Fly ash reinforced thermoplastic vulcanizates obtained from waste tire powder

Novel thermoplastic composites made from two major industrial and consumer wastes, fly ash and waste tire powder, have been developed. The effect of increasing fly ash loadings on performance characteristics such as tensile strength, thermal, dynamic mechanical and magnetic properties has been investigated. The morphology of the blends shows that fly ash particles have more affinity and adhesion towards the rubbery phase when compared to the plastic phase. The fracture surface of the composites shows extensive debonding of fly ash particles. Thermal analysis of the composites shows a progressive increase in activation energy with increase in fly ash loadings. Additionally, morphological studies of the ash residue after 90% thermal degradation shows extensive changes occurring in both the polymer and filler phases. The processing ability of the thermoplastics has been carried out in a Monsanto processability testing machine as a function of shear rate and temperature. Shear thinning behavior, typical of particulate polymer systems, has been observed irrespective of the testing temperatures. Magnetic properties and percolation behavior of the composites have also been evaluated.     

Medical waste production at hospitals and associated factors

This study was conducted to evaluate the quantities of medical waste generated and the factors associated with the generation rate at medical establishments in Taiwan. Data on medical waste generation at 150 health care establishments were collected for analysis in 2003. General medical waste and infectious waste production at these establishments were examined statistically with the potential associated factors. These factors included the types of hospital and clinic, reimbursement payment by National Health Insurance, total number of beds, bed occupancy, number of infectious disease beds and outpatients per day. The average waste generation rates ranged from 2.41 to 3.26kg/bed/day for general medical wastes, and 0.19-0.88kg/bed/day for infectious wastes. The total average quantity of infectious wastes generated was the highest from medical centers, or 3.8 times higher than that from regional hospitals (267.8 vs. 70.3Tons/yr). The multivariate regression analysis was able to explain 92% of infectious wastes and 64% of general medical wastes, with the amount of insurance reimbursement and number of beds as significant prediction factors. This study suggests that large hospitals are the major source of medical waste in Taiwan. The fractions of medical waste treated as infectious at all levels of healthcare establishments are much greater than that recommended by the USCDC guidelines.     

Effect of sulfate on the simultaneous bioreduction of iron and uranium

The biogeochemistry related to iron- and sulfate-reducing conditions influences the fate of contaminants such as petroleum hydrocarbons, trace metals, and radionuclides (i.e., uranium) released into the subsurface. An understanding of these processes is imperative to successfully predict the fate of contaminants during bioremediation scenarios. A series of flow-through sediment column experiments were performed to determine if the commencement of sulfate-reducing conditions would occur while bioavailable Fe(III) was present and to determine how the bioreduction of a contaminant (uranium) was affected by the switch from iron-dominated to sulfate-dominated reducing conditions. The results presented herein demonstrated that, under biostimulation, sulfate reduction can commence even though a significant pool of bioavailable Fe(III) is present. In addition, the rate of U(VI) reduction was not negatively affected by the commencement of sulfate-reducing conditions.     

Effects of earthworm cast and powdered activated carbon on methane removal capacity of landfill cover soils

Landfill gases could be vented through a layer of landfill cover soil that could serve as a biofilter to oxidize methane to carbon dioxide and water. Properly managed landfill cover soil layers may reduce atmospheric CH4 emissions from landfills. In the present study, the effects of earthworm cast and powdered activated carbon (PAC) on the CH4 removal capacity of the landfill cover soil was investigated. For this purpose, column and batch tests were conducted using three different materials: typical landfill cover soil, landfill cover soil amended with earthworm cast, and landfill cover soil amended with PAC. The maximum CH4 removal rate of the columns filled with landfill cover soil amended with earthworm cast was 14.6mol m(-2)d(-1), whereas that of the columns filled with typical landfill cover soil was 7.4mol m(-2)d(-1). This result shows that amendment with earthworm cast could stimulate the CH4-oxidizing capacity of landfill cover soil. The CH4 removal rate of the columns filled with landfill cover soil amended with PAC also showed the same removal rate, but the vertical profile of gas concentrations in the columns and the methanotrophic population measured in the microbial assay suggested that the decrease of CH4 concentration in the columns is mainly due to sorption. Based on the results from this study, amendment of landfill cover soil with earthworm cast and PAC could improve its CH4 removal capacity and thus achieve a major reduction in atmospheric CH4 emission as compared with the same landfill cover soil without any amendment.     

Spore release by the green alga Ulva: a quantitative assay to evaluate aquatic toxicants

A toxicity test using spore release of the aquatic green alga, Ulva, was developed and evaluated by assessing the toxicity of different organic and inorganic chemicals and elutriates of sewage or waste sludge. The toxic ranking of four metals was: Cu (EC50 of 0.040mgL(-1))>Cd (0.095mgL(-1))>Pb (0.489mgL(-1))>Zn (0.572mgL(-1)). The EC50 for TBTO ranged from 24 to 63microgL(-1). The most toxic VOC was formalin (EC50 of 0.788microlL(-1)) and the least toxic was acetone. Spore release was significantly inhibited in all elutriates; the greatest and least toxic effects were for industrial sewage (3.29%) and filtration bed (10.08%), respectively. The bioassay is simple, inexpensive and sensitive. The cosmopolitan distribution of Ulva means that the test would have a potential application worldwide.     

Exposure of acid aerosol for schoolchildren in metropolitan Taipei

Metropolitan Taipei, which is located in the subtropical area, is characterized by high population and automobile densities. For convenience, most primary schools are located near major roads. This study explores the exposure of acid aerosols for schoolchildren in areas in Taipei with different traffic densities. Acid aerosols were collected by using a honeycomb denuder filter pack sampling system (HDS). Experimental results indicated that the air pollutants were significantly correlated with traffic densities. The ambient air NO₂, SO₂, HNO₃, NO₃⁻, SO₄²⁻, and aerosol acidity concentrations were 31.3 ppb, 4.7 ppb, 1.3 ppb, 1.9 μg m⁻³, 18.5 μg m⁻³, and 49.5 nmol m⁻³ in high traffic density areas, and 6.1 ppb, 1.8 ppb, 0.9 ppb, 0.7 μg m⁻³, 8.8 μg m⁻³ and 14.7 nmol m⁻³ in low traffic density areas. The exposure levels of acid aerosols for schoolchildren would be higher than the measurements because the sampling height was 5 m above the ground. The SO₂ levels were low (0.13–8.03 ppb) in the metropolitan Taipei. However, the SO₄²⁻ concentrations were relatively high, and might be attributed to natural emissions of sulfur-rich geothermal sources. The seasonal variations of acid aerosol concentrations were also observed. The high levels of acidic particles in spring time may be attributed to the Asian dust storm and low height of the mixture layer. We conclude that automobile contributed not only the primary pollutants but also the secondary acid aerosols through the photochemical reaction. Schoolchildren were exposed to twice the acid aerosol concentrations in high traffic density areas compared to those in low traffic density areas. The incidence of allergic rhinitis of schoolchildren in the high traffic density areas was the highest in spring time. Accompanied by high temperature variation and high levels of air pollution in spring, the health risk of schoolchildren had been observed.     

Estimation of fecal Coliform removal from domestic sewage in two sand filter column systems

The objective of the present research is to compare fecal coliform removal from two different sand column systems treating septic tank effluent over a range of hydraulic loading rates. Drain time measurements were performed to compare the hydraulic characteristic of the column systems at different hydraulic loading rates. Biochemical oxygen demand (BOD), total suspended solids (TSS), and pH were also measured for the septic tank effluent. A removal of the order of 99% for fecal coliform, TSS, and BOD in column effluent was achieved using the sand filter columns. The ‘break‐in’ period for determining the effectiveness of the sand filter columns is also discussed.     

A comparison study of the potential risks induced in arable land and forest soils by carcass-derived pollutants

Environmental Geochemistry and Health - Improper decisions concerning animal carcass disposal sites pose grave threats to environmental biosecurity. However, only a few studies have focused on the...     

Factors affecting the spatial pattern of nitrate contamination in shallow groundwater

The elevated level of nitrate in groundwater is a serious problem in Korean agricultural areas. To control and manage groundwater quality, the characterization of groundwater contamination and identification of the factors affecting the nitrate concentration of groundwater are significant. The characterization of groundwater contamination at a hydrologically complex agricultural site in Yupori, Chuncheon (Korea) was undertaken by analyzing the hydrochemical data of groundwater within a statistical framework. Multivariate statistical tools such as cluster analyses and Tobit regression were applied to investigate the spatial variation of nitrate contamination and to analyze the factors affecting the NO3-N concentration in a shallow groundwater system. The groundwater groups from the cluster analysis were consistent with the land use pattern of the study area. The clustered group of a gentle-slope area with lower elevations showed higher NO3-N contamination of groundwater than groups on a hillside with higher elevations. Tobit regression results indicated that the agricultural activity in the vegetable fields and barns were the major factors affecting the elevated NO3-N concentration while the land slopes and elevations were negatively correlated with the NO3-N concentration. This shows that topographic characteristics such as land slopes and elevations should be considered to evaluate the land use impact on shallow groundwater quality.