Cytotoxicity of municipal solid waste incinerator ash wastes toward mammalian kidney cell lines

In this study, three municipal solid waste incinerator (MSWI) ash wastes-bottom ash, scrubber residue, and baghouse ash-were extracted using a toxicity characteristic leaching procedure (TCLP) extractant. These so-called final TCLP extracts were applied to African green monkey kidney cells (Vero), baby hamster kidney cells (BHK-21), and pig kidney cells (PK-15), multi-well absorption reader analysis was performed to test how the cytotoxicity of the incineration ashes would affect the digestive systems of animals. Ion-coupled plasma analyses indicated that the baghouse ash extract possessed the highest pH and heavy metal concentration, its cytotoxicity was also the highest. In contrast, the bottom ash and the scrubber residue exhibited very low cytotoxicities. The cytotoxicities of mixtures of baghouse ash and scrubber residue toward the three tested cell lines increased as the relative ratio of the baghouse ash increased, especially for the Vero cells. The slight cytotoxicity of the scrubber residue arose mainly from the presence of Cr species, whereas the high cytotoxicity of the baghouse ash resulted from its high content of heavy metals and alkali ions. In addition, it appears that the dissolved total organic carbon content of these ash wastes can reduce the cytotoxicity of ash wastes that collect in animal cells.     

Determinations and residual characteristics of triclosan in household food detergents of Taiwan

Triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) is a widely used antibacterial agent. However, it was concerned recently that triclosan might act as an antibiotic and will cause resistant bacterial strains. Furthermore, possible formation of toxic chloroform was also reported when the triclosan contained in household dishwashing soaps reacted with the chlorinated water. To assess the associate risks from possible exposures, concentrations of triclosan in household food detergents of Taiwan were determined in this study. High performance liquid chromatography (HPLC) with UV detector at 280 nm was used to analyze the triclosan in samples. Factors that might affect the residual characteristics of triclosan from detergents on dishware and fruits, including the concentrations of detergents used, the temperature and immersion time for water before the cleaning processes, the temperatures of water used for the cleaning processes, and the materials of dishware made of, were evaluated under the orthogonal experiment design by the Taguchi method. By the analysis of variance, the orders of importance of different parameters were determined. The concentrations of triclosan detected in household food detergents were found to be 1.7 x 10(-2) -5.6 x 10(-1) (triclosan/detergent, mg g(-1)). For residual characteristics, the concentration of detergents used as well as the materials of dishware were found to be the significant factors that will affect the triclosan left on the dishware. On the other hand, the concentration of triclosan in the detergents was found to be the only factor that will affect the triclosan left on fruits. The maximum dose of triclosan exposures from the use of household food detergents in Taiwan was also estimated in the study.     

Preliminary investigation of greenhouse gas emissions from the environmental sector in Taiwan

The United Nations Framework Conventions on Climate Change (UNFCCC) asks their Parties to submit a National Inventory Report (NIR) for greenhouse gas (GHG) emissions on an annual basis. However, when many countries are quickly growing their economy, resulting in substantial GHG emissions, their inventory reporting systems either have not been established or been able to be linked to planning of mitigation measures at national administration levels. The present research was aimed to quantify the GHG emissions from an environmental sector in Taiwan and also to establish a linkage between the developed inventories and development of mitigation plans. The "environmental sector" consists of public service under jurisdiction of the Taiwan Environmental Protection Administration: landfilling, composting, waste transportation, wastewater treatment, night soil treatment, and solid waste incineration. The preliminary results were compared with that of the United States, Germany, Japan, United Kingdom, and Korea, considering the gaps in the scopes of the sectors. The GHG emissions from the Taiwanese environmental sector were mostly estimated by following the default methodology in the Intergovernmental Panel on Climate Change guideline, except that of night soil treatment and waste transportation that were modified or newly developed. The GHG emissions from the environmental sectors in 2004 were 10,225 kilotons of CO2 equivalent (kt CO2 Eq.). Landfilling (48.86%), solid waste incineration (27%), and wastewater treatment (21.5%) were the major contributors. Methane was the most significant GHG (70.6%), followed by carbon dioxide (27.8%) and nitrous oxide (1.6%). In summary, the GHG emissions estimated for the environmental sector in Taiwan provided reasonable preliminary results that were consistent and comparable with the existing authorized data. On the basis of the inventory results and the comparisons with the other countries, recommendations of mitigation plans were made, including wastewater and solid waste recycling, methane recovery for energy, and waste reduction/sorting.     

Dioxin contents in fly ash from large-scale MSW incinerators in Taiwan

In this study, fly ash samples were collected from three municipal waste incinerators (MWI) in Taiwan. These MWIs investigated are equipped with different air pollution control devices (APCDs). Preliminary results indicated that 2,3,7,8-PCDD/Fs homologue patterns of various types of fly ash were quite similar for all three MWIs. Concentrations of higher-chlorinated congeners of PCDDs and PCDFs were remarkably higher than those of lower-chlorinated congeners. In the case of MSW-A, the PCDD/PCDF ratios of ashes were found in the decreasing order for cyclone, boiler and baghouse. The PCDD/PCDF ratios in various types of fly ash of MWI-B was boiler-A < boiler-B < ESP < boiler-C. As for MSW-C, no obvious trend has been observed for PCDD/PCDF ratio. However, the ratio in boiler ash was higher than that in baghouse ash of MWI-A. The dioxin contents in fly ash would increase as the fly ash passed through APCD zones. In other words, the environmental conditions of APCD may actually cause the increase of the dioxin contents in fly ash. The trend for dioxin contents in fly ash collected from three MSW incinerators investigated was MSW-C < MSW-A < MSW-B.     

Experimental studies on the ignition behavior of pure silane released into air

Silane is a well known pyrophoric gas which normally ignites upon contact with air. However, a silane release from a pressure source may not always lead to prompt ignition and frequently the ignition occurs when the release is shutoff. In a confined space, significant quantities of silane can accumulate prior to autoignition leading to an explosion, causing significant damage. To date, the mechanism and condition of pure silane ignition upon release into air has not been completely explained. Thus there is a need for additional experimental investigations covering a wide range of release conditions to enable a full understanding of silane ignition and explosion characteristics.This work presents a series of tests that aims to uncover the precise condition for pure silane ignition upon release into air. Tests were performed for releases at controlled and steady velocities. Steady flow of silane to a burn box and nitrogen to the desired vent stub are first established through mass flow controllers. An electrically controlled four-way switching valve is used to switch the silane and nitrogen flow such that steady silane flow without acceleration to the vent stub can be established. With careful control of vent conditions, we are able to find a reproducible critical exit velocity for prompt ignition of steady silane releases for different vent diameters. If the releases are reduced to below the critical exit velocity, prompt ignition of silane release is ensured. Above this critical exit velocity, silane can be released indefinitely into air without any ignition. The critical exit velocity is found to vary with the vent diameter. This relationship between the critical exit velocity and the vent diameter suggests that the silane release without prompt ignition was most likely caused by quench of the reactive kernel from the scalar dissipation between the release gas and the ambient air. Analysis of locations where prompt ignition occurred from the clips from high speed video camera found that the most reactive ignition kernel occurs in the range when the ratio of volumetric flow rate of entrained air to the silane flow reaches 0.322 ± 0.076, which is equivalent to the most reactive silane concentration of 75.6% in air. The implications from these results are discussed with emphasis on the safety of silane supply systems and operation practices.     

Effect of metal chlorides on thermal degradation of (waste) polycarbonate

In this study, we investigated how to treat (waste) polycarbonate efficiently to reduce its degraded residue. The study was carried out in an isothermal reactor under continuous nitrogen flow at atmospheric pressure to pyrolyze polycarbonate (PC) alone and in the presence of metal chloride. Some metal chlorides were shown to be catalytic active for the degradation of PC at 400 degrees C, which increased degradation conversion from 8.5% to more than 58.3%. Among those active metal chlorides, ZnCl2 and SnCl2 can produce higher liquid product yields. Effects such as particle size of PC, temperature, the weight ratio of metal chloride/PC, and degradation time on the degradation conversion of PC without and with these two most active metal chlorides were studied. Results of the liquid product analysis by GC/MS demonstrated the product composition of PC degradation over the metal chlorides is much simpler than that of degradation alone. The main liquid product is phenol, p-isopropylphenol, diphenyl carbonate, and bisphenol A for all cases.     

Statistical determination of the optimal sample size of secondary effluent BOD5 and SS

A statistical technique is presented for determining the optimal sample size required to estimate the true geometric mean with an allowable error at a desired level of confidence. Attention is focused on its application in the monitoring of secondary effluent BOD₅ and SS. It is concluded that continuous monitoring of effluent BOD₅ or SS throughout the year may generate much more data than are required for practical purposes. This statistical method may be used by operators or regulatory agencies to formulate cost-effective monitoring schemes. Records of the sample size data of secondary effluent BOD₅ and SS across Canada are also discussed.     

VELOCITY AND CONCENTRATION DISTRIBUTIONS OF SEDIMENT‐LADEN OPEN CHANNEL FLOW1

ABSTRACT: A mathematical model to predict both velocity and concentration distributions for sediment‐laden open channel flow is developed. Velocity profiles are derived by theoretical analysis and numerical method. Logarithmic law and semi‐empirical wake function concept are not adopted. An empirical equation for the ratio of sediment exchange and fluid diffusion coefficients is considered to solve the diffusion equation for suspended‐sediment concentration profiles. Four sets of experimental data from previous researchers are compared to numerical calculation. In the engineering applications, velocity and concentration profiles of sediment‐laden flow can be predicted simultaneously by the present model with the measured velocity and sediment‐concentration at reference level.     

Acoustic Observations of Bottom Surge From Dredged Material Discharge in the Open Ocean

Abstract

Bottom surges generated from dredged material discharges in the open ocean have been observed using high frequency acoustic concentration profilers in several field studies during the past five years. the locations, water depths, bottom slopes, oceanographic conditions, and dredged material composition differed from study to study. Observed surges at three dredged material disposal sites may develop more than one surge peak for a single discharge. for water depths of the order of 10 m, surge height of the leading peak was estimated to be about one quarter of the water depth. for water of greater depth, of the order of 100 m, surge height reached 70 m, about 70% of the water depth. Surge height is established instantaneously when dredged material hits the bottom, and remains relatively constant as the surge advances horizontally. Total surge length reached 150 m for water depths of 10 m when measured from the impact point to the leading edge. for water depths of more than 100 m, the surge length reached more than 100 m. Length of the leading surge peak was as large as 45 m at this water depth.

Dimensional analysis was applied to relate the surge height of the leading surge peak to discharge parameters and oceanographic conditions. Results showed that the ratio of surge height to water depth was proportional to 1/10 power of the ratio of discharge volume to the third power of water depth.