Wei-Hsiang Chen

Multivariate analysis of heavy metal contaminations in seawater and sediments from a heavily industrialized harbor in Southern Taiwan

Heavy metal pollution, including chromium, zinc, arsenic, cadmium, mercury, copper, lead, and aluminum, in the largest industrial harbor in southern Taiwan was investigated. Increasing metal contamination was observed by monitoring heavy metal concentrations in seawater and sediments and estimating the enrichment factors, particularly those inside the harbor. Compared to other metal-polluted harbors worldwide, the presence of chromium in the sediments was relatively high. Excluding the background contribution, the harbor area was polluted by outflows from river mouths, wastewater discharging pipes, and point sources near industrial activities within the harbor. It is shown by principal component and cluster analyses that metal contamination was affected by a wide range of different and complex contamination mechanisms inside and outside the harbor, suggesting managing the pollution using straightforward strategies, i.e., solutions that only consider a single source or single pathway of metal emissions, is problematic.

Effect of interferences on the breakthrough of arsenic: rapid small scale column tests.

The influences of three important interferences (silica, phosphate, and vanadate) and the effect of different pH levels and initial arsenate concentrations on the breakthrough of arsenic in adsorptive media columns were examined by using the Rapid Small Scale Column Test with a 3 fractional factorial design. Three commercially available adsorbents used for arsenic removal (E33, GFH and Metsorb) were tested. Results indicated that GFH was more susceptible to water quality changes than Metsorb and E33 under conditions tested. GFH also adsorbed more anions than the other two media. The pH was the factor that had the most impact on the performance of the columns, followed by arsenic concentration and silica concentration. Lowering pH from 8.3 to 7.0 resulted in an increase of the mean bed volume treated until 10 μg/L arsenic breakthrough by 40, 12 and 18 thousands BV treated by GFH, E33 and Metsorb columns, respectively. However, at high silica concentration, lowering pH did not increase the performance of the media. GFH and Metsorb were more sensitive to changes in arsenic concentration at low pH than at high pH. Although vanadium and phosphate were previously reported to reduce arsenic adsorption in batch tests, in column mode with the presence of competitors, their effect was insignificant compared to that of pH, arsenic or silica under the conditions used in this study.

Enhanced photocatalytic oxidation of gaseous elemental mercury by TiO2 in a high temperature environment

The photo-oxidation of Hg(0) in a lab-scale reactor by titanium dioxide (TiO2) coated on the surface of glass beads was investigated at high temperatures. TiO2 was calcinated at four different temperatures of 300 °C, 400 °C, 500 °C and 600 °C (noted as Ti300, Ti400, Ti500 and Ti600) and characterized for its physicochemical properties. The calcinated TiO2 coating on the glass beads was then tested to compare the photo-oxidation efficiencies of Hg(0) with an incident light of 365 nm. The results showed that the oxidation efficiencies of Hg(0) for Ti400 and Ti500 were higher than those of Ti300 and Ti600. To enhance the photo-oxidation efficiency of Hg(0), Ti400 was selected to examine the wave lengths (λ) of 254 nm, 365 nm and visible light with various influent Hg(0) concentrations. The effects of irradiation strength and the presence of oxygen on the photo-oxidation efficiency of Hg(0) were further investigated, respectively. This study revealed that the wave length (λ) of 254 nm could promote the photo-oxidation efficiency of Hg(0) at 140 and 160 °C, while increasing the influent Hg(0) concentration and could enhance the photo-oxidation rate of Hg(0). However, the influence of 5% O2 present in the flue gas for the enhancement of Hg(0) oxidation was limited. Moreover, the intensity of the incident wave length of 365 nm and visible light were demonstrated to boost the photo-oxidation efficiency of Hg(0) effectively.

Fates of chlorinated volatile organic compounds in aerobic biological treatment processes: The effects of aeration and sludge addition

The emission of volatile organic compounds (VOCs) from wastewater treatment plants (WWTPs) is becoming an environmental issue of increasing concern. As biological treatment has been considered as one important approach for VOC removal, lab-scale batch experiments were conducted in this study to investigate the fates of four chlorinated hydrocarbons, including chloroform, carbon tetrachloride, trichloroethylene (TCE), and tetrachloroethylene (PERC), in the biological treatment processes with respect to the effects of aeration and sludge addition. The VOC concentrations in the phases of air, water, and sludge under four simulated treatment stages (the first sedimentation, the forepart and rear part of aerobic biological treatment, and the second sedimentation) were analyzed. The results were used to understand the three-phase partitioning of these compounds and to estimate their potentials for volatilization and biological sorption and degradation in these technologies with the concept of fugacity. It was observed that the VOCs were mainly present in the water phase through the experiments. The effects of aeration or sludge addition on the fates of these VOCs occurred but appeared to be relatively limited. The concentration distributions of the VOCs were well below the reported partitioning coefficients. It was suggested that these compounds were unsaturated in the air and sludge phases, enhancing their potentials for volatilization and biological sorption/degradation through the processes. However, the properties of these chlorinated VOCs such as the volatility, polarity, or even biodegradability caused by their structural characteristics (e.g., the number of chlorine, saturated or unsaturated) may represent more significant factors for their fates in the aerobic biological treatment processes. These findings prove the complication behind the current knowledge of VOC pollutions in WWTPs and are of help to manage the adverse impacts on the environment and public health by the VOCs from these particular sources.

Assessing the altitude effect on distributions of volatile organic compounds from different sources by principal component analysis

Emissions of volatile organic compounds (VOCs), particularly those from industrial sources, have been of substantial concern because they have had adverse effects on the nearby environment and human health. In this study, the effect of altitude on the distributions of VOCs from petrochemical industrial sources was studied by analyzing the VOC concentrations at ground level and three different altitudes (100, 300, and 500 m above the ground) during three monitoring seasons from 2009 to 2010 and assessing the results by principal component analysis (PCA) and cluster analysis. Kaohsiung city in southern Taiwan, known for its high levels of air contaminants due to many pollution-intensive industries in the city, was selected as the area to be examined. Of various types of aliphatic and aromatic hydrocarbons being detected, acetone and toluene were the dominant VOC species with relatively high concentrations. By PCA application and cluster analysis, aromatic and aliphatic compounds were found to be the main VOCs accounting for the maximum variance of the data observed at ground level and high altitude, respectively. The presence of mono-aromatic hydrocarbons at ground level suggested an important contribution from traffic, while the presence of both saturated and unsaturated hydrocarbons at high altitudes was likely to be due to the local petrochemical industries given the heights of flare stacks in the examined areas and short lifetimes of unsaturated hydrocarbons such as alkenes. 3-D loading plots exhibited clear grouping of the VOCs in terms of their chemical structures and/or physicochemical characteristics for the data at ground level and 500 m and less clear differentiation for the data at 100 and 300 m, possibly resulted by atmospheric dispersion and mixing. The influence of altitude on the VOC distributions appeared not to be negligible and was greatly impacted by the location (e.g., height) of emission sources and the physicochemical properties of the VOCs including their molecular weights/sizes and lifetimes in the atmosphere. These findings prove the complications in the current knowledge of VOC pollution and are of help in managing the adverse impacts on the environment and public health by VOCs from industrial or other sources.

Formation and fates of nitrosamines and their formation potentials from a surface water source to drinking water treatment plants in Southern Taiwan

Nitrosamines are toxic and emerging disinfection byproducts. In this study, three drinking water treatment plants (DWTPs) in southern Taiwan treating the same source water in Gaoping River with comparable technologies were selected. The objective was to evaluate the formation and fates of six nitrosamines and their formation potentials (FPs) from a surface water source to drinking water. Albeit decreased further downstream in the river, four nitrosamine-FPs were observed in the source water due to anthropogenic pollution in the upstream areas. In the DWTPs, nitrosamines were formed and NDMA was the main species. While high organic carbon concentrations indicated elevated nitrosamine-FPs in the source water, NDMA formation in the DWTPs was more positively associated with reductions of water parameters that quantify organic matters with double bonded ring structures. Although precursor removal via pre-oxidation is a viable approach to limit nitrosamine formation during post-disinfection, this study clearly indicates that a great portion of NDMA in treated water has been formed in the 1st oxidation step of drinking water treatment. The pre-oxidation simulations in the lab demonstrated the impact of pre-chlorination on nitrosamine formation. Given the limited removal in conventional treatment processes, avoiding nitrosamine-FPs in sources and/or nitrosamine formation during pre-oxidation become important issues to control the threats of nitrosamines in drinking water. Under current circumstance in which pre-oxidation is widely used to optimize the treatment effectiveness in many DWTPs, its adverse effect by forming nitrosamines needs to be carefully minimized and using technologies other than pre-chlorination (e.g., pre-ozonation) may be considered.

Disposal of Arsenic-Laden Adsorptive Media: Economic Analysis for California

Due to California’s stringent hazardous waste (HW) classification regulations, high-capacity adsorptive media (AM) used for the removal of arsenic from potable water are likely to be classified as HW if operated to breakthrough. An alternative is to prematurely retire the AM, avoiding generation of HW. The impact of waste classification of spent AM on annual costs for arsenic systems was investigated. For a typical small water system (SWS), the media replacement cost alone was predicted to range from

Multivariate analysis of effects of diurnal temperature and seasonal humidity variations by tropical savanna climate on the emissions of anthropogenic volatile organic compounds.

0.80 to

Removal of Trihalomethanes and Haloacetic Acids from Treated Drinking Water by Biological Activated Carbon Filter

2.00 per 1,000 L treated, in comparison to the average cost of tap water in the U.S. of

NDMA Formation during Chlorination and Chloramination of Aqueous Diuron Solutions

0.53 per 1,000 L treated, highlighting the financial burden for SWS. The costs of media replacement dominated over costs for transport and disposal regardless of whether spent media were designated as HW or non-HW. Media costs and influent arsenic concentration were more significant factors than transport distance or disposal fees. Under typical conditions for SWS, it was found to be cost effective to load the m...