Studies on enhanced degradable plastics. II. Weathering of enhanced photodegradable polyethylenes under marine and freshwater floating exposure

The weatherability of three types of enhanced photodegradable polyethylene films and corresponding control films were studied under outdoor and marine floating conditions at two exposure sites. Progress of weathering was monitored using tensile elongation at break. In general, both the enhanced-degradable plastics and the corresponding controls degraded slower in marine exposure than in outdoor exposure. This is attributed to the lower sample temperatures (compared to samples exposed outdoors) and to shielding from light afforded by surface fouling in samples exposed floating in sea water. Enhanced-photodegradable polyethylenes disintegrated faster than the control samples in the case of both outdoor and marine exposures. The improvement obtained in marine exposures was greater than that for outdoor exposure of corresponding sample types. This is due to the extremely slow rates of disintegration of control films under marine floating conditions.     

Studies on enhanced degradable plastics. III. The effect of weathering of polyethylene and (ethylene-carbon monoxide) copolymers on moisture and carbon dioxide permeability

Two enhanced-photodegradable polyethylenes were studied to determine the effect of photooxidative degradation upon transport properties. Water vapor permeability of LDPE films containing metal compound prooxidants, weathered to different extents under outdoor exposure was studied. A film made of LDPE blended with 20 wt% of polycaprolactone was also examined to determine if biodegradation over a 40-day period resulted in a measurable change in its water vapor transport characteristics. A gravimetric technique was used to study the effects of outdoor and weather-ometer exposures on the permeability of carbon dioxide of both the LDPE film and (ethylene-carbon monoxide) copolymer films. Generally, photooxidative degradation was seen to be accompanied by a change in transport characteristics of the polymer films.     

Changes in carbonyl index and average molecular weight on embrittlement of enhanced-photodegradable polyethylenes

Weathering behavior of two types of enhanced-photodegradable polyethylenes was studied using FTIR spectroscopy, tensile property changes, and gel-permeation chromatography to monitor structural changes accompanying photodegradation. Changes in elongation at break and carbonyl index during degradation showed a strong correlation with the average molecular weight of the polymers. At the point of embrittlement, the highest extent of degradation measured using tensile properties, the number-average molecular weights for both polymers were in the 10⁴ g/mol range. Facile biodegradation is not expected of polyethylenes of this degree of polymerization.     

A risk assessment of chlorinated aliphatics in bioremediated soils

Natural microbes living in contaminated subsurface media can be enhanced to degrade large concentrations of contaminating compounds at a faster rate than the microbes could degrade under natural conditions. A feasibility study demonstrating this principle was performed on-site in southern Louisiana to evaluate the effectiveness of two microbial degradation remediation methods used to decrease the human carcinogenic risks associated with exposure to ethylene dichloride and vinyl chloride concentrations in contaminated clay and sludge soils at the site. The results of the study are compared to an acceptable Louisiana Department of Environmental Quality closure level to evaluate in-situ microbial enhancement in chlorinated aliphatic-contaminated sludge and clay soils as a remediation/cleanup alternative in similar industrial situations.     

曝气强化非离子表面活性剂洗涤法修复柴油污染土壤

采用异位修复法,利用非离子表面活性剂洗涤柴油污染土壤,并在洗涤过程中曝气强化。考察了洗涤效果的影响因素,并通过表面张力和接触角的测定探讨了洗涤机理。实验结果表明:曝气对污染土壤中柴油的洗脱有强化作用,可提高洗脱率10%~20%;3种非离子表面活性剂的洗脱效果优劣次序为聚氧乙烯月桂醚(Brij-35)曲拉通X-100(TX-100)吐温-80(Tw-80);在表面活性剂浓度为1倍临界胶束浓度、曝气量为7.5 L/min、洗涤时间为60 min、洗涤液pH为11.0的优化条件下,Brij-35对柴油的洗脱率达77.4%,污染土样的含油率从7.0%降至1.6%,接触角从24.12°降至6.65°,可基本恢复土壤的亲水性;洗涤液的表面张力随表面活性剂浓度的增加而降低,但不受洗涤液pH的影响。     

Investigations on enhanced in situ bioxidation of methane from landfill gas (LFG) in a lab-scale model

The performance of an exogenous bacterium, Methylobacterium extorquens, in inducing bioxidation of methane from landfill gas (LFG) was assessed in a laboratory scale bioreactor. The study show that enhanced oxidation of methane is attained when the bacteria are introduced into the landfill soil. The maximum percentage reduction of methane fraction from LFG when the bioreactor was inoculated with the methanotrophic bacteria was 94.24 % in aerobic treatment process and 99.97 % in anaerobic process. In the experiments with only the indigenous microorganisms present in the landfill soil, the maximum percentage reduction of methane for the same flow rate of LFG was 59.67 % in aerobic treatment and 45 % in anaerobic treatment. The methane oxidation efficiency of this exogenous methanotrophic bacterium can be considered to be the optimum in anaerobic condition and at a flow rate of 0.6 L/m²/min when the removal percentage is 99.95 %. The results substantiate the use of exogenous microorganisms as potential remediation agents of methane in LFG.     

Thermally enhanced hydrolysis for treatment of pesticides and explosives

Thermally enhanced hydrolysis of halogenated alkanes such as 1,1,1‐trichlorethane has become a proven method of in situ soil and groundwater remediation. Electrical resistance heating is commonly used to heat soil and groundwater to accelerate the rate of hydrolysis. This article provides practical information to extend the hydrolysis remediation toolkit to include treatment of common pesticides and explosives. Sites with comingled volatile compounds, pesticides, and/or explosives can also be treated via a single solution.     

转盘式光催化燃料电池处理染料废水

采用阳极氧化法制备转盘式TiO_2阳极,设计并开发了转盘式光催化燃料电池(PFC),探讨了圆盘转速对PFC中染料降解效果的影响。实验结果表明:随着圆盘转速的提高,污染物和光电界面反应产物的传质作用得以强化,罗丹明B降解率提高;在圆盘转速为1 600 r/min、反应时间为60 min的条件下,罗丹明B降解率达90.8%,是圆盘转速为0 r/min时的8.5倍;光电流也随着圆盘转速的提高而提高,但提高幅度远小于罗丹明B降解率的提高幅度;同时,加强传质作用后再外加电压对PFC催化降解性能的提高作用有限。     

制药废水生化出水的强化混凝—高级氧化深度处理组合工艺比较

采用强化混凝和高级氧化法对制药废水生化出水进行深度处理,比较了不同混凝剂、不同氧化方法（包括Na₂S₂O₈氧化、电化学氧化、Fenton/类Fenton氧化）的处理效果。实验结果表明：经聚合硫酸铁与聚丙烯酰胺强化混凝处理后,废水的COD去除率达18.5%;强化混凝与不同氧化方法联用均可使废水脱色至无色,COD去除率达70.1%~92.4%。强化混凝—电化学氧化组合工艺的出水COD为27.1 mg/L,达到GB 8978—1996《污水综合排放标准》一级标准限值要求,且成本较低,适于实际应用。     

Ozone Dry Deposition Velocities for Coastal Waters

Air-sea exchange rates for ozone were measured by the eddy correlation technique at a site on the north Norfolk coast in the UK. The average surface resistance to ozone uptake was found to be, r_s(O₃) = 1,000 ± 100 s m^-1. Micrometeorological measurements of trace gas fluxes to ocean surfaces are rare but a review of available measurements suggests that we can constrain sea water surface resistance for ozone to between 1,000 (Regener (1974), and this work) and 1,890 s m^-1 (Lenschow et al., 1982), yielding surface deposition velocities between 0.53 and 1.0 mm s^-1. These values are more than an order of magnitude greater than can be explained by laboratory determined mass accommodation coefficients for ozone to water. The importance of dry deposition with respect to process air-sea exchange models is highlighted. A trend in surface deposition velocity with wind speed was also observed supporting a surface chemical enhancement mechanism of ozone uptake which in turn is enhanced by near surface mixing processes.     

A practical approach to steam‐enhanced dual‐phase extraction: A case study

This article presents the results of a pilot test that was conducted to determine the effectiveness of using steam‐enhanced dual‐phase extraction (DPE) at a former industrial site in New York. The pilot test proved that steam‐enhanced DPE was very effective at removing significant contaminant mass from the subsurface in a relatively short time period. Concentrations of volatile organic compounds and semivolatile organic compounds in the vapor stream and groundwater were successfully reduced, in some cases by orders of magnitude. Based on the results of the steam‐enhanced DPE pilot test, the final remedy for the site includes implementing this technology at selected areas as an alternative to DPE alone or other remedial alternatives, such as excavation or groundwater pump and treat. © 2003 Wiley Periodicals, Inc.     

微波强化CWPO工艺CuO_x-CeO_2/GAC催化剂的制备及其对二甲亚砜的降解

以颗粒活性炭(GAC)为载体、铜为活性组分、铈为助剂组分、草酸钠为沉淀剂,采用浸渍焙烧法制得CuO_x-CeO_2/GAC催化剂。以H_2O_2为氧化剂,微波强化催化湿式过氧化氢氧化(CWPO)处理二甲亚砜(DMSO)初始质量浓度为1 000 mg/L的废水,处理3 min后DMSO去除率达93.8%。催化剂第7次使用时DMSO去除率仍保持在75%以上。初始废水pH在3~9范围内,DMSO去除率均在85%以上。助剂Ce的加入提高了催化剂表面活性组分的分散性和稳定性,使催化剂的活性稳定性和使用寿命显著提高。     

Assessment of the Whole Environmental Degradation of Oxo-Biodegradable Linear Low Density Polyethylene (LLDPE) Films Designed for Mulching Applications

The current paper is aimed at understanding the environmental fate of linear low density polyethylenes (LLDPE) films designed for mulching purposes and loaded with different pro-degradant additives. These were analyzed, upon exposure to natural sunlight for a period intended to mimick a general crop season in the mediterranean region. The selected samples underwent a relatively low extent of degradation as monitored by carbonyl index, molecular weight variation, extractability by solvent, changes in the onset of the decomposition temperature and crystallinity. The tendency to biodegradation of outdoor exposed LLDPE was then assessed under different environmental compartments including soil medium, aqueous medium as well as in axenic culture of white-rot fungus Phanerochaete chrysosporium. That fungus is known to be effective in the degradation of recalcitrant organic materials and plastic items. During the soil burial biodegradation test, lasted for 27?months, samples specimen were withdrawn at time intervals and characterized by means of structural and thermal analysis. These analytical assessments allowed to monitor any progress of oxidative degradation as a direct effect of the incubation in an active microbial environment. Analogous characterizations were carried out at the end of the biodegradation tests in aqueous medium and in P. chrysosporium axenic cultures. Data presented here are in keeping with the initial abiotic oxidation via a free radical chain reaction promoted by a pro-degradant additive acting on hydroperoxides and peroxide moieties present initially in the polymer bulk. This step was followed by a free radical cascade reactions leading to degradation once the oxidation started under relatively mild conditions (sunlight exposure). During the incubation step in soil, the abiotically degraded samples underwent significant variation in the level of oxidation and degradation with respect to the detected starting values. Indications were gained on the synergistic effect of a random fashion microbial metabolization coupled to biotically mediated oxidation of the original abiotically fragmented samples. Similar results were obtained in the biodegradation tests carried out in the aqueous media and in presence of P. chrysosporium axenic cultures. These evidences are suggesting the role of natural occurring microorganisms in promoting both partial oxiditation and degradation of LLDPE samples in combination with contextual mineralization process of the oxidized fragments.     

Optimization and validation of enhanced biological reduction of 1,2,3‐trichloropropane in groundwater

Laboratory and field demonstration studies were conducted to assess the efficacy of enhanced biological reduction of 1,2,3‐trichloropropane (TCP) in groundwater. Laboratory studies evaluated the effects of pH and initial TCP concentrations on TCP reduction and the activity of a microbial inoculum containing Dehalogenimonas (Dhg). Laboratory results showed successful reduction at a pH of 5 to 9 with optimal reduction at 7 to 9 and at initial TCP concentrations ranging from 10 to over 10,000 micrograms per liter (μg/L). Based on findings from the laboratory study, the effects of TCP concentration, geochemical conditions, and amendment concentration on bioremediation efficacy were investigated during a field demonstration at a site with relatively low initial concentrations of TCP (< 2 μg/L). The field demonstration included injection of emulsified vegetable oil (EVO) and lactate as a carbon substrate for biostimulation, followed by bioaugmentation using the microbial inoculum containing Dhg. Post‐injection performance monitoring demonstrated reduction of TCP to below laboratory detection limits (< 0.005 μg/L) after an initial lag period of approximately six months following injections. TCP reduction was accompanied by generation of the degradation byproduct propene. A marginal increase in TCP concentrations, potentially due to an influx of upgradient aerobic groundwater containing TCP, was observed eight months after injections thereby demonstrating the sensitivity of this bioaugmentation application to changes in geochemical parameters. Despite this marginal increase, performance monitoring results indicate continued TCP biodegradation 15 months after implementation of the injection program. This demonstration suggests that enhanced biodegradation of TCP by combining biostimulation and bioaugmentation may be a promising solution to the challenges associated with remediation of TCP, even when present at low part per billion concentrations in groundwater.     

Integrated effects of applied pressure,time, and polymer doses on alum sludge dewatering behaviour

In this study, combinations of applied pressure, pressing time and polymer dose were examined in an air pressure plate apparatus to explore their integrated influence on the dewatering of an alum sludge. Results of the investigation demonstrated that dewatering can be enhanced by increases in pressure and time. However, a point is reached at which continued increases in pressure and time offer little benefit. The data also confirmed that polymer affects the rate of water release rather than the extent of dewatering. Increased rates of water release due to increasing polymer dose can be attributed to the aggregation of sludge particles by polymer addition. It was also evident in this study that the initial sludge depth has a major impact on the average cake moisture content at a given dewatering time. It was apparent that once the initial sludge thickness exceeds about 2 cm, the water release follows a fairly similar pattern, which can be represented by a simple empirical model.     

An evaluation of the performance of multiple passive diffusion devices for indoor air sampling of VOCs

The United States Environmental Protection Agency is considering recommending longer‐term sampling to achieve more accurate time‐weighted‐average detections for indoor air monitoring of volatile organic chemicals. The purpose of the research presented herein was to compare longer sampling times using passive diffusion samplers to the results from shorter‐term testing periods using sorbent tubes and low‐flow pumps (US EPA Method TO‐17) at great frequency for trichloroethene (TCE) in indoor air. A controlled release of TCE in a large room allowed for over two‐orders‐of‐magnitude daily concentration variability over the course of the two‐week monitoring event. The daily concentration measurements by US EPA Method TO‐17 and the passive diffusion samplers were performed in triplicate and had excellent reproducibility. The results of daily tests were averaged and compared with four passive diffusion devices exposed to indoor air for three, seven, ten, and fourteen days in accordance with ASTM D6196‐02. A specific uptake rate for each of the passive devices at the four different time intervals and the statistical significance of the time‐varying uptake rates were evaluated. The performance of each passive diffusion device was determined using a statistical performance criterion. The average concentration for all of the exposure periods could be reliably predicted using the established uptake rates for two of the four passive devices. © 2009 Wiley Periodicals, Inc.     

Risk Analysis of Volatile Organic Compounds Through Daily Life Cycle in the Industrial City in Korea

This study analyzed the risk of exposure to volatile organic compounds (VOCs) through a study of activity patterns in the Korean industrial city, Ulsan. The daily life cycle patterns(LCPs) of 331 people in Ulsan were surveyed and the average LCPs in Ulsan were obtained by statistical analysis. Nine to twelve personal air samples of VOC exposure at the breathing zones were collected at each LCP. This included hours for sleeping,cooking and eating, going to and from work, working, participating in field or outdoor activities, reading, watchingTV, and shopping. The components and concentrations of the collected VOCs were identified by a Gas Chromatography-MassDetector (GC-MS). The overall reproducibility of all GC analytical procedures of the simultaneously collected duplicatesample pairs represented a mean of percent differences rangingfrom about 9 to 13%. For the general population of Ulsan, thecarcinogenic and non-carcinogenic risk of exposure to theVOCs during the LCPs was evaluated. The carcinogenic riskwas analyzed using both the chronic daily exposure orlifetime average daily exposure (CDI) and the cancerpotency factor. The non-carcinogenic risk was analyzedusing both the CDI and the chronic reference dose.The major chemical forms of the identified VOCs were oxidized forms (43%), aliphatic alkanes (29%) and aromatics (15%). Even though the highest total exposure strength per unit time of each activity was observed during shopping, the highest totalamount of exposure to VOCs was identified as the exposure duringwork. The total carcinogenic risk of exposure to the carcinogenicVOCs through daily life cycle in Ulsan was 2.0 × 10^-4which is substantially exceeding the permissible carcinogenicrisk level, 10^-5 10^-6. The carcinogenic riskduring most of the life cycle activities, except forreading, mainly performed indoors, was higher than that ofthe activities performed outdoors. The carcinogenic risk bybenzene exposure was about 56% (time weighted average) ofthe total carcinogenic risk by the exposure to thecarcinogenic VOCs. During cooking and eating, shopping andout door activities, however, the carcinogenic risk by theexposure to chlorinated compounds like chloroform exceededthe exposure to benzene. The overall hazard index (non-carcinogenic risk) by a chronic exposure to carcinogenicand non-carcinogenic VOCs through daily life cycle in Ulsanwas evaluated as 3.91 × 10^-1, which is much less than1.0 considered as a hazard level to human health, and thusit seems likely not to produce a severe health hazard.     

A lysimeter study of the aerobic landfill concept

An investigation was undertaken concerning the enhancement of degradation in a landfill. Degradation can be enhanced by the application of water, the recycling of leachate and the addition of air. A lysimeter study was undertaken to determine the quantities of moisture and air that would optimize degradation. The final concept involved application of moisture levels greater than those usually found in composting, combined with the addition of air forced by blowers. Aerobic operation provided significantly faster rates of degradation. The principal measure was that of settlement. In conclusion, some very preliminary economic considerations are presented.     

Structure,Mechanical, Thermal and Fire Behavior Assessments of Environmentally Friendly Crude Glycerol-Based Rigid Polyisocyanurate Foams

In this work, rigid polyisocyanurate foams were prepared at partial substitution (0–70 wt%) of commercially available petrochemical polyol, with previously synthesized biopolyol based on crude glycerol and castor oil. Influence of the biopolyol content on morphology, chemical structure, static and dynamic mechanical properties, thermal insulation properties, thermal stability and flammability was investigated. Incorporation of 35 wt% of crude glycerol-based polyol had reduced average cell size by more than 30% and slightly increased closed cell content, simultaneously reducing thermal conductivity coefficient of foam by 12% and inhibiting their thermal aging. Applied modifications showed also positive impact on the mechanical performance of rigid foams. Increase of crosslink density resulted in enhancement of compressive strength by more than 100%. Incorporation of prepared biopolyol resulted in enhancement of thermal stability and changes in degradation pathway. Up to 35 wt% share of crude glycerol-based polyol, foams showed similar flammability as reference sample, which can be considered very beneficial from the environmental point of view.     

The use of enhanced bioremediation at the Savannah River Site to remediate pesticides and PCBs

Enhanced bioremediation is quickly developing into an economical and viable technology for the remediation of contaminated soils. Until recently, chlorinated organic compounds have proven difficult to bioremediate. Environmentally recalcitrant compounds, such as polychlorinated biphenyls (PCBs) and persistent organic pesticides (POPs) such as dichlorodiphenyl trichloroethane (DDT) have shown to be especially arduous to bioremediate. Recent advances in field‐scale bioremedial applications have indicated that biodegradation of these compounds may be possible. Engineers and scientists at the Savannah River Site (SRS), a major DOE installation near Aiken, South Carolina, are using enhanced bioremediation to remediate soils contaminated with pesticides (DDT and its metabolites, heptachlor epoxide, dieldrin, and endrin) and PCBs. This article reviews the ongoing remediation occurring at the Chemicals, Metals, and Pesticides (CMP) Pits using windrow turners to facilitate microbial degradation of certain pesticides and PCBs. © 2003 Wiley Periodicals, Inc.