CAREAIR: A Computer Aided Modeling Toolbox to Generate and Analyze Emission Data in High Temporal and Spatial Resolution

ABSTRACT

For the evaluation of air quality improvement strategies, emission data in high temporal and spatial resolution is necessary, including all emission sources and all relevant pollutant species. Computer aided models are usually used to generate this emission data because it is not possible to obtain measurements from all sources, and, furthermore, a large amount of data has to be handled. For the development of emission modeling systems, a software tool called CAREAIR has been created. The intention of this paper is to introduce CAREAIR to the international community dealing with emission inventories and air quality improvement strategies.

CAREAIR is not just a single emission model but a flexible modeling toolbox. The database contains data and formulas for data manipulation, which is performed by using a set of flexible operators with different specifications. The emission calculation is carried out by combining several data manipulation operators. The CAREAIR modeling toolbox allows model implementation for the calculation of emissions from different pollutants in a high spatial and temporal resolution. The application of CAREAIR within various investigation projects in Germany, Europe, and Nigeria shows that CAREAIR is an appropriate instrument for the development of flexible emission models by meeting the various demands of these projects. The function and the data structures of this modeling toolbox are described and, towards the end of the paper, an example of an emission calculation with CAREAIR is given.     

Anoxic gas recirculation system for fouling control in anoxic membrane reactor

Anoxic gas recirculation system was applied to control the membrane fouling in pilot-scale 4-stage anoxic membrane bioreactor(MBR). In the anaerobic-anoxic-anoxic-aerobic flow scheme,hydrophilic polytetrafluoroethylene(PTFE) membrane(0.2 μm, 7.2 m2/module) was submerged in the second anoxic zone. During 8 months operation, the average flux of the membrane was 21.3L/(m2·hr). Chemical cleaning of the membrane was conducted only once with sodium hydroxide and sodium hypochlorite. Dissolved oxygen(DO) concentration in the second anoxic zone was maintained with an average of 0.19 ± 0.05 mg/L. Gas chromatography analysis showed that the headspace gas in the second anoxic reactor was mainly consisted of N2(93.0% ± 2.5%), O2(3.8% ± 0.6%), and CO2(3.0% ± 0.5%), where the saturation DO concentration in liquid phase was 1.57 mg/L. Atmospheric O2 content(20.5% ± 0.8%) was significantly reduced in the anoxic gas. The average pH in the reactor was 7.2 ± 0.4. As a result, the recirculation of the anoxic gas was successfully applied to control the membrane fouling in the anoxic MBR.     

Structural effect of the in situ generated titania on its ability to oxidize and capture the gas-phase elemental mercury

Structural effect of the in situ generated TiO(2) sorbent particle was examined for its ability to capture elemental mercury under UV irradiation in a simulated combustion flue gas. Titania particles were prepared by thermal gas-phase oxidation of Titanium (IV) isopropoxide (TTIP) using a high temperature electric furnace reactor. The structural characteristics of the in situ generated TiO(2) at various synthesis temperatures were investigated; size distribution and the geometric mean diameter were measured using a scanning mobility particle sizer, while fractal dimension and radius of gyration were evaluated from the transmission electron microscopy images. Results from the Hg(0) capture experiment show that with increasing titania synthesis temperature, the overall aggregate size increases and the morphology becomes more open-structured to gas-phase Hg(0) and UV light, resulting in the improved mercury removal capability.     

Phosphate removal and recovery with a synthetic hydrotalcite as an adsorbent

Phosphate removal is important to control eutrophication and an ion exchange process is one of several treatment processes for this purpose. Hydrotalcite compounds (HTALs) are useful as adsorbents for phosphate removal because of their ion exchange properties. In this study, the adsorption properties of a granular synthetic HTAL for phosphate and the method of regeneration of the granular HTAL were examined. The adsorption isotherm of the granular HTAL was approximated by a modified Langmuir type, and the maximum adsorption capacity was 47.3 mg P g(-1), which corresponded to the content of HTAL in the granular one. Phosphate adsorbed on the HTAL was effectively desorbed with alkaline NaCl solutions and the HTAL was regenerated with 25 w/v% MgCl(2) solution. The regenerated HTAL could be reused repeatedly for the phosphate removal. Phosphate in the exhausted desorption solution was recovered as a precipitate of calcium phosphate by addition of CaCl(2), and the residual exhausted desorption solution could be also reused after supplying NaOH. The results suggest the possibility of an effective system for phosphate removal and recovery, which includes the following processes: adsorption, desorption, recovery of phosphate, and regeneration of the HTAL and the desorption solution.     

Modification of Aliphatic Polyesters and Their Reactive Blends with Starch

Modified polycaprolactone was synthesized by melt reaction of PCL and reactive monomers such as glycidyl methacrylate (GMA) and maleic anhydride (MAH) in the presence of benzoyl peroxide in Brabender mixer. MAH showed a different grafting phenomenon compared to GMA. The reaction mechanism was discussed with different reactive monomers. Reactive blends of the PCL-g-GMA and the gelatinized starch with glycerin were prepared and their mechanical properties and biodegradabilities were investigated. Reactive blends of PCL-g-GMA and starch showed well-dispersed starch domain in the matrix and better mechanical strength than the unmodified PCL/starch blend. However, the reaction between PCL-g-GMA and starch induced a crosslinking during the reactive blending and this crosslinking in the blend lowered the biodegradation of the blend during the composting test. The biodegradability was investigated by the weight loss and surface morphology change of the blend in the composting medium.     

Chamber evaluation of a portable GC with tunable retention and microsensor-array detection for indoor air quality monitoring

The evaluation of a novel prototype instrument designed for on-site determinations of VOC mixtures found in indoor working environments is described. The instrument contains a miniature multi-stage preconcentrator, a dual-column separation module with pressure-tunable retention capabilities, and an integrated array of three polymer-coated surface acoustic wave sensors. It was challenged with dynamic test-atmospheres of a set of 15 common indoor air contaminants at parts-per-billion concentrations within a stainless-steel chamber under a range of conditions. Vapours were reliably identified at a known level of confidence by combining column retention times with sensor-array response patterns and applying a multivariate statistical test of pattern fidelity for the chromatographically resolved vapours. Estimates of vapour concentrations fell within 7% on average of those determined by EPA Method TO-17, and limits of detection ranged from 0.2 to 28 ppb at 25 degrees C for 1 L samples collected and analyzed in <12 min. No significant humidity effects were observed (0-90% RH). Increasing the chamber temperature from 25 to 30 degrees C reduced the retention times of the more volatile analytes which, in turn, demanded alterations in the scheduling of column-junction-point pressure (flow) modulations performed during the analysis. Reductions in sensor sensitivities with increasing temperature were predictable and similar among the sensors in the array such that most response patterns were not altered significantly. Short-term fluctuations in concentration were accurately tracked by the instrument. Results indicate that this type of instrument could provide routine, semi-autonomous, near-real-time, multi-vapour monitoring in support of efforts to assess air quality in office environments.     

Leaching characteristics of rare metal elements and chlorine in fly ash from ash melting plants for metal recovery

In terms of resource recovery and environmental impact, melting furnace fly ash (MFA) is attracting much attention in Japan due to its high metal content. The study aims to obtain fundamental information on using a water extraction method not only to concentrate valuable rare metals but also to remove undesirable substances such as chlorine for their recovery from MFA. The composition and leaching characteristics of MFA was investigated. The results revealed that the metal content in MFA is nearly equal to raw ore quality. The content of Ag, In, Pd, Pb, and Zn is, in fact, higher than the content of raw ore. As for leaching behavior, Ag, Bi, In, Ga, Ge, Sb, Sn, and Te showed the lowest release at a neutral pH range. Pd was leached constantly regardless of pH, but its concentration was quite low. On the other hand, most of the Tl was easily leached, revealing that water extraction is not appropriate for Tl recovery from MFA. Major elements Cl, Ca, Na, and K, occupying about 70% of MFA, were mostly leached regardless of pH. Base metal elements Cu, Pb, and Zn showed minimum solubility at a neutral pH. The leaching ratio of target rare metal elements and base metal elements suggests that the optimal pH for water extraction is 8-10, at which the leaching concentration is minimized. The water extraction process removed most of the Cl, Ca, Na, and K, and the concentration of rare metals and base metals increased by four or five times.     

Field application of electrokinetic remediation for multi-metal contaminated paddy soil using two-dimensional electrode configuration

In this study, we evaluated the feasibility of in situ electrokinetic remediation for arsenic (As)-, copper (Cu)-, and lead (Pb)-contaminated soil, in a pilot-scale field application with two-dimensional electrode configurations. Square and hexagonal configurations with different electrode spacing, 1 m and 2?m, were investigated under a constant 100 V. A square configuration with electrode spacing of 2 m removed 61.5 % of As, 11.4 % of Cu, and 0.9 % of Pb, respectively, and a hexagonal configuration with the same spacing showed a higher removal efficiency in top (59 % of As, 0–0.5 m) and middle (53 % of As, 0.5–1.0 m) layers, but much lower removal efficiency in the bottom layer (1–1.5 m), which was thought to be due to groundwater flow through periodic rise and fall of tides. Fractionation analysis showed that As bound to Fe–Mn oxyhydroxide was the main form of As removed by the electrokinetic process. The two-dimensional configuration wasted less electrical energy by Joule heating, and required fewer electrode installations, compared to the one-dimensional electrode configuration.