Evaluation of a sustainable remediation option: Beneficial reuse of petroleum-contaminated sediment as an energy source

The characteristics of petroleum-contaminated sediment (PCS) have been evaluated to assess whether the practice of its beneficial reuse as a sole or supplemental energy source is sustainable relative to other sediment remediation options such as monitored natural recovery (MNR), capping, or off-site disposal. Some of these remediation options for PCS are energy-intensive and/or require land utilization. The energy and compositional analysis results indicate a low carbon content (15–17%(wt)) and corresponding low energy values of 5,200 kJ/kg (2,200 Btu/lb) to 5,600 kJ/kg (2,400 Btu/lb). However, given other decision-making criteria, the sediment may contain enough value to be added as a supplemental fuel given that it is normally considered a waste product and is readily available.

The thermogravimetric profiles obtained under both combustion and pyrolytic conditions showed that the sulfur contents were comparable to typical low sulfur bituminous or lignite coals found in the United States, and most of the volatiles could be vaporized below 750°C. The heavy metal concentrations determined before and after combustion of the PCS indicated that further engineering controls may be required for mercury, arsenic, and lead. Due to the potential for reduction of public health and environmental threats, potential economic savings, and conservation of natural resources (petroleum and land), removal of PCS by dredging and beneficial reuse as a supplemental fuel clearly has merit to be considered as a sustainable remediation option.

Implications: This study will provide a logical evaluation process to determine whether petroleum-contaminated sediment can be reused as an energy source. The energy and emissions values were determined and evaluated whether the sediment could be combusted for viable and sustainable use, considering several factors pertinent to evaluate in the remediation decision process. Various analysis methods were employed to determine elemental compositions, heating values, thermal and emission characteristics. This evaluation process may be used as a general methodology for the determination of petroleum-contaminated sediment as a supplemental fuel that may have merit to be considered as a sustainable remediation option.     

Control of diesel gaseous and particulate emissions with a tube-type wet electrostatic precipitator

In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NOx) from diesel exhaust emissions. The concentration of ozone (O3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O3 analyzer were used for quantifying the inlet and outlet concentrations of CO and NOx (nitric oxide [NO] + nitrogen dioxide [NO2]), and O3 in the diesel exhaust stream. The wESP was capable of removing approximately 67-86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NOx concentration in diesel exhaust. The O3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed.     

个体防护装备国家标准制修订工作流程

个体防护装备国家标准作为国家标准的一个重要组成部分．其制修订工作除了要符合国家的各项规定外，还有其特殊性。现就其具体的工作流程，进行详细的介绍，供个体防护装备科研单位和企业参考。     

Formation and biodegradation of toluene in the anaerobic sludge digestion process.

The formation of toluene in municipal anaerobic primary and secondary sludge digestion processes was investigated. Experiments were carried out in a large laboratory-scale reactor using sludge from a primary settling tank of a municipal treatment plant. It was found that toluene was produced in the supernatant in relatively large concentrations for almost all cases tested. The concentration of toluene varied and was found to depend on the stage of the anaerobic process. During the acidity phase, which is the first stage of anaerobic digestion, an increase of toluene concentration was observed, while in the transition period, from the acidity phase to methanogenesis, the toluene concentration decreased. It was concluded that biosynthesis of toluene occurs in the acidogenic phase, while biodegradation was prevalent in the methanogenic stage. Depending on the type of experiments, an increase of toluene from a base value of approximately 200 microg/L up to 20,000 and 42,000 microg/L was measured in the first stage of anaerobic digestion. In the subsequent methane-production stage of digestion, the estimated rate of toluene decrease (biodegradation) varied from 400 to 900 microg/L-d.     

用于CO2捕集的Mg(OH)2粉末溶解速率

氢氧化镁是一种正在研究的用于脱除烟气中低浓度CO2的化学吸收剂。为了掌握工业用氢氧化镁粉末的溶解速率,利用缓冲溶液,在不改变溶液体积的情况下对不同悬浊液浓度、溶液温度、溶液pH值和搅拌速率情况下的氢氧化镁粉末溶解速率进行了研究。提高悬浊液浓度、提高溶液温度、降低溶液pH值和提高搅拌速率均能增大氢氧化镁的溶解速率。悬浊液浓度从0.1 mol/L增加到1 mol/L时,溶解速率增大了2.2倍;温度从23℃增加到52℃时,溶解速率增大了4.3～9.5倍;pH值从9.8降低到6.6时,溶解速率增大了78～225倍;搅拌速率从350 r/min增加到700 r/min时,溶解速率增大了1～2倍。