC/MS) revealed that duckweed released fatty acid methyl esters and fatty acid amides, specifically: methyl hexadecanoate, methyl (Z)-7-hexadecenoate, methyl dodecanoate, methyl-12-hydroxystearate, oleamide, and erucamide. Methyl (Z)-7-hexadecenoate and erucamide emerged as the effective N-removal stimulants (maximum stimulation of 25.9 and 33.4%, respectively), while none of the other tested compounds showed stimulatory effects. These findings provide the first evidence for a function of fatty acid methyl esters and fatty acid amides in stimulating N removal of denitrifying bacteria, affording insight into the "crosstalk" between aquatic plants and bacteria in the rhizosphere.

Human factors and tidal influences on water quality of an urban river in Can Tho, a major city of the Mekong Delta, Vietnam

In this study, we focused on water quality in an urban canal and the Mekong River in the city of Can Tho, a central municipality of the Mekong Delta region, southern Vietnam. Water temperature, pH, electrical conductivity, BOD5, CODCr, Na(+), Cl(-), NH4 (+)-N, SO4 (2-)-S, NO3 (-)-N, and NO2 (-)-N for both canal and river, and tide level of the urban canal, were monitored once per month from May 2010 to April 2012. The urban canal is subject to severe anthropogenic contamination, owing to poor sewage treatment. In general, water quality in the canal exhibited strong tidal variation, poorer at lower tides and better at higher tides. Some anomalies were observed, with degraded water quality under some high-tide conditions. These were associated with flow from the upstream residential area. Therefore, it was concluded that water quality in the urban canal changed with a balance between dilution effects and extent of contaminant supply, both driven by tidal fluctuations in the Mekong River.

[Factors affecting benzene diffusion from contaminated soils to the atmosphere and flux characteristics]

The influencing factors of benzene diffusion fluxes from sand and black soil to atmosphere were investigated using a flux chamber (30.0 cm x 17.5 cm x 29.0 cm). In this study, the benzene diffusion fluxes were estimated by measuring the benzene concentrations both in the headspace of the chamber and in the soils of different layers. The results indicated that the soil water content played an important role in benzene diffusion fluxes. The diffusion flux showed positive correlation with the initial benzene concentration and the benzene dissolution concentration for both soil types. The changes of air flow rate from 300 to 900 mL x min(-1) and temperature from 20 degrees C to 40 degrees C resulted in increases of the benzene diffusion flux. Our study of benzene diffusion fluxes from contaminated soils will be beneficial for the predicting model, and emergency management and precautions.

Degradation of polychlorinated naphthalene by mechanochemical treatment

Polychlorinated naphthalene (PCN) is a hazardous compound that is listed as a new persistent organic pollutants candidate by the United Nations Environment Program. The production, import and use of PCNs are prohibited by the Chemical Substances Control Law in Japan. PCN was milled with calcium oxide as an additive to investigate the feasibility of its degradation by mechanochemical treatment. The milling process cleaved the C-C and C-Cl bonds by the mechanically induced solid-state reaction. Gas chromatography/mass spectrometry analysis confirmed that the PCN was decomposed after 1h milling. The yield of chloride ions reached 100% after 3h milling. This indicates that all PCN was broken down into inorganic compounds after milling, thereby maintaining the chlorine mass balance through the reaction. This experiment, for the first time, exhibited the effectiveness of mechanochemical treatment as a PCN degradation method.

Removal of PCDD/Fs from contaminated sediment and released effluent gas by charcoal in a proposed cost-effective thermal treatment process

A novel cost-effective thermal treatment technology has been proposed for the removal of PCDD/Fs from contaminated sediment and released effluent gas using charcoal as both an adsorbent and a thermal source. When a reactor was used for thermal treatment, the PCDD/Fs removal efficiency exceeded 98% from the sediment at the three different air superficial velocities employed in this study. The total PCDD/F international toxic equivalent (I-TEQ) contents, both in the treated sediments and effluent gas, were below the Japanese emission standard limit. Analysis of the PCDD/F contents in different fractions showed that large quantities of PCDDs but not PCDFs were evaporated from the sediment and adsorbed in the moist sediment column. This difference was attributed to the formation of PCDDs from pentachlorophenol (PCP) during the cooling process following the thermal treatment process in the reactor. This proposed thermal process provides a promising alternative to the conventional methods.

Formation pathways of polychlorinated dibenzofurans (PCDFs) in sediments contaminated with PCBs during the thermal desorption process

Thermal desorption has attracted considerable interest as a remediation technology for the removal of dioxins and polychlorinated biphenyls (PCBs) from contaminated soils and sediments. Although several research groups have confirmed that polychlorinated dibenzofurans (PCDFs) are formed from PCBs during the thermal desorption of sediments contaminated with PCB, the formation pathways remain poorly understood. Herein, thermal desorption has been used to develop a greater understanding of the formation pathways of PCDFs from sediments contaminated with PCBs. PCB decomposition experiments of sediments contaminated with PCBs were performed over 5 min at 450 °C with a gas composition of 10% O(2)/90% N(2), either in the absence (Run 1) or presence (Run 2-4) of one of three different (13)C(12)-labeled PCB individual standards. The results of Run 1 showed that 99.96% of PCBs and 98.40% of polychlorinated dibenzo-p-dioxins (PCDDs) in the treated sediments had decomposed, whereas the concentration levels of PCDFs had increased by a factor of 31. The addition of different (13)C(12)-labeled PCBs to the sediment sample yielded different (13)C(12)-PCDFs isomer patterns, with formation pathways including loss of ortho-Cl(2), loss of HCl involving a 2,3-chlorine shift, loss of ortho-H(2) and dechlorination.

Utilization of recycled charcoal as a thermal source and adsorbent for the treatment of PCDD/Fs contaminated sediment

A novel heat treatment process in which charcoal was used as both a thermal source and an adsorbent was investigated as a low-cost method for removal of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from solids. Three laboratory scale experiments involving various ratios of charcoal to contaminated sediment and air superficial velocities were performed. The results indicated that the total and toxic equivalency quantities (TEQ) concentrations of PCDD/Fs decreased significantly in the treated sediment of all runs with removal efficiencies greater than 96% and 90%, which resulted in residual concentrations below the Japanese standard limit of 0.15ng-TEQg(-1). The charcoal/contaminated sediment ratio and air superficial velocity were determinant factors controlling the PCDD/Fs concentrations and homologue profiles in effluent. As the air superficial velocity increased and charcoal/contaminated sediment ratio decreased, more PCDD/Fs were released from the sediment as fly ash, making them less likely to remain in the treated sediment. These phenomena were likely a result of the vapor pressure of PCDD/Fs, contact time with effluent gas and amount of PCDD/Fs adsorbed by charcoal. The developed process would promise an alternative to a conventional remediation process for PCDD/Fs contaminated solids.

Assessing nitrification and denitrification in a paddy soil with different water dynamics and applied liquid cattle waste using the ¹⁵N isotopic technique

Using livestock wastewater for rice production in paddy fields can remove nitrogen and supplement the use of chemical fertilizers. However, paddy fields have complicated water dynamics owing to varying characteristics and would influence nitrogen removal through nitrification followed by denitrification. Quantification of nitrification and denitrification is of great importance in assessing the influence of water dynamics on nitrogen removal in paddy fields. In this study, nitrification and nitrate reduction rates with different water dynamics after liquid cattle waste application were evaluated, and the in situ denitrification rate was determined directly using the (15)N isotopic technique in a laboratory experiment. A significant linear regression correlation between nitrification and the nitrate reduction rate was observed and showed different regression coefficients under different water dynamics. The regression coefficient in the continuously flooded paddy soil was higher than in the drained-reflooded paddy soil, suggesting that nitrate would be consumed faster in the flooded paddy soil. However, nitrification was limited and the maximum rate was only 13.3 μg Ng(-1)day(-1) in the flooded paddy soil with rice plants, which limited the supply of nitrate. In contrast, the drained-reflooded paddy soil had an enhanced nitrification rate up to 56.8 μg Ng(-1)day(-1), which was four times higher than the flooded paddy soil and further stimulated nitrate reduction rates. Correspondingly, the in situ denitrification rates determined directly in the drained-reflooded paddy soil ranged from 5 to 1035 mg Nm(-2)day(-1), which was higher than the continuously flooded paddy soil (from 5 to 318 mg Nm(-2)day(-1)) during the vegetation period. The nitrogen removal through denitrification accounted for 38.9% and 9.9% of applied nitrogen in the drained-reflooded paddy soil and continuously flooded paddy soil, respectively.

CH₄ and N₂O emissions from different varieties of forage rice (Oryza sativa L.) treating liquid cattle waste

To evaluate global warming potential (GWP) on livestock waste treatment and biomass production in rice field, methane (CH(4)) and nitrous oxide (N(2)O) fluxes from forage rice fields planted with 4 different cultivars (Oryza sativa L. cv. Hamasari, Leafstar, Kusahonami and Takanari) were measured. Each of the cultivars were subjected either to basal fertilization alone (control plots) (84 kg N ha(-1)), or to basal fertilization plus topdressing with liquid cattle waste or LCW (treatment plots) (567 kg N ha(-1)). Liquid cattle waste application to the rice field resulted in peak CH(4) fluxes ranging from 22.0 to 32.1 mg m(-1)h(-1) during flooded conditions and large N(2)O fluxes ranging from 526 to 8591 μg m(-1)h(-1) after midsummer drainage and final drainage. The GWP of the control plots was between 1358 and 3872 kg CO(2)eq ha(-1), while the treatment plots ranged between 4503 and 8426 kg CO(2)eq ha(-1) and more than 60% of the GWP was from the N(2)O emission in treatment plots. In both the control and treatment plots, the lowest GWPs per ton of above-ground biomass were found to be from the Leafstar cultivar, which had a higher aboveground biomass than other cultivars; 117 kg CO(2)eq t(-1) from the control and 257 kg CO(2)eq t(-1) from the treatment plots. Thus, both forage production and suitable disposal of the LCW may be able to be achieved concomitantly with lower levels of GWP by cultivation of Leafstar in our field.

Mechanochemical degradation of γ-hexachlorocyclohexane by a planetary ball mill in the presence of CaO

Although the use of the insecticide γ-hexachlorocyclohexane (HCH) is now prohibited in many countries because of its hazardousness, stockpiles of γ-HCH still exist. In this study, we subjected γ-HCH to mechanochemical (MC) treatment with a planetary ball mill in the presence of CaO to investigate the feasibility of using this method for the treatment of γ-HCH stockpiles. We confirmed the degradation of γ-HCH and investigated the degradation mechanism. The major intermediates were identified to be 1,3,4,5,6-pentachlorocyclohexene (γ-PCCH) and chlorobenzenes (CBzs). Analysis of the steric structure of γ-HCH and identification of the degradation intermediates suggested that successive dehydrochlorination led to the formation of trichlorobenzenes. Products of further degradation (dichlorobenzenes, monochlorobenzene, and benzene) were also detected. Surprisingly, methane and ethane were also detected, which suggests cleavage of the C-C bonds of the cyclohexane ring and hydrogenation. All of the chlorine atoms in the γ-HCH could be transformed into inorganic chloride compounds by the MC treatment with CaO. Our results indicate that γ-HCH can be completely dechlorinated by MC treatment.

Polyphenols and fatty acids responsible for anti-cyanobacterial allelopathic effects of submerged macrophyte Myriophyllum spicatum

Myriophyllum spicatum is known to inhibit the growth of cyanobacteria such as Microcystis aeruginosa by releasing anti-cyanobacterial allelochemicals. The allelochemicals possibly responsible for the inhibition include five polyphenols and three fatty acids, but the extent to which these are indeed responsible for the anti-cyanobacterial effects is unclear. The goal of this research was to determine the contribution of these compounds to the allelopathic effect of M. spicatum on M. aeruginosa. We first collected information on the release rates of these compounds and then added the compounds to a cyanobacterial medium on the basis of their release rates so as to simulate their excretion by M. spicatum. Addition of the polyphenols and fatty acids inhibited the growth of M. aeruginosa, and the interaction of the polyphenols and fatty acids was additive. The EC50 of a polyphenol and fatty acid mixture was compared with that of M. spicatum itself as previously determined in a mixed culture system in which M. spicatum and M. aeruginosa were incubated. The former was about 1.9 times higher than that of the latter, the implication being that the inhibitory effect of the polyphenols and fatty acids contributed about 53% of the allelopathic effect of M. spicatum. This paper is the first to describe allelochemicals that account for a half of the anti-cyanobacterial allelopathic effect of a macrophyte.

Evaluation of anaerobic biodegradability of forage rice straw fertilized with livestock waste

Fertilizing livestock waste for forage rice production can remove nitrogen and reduce the need for chemical fertilizers. Furthermore, rice straw can be used for biogas production. Here, the growth characteristics of different forage rice varieties in Japanese paddy fields fertilized with liquid cattle waste were investigated. Six experimental plots were established in a paddy field planted with three varieties of forage rice developed for livestock feed. Methane production potential assays were then conducted to investigate the anaerobic digestion characteristics of the stems and leaves of these three varieties. The total methane production potential of the Leafstar variety was higher than that of other varieties, while its lag phase was significantly shorter. Co-digestion of ethanol fermentation residue with Leafstar straw revealed that the NH(4)(+)-N concentration decreased as the C/N ratio increased. Additionally, the methane production potential of the mixed substrate was higher than that of ethanol fermentation residue or forage rice straw applied alone. Hence, Leafstar forage rice is a promising variety for establishment of agricultural resource recycling systems in which higher straw biomass can be achieved by applying liquid cattle waste and more biogas can be produced due to the potential for increased methane production.

Prevention of lead leaching from fly ashes by mechanochemical treatment

Fly ashes from a municipal solid waste incinerator were subjected to mechanochemical (MC) treatment in a planetary ball mill, and the treated fly ashes were cemented with a binder. The leachability of lead (Pb) from the treated fly ashes and from the cement product were investigated, and the speciation of lead in the treated and untreated ashes was determined by X-ray absorption fine structure (XAFS) analysis. MC treatment of the fly ashes and subsequent cementation prevented Pb leaching by 99.9%, whereas MC treatment alone prevented Pb leaching by 92.8%. Analysis of the X-ray absorption near-edge spectrum of the untreated fly ashes revealed that the predominant Pb species in the ashes was PbCl(2). In contrast, the counterpart in the treated fly ashes was Pb(3)O(4) insoluble in water. The formation of a species of Pb with a lower solubility in water than that of PbCl(2) was confirmed by MC treatment of PbCl(2)-spiked fly ashes for 48h, indicating the reduction of PbCl(2) in the spiked fly ashes to Pb via Pb(3)O(4) during MC treatment. Our results indicate that such reduction to an insoluble species prevented Pb from leaching and that MC treatment followed by cementation is a feasible method for the recycling of fly ashes.

Behavior of PCDDs/PCDFs in remediation of PCBs-contaminated sediments by thermal desorption

Thermal desorption is an effective method for removing volatile and semivolatile organic matter in contaminated solid remediation. Formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in many polychlorinated biphenyls (PCBs) destruction processes has been reported, but the removal pathways are poorly understood. We therefore investigated the behaviors of PCBs and PCDDs/PCDFs in thermal desorption of PCBs-contaminated sediment and predicted the reaction pathways. Four thermal desorption experiments using PCB-contaminated sediments containing different doses of PCBs were carried out. In all the experiments, decomposition of 48-70% of PCBs was achieved, resulting in formation of PCDFs. Despite the PCBs decomposition levels, toxic equivalencies (TEQs) in the treated and volatilized samples were 2.8-6.3 times and 8.0-10.5 times as high as the TEQs in the initial samples, respectively, indicating increased toxicity after treatment. Further analysis revealed that PCDFs with higher numbers of chlorine atoms are likely to remain in the sediments than those of volatilized PCDFs; this is supported by the positive correlation between the vapor pressures of PCDFs and the ratios of volatilized PCDFs.

Photodechlorination of octachlorodibenzothiophene and octachlorodibenzofuran: comparison of experimental degradation pathways with degradation pathways predicted by DFT

Polychlorodibenzothiophenes (PCDTs) are sulfur analogues of polychlorodibenzofurans (PCDFs) and have been detected in environmental samples. We used density functional theory calculations (Gaussian 98W) to predict the photodechlorination pathways of octachlorodibenzothiophene (OCDT) and octachlorodibenzofuran (OCDF) in hexane, and we compared the predicted pathways with those observed during UV irradiation experiments. OCDT and OCDF were observed to degrade through first-order dechlorination processes, and the rate constant for OCDT was less than one-third that for OCDF. The main experimental photodechlorination pathways of OCDT and OCDF led to hexachlorinated and tetrachlorinated congeners, respectively; that is, the photodechlorination pathway of OCDT differed from that of OCDF. On the assumption that the dechlorination mechanisms involved radical reactions, we used DFT calculations to estimate bond-dissociation energies and single-point energies of OCDT and OCDF and their dechlorinated congeners, and we used the resulting information, along with hypotheses regarding the rate-controlling step of the degradations, to predict theoretical degradation pathways. We propose that reaction of dechlorinated radicals with a hydrogen donor was the rate-controlling step for OCDT and that C-Cl bond dissociation by UV light was the rate-controlling step for OCDF.

Evaluation of ethanol washing on dioxins-polluted soil and sediment based on adsorption relationships

Multi-stage ethanol washing on dioxins-polluted soil and sediment were performed. The results indicated the existence of limit washing concentration (LWC), where no more dioxins were removed from the soil or the sediment by further washing. In each stage, dioxins concentration in the soil, sediment and ethanol could be described satisfactory by the Freundlich equation. The Freundlich capacity factor, K(ef) correlated with the LWC which was estimated to be ca. 1000 pmol g(-1) in the case of soil, and about 150 pmol g(-1) in the case of sediment. Organic contents in the soil and sediment affected the Freundlich intensity parameter, n(-1) but not K(f). A model, which enables the calculation of removal efficiency of PCDD/DFs at each stage using K(f), n, and initial PCDD/DFs concentration, is presented.

Photodegradation fates of cis-chlordane, trans-chlordane, and heptachlor in ethanol

cis-Chlordane, trans-chlordane, and heptachlor were photodegraded in ethanol, and their degradation fates and degradation products were determined by a computational chemical method. The most degradable material was heptachlor (first-order reaction constant k=0.13 min(-1)). Chlorine balances changed during UV irradiation, and the chlorine atoms in chlordane and heptachlor were eventually mineralized. cis-Chlordane, trans-chlordane and heptachlor each generated two di-dechlorinated products. Reactivities at various positions in these compounds were predicted on the basis of bond dissociation energies calculated by nonempirical molecular orbital calculation (Gaussian 98W).

Photodegradation of hexachlorobenzene and theoretical prediction of its degradation pathways using quantum chemical calculation

Experimentally determined photodegradation pathways of hexachlorobenzene (HCB), a chlorinated aromatic compound, in hexane, 2-propanol (IPA), and methanol were compared with those predicted by quantum chemical calculation based on density functional theory (DFT), and the adequacy of the prediction method was evaluated. The experimental main degradation pathways of HCB were virtually the same for the three solvents and also agreed with the predicted main degradation pathways. In the DFT method, the main degradation product was the dechlorinated benzene at the position where the C-Cl bond was predicted to have the lowest bond dissociation energy. This result suggested that the photodechlorination pathways of chlorinated aromatic compounds could be predicted by comparing the bond dissociation energies calculated with the DFT method.

Polychlorinated dibenzothiophenes in Japanese environmental samples and their photodegradability and dioxin-like endocrine-disruption potential

Polychlorinated dibenzothiophenes (PCDTs) in sediment, soil, and fly ash samples collected in Japan were analyzed and their dioxin-like endocrine-disruption potential and photodegradability investigated. PCDTs were detected in all three types of sample, although the concentrations were lower than those of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). An Ah-immunoassay confirmed that 2,3,7,8-TeCDT, 1,2,3,7,8-PeCDT, 1,2,3,7,8,9-HxCDT, and 1,2,3,4,7,8,9-HpCDT had Ah receptor-binding activities, which means that these PCDTs have the potential to cause dioxin-like endocrine-disruption. Photodegradation of PCDTs by UV irradiation was accompanied by dechlorination. The photodegradation rates of 2,3,7,8-TeCDT and OCDT were lower than the rates for the corresponding PCDF isomers (2,3,7,8-TeCDF and OCDF), which indicates that PCDTs are more stable than PCDFs to photodegradation.

Estrogenic activity removal of ethynylestradiol by nitrifying activated sludge and microorganisms involved in its degradation

A solid-phase extraction of ethynylestradiol (EE2) and its degradation intermediates and products by nitrifying activated sludge (NAS) was performed to measure estrogenic activity during the degradation by NAS. The yeast two-hybrid assay of the extract showed that NAS not only degraded EE2, but also removed the estrogenic activity originating from EE2, its degradation intermediates and products. This means that estrogenic activity decreases when EE2 concentrations are decreased by NAS. Although gas chromatography/mass spectrometer (GC/MS) analyses suggested the existence of nitrated EE2 as a degradation intermediate, its estrogenic activity was unmeasurable due to the lack of an authentic sample. However, on the basis of the dose-response relationship between EE2 concentration and estrogenic activity in the yeast two-hybrid assay, it was surmised that the estrogenic activity in the culture medium of NAS may have been produced mostly by the remaining EE2 and not by its degradation intermediates and products. The partial nucleotide sequence analyses of microorganisms in the consortiums acclimatized for EE2 and natural estrogens E2 and E1 enabled the identification of candidates that may be responsible for estrogen degradation by NAS.

Photodegradation of pentachlorophenol and its degradation pathways predicted using density functional theory

The objectives of the present research were (i) to report the mass balance of chlorine during pentachlorophenol (PCP) photodegradation and (ii) to reveal the photodegradation pathway experimentally with a theoretical proof based on the density functional theory (DFT). The chlorine of PCP was completely mineralized to produce chloride ions after 24h of UV irradiation. As intermediates, 2,3,5,6-tetrachlorophenol, 2,3,4,6-tetrachlorophenol and 2,5-dichlorophenol were identified. At least 80% of the chlorine balance during PCP photodegradation was accounted by PCP, these intermediates, and chloride ions. A DFT calculation showed differences in the C-Cl bond dissociation energy level and the positions of respective PCP molecular and the PCP intermediates. The dechlorination intermediates predicted using the calculated C-Cl bond dissociation energy were consistent with those experimentally confirmed, indicating the feasibility of this theoretical method in predicting the dechlorination pathway.

Elucidation of degradation mechanism of dioxins during mechanochemical treatment

Model dioxin compounds 4-chlorobiphenyl (4CB), octa-chlorodibenzo-p-dioxin (OCDD), and octachlorodibenzofuran (OCDF) were degraded by a mechanochemical (MC) process that involved milling with calcium oxide by use of a planetary ball mill. The degradation of 4CB produced mainly chloride ions and biphenyl, with the chlorine removal efficiency reaching about 100%. Biphenyl was transformed into terphenyls, quaterphenyls, cyclohexylbenzene, and bicyclohexyl through polymerization and hydrogenation reactions. Measurements of chloride ions after MC treatment of OCDD and OCDF showed about 100% dechlorination of both compounds; tetra- to heptachlorinated dibenzo-p-dioxins/furans (T4-H7CDD/Fs) were detected only at trace levels, and no other chlorinated organic compounds were observed. The residue after MC treatment was gray in color, indicating the possibility of carbonization, but the presence of amorphous graphite could not be confirmed.

Biodegradation of natural and synthetic estrogens by nitrifying activated sludge and ammonia-oxidizing bacterium Nitrosomonas europaea

This report describes the uses of nitrifying activated sludge (NAS) and ammonia-oxidizing bacterium Nitrosomonas europaea to significantly degrade estrone (E1), 17beta-estradiol (E2), estriol (E3), and 17alpha-ethynylestradiol (EE2). Using NAS, the degradation of estrogens obeyed first-order reaction kinetics with degradation rate constants of 0.056 h(-1) for E1, 1.3 h(-1) for E2, 0.030 h(-1) for E3, and 0.035 h(-1) for EE2, indicating that E2 was most easily degraded. Then, we confirmed that E2 was degraded via E1 by NAS. With/without the ammonia oxidation inhibitor, it was observed that ammonia-oxidizing bacteria in conjunction with other microorganisms in NAS degraded estrogens. Using N. europaea, the degradation of estrogens reasonably obeyed zero-order reaction kinetics, and no remarkable difference is present among the four estrogens degradation rates and it was found that E1 was not detected during E2 degradation period. We suggested that E2 was degraded to E1 in NAS could be caused by other heterotrophic bacteria, not by ammonia-oxidizing bacteria.

Microbial degradation of estrogens using activated sludge and night soil-composting microorganisms

In order to investigate the potential for microbial degradation of estrogens, and the products formed, activated sludge collected from Korea (ASK) and night soil-composting microorganisms (NSCM) were used to degrade estrogens. Results showed that both ASK and NSCM degraded almost 100% of the natural estrogens estrone (E1), 17beta-estradiol (E2), and estriol (E3) from initial concentrations of 20-25 mg/L, while synthetic estrogen, ethynylestradiol (EE2), was not degraded. Analysis of degradation products of E2 by using HPLC-ECD and a consecutive first-order reaction calculation confirmed that E2 was sequentially degraded to E1, which was further degraded to other unknown compounds by ASK and NSCM. We then used the yeast two-hybrid assay to show that the unknown degradation products did not appear to possess estrogenic activity when E1, E2 or E3 were degraded to below the detection limit after 14 days of incubation, indicating that ASK and NSCM not only degrade natural estrogens, but also remove their estrogenic activities.

The characteristics of the bacterial community structure and population dynamics for phosphorus removal in SBR activated sludge processes

The characteristics of the bacterial community structure and population dynamics for phosphorus removal in activated sludge were investigated using laboratory-scale sequencing batch reactor (SBR) activated sludge processes fed with four different carbon sources. Phosphorus removal activity, quinone profile of the activated sludge and isolated bacterial strains were monitored. An enhanced phosphorus removal activity was accompanied by the increase in ubiquinone-9 (Q-9). The relationships between phosphorus removal activity and Q-9 contents of the isolated bacterial strains were dependent neither on the organic substrates nor on the species of isolated bacterial strains. The enhanced phosphorus removal capability of activated sludge seemed to be due to the increase in the populations of bacteria with activity of phosphorus removal, i.e. species succession of bacteria in activated sludge ecosystems, rather than the increase in the phosphorus removal capability of phosphorus removal bacteria. Not only Acinetobacter but also Pseudomonas identified from isolated strains were regarded as representative polyphosphates-accumulating organisms and predominant species to the whole of bacterial population in activated sludge for phosphorus removal.

Survey of dioxins in Tokyo Bay bottom sediment

This paper examines dioxin profiles in bottom sediments from Tokyo Bay, Japan using sedimentation dating based on 210Pb measurements and dioxin measurements based on particle size distributions. Dioxin concentrations in surface sediment ranged from 3.2 to 52 pg-TEQ g(-1), with the concentrations in the bay back and central region being higher than those at the front of the bay. The vertical dioxin concentration in sediment core samples showed peak levels from years 1962 to 1980, with the maximum being 110 pg-TEQ g(-1). Principal component analysis indicates that the main source of dioxins in bottom sediment from the back of bay are herbicides such as CNP, while in the front of bay atmospheric deposition due to incineration activities are responsible. Dioxins in bottom sediment were mainly found in the particles <75 microm in size.

Effects of high salinity and constituent organic compounds on treatment of photo-processing waste by a sulfur-oxidizing bacteria/granular activated carbon sludge system

To achieve practical treatment of photo-processing waste (PW) using our previously proposed sulfur-oxidizing bacteria (SOB)/granular activated carbon (GAC) sludge system, this paper elucidates why 3- to 5-X dilution of PW was required. That is, a series of experiments were carried out to show the effects of high salinity and constituent organic compounds in PW, respectively. Both an inorganic salts system and calcination PW system showed that SOB completely oxidizes S2O(3)2- -S to SO(4)2- -S even at 12.3 or 13.6% salinity, respectively; hence the dilution requirement is not attributable to high salinity. In experiments employing SOB and SOB/GAC systems to investigate the effects of 23 constituent compounds in PW, compounds were classified into Groups I, II, IIIa, and IIIb. Even with 10 g/l GAC, the nine compounds in Group IIIb still exhibited a toxic effect on SOB activity at 1- and 3-X dilutions; thus it is these compounds that are responsible for requiring dilution of PW. Accordingly, a reduction in their use within the photodeveloping and fix-stabilizing industry, and/or use of > 10g/l GAC, are new considerations for establishing a more practical PW treatment process.

Removal of polychlorinated biphenyls from capacitors and pressure-sensitive paper by vacuum thermal recycling

This paper describes a new vacuum thermal recycling (VTR) method for treating discarded polychlorinated biphenyls (PCB)-contaminated capacitors and pressure-sensitive paper. Based on results demonstrating an exceptionally high PCB separation efficiency and recovery ratio from capacitors containing high-concentration PCBs, i.e. > 99.9%, respectively, the presented VTR method is verified to effectively remove PCBs. In addition, associated safety aspects of the employed procedure were confirmed.