Prediction of Cadmium uptake by brown rice and derivation of soil–plant transfer models to improve soil protection guidelines

Cadmium (Cd) levels in paddy fields across Taiwan have increased due to emission from industry. To ensure the production of rice that meets food quality standards, predictive models or suitable soil tests are needed to evaluate the quality of soils to be used for rice cropping. Levels of Cd in soil and rice grains were measured in 19 paddy fields across the western plains in Taiwan. Cadmium levels in soil range from less than 0.1 mg kg^?1 to 30 mg kg^?1. Measured Cd levels in brown rice were predicted very well (R² > 0.8) based on Cd and Zinc in a 0.01 M CaCl₂ extract or a soil–plant transfer model using the reactive soil Cd content, pH, and cation exchange capacity. In contrast to current soil quality standards used in Taiwan, such models are effective in identifying soils where Cd in rice will exceed food quality standards.     

Characteristics of exhaust gas,liquid products,and residues of printed circuit boards using the pyrolysis process

Introduction  

The pyrolytic method was employed to recycle metals and brominated compounds blended into printed circuit boards (PCBs).     

Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong

As Hong Kong is a compact city with limited available land and high land prices, the construction of high-rise buildings is prevalent. The construction industry produces a significant amount of building waste. In 2005, about 21.5 million tonnes of construction waste were generated, of which 11% was disposed of in landfills and 89% in public filling areas. At the present rate, Hong Kong will run out of both public filling areas and landfill space within the next decade. The government is taking action to tackle the problem, such as by introducing a construction waste landfill charge, and promoting prefabrication to reduce on-site waste generation. This paper reports an ongoing study on the use of prefabrication in buildings and its impact on waste reduction in Hong Kong. A questionnaire survey was administered to experienced professionals, and case studies of recently completed building projects were conducted. The results revealed that construction waste reduction is one of the major benefits when using prefabrication compared with conventional construction. The average wastage reduction level was about 52%. This implies that a wider use of prefabrication could considerably reduce construction waste generation in Hong Kong and alleviate the burdens associated with its management.     

The mechanisms of arsenic removal from soil by electrokinetic process coupled with iron permeable reaction barrier

An innovative remediation system of electrokinetic process coupled with permeable reaction barrier (PRB) was proposed for arsenic removal in soil matrix. Batch tests with PRB media of Fe(0) and FeOOH under potential gradient of 2 V cm(-1) for 5d duration were conducted to evaluate the removal mechanisms of arsenic. Arsenic enhancement of 1.6-2.2 times was achieved when a PRB system was installed in an electrokinetic system. A best performance was found in system with FeOOH layer located in the middle of elctrokinetic cell. This was largely because of higher surface area of FeOOH and the moving of HAsO(4)(2-) to the anode side by electromigration effect was inhibited by the electroosmosis flow. The surface characteristics of PRB media, which were qualified by SEM coupled with energy dispersive spectroscopy (EDS), were clearly confirmed that arsenic was found on the passive layer surface. Results indicated that the removal of As in EK/PRB systems was much more contributed by surface adsorption/precipitation on PRB media than by EK process. Furthermore among the electrical removal mechanisms, electromigration was predominant than electrosmotic flow. Surface adsorption and precipitation were respectively the principal removal mechanism under acid environment, e.g. near anode side, and under basic environment, e.g. near cathode side. The results reported in the present work will be beneficial to optimizing design of batch EK/PRB system and enlarging to the field scale system.     

Silane removal at ambient temperature by using alumina-supported metal oxide adsorbents

Copper, zinc, and cerium oxide adsorbents supported on alumina were used to remove silane gas (SiH4). The adsorbents were prepared using a coprecipitation method and characterized by the inductively coupled plasma mass spectrometry, X-ray powder diffractometer, and Brunauer-Emmett-Teller method (BET). The silane removal efficiency and adsorption capacity of the adsorbents were investigated in this study. Test results showed that the adsorbents containing active species had a removal efficiency >99.9% for SiH4 before breakthrough. Adsorbents containing mixed oxides (CuO-CeO2/ Al2O3 and CuO-ZnO/Al2O3), which showed well-dispersed active species and high BET surface areas, had a greater adsorption capacity than the adsorbents containing single metal oxide. However, when the CuO-ZnO/ Al2O3 adsorbents contain >40 wt% of active metal oxides, the increase of active species lowered the BET surface area leading to a decrease of the adsorption capacity. Additionally, when the content of the active metal oxides was between 20% and 40%, the CuO-ZnO/Al2O3 adsorbents demonstrated higher adsorption capacity.     

Effect of recycle-to-influent ratio on activities of nitrifiers and denitrifiers in a combined UASB-activated sludge reactor system

A laboratory study using a combined upflow anaerobic sludge bed (UASB)-activated sludge (AS) reactor system was undertaken to explore the effect of recycle-to-influent ratio (R(e)=1, 2, and 3) on the activities of nitrifiers and denitrifiers. Suspended-solids pre-settled piggery wastewater was used as the substrate-feed wastewater. At the R(e) of 1-3, the combined reactor system achieved efficient removal of COD (96-97%), TKN (100%) and total nitrogen TN (54-77%). Methanogenesis occurred with nearly-complete denitrification in the UASB reactor, whereas complete nitrification took place in the AS reactor. A higher R(e) (i.e., accompanied with a shorter solids retention time) resulted in a larger amount of high-activity denitrifiers and thereby achieved a higher TN removal efficiency. Compact granules and a high biomass concentration in the UASB reactor were observed. At the R(e) of 1-3, the maximum specific reaction rate of nitrifiers (0.45-0.49 NH(4)(+)-NmgVSS(-1)d(-1)) and the specific nitrification rates of mixed culture (0.18-0.22mg NH(4)(+)-NmgVSS(-1)d(-1)) in the AS reactor varied slightly; whereas the maximum specific reaction rate of denitrifiers (0.18-0.27mg NO(x)(-)-NmgVSS(-1)d(-1)) and the specific denitrification and COD removal rates of mixed culture (0.025-0.050mg NO(x)(-)-NmgVSS(-1)d(-1); 0.24-0.31mgCODmgVSS(-1)d(-1)) in the UASB reactor increased with increasing R(e). The primary finding of the study is that the combined UASB-AS reactor system should be operated at a higher R(e) to maintain high-activity denitrifiers to remove organic materials and nitrogen from piggery wastewater.     

Ambient Air Particulates Bound Mercury Hg(p) Study Among Four Crops (Rice,White Cabbage,Arden Lettuce,and Gynura) at a Characteristic Sampling Site

The main purpose of this study was to monitor ambient air particulates and particulate-bound Hg (Hg[p]) compositions in different crops in the coastal zone in the Taichung, Taiwan, area at a sampling site during 2013 October to 2013 December. In addition, a direct mercury analyzer (DMA-80) was used to directly detect the concentration with measured results by the regression equation of Hg in the ambient air. The results indicated that: 1) the mean values of ambient air Hg(p) compositions in rice displayed no significant differences for weeks one, two, and three versus those of the other crops (white cabbage, Arden lettuce, and Gynura procumbens); 2) for white cabbage, the higher the humidity, the lower the average ambient air Hg(p) compositions that were obtained, a phenomenon that was also reflected on the crops of white cabbage and G. procumbens; 3) Arden lettuce displayed no significant differences in the leaf Hg(p) compositions during weeks one, two, and three; however, the stem portions displayed significant differences in Hg(p) compositions during weeks two and three; and 4) the Spearman statistical method showed the mean differences for ambient air Hg(p) at the Long-jing sampling site (coastal regions) with four different crops (rice, white cabbage, Arden lettuce, and Gynura) in central Taiwan. The results further revealed no significant differences in mean values.     

Electrochemical oxidation of PFOA and PFOS in concentrated waste streams

The electrochemical oxidation (EO) of environmentally persistent perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) with a Magnéli phase Ti₄O₇ electrode was investigated in this study. After 3 hours (hr) of electrolysis, 96.0 percent of PFOA (10 milligrams per liter [mg/L] in 100 milliliters [mL] 100 millimolar [mM] Na₂SO₄ solution) was removed following pseudo first‐order kinetics (k = 0.0226 per minute [min]) with the degradation half‐life of 30.7 min. Under the same treatment conditions, PFOS (10 mg/L in 100 mL 100 mM Na₂SO₄ solution) removal reached 98.9 percent with a pseudo first‐order degradation rate constant of 0.0491/min and the half‐life of 14.1 min. Although, the degradation of PFOA was slower than PFOS, when subjected to EO treatment in separate solutions, PFOA appeared to degrade faster than PFOS when both are present in the same solution, indicating possible competition between PFOA and PFOS during Ti₄O₇ anode‐based EO treatment with PFOA having the competitive advantage. Moreover, the EO treatment was applied to degrade highly concentrated PFOA (100.5 mg/L) and PFOS (68.6 mg/L) in ion‐exchange resin regenerant (still bottom) with high organic carbon content (15,800 mg/L). After 17‐hr electrolysis, the total removal of PFOA and PFOS was 77.2 and 96.5 percent, respectively, and the fluoride concentration increased from 0.84 mg/L to 836 mg/L. Also, the dark brown color of the original solution gradually faded during EO treatment. In another test using still bottom samples with lower total organic carbon (9,880 mg/L), the PFOA (15.5 mg/L) and PFOS (25.5 mg/L) concentrations were reduced to levels below the limits of quantification after 16‐hr treatment. In addition, the performance of EO treatment using different batch reactor setups was compared in this study, including one‐sided (one anode:one cathode) and two‐sided (one anode:two cathodes) setups. The two‐sided reactor configuration significantly enhanced the degradation efficiency, likely due to the larger anode area available for reactions.     

Respirometric Evaluation by Graphical Analysis for Microbial Systems

Analysis of respirometric graphs for system diagnosis has recently drawn much attention due to the nature of the test being a fast method with reliable oxygen uptake (Ou) data. In this study, a new graphical analysis procedure is proposed, using the oxygen uptake rate (OUR) vs. Ou respirogram because of its distinct characteristics that provides easy visual inspection. The OUR plot is typically divided into two respiration phases, and each one of these phases can be simulated by a previously derived analytical equation. Based on the 2-phase model, five characteristic parameters (CPs) were derived for the OUR respirogram. Mathematically the 5 CPs can be related to the system parameters (SPs), including the four Monod kinetic parameters and two operating conditions (initial substrate and biomass concentration). Sensitivity analyses were then conducted to assess the 5 CPs for the level of effect caused by system parameters (SPs). This study also conducted respirometric tests under batch operation to evaluate the applicability of the graphical analysis method. Based on the 5 CPs estimated from the OUR respirogram of the tests, it can be concluded that respirometric tests normally experience the problems associated with initial lag, non-uniform seeding, and inadequate mixing.     

The occurrence of disinfection by‐products in Taiwan drinking water

In this study, samples were taken from six conventional water treatment plants for disinfection by‐products analysis. Results from the analysis revealed that trihalomethanes (THMs) concentrations in all samples were below regulatory levels (100 μg/L). Although the national standard for haloacetic acids (HAA5) has not yet been promulgated in Taiwan, samples from two water plants contained HAA5 concentrations exceeding the USEPA limit (MCL of HAA5 of Stage 1, 60 μg/L). THMs and HAA5 were found to be the major disinfection by‐products in all water treatment plants. It was noted that the concentration of HAA5 in most samples was higher than that of the trihalomathanes. However, the formation potential of THM (THMFP) was found to be higher than that of HAA (HAAFP). Good correlation also was found between THMFP (or THMFP) and HAA5 (or THMs). In evaluating the performance of the treatment processes, it was found that conventional water treatment processes followed by activated carbon were effective in removing disinfection by‐products (DBPs) from source water with pre‐ozonation. The treatment processes were at their optimum performance in removing contaminants when O₃/TOC₀ was held at 0.75.