Biodegradation of nitrogen-enriched lignite

Biodegradation of nitrogen-enriched lignite by soil bacteria previously acclimated in hydrogen peroxide-acetic acid lignitic substrate was carried out to assess the effects of nitrogen functional groups on the biodegradation of lignite. Chlorination, oxidation plus nitration, and ammoniation were applied in an attempt to modify the chemical structure of lignite so as to obtain a lignitic substrate that is more compatible to the enzymatical system of ordinary soil bacteria than that of unmodified lignite. Incorporation of nitrogen containing functional groups into lignite structure achieved 4.71 wt%, a value five times higher than that usually found in unmodified (raw) lignite. Data collected through a 16 day incubation time, monitoring production as well as depletion of both nitrate and organic acids, concluded that biodegradation was expedited by the incorporation of nitrogen into the structure of lignite. Twenty-eight compounds were identified based on the results from GC/MS analysis of the products.     

Energy reduction of a submerged membrane bioreactor using a polytetrafluoroethylene (PTFE) hollow-fiber membrane

The fiber length and packing density of the PTFE membrane element were increased. The MBR was stably operated under an SAD^m of 0.13 m³·m^-2·hr^-1. Specific energy consumption was estimated to be less than 0.4 kWh·m^-3. In this study, we modified a polytetrafluoroethylene (PTFE) hollow-fiber membrane element used for submerged membrane bioreactors (MBRs) to reduce the energy consumption during MBR processes. The high mechanical strength of the PTFE membrane made it possible to increase the effective length of the membrane fiber from 2 to 3 m. In addition, the packing density was increased by 20% by optimizing the membrane element configuration. These modifications improve the efficiency of membrane cleaning associated with aeration. The target of specific energy consumption was less than 0.4 kWh·m^-3 in this study. The continuous operation of a pilot MBR treating real municipal wastewater revealed that the MBR utilizing the modified membrane element can be stably operated under a specific air demand per membrane surface area (SAD_m) of 0.13 m³·m^-2·hr^-1 when the daily-averaged membrane fluxes for the constant flow rate and flow rate fluctuating modes of operation were set to 0.6 and 0.5 m³·m^-2·d^-1, respectively. The specific energy consumption under these operating conditions was estimated to be less than 0.37 kWh·m^-3. These results strongly suggest that operating an MBR equipped with the modified membrane element with a specific energy consumption of less than 0.4 kWh·m^-3 is highly possible.     

Speciation of mercury in the strongly polluted sediments of the Deûle River (France)

The De?le River in Northern France experienced serious contamination from the metallurgical industry, especially from the smelter Metaleurop prior to 2003. In 2002 the surface sediments were collected from the bed of the river around 10 km above and 10 km below the smelter. Total mercury (HgT) and methylmercury (MeHg) concentrations exceeded the background value of 0.1 mg kg(-1). The average concentrations were 19.67 ± 1.02 mg kg(-1) and 10.88 ± 1.08 μg kg(-1), respectively. In 2003 the sediment core samples were collected at two different sites near the factory for survey depth profiles of Hg contamination. The concentrations of HgT and MeHg in sediment cores varied from 10.47 to 259.44 mg kg(-1) and from 3.24 to 82.61 μg kg(-1), respectively. The concentration of total mercury was significantly correlated with the methylmercury concentration in the sediment below a depth of 23.5 cm (R(2) = 0.81, p < 0.01). This may suggest that the production of MeHg is directly related to the HgT concentration. Nevertheless the MeHg/HgT ratio in the upper part of the sediment core was higher than that in the lower part. This suggests that HgT and MeHg may have been co-deposited together. However, the methylmercury production takes place in the surface sediment by microorganisms. The strong correlation observed between MeHg and acid volatile sulfides (AVS) suggests that MeHg variability is associated with the bacterial activity (presence of AVS).     

金华市义乌江沉积物磁性特征与重金属污染

对浙江省金华市义乌江采集的边滩沉积物柱样,进行了系统的环境磁学、粒度、地球化学分析,以探讨环境磁学方法诊断河流沉积物重金属污染的可行性.结果表明,柱样磁性特征由亚铁磁性矿物主导,其垂向变化受到粒度和早期成岩作用的一定影响.柱样中重金属Cr、Ni、Cu、Zn、Cd、Pb含量及其富集因子除底部外,自下而上呈增加趋势,指示了柱样上部存在人为来源的重金属污染.柱样沉积物磁性特征与重金属含量及其富集因子的垂向变化存在相似性,其中磁化率(χ)、频率磁化率(χfd%)和硬剩磁(HIRM)与Cr、Cu、Zn、Cd、Pb的含量具有显著的正相关关系,反映了磁性矿物与重金属具有相同的来源,或者细颗粒磁性矿物对重金属的吸附作用.上述结果表明,磁学方法可用于指示义乌江的重金属污染.但由于义乌江属于开放性的河流环境系统,磁性特征变化受多重因素影响,增加了利用磁学手段定量诊断重金属污染的复杂性.     

Source discrimination of heavy metals in sediment and water of To Lich River in Hanoi City using multivariate statistical approaches

The concentrations of Mn, Fe, Ni, Cr, Cu, Pb, Zn, As, and Cd were determined to evaluate the level of contamination of To Lich River in Hanoi City. All metal concentrations in 0–10-cm water samples, except Mn, were lower than the maximum permitted concentration for irrigation water standard. Meanwhile, concentrations of As, Cd, and Zn in 0–30-cm sediments were likely to have adverse effects on agriculture and aquatic life. Sediment pollution assessment was undertaken using enrichment factor and geoaccumulation index (I _geo). The I _geo results indicated that the sediment was not polluted with Cr, Mn, Fe, and Ni, and the pollution level increased in the order of Cu < Pb < Zn < As < Cd. Meanwhile, significant enrichment was shown for Cd, As, Zn, and Pb. Cluster and principal component analyses suggest that As and Mn in sediment were derived from both lithogenic and anthropogenic sources, while Cu, Pb, Zn, Cr, Cd, and Ni originated from anthropogenic sources such as vehicular fumes for Pb and metallic discharge from industrial sources and fertilizer application for other metals.     

Design of a representative and cost-effective sampling programs for industrial wastewater with examples from bleached kraft pulp and paper mills

The diagram constructed for selection of sampling methods indicates that, for a systematic error, E ≤ 13%, grab sampling (GS) may be used to characterize effluents with variation coefficient of flow ≤ 120% and of contaminant concentrations ≤ 10%. For the whole studied range of variation coefficient of contaminant concentrations (2–82%), time-proportional compositing (TC) method may be applied with E ≤ 10% for effluents characterized by variation coefficients in flow < 90%. The more complicated flow-proportional compositing (FC) method is required only for effluents with larger variation coefficients or to produce more precise results. The diagram constructed for selection of sampling frequencies indicates that sequential sampling at intervals of approximately 60 min may be applied with E ≤ 10% for effluents characterized by variation coefficients ≤ 30%. Practical application of the diagrams, constructed using normal series, was checked against monitoring data from two pulp and paper mills in Vietnam. The two diagrams provided results on sampling methods and frequencies in good agreement with those obtained from actual monitoring data with percentages of agreement cases of 80 and 75%, respectively. The approach was applied in design of a monitoring program at the Bai Bang integrated pulp and paper mill in Vietnam.     

Photochemical Smog Modelling Using the Air Pollution Chemical Transport Model (TAPM-CTM) in Ho Chi Minh City,Vietnam

Environmental Modeling & Assessment - This paper describes the application of the air pollution model (TAPM-CTM) for photochemical airshed modelling in the Ho Chi Minh region. The model was...     

Temperature Effect on Migration of Zn and Cd Through Natural Clay

To investigate the effect of temperature on effective diffusion coefficients and retardation factors for Zn and Cd, combined diffusion and sequential extraction analyses were conducted at 15 ^˚C and 55 ^˚C. The effective diffusion coefficients of the metals increased up to ten times according to the increased temperature. On the other hand, the effect of temperature on the retardation factor depended on the retention mechanisms of the metals. The distribution coefficient for Zn, which was mainly partitioned in the carbonate phase, increased up to two times with the increase in temperature. On the other hand, the distribution coefficient for Cd, which was mainly partitioned in the exchangeable phase, was hardly affected by the temperature change. Results of combined diffusion and sequential extraction analysis showed that the effect of temperature on the heavy metals’ (Zn and Cd) migration through the compacted natural clay was influenced by the combined effects of the diffusion coefficient and the retardation factor. Additionally, we could also observe the change in retention mechanism for the metals with the change in pore water concentration.     

Changes in motorcycle-related injuries and deaths after mandatory motorcycle helmet law in a district of Vietnam

Objective: Our study measured the change in head injuries and deaths among motorcycle users in Cu Chi district, a suburban district of Ho Chi Minh City.

Methods: Hospital records for road traffic injuries (RTIs) were collected from the Cu Chi Trauma Centre and motorcycle-related death records were obtained from mortality registries in commune health offices. Head injury severity was categorized using the Abbreviated Injury Score (AIS). Rate ratios (RRs) were used to compare rates pre- and post-law (2005/2006–2009/2010). Cu Chi's population, stratified by year, age, and sex, was used as the denominator.

Results: Of records identifying the transportation mode at the time of injury, motorcyclists accounted for most injuries (3,035, 87%) and deaths (238, 90%). Head injuries accounted for 70% of motorcycle-related hospitalizations. Helmet use was not recorded in any death records and not in 97% of medical records. Males accounted for most injuries (73%) and deaths (88%). The median age was 28 years and 32 years for injuries and deaths, respectively. Compared to the pre-law period, rates of motorcycle injuries (RR = 0.53; 95% confidence interval [CI], 0.49–0.58), head injuries (RR = 0.35; 95% CI, 0.31–0.39), severe head injuries (RR = 0.47; 95% CI, 0.34–0.63), and deaths (RR = 0.69; 95% CI, 0.53–0.89) significantly decreased in the post-law period.

Conclusions: Rates of head injuries and deaths among motorcycle riders decreased significantly after implementation of the mandatory helmet law in Vietnam. To further examine the impact of the motorcycle helmet law, including compliance and helmet quality, further emphasis should be placed on gathering helmet use data from injured motorcyclists.