This research focuses on the performance study of a full-scale biofilter for treating a stream of vent gas with airborne VOCs generated from a chemical plant wastewater treatment facility. The biofilter consists of two parallel 20-ft standard containers in each a space of 5.98 m in length, 2.35 m in width and 0.50 m in height were filled with biofiltering media prepared by blending swine-manure compost and fern chips in a certain proportion. The vent gas contains methane, methanol, ethanol, acetone, dichloromethane, methyl ethyl ketone, ethyl acetate and toluene as major components and has an average flow rate of 1,320 m3/h (22 m3/min) and a temperature of 16-40oC. The purposes of this research were to confirm the VOC removal efficiency and to evaluate the elimination capacity for each VOC by monitoring operating parameters, including gas flow rate, system temperature, influent and effluent VOC concentrations of the biofilter. Experimental results show the system has a volumetric influent gas flow rate 1,153-1,470 m3/h which resulted in an average gas empty bed retention time (EBRT) of 0.64 min through the bed, a moisture of 25-70% and a pH of 2.4-6.9 for the media. Removal efficiencies of methane, methanol, ethanol, acetone, dichloromethane, MEK, ethyl acetate, toluene, NMHC and THC were 23.1, 79.3, 95.2, 82.9, 53.5, 63.7, 83.9, 41.2, 76.2 and 50.5%, respectively. Results also indicate that the VOC removal efficiency for each compound was not directly related to such important operating parameters of the biofilter as influent gas flow rate, media temperature, media pH, and the VOC concentration of the influent gas. However, the volumetric elimination rate (K) was approximately linearly varied with the corresponding loading (L) for the biodegradable VOCs in the influent gas. An average removal efficiency (K/L) of 24.5% was obtained with loadings of L < 70 g/m3h for methane. K/L of 91 and 54% were obtained for methanol with L = 0-7 and 15-22 g/m3h, respectively. Average K/L of 95% was obtained for both ethanol and acetone with L < 40 g/m3h. Removal efficiencies of 48 and 76% were obtained for methanol with L = 0-10 and 18-35 g/m3h, respectively. For MEK, an average removal of 89% was obtained with L = 0.5-4 g/m3h. Removal efficiencies of 84, 37, 48, 76 and 51% were obtained with L < 20, 0-0.2, 0.3-0.8 <60 and <120 g/m3h for ethyl acetate, toluene, NMHC and THC, respectively. This full-scale biofilter is effective in removing ethanol, ethyl acetate, acetone, methanol, and MEK. There is no significant removal efficiency for dichloromethane, toluene and methane. The performance can hopefully be improved by controlling the media in suitable conditions of moisture 50-60% and pH 7-8.

Abstract Biological processes have been proven to be economical and effective for control of VOCs with concentration of <1,000 mg C/m3. This study armed to develop a biofilter packed only with fern chips for the removal of airborne isopropyl alcohol (IPA). A three-stage down-flow biofilter (2.2 m in height and 0.4 m¡Ñ0.4 m in cross-sectional area) was constructed for the performance test. The first stage serviced as a humidifier for the incoming gas and the following two stages, both packed with fern chips with a packing space of 0.30 m ¡Ñ 0.40 m ¡Ñ0.40 m, as trickling bed biofilters for the VOC removal. Air with a nearly constant IPA concentration of 100 mg/Am3 (@ an average temperature of 34 oC) and a flow rate in the range of 100-400 L/min was fed to the reactor in Phase I test. The flow rate gave an empty bed retention time (EBRT) in the range of 12-48 s for the gas flowing through the two bed media. Solutions of urea-N, phosphate-P, and milk powder were supplied daily to the fern chips for the microbial nutrition in Phase I experiment which lasted for 26 days. Following the Phase, Phase II test operated with a constant EBRT of 12 s and without any nutrient supplementation for 30 days. Experimental results show that with an influent gas temperature of 29-40oC (average 34 oC) and relative humidity of 43-93% (average 73%), with a proper moistening of the bed media, the effluent gas could achieved a temperature of 26-35oC (average 29 oC) and a relative humidity of 98%. The proceeding medium experienced a greater moisture variation (12-68%, average 38%) than that (65-82%, average 72%) of the following one. The former and the latter media had pH in the range of 6.11-7.78 (average 6.77) and 6.13-7.36 (average 6.59), respectively. With no additional nutrient supplementation for 30 days, approximately 98% of the influent IPA of 100 mg/m3 could be removed at the EBRT of as short as 12 s which corresponded to a loading of 60 g IPA/m3.h.

Adsorption/desorption behaviors of three volatile organic compounds (VOCs) emitted from the optoelectronics industry by Y-type and ZSM-5 zeolites were studied in this work. Target VOCs include acetone, isopropyl alcohol (IPA), and propylene glycol monomethyl ether acetate (PGMEA). Adsorption/desorption experiments were conducted in a fixed-bed column using various operating conditions to mimic the commercial ones. Also studied include the adsorption kinetics for single-component, two-component, and three-component cases. Experimental results of the single-adsorbate case by both model zeolites have shown that the amount of VOC adsorbed follows the order of PGMEA > IPA > Acetone. This is ascribed to the greatest molecular weight of PGMEA among three VOCs tested. The adsorption capacity of each zeolite for each target VOC was found to increase with its increasing initial concentration. Freundlich isotherm and Langmuir isotherm were found to be suitable for describing the adsorption behaviors for the single-adsorbate case. Results of the desorption experiments also showed that most of the target VOCs could be desorbed at 180¢J in 100 minutes. The adsorption capacities of the regenerated model zeolites were found to be decreasing as the regeneration times increased. As compared with the fresh ones, the regenerated zeolites had reduced specific surface areas, but increased pore sizes. In addition, the Yoon and Nelson equation was employed to study the kinetic behaviors of adsorbing the target VOCs by the model zeolites. A good agreement of the experimental results and predictions by the Yoon & Nelson model was obtained for the single-adsorbate case. However, the Yoon and Nelson model was found to be incompetent to simulate and predict all the multi-adsorbate cases including two-component adsorption and three-component adsorption in this work. Again, it is speculated that the displacement of lower-molecular-weight adsorbates (i.e., acetone and IPA) by PGMEA (an adsorbate of a much greater molecular weight) would be responsible for this finding. For the two-adsorbate case, nevertheless, the Yoon and Nelson equation was found to be capable of describing the adsorption behavior under the circumstance of C/C0 < 1.

This study armed to develop a biofilter packed only with fern chips for the removal of air-borne propylene glycol monomethyl ether acetate (PGMEA). The fern chip biofilters could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. In the present study, a three stage down-flow biofilter (2.18 m in height and 0.4 m¡Ñ0.4 m in cross-sectional area) was constructed for the performance test. The first stage serviced as a humidifier for the incoming gas and the following two stages, both packed with fern chips of 0.30 m ¡Ñ 0.40 m ¡Ñ0.40 m, as trickling bed biofilters for the VOC removal. The experiment was divided into four phases. Operation conditions of an empty bed retention time (EBRT) of 1.60min and influent PGMEA concentrations of 9.33-329 (average 78.4) mg/m3 were used in the Phase I experiment which lasted for 99 days. An average PGMEA removal of only 68% was obtained in this phase. For improving the PGMEA removal in the following phases, a fixed dosage of milk powder of 1.0 g/(m3 media. day) added as aqueous milk suspension was added to the media for nutrition of the biofilms on the fern chip surfaces. After an additional operation time of 20 days (the 127th day from the startup time), a stable PGMEA removal of 91% was achieved. Following Phase II, PGMEA removals of 93 and 94% were obtained with EBRTs of 0.40 and 0.27 min, respectively, in Phases III and IV experiments. The results indicate that EBRT was not a key influencing factor to the PGMEA removal as long as the media had a high ability for the VOC degradation. Experimental data obtained from Phases II-IV reveal that with volumetric loadings (L) of less than 250 g PGMEA/(m3.h) to the up-streaming half of the whole media, 90% of the influent PGMEA could be removed in this half media. An additional 80% of the influent PGMEA to the following half media could be removed with L < 100 g PGMEA/(m3.h) to the half media. The PGMEA elimination capacities were proportional to the volumetric loadings of less than 250 g PGMEA/(m3.h). From the results, it could be proposed that for achieving over 93% of the PGMEA removal, appropriate operation conditions are media moisture content = 52-65%, media pH = 7.2-7.4, influent PGMEA concentration = 100-400 mg/Am3, EBRT = 0.27-0.40 min, and L to the whole media = 45-180 g PGMEA/(m3.h).

This study investigates characteristics of odorous materials and their odor intensities emitted from various commercial and industrial sources in the Kaohsiung City. An overview of odor complaints from the city people is presented and discussed. Results indicate that, due to the increasing people concerns about the odor emission problems, more frequent checks done by the City EPA officers, governmental assistances to the pollution makers on the pollution control technologies, and the enforcement of more stringent environmental protection regulations, odor-complaint cases in this city are decreasing in recent years. However, people are giving more attention to odors from food-cooking emissions and the associated complaint cases are increasing. Emissions from restaurants and plants become the two major odor sources in this city. For the plant emissions, odorous chemicals emitted from the Kaohsiung Refinery, located in northern Zouying District, were detected to be benzene, toluene, xylenes, and styrene. The Chianjhen storage and pumping station, located by the Kaohsiung Harbor, emits some 40 different chemicals. The majors among them are methanol, ammonia, ethylene, n-pentane, chlorodifluoromethane, methyl tert-butyl ether (MTBE), propylene, cyclohexane, styrene, acetone, 1,2-dichloroethane, propylene oxide and vinyl chloride. Prompt leaks from the storage tanks and during the loading and unloading operations account for the emissions. Plants located in the Chianjhen Export Processing Zone emit chemicals, mainly methyl methacrylate, toluene, propylene glycol monomethyl ether acetate (PGMEA), ammonia, ethyl acetate and ethanol, which cause only a few complaint cases. The emitted chemicals are among the ones used by the plants as feed stokes or solvents. Restaurant located in Chianjhen and Hsiogang Districts emit large amount of food-cooking odorants, however, the percentage of odorous complaining for the emissions is relatively high in the Zouying District as compared to the other administrative districts investigated in this study. Major components of the food-cooking emissions include hydrogen sulfide, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), ammonia, and methylamine. Relative percentages among these chemicals depend on the cooking materials and styles. Results also indicate that industries or businesses, such as petrochemical, surface coating, paint manufacturing, fuel station, storage vessels, semiconductor manufacturing, adhesive tape manufacturing and cloth dry-cleaning, are major odor and chemical emission sources which need to be continuously implemented for getting more emission reductions in the near future.

This study armed to develop a biofilter packed only with fern chips for the removal of air-borne low concentration VOCs (volatile organic compounds) emitted from semiconductor manufacturing industries. The fern chip biofilters could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. Performance of biofiltration for removal of simulated semiconductor manufacturing emitted gases consisting of IPA (isopropyl alcohol), acetone, HMDS (hexamethylene disilazane), PGME (propylene glycol monomethyl ether), and PGMEA (propylene glycol monomethyl ether acetate) was studied in a pilot-scale biofilter consisted of two columns (40-cmW x 40-cmL x 70-cmH acrylic column) arranged in series. Each column was packed with fern chips to a packing volume of around 56 L (0.40 m¡Ñ0.40 m¡Ñ0.35 mH). A sprinkler was set over the packed fern chips for providing them with water and nutrition solutions. Liquid leached from both layers of chips were collected in the bottom container of the column. The experiment lasted for 182 days which was divided into four phases with varying influent gas flow rates and VOC concentrations. Gas samples collected around 3 times per week from the influent as well a the first and second stage effluents were analyzed for VOC concentrations. On a weekly basis, fern chips sampled from each column were also analyzed for getting pH, moisture, and the absorbed VOC content of the chips. Phase shifted if it obtained a quasi-steady state which was judged by the nearly unchanging VOC removal efficiencies. Operation conditions of an empty bed retention time (EBRT) of 1.50 min and influent VOC concentrations of 159-284 mg/m3 were used in the Phase I experiment which lasted for 15 days. Nutrition of 1.34 g milk powder/m3.d was used in this phase and the conditions gave an average volumetric VOC loading (L) of 15.1 g/m3.h. Effluent VOC concentrations were 3-18 mg/m3 and an average VOC removal of 96% was obtained in this phase. An EBRT of 0.75 min, L of 11.44 g/m3.h, and nutrition of 1.34 g milk powder/m3.d were used in the Phase II experiment. VOCs in the gas could be removed from 90-126 to 1-19.6 mg/m3 and an average efficiency of 94% was obtained. Following Phase II, an average VOC removal of only 48% was obtained with an EBRT of 0.75 min, nutrition of 2.0 g milk powder/m3.d, and L of 22.8 g/m3.h in Phases III experiment during the 56-97th days from the startup time. Additional nitrogen (urea) and phosphorus (potassium dihydrogen phosphate) was added to the media from the 105th day and the VOC removal increased to 80% at the 107th day. An average VOC removal of around 93% was obtained in phase III experiment. The results showed that enough nutrition is essential to the successful performance for the biofiltration process. Phase IV experiment lasted for 59 days with an EBRT of 0.75 min, L of 34.1 g/m3.h, and nutrition of 2.0-6.0 g/m3.d. During the initial period of this phase, media pH dropped from 7.8 to 5.8 due to an excess nitrogen (ammonium chloride) addition as high as 12.35 g N/m3.d which resulted in nitrification reaction in the media. By stopping nitrogen, increasing milk powder dosing, and addition of NaHCO3 at the 140th day, pH restored to 7.5 in the following days. VOC removal increased to an average of 92% in the rest operation days. From the results, it could be proposed that for achieving over 90% of the VOC removal, appropriate operation conditions are media moisture content = 52-65%, media pH = 7-8, influent VOC concentration = 150-450 mg/Am3, EBRT = 0.75 min, and L to the whole media = 11-34 g/m3.h.

In this study, two regenerative thermal oxidizers (RTO) were used to test the thermal destruction, thermal recovery efficiency and the gas pressure drop over the beds characteristics when burning, respectively, airborne chlorine- and nitrogen-containing volatile organic compounds (VOCs). First, an electrically-heated RTO containing two 0.5 m ¡Ñ 0.5 m ¡Ñ 2.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0116 m and a height of up to 1.48 m with a void fraction of 0.41 in the packed section was used to study the destruction characteristics of chlorine-containing VOCs (trichloroethane, TCE and dichloromethane, DCM). With a valve switch time (ts) of 1.5 min, preset maximum destruction temperatures (TS) of 500-800 oC and superficial gas velocity (Ug) of 0.17-0.33 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the thermal recovery efficiency (TRE) and the pressure drop for the air stream without VOC in the influent air stream have been performed. With a ts of 1.5 min, Ts of 500-800 oC and Ug of 0.17-0.24 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the degree thermal destruction of VOCs with influent air streams containing one of the two VOCs: trichloroethylene (TCE) and dichloromethane (DCM) have been done. Second, an electrically-heated RTO containing two 0.152 m ¡Ñ 0.14 m ¡Ñ 1.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0111 m and a height of up to 1.0 m with a void fraction of 0.42 in the packed section was used to study the destruction and NOx formation characteristics of DMF (N, N-dimethylformamide). With a ts of 1.5 min, Ts of 750-850 ¢Jand Ug of 0.39-0.78 m/s (evaluated at an influent air temperature of around 30 ¢J), TRE and the pressure drop for the air stream without VOC in the influent air stream have been tested. With a ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 ¢J), and Ts of 750-950 ¢J and, thermal destruction efficiencies and nitrogen oxides (NOx) formation characteristics in burning air streams containing either DMF or DMF mixed with methyl ethyl ketone (MEK) were performed. Results demonstrate that: (1) a RTO is suitable for destruction of low concentrations (<1,000 ppm as methane) of airborne highly chlorinated VOCs such as TCE and DCM and the destructed products contain no chlorine and only trace of COCl2 (< 1% of the influent VOC); (2) for TS = 800 oC and Ug = 0.17-0.24 m/s, complete oxidation products of TCE and DCM are HCl, CO2, and H2O, and the main intermediates are CO and COCl2; (3) with ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 oC) and TS of 750-950 ¢J, no NOx was present in the effluent gas from the RTO when it was loaded with DMF-free air; (4) when only DMF was present in the influent air, the average destruction efficiencies exceeded 96%, and increased with the influent DMF concentration from 300 to 750 mg/Nm3. The ¡§NOx-N formation/DMF-N destruction¡¨ mass ratios were in the range 0.76-1.05, and decreased as the influent DMF concentration increased within the experimental range; (5) when both DMF and MEK were present in the influent gas, the NOx formation ratio was almost the same and the DMF destruction efficiency increased with the influent MEK/DMF ratio from 150/300 to 4500/300 (mg/mg) and in the preset temperature range. The NOx formation ratios were in the range 0.75-0.96; (6) the TRE decreased as Ug increased but was invariant with Ts; and (7) the Ergun equation was found to suffice in the estimation of the pressure drop when the gas flowed over the packing beds.

Performance studies on the treatment of VOCs in air streams by a pilot-scale regenerative catalytic oxidizer (RCO) and a full-scale regenerative thermal oxidizer (RTO) were conducted. The pilot-scale RCO was constructed with two 20-cm x 200-cm (inside diameter x packing height) regenerative beds packed with gravel (average particle size = 1.25 cm) used as the thermal regenerative solid material. Experimental results indicate that destruction efficiencies of 97 and 90%, respectively, were obtained for methyl ethyl ketone and toluene at a superficial gas velocity of 0.372 m/s (evaluated at 25¢J) and a maximum bed temperature of 400¢J. It was estimated that an electrical thermal energy of approximately 84 kWh was required for treating 1,000 m3 of the waste air stream by the RCO. The full-scale RTO was constructed with two regenerative beds of 100-cm square x 200-cm height packed with the gravel used in the RCO. A paint solvent containing methyl ethyl ketone, ethyl benzene, xylenes, and ethyl acetate was used for the target VOCs. Experimental results indicate that, at a superficial gas velocity of 0.372 m/s (evaluated at 25¢J), VOC destruction efficiencies of 84, 92, 95 and 98% were obtained for the beds at temperature ranges of 200-300, 300-500, 400-700, and 500-700¢J. These conditions corresponded to empty gas retention times of 1.07, 0.85, 0.41, and 0.39s, respectively, for the cited temperature ranges. Finally, it was estimated that electrical watts of approximately 0.10, 0.45, 1.78, 2.43 kWh were required for treating 1,000 m3 of the waste air stream, respectively, at bed temperature ranges of 200-300, 300-500, 400-700, and 500-700¢J.

This study investigated the characteristics of volatile organic compounds (VOCs) in the atmosphere at the surrounding area of an oil storage and pumping station from March to June, 2001. The influence of operation condition of storage and pumping station as well as meteorological factors on the distribution of VOCs was also investigated. In this study, a sampling network including six sites around the boundary of the oil storage and pumping station and one site at a nearby village was established for the sampling of VOCs near ground level. Air samples were collected by a carbontrap 300 multi-bed stainless steel sampling tube and were desorbed by a thermal desorption unit (TDU). The desorbed VOCs samples were then analyzed by a gas chromatography with flame ionization detector (GC/FID). In addition, hydrocarbons (both methane and non-methane hydrocarbons) and meteorological condition including wind speed and wind direction were detected automatically in order to correlate with the concentration of VOCs. Results from field measurement indicated that up to twelve VOCs were detected in the atmosphere, which quite consisted with the composition of stored oil including petroleum crude oil, aviation turbine fuel, 95 unleaded gasoline, and naphtha. Major VOCs observed at the surrounding area of the oil storage and pumping station were benzene and toluene, however, in most cases high boil-point organic compounds were also detected. It suggested that the nearby village could not be solely affected by VOCs emitted from oil storage tanks but also from other local sources such as steel plating plants. Furthermore, meteorological condition played an important role on the dispersion of fugitive VOCs at the surrounding area. For instance, the concentration of VOCs at the downwind sites were generally higher than that at the upwind sites while northern and northwestern winds blew in late Spring. Besides, toluene to benzene concentration ratios (T/B) ranged from 1.5 to 2.1 during the southwestern wind period in Summer, which were higher than those (T/B&#x00A3;1.5) during the northern and northwestern wind periods in late Spring. It suggested that the nearby village as a sensitive location could be much more easily affected by local traffics than the oil storage and pumping station during the summer time since T/B ratios were approximately 2.0 in the tail gas exhausted from automobiles. From the viewpoint of health risk assessment, the location with highest potential risk at the surrounding area of the oil storage and pumping station was the floating oil tank zone which required better operation strategies of the oil storage and pumping station for the protection of ambient air quality.

This study investigated the feasibility of glassfiber filter coated with titanium dioxide (TiO2) on removing indoor VOCs using photocatalytic technology, which could further expand the electronic filter¡¦s function . First of all, we coated the titanium dioxide (TiO2) photocatalysts on the glassfiber filter with chemical vapor desposition (CVD) method, then dried it at 120¢J, and calcined it to prepare a nano-sized TiO2 coated filter . Secondly, we collected VOC samples in a printery and analyzed their chemical components. The main components of VOCs (benzene¡Btoluene and acetone) were then conducted in a self-designed laboratory-scaled batch photocatalytic reactor. The decomposition of acetone for different operating parameters, including initial VOC concentration, CVD coating time, and calcination temperature, was further conducted. Besides, a nano-sized photocatalyst indoor air purifier was self-designed for this particular study. The air purifier consists of a set of near-UV light source, a nano-sized photocatalyst glassfiber filter, a stainless shelter, and a circulating fan. The air purifier was tested to ascertain its capability on the removal of indoor VOCs in a well-tight environmental chamber. The testing results indicated the nano-sized photocatalyst glassfiber filter can be used to remove indoor VOCs . In the final stage, a nano-sized TiO2 photocatalyst electronic air cleaner was self-designed for this particular further study in a printery. The air cleaner consists of a set of UV light source, a nano-sized photocatalyst glassfiber filter, a set of electronic filter, carborn filter and a pain coated steel plate shelter. The air cleaner was tested to ascertain its capability on the removal of indoor VOCs in a return air channel of air condition system. The testing results indicated that the nano-sized photocatalyst glassfiber filter can be used to remove indoor VOCs