Biotrickling filtration of nitric oxide

A biotrickling filter with blast-furnace slag packings (sizes = 20-40 mm and specific surface area = 120 m2/m3) was utilized to treat NO in an air stream. The operational stability, as well as the effects of gas empty-bed retention time (EBRT) and nutrient addition on the removal ability of NO, were tested. Approximately six weeks were required for the development of a biofilm for NO degradation, and a two-week organic carbon deficiency resulted in the detachment of biofilms from the packing surfaces. A steady removal rate of 80% was attained at specified influent NO concentrations of 892 to 1237 ppm and an EBRT of 118 sec. The effluent NO concentration diminished exponentially with enlarging EBRT, with influent NO concentrations of 203-898 ppm, and EBRTs of 25 to 118 sec. Nutrient addition is essential for efficient removal of the influent NO. Mass ratios of C: P: N = 7: 1: 30 and NaHCO3: NO-N = 6.3 could be used for practical applications.     

Effect of Water and Carbon Dioxide in Chemiluminescent Measurement of Oxides of Nitrogen

ABSTRACT

This paper reports results of studies using a biotrickling filter with blast-furnace slag packings (sizes = 2–4 cm and specific surface area = 120 m²/m³) for treatment of ethylether in air stream. Effects of volumetric loading, superficial gas velocity, empty bed gas retention time, recirculation liquid flow rate, and biofilm renewal on the ethylether removal efficiency and elimination capacity were tested. Results indicate that ethylether removal efficiencies of more than 95% were obtained with an empty bed retention time (EBRT) of 113 sec and loadings of lower than 70 g/m³/hr. At an EBRT of 57 sec, removal efficiencies of more than 90% could only be obtained with loadings of lower than 35 g/m³/hr. The maximum elimination capacities were 71 and 45 g/m³/hr for EBRT = 113 and 57 sec, respectively. The maximum ethylether elimination capacities were 71 and 96 g/m³/hr, respectively, before and after the renewal at EBRT = 113 sec. With an EBRT of 113 sec and a loading of lower than 38 g/m³/hr, the removal efficiency was nearly independent of the superficial liquid recirculation velocity in the range of 3.6 to 9.6 m³/m²/hr. From data regression, simplified mass-transfer limited, and reaction- and mass-transfer limited models correlating the contaminant concentration and the packing height were proposed and verified. The former model is applicable for cases of low influent contaminant concentrations or loadings, and the latter is applicable for cases of higher ones. Finally, CO₂ conversion efficiencies of approximately 90% for the influent ethylether were obtained. The value is comparable to data reported from other related studies.     

Adsorptive conversion of nitrogen dioxide from etching vent gases over activated carbon

Some metal etching operations emit limited flow rates of waste gases with reddish-brown NO₂ fume, which may cause visual and acidic-odor complaints, as well as negative health effects. In this study, tests were performed by passing caustic-treated waste gases vented from Al-etching operations through columns packed either with virgin or regenerated granular activated carbon (GAC) to test their adsorptive conversion performance of NO₂ in the gases. The gases contained 5–55 ppm NO₂ and acetic and nitric acids of below 3 ppm. Exhausted carbon was regenerated by scrubbing it with caustic solution and water, and dried for further adsorption tests. Results indicate that with an (empty bed residence time (EBRT) of 0.15 sec for the gas through the GAC-packed space, around 60% of the influent NO₂ of 54 ppm could be removed, and 47% of the removed NO₂ was converted by and desorbed from the carbon as NO. GAC used in the present study could be regenerated at least twice to restore its capacity for NO₂ adsorption. Within EBRTs of 0.076–0.18 sec, the adsorptive conversion capacity was linearly varied with EBRT. In practice, with an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO₂ (kg GAC)^?1 with an influent NO₂ of 40 ppm can be used as a basis for system design.

Implications: Some metal etching operations emit waste gases with reddish-brown (yellow when diluted) NO₂ fume which may cause visual and acidic-odor complaints, as well as negative health effects. This study provides a simple process for the adsorptive conversion of NO₂ in caustic-treated waste gases vented from metal-etching operations through a GAC column. With an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO₂ (kg GAC)^?1 with an influent NO₂ of 40 ppm can be used as a basis for system design. Saturated GAC can be regenerated at least twice by simply scrubbing it with aqueous caustic solution.     

Carbon Disulfide and Hydrogen Sulfide Removal with a Peat Biofilter

ABSTRACT

Simultaneous removal of H₂S and CS₂ was studied with a peat biofilter inoculated with a Thiobacillus strain that oxidizes both compounds in an acidic environment. Both sulfurous gases at concentrations below 600 mg S/m³ were efficiently removed, and the removal efficiencies were similar, 99%, with an empty bed retention time (EBRT) of more than 60 sec. Concentrations greater than 1300-5000 mg S/m³ caused overloading of the filter material, resulting in high H₂SO₄ production, accumulation of elemental sulfur, and reduced removal efficiency. The highest sulfur removal rate achieved was 4500 g-S/day/m³ filter material. These results indicate that peat is suitable as a biofilter material for the removal of a mixture of H₂S and CS₂ when concentrations of gases to be purified are low (less than 600 mg/m³), but it is still odorous and toxic to the environment and humans.     

Treatment of Propylene Glycol Monomethyl Ether Acetate in Air Streams by a Biofilter Packed with Fern Chips

Abstract

This study aimed to develop a biofilter packed only with fern chips for the removal of airborne propylene glycol monomethyl ether acetate (PGMEA). Fern chips could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. In addition, the fern chip medium has the following merits: (1) simplicity in composition; (2) low pressure drop for gas ?ow (<20 mmH₂O?m^-1); (3) simple in humidification, nutrient addition, pH control, and metabolite removal; (4) economical (US$174–385?m^-3), and (5) low weight (wet basis around 290 kg?m^-3). A two-stage down?ow biofilter (2.18 m in height and 0.4×0.4 m in cross-sectional area) was constructed for the performance test. Both stages were packed with fern chips of 0.30 m in height and 0.40×0.40 m in cross-section. Results indicate that with operation conditions of media moisture content controlled in the range of 50–74%, media pH of 6.5–8.3, empty bed retention time (EBRT) of 0.27–0.4 min, in?uent PGMEA concentrations of 100–750 mg?m^-3, volu-metric organic loading of <170 ?m^-3 ?hr^-1, and nutrition rates of Urea-nitrogen 66 g?m^-3 ?day^-3, potassium dihydrogen phosphate (KH₂PO₄)-phosphorus 13.3 g ?m^-3 ?day^-3, and milk powder 1.00 g?m^-3?day^-1, the fern-chip-packed biofilter could achieve an overall PGMEA removal efficacy of around 94%. Instant milk powder or liquid milk was essential to the good and stable performance of the biofilter for PGMEA removal.     

Biofiltration of odorous fume emitted from recycled nylon melting operations

This study aimed to develop a biofilter packed only with fern chips for the removal of odorous compounds from recycled nylon melting operations. 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. A pilot-scale biofilter consisting of an acrylic column (14 cm²?×?120 cm height) packed with fern chips to a volume of around 19.6 L was used for the test. Experimental results indicate that oxygen- and nitrogen-containing hydrocarbons as well as paraffins were major volatile organic compounds (VOCs) emitted from thermal smelting of recycled nylon at 250 °C. With operation conditions of medium pH of 5.5–7.0, empty bed retention time (EBRT) of 6–12 sec, influent total hydrocarbon (THC) concentrations of 0.65–2.61 mg m^?3, and volumetric organic loading of 0.05–0.85 g m^?3 hr^?1, the fern-chip-packed biofilter with nutrients of milk, potassium dihydrogen phosphate, and glucose could achieve an overall THC removal efficiency of around 80%. Burnt odor emitted from the smelting of the recycled nylon could be eliminated by the biofilter.

Implications: Biotreatment of contaminants in air streams offers an inexpensive and efficient alternative to conventional technologies. Biofiltration have a great potential for the degradation of gas-borne odorous compounds. THC removal efficiency of around 80% can be achieved. Burnt odor emitted from the smelting of the recycled nylon could be eliminated by the biofilter. This study provides an experimentally verified model for the design and operation of such biotreatment systems.     

Treatment of ethylether in air stream by a biotrickling filter packed with slags.

This paper reports results of studies using a biotrickling filter with blast-furnace slag packings (sizes = 2-4 cm and specific surface area = 120 m2/m3) for treatment of ethylether in air stream. Effects of volumetric loading, superficial gas velocity, empty bed gas retention time, recirculation liquid flow rate, and biofilm renewal on the ethylether removal efficiency and elimination capacity were tested. Results indicate that ethylether removal efficieincies of more than 95% were obtained with an empty bed retention time (EBRT) of 113 sec and loadings of lower than 70 g/m3/hr. At an EBRT of 57 sec, removal efficiencies of more than 90% could only be obtained with loadings of lower than 35 g/m3/hr. The maximum elimination capacities were 71 and 45 g/m3/hr for EBRT = 113 and 57 sec, respectively. The maximum ethylether elimination capacities were 71 and 96 g/m3/hr, respectively, before and after the renewal at EBRT = 113 sec. With an EBRT of 113 sec and a loading of lower than 38 g/m3/hr, the removal efficiency was nearly independent of the superficial liquid recirculation velocity in the range of 3.6 to 9.6 m3/m2/hr. From data regression, simplified masstransfer limited, and reaction- and mass-transfer limited models correlating the contaminant concentration and the packing height were proposed and verified. The former model is applicable for cases of low influent contaminant concentrations or loadings, and the latter is applicable for cases of higher ones. Finally, CO2 conversion efficiencies of approximately 90% for the influent ethylether were obtained. The value is comparable to data reported from other related studies.     

容积负荷对ANAMMOX生物滤池脱氮效能的影响及其基质动力学

采用2套启动成功的上向流厌氧氨氧化（ANAMMOX）生物滤柱，通过调节进水NaNO₂和（NH₄）₂SO₄ 的浓度负荷及水力负荷，改变进水容积负荷，探讨容积负荷对ANAMMOX生物滤柱脱氮效能的影响及其动力学模型。结果表明，滤速恒定条件下，通过提高进水基质浓度来提高进水TN容积负荷，其容积负荷去除动力学过程符合Monod-Haldane基质抑制模型。进水NH₄⁺-N与NO₂^--N浓度分别低于100 mg/L和133 mg/L时，反应器脱氮效果不受明显影响，TN容积去除负荷可达4.21 kg/（m³·d），TN去除率可达80%以上。进水基质浓度恒定条件下，通过提高滤速来提高进水TN容积负荷，其容积负荷去除动力学过程符合零级动力学方程。不受基质浓度抑制的条件下，滤速为3.0 m/h、进水容积负荷为8.82 kg/（m³·d）时，反应器总氮容积负荷去除量可达7.15 kg/（m³·d），总氮去除率可达81.1%。     

Long-term evaluation of activated carbon as an adsorbent for biogas desulfurization

ABSTRACT

In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. Biogas containing 932–2,350 ppm of H₂S was collected from an anaerobic digester to treat the wastewater from a dairy farm with about 200 cows. An adsorption test was performed by introducing the biogas to a column that was packed with approximately 50 L of commercial GAC. The operation ceased if the effluent gas had an H₂S concentration of over 100 ppm. The GAC was replaced by a given weight of new GAC in a subsequent test. According to the results, for H₂S concentrations in the range of 932–1,560 ppm (average±SD = 1,260 ± 256 ppm), 1 kg of the GAC yielded biogas treatment capacities of 568 ± 112 m³ and H₂S adsorption capacities of 979 ± 235 g. For the higher influent H₂S concentrations of 2,110 ± 219 ppm, the biogas treatment and H₂S-adsorption capacities decreased to 229 ± 18 m³ and 668 ± 47 g, respectively. An estimation indicated a requisite cost of US$16.5 for the purification of 1,000 m³ of biogas containing 2,110 ppm of H₂S. This cost is approximately 5% of US$330, the value of 1,000 m³ of biogas.     

1-Butanol Removal from a Contaminated Airstream under Continuous and Diurnal Loading Conditions

Abstract

A polysulfone microporous membrane module was investigated for control of 1-butanol-contaminated gas streams. A diurnal loading condition, using two different butanol concentrations, was used to simulate startup and stop conditions associated with shift work. The membrane module was also used to remove 1-butanol from air under continuous loading conditions in a bioreactor. The reactors were seeded with a mixed bacterial consortium capable of butanol biodegradation. Biokinetic parameters for butanol utilization were determined for the culture to be a maximum specific utilization rate (k) equal to 4.3 d^?1 and a half saturation constant (K_s) equal to 8.9 mg L^?1. A biofilter running only with diurnal loading conditions giving a “40-hr workweek” had an average 1-butanol removal rate of 29% (111 ppm, 74 gm^?3 hr^?1) from a 350-ppm influent at the end of an 8-hr operational day. End-of-day removal varied between 4 and 67% during the operational period. With continuous steady-state operation followed by placement on a diurnal loading schedule and influent butanol concentrations increased to 700 ppm, butanol removal averaged 38% (269 ppm, 145 gm^?3 hr^?1). Under continuous loading, steady-state conditions, 1-butanol removal from the airstream was greater than 99% (200 ppm, 73 gm^?3 hr^?1). These results suggest that the bioreactor can be operated on a diurnal schedule or 40-hr week operational schedule without any decline in performance.     

Public Reaction to SIP Revisions for Ozone Reduction

ABSTRACT

This study utilized a biotrickling filter with blast-furnace slag packings (sizes = 20-40 mm; specific surface area = 120 m²/m³) to treat toluene in an air stream. Also studied were the effects of volumetric loading (L), nutrient addition, and superficial gas velocity (U_g) or gas retention time on toluene elimination capacity. Experimental results indicate that, for a test period of 121 days, with no excess biomass removal, toluene removal efficiencies of over 90% were obtained with U_g < 80 m/hr and L < 30 g/m³.hr. For a test period of 49 days, with U_g < 80 m/hr and L increased from 1.2 to 81 g/m³.hr, the absence of nutrient supplementation did not limit the toluene elimination capacity. Nutrients stored in the biofilm could adequately support the microbial activity for the toluene elimination. According to data regression, a simplified mass-transfer model is proposed, which correlates the contaminant concentration with the packing height or gas empty bed retention time. As verified, the model proposed herein can be applied to cases involving low influent contaminant concentrations or loadings to the extent that none or only a trace amount of the contaminant can be found in the recirculation liquid. Although small media with larger specific surface areas can achieve a better mass transfer, the problems of frequent backwashing and relatively greater gas resistance in using this type of media probably outweigh the advantages, particularly for full-scale systems that would not be watched as closely as laboratory test systems.     

复合人工湿地中低浓度有机物的去除及Monod模型模拟

以复合人工湿地工程实例为研究对象,研究了其在连续5个月内对低浓度有机污染物的深度处理效果,采用简化的Monod动力学模型对研究湿地进行模拟并验证,讨论了污染负荷与去除率的相关性以及BOD/COD比值对有机污染物降解系数的影响。研究湿地总面积为5 000 m2,进水水量为860～1 560 m3/d,水力停留时间为1.48～2.69 d,水力负荷为0.17～0.31 m/d,进水中有机污染物浓度较低(BOD53.0～25.6 mg/L;COD 22.9～89.8 mg/L)。结果表明,复合湿地组合形式对BOD5和COD的去除率分别介于37.9%～79.0%和41.0%～68.7%之间,简化的Monod模型对湿地中BOD5和COD去除的预测值与实验观测值吻合程度较好;BOD5、COD的去除率分别随着进水BOD5和COD浓度的增加而增大,而增长趋势逐渐变缓,当有机污染负荷低时,模型的K值较小;低浓度有机污染物在VSF、FWS和HSF湿地中的去除效率与有机物是否容易或者缓慢被微生物降解的性质相关性较差,这可能与人工湿地中存在的其他因素促进了有机污染物的去除有关。     

Treatment of hydrophobic VOCs in trickling bed air biofilter: Emphasis on long-term effect of initial alternate use of hydrophilic VOCs and microbial species evolution

The main research objective of this study is to enhance the removal of recalcitrant compounds that are not readily bioavailable due to limiting mass transfer rate between the liquid and gas phases. Four trickle-bed air biofilters (TBABs), loaded with pelletized diatomaceous earth support media, were run at an empty bed residence time (EBRT) of 120 sec. After an acclimation period at constant loading rate (LR) of n-hexane (13.2 g m^?3 hr^?1) and intermittent feeding of methanol, n-hexane influent LR was then increased in step-wise fashion to 47.7 g m^?3 hr^?1 for biofilters receiving acidic nutrients (pH 4), and to 36.3 g m^?3 hr^?1 for biofilters receiving nutrient at pH 7. The results have shown that for TBABs receiving nutrient at pH 4, greater elimination capacities were obtained as compared to TBABs working at pH 7. n-Hexane removal efficiency of more than 84% at LR up to 47.7 g m^?3 hr^?1 was obtained for pH 4 nutrient-fed biofilters, while for biofilters with nutrients fed at pH 7, the removal efficiency did not exceed 64% for n-hexane LR of 36.3 g m^?3 hr^?1. The microbial analysis revealed that no fungal community was detected in TBABs run at neutral pH. The fungi communities that were initially acclimating TBABs run at pH 4, namely, Aspergillus niger and Fusarium solani, were not detected at the end of the experiment, while Gibberella moniliformis (Fusarium verticillioides) genus became the dominant species. Gibberella moniliformis (Fusarium verticillioides) was present along all the biofilter media and sustained very high n-hexane elimination at steady-state condition.

Implications:With growing apprehension about sustainability and environmental protection, with limited resources available, and with the passage of the 1990 Amendments to the Clean Air Act, there is more need for using air pollution control techniques that are sound economically and proven environmentally friendly. Biofiltration systems, namely, trickle-bed air biofilters, were for decades recognized as efficient in treating air pollutants. Thus, the application of this technique over a wide industrial spectrum would certainly contribute to reduction of hazardous gas emissions.     

Performance of a Semi-Industrial Scale Gasification Process for the Destruction of Polychlorinated Biphenyls

Abstract

A semi-industrial scale test was conducted to thermally treat mixtures of spent oil and askarels at a concentration of 50,000 ppm and 100,000 ppm of polychlorinated biphenyls (PCBs) under a reductive atmosphere. In average, the dry-basis composition of the synthesis gas (syngas) obtained from the gasification process was: hydrogen 46%, CO 34%, CO₂ 18%, and CH₄ 0.8%. PCBs, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans (PCDDs/PCDFs) in the gas stream were analyzed by high-resolution gas chromatography (GC)-mass spec-trometry. The coplanar PCBs congeners 77, 105, 118, 156/157, and 167 were detected in the syngas at concentrations <2 ×10^?7 mg/m³ (at 298 K, 1 atm, dry basis, 7% O₂). The chlorine released in the destruction of the PCBs was transformed to hydrogen chloride and separated from the gas by an alkaline wet scrubber. The concentration of PCBs in the water leaving the scrubber was below the detection limit of 0.002 mg/L, whereas the destruction and removal efficiency was >99.9999% for both tests conducted. The concentration of PCDDs/PCDFs in the syngas were 8.1 ×10^?6 ng-toxic equivalent (TEQ)/m³ and 7.1 × 10^?6 ng-TEQ/m³ (at 298 K, 1 atm, dry basis, 7% O₂) for the tests at 50,000 ppm and 100,000 ppm PCBs, respectively. The only PCDD/F congener detected in the gas was the octachloro-dibenzo-p-dioxin, which has a toxic equivalent factor of 0.001. The results obtained for other pollutants (e.g., metals and particulate matter) meet the maximum allowed emission limits according to Mexican, U.S., and European regulations for the thermal treatment of hazardous waste (excluding CO, which is a major component of the syngas, and total hydrocarbons, which mainly represent the presence of CH₄).     

Biological Removal of Gaseous Ammonia in Biofilters: Space Travel and Earth-Based Applications

ABSTRACT

Gaseous NH₃ removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH₃ concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH₃ for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH₃ removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH₃ could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO₃ ^- early in the operation, but later both NO₂ ^- and NO₃ ^- accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N₂O, which were detected in the biofilter exhaust.     

Treatment of 1,3-Butadiene in an Air Stream by a Biotrickling Filter and a Biofilter

ABSTRACT

This paper presents results obtained from a performance study on the biotreatment of 1,3-butadiene in an air stream using a reactor that consisted of a two-stage, in-series biotrickling filter connected with a three-stage, in-series biofilter. Slags and pig manure-based media were used as packing materials for the biotrickling filter and the biofilter, respectively. Experimental results indicated that, for the biotrickling filter portion, the butadiene elimination capacities were below 5 g/m³/hr for loadings of less than 25 g/m³/hr, and the butadiene removal efficiency was only around 17%. For the biofilter portion, the elimination capacities ranged from 10 to 107 g/m³/hr for loadings of less than 148 g/m³/hr. The average butadiene removal efficiency was 75–84% for superficial gas velocities of 53–142 m/hr and a loading range of 10–120 g/m³/hr. The elimination capacity approached a maximum of 108 g/m³/hr for a loading of 150 g/m³/hr. The elimination rates of butadiene in both the biotrickling filter and biofilter were mass-transfer controlled for influent butadiene concentrations below about 600 ppm for superficial gas velocities of 29–142 m/hr. The elimination capacity was significantly higher in the biofilter than in the biotrickling filter. This discrepancy may be attributed to the higher mass-transfer coefficient and gas-solid interfacial area offered for transferring the gaseous butadiene in the biofilter.     

Surface Flux Measurements of CO2 and N2O from a Dried Rice Paddy in Japan during a Fallow Winter Season

Abstract

The CO₂ and N₂O soil emissions at a rice paddy in Mase, Japan, were measured by enclosures during a fallow winter season. The Mase site, one of the AsiaFlux Network sites in Japan, has been monitored for moisture, heat, and CO₂ fluxes since August 1999. The paddy soil was found to be a source of both CO₂ and N₂O flux from this experiment. The CO₂ and N₂O fluxes ranged from -27.6 to 160.4μg CO₂/m²/sec (average of 49.1 ± 42.7 μg CO₂/m²/sec) and from -4.4 to 129.5 ng N₂O/m²/sec (average of 40.3 ± 35.6 ng N₂O/m²/sec), respectively. A bimodal trend, which has a sub-peak in the morning around 10:00 a.m. and a primary peak between 2:00 and 3:00 p.m., was observed. Gas fluxes increased with soil temperature, but this temperature dependency seemed to occur only on the calm days. Average CO₂ and N₂O fluxes were 27.7 μg CO₂/m²/sec and 13.4 ng N₂O/m²/sec, with relatively small fluctuation during windy days, while averages of 69.3 μg CO₂/m²/sec and 65.8 ng N₂O/m²/sec were measured during calm days. This relationship was thought to be a result of strong surface winds, which enhance gas exchange between the soil surface and the atmosphere, thus reducing the gas emissions from soil surfaces.     

矿化污泥生物反应器处理生活垃圾填埋场老龄渗滤液

经长时间稳定化形成的矿化污泥中,含有种类丰富和数量繁多的降解性微生物,具有处理渗滤液的潜力。建立3个矿化污泥生物反应器,即C1(粉煤灰0%),C2(粉煤灰9.1%),C3(粉煤灰16.7%),以处理垃圾填埋场老龄渗滤液。在单级矿化污泥反应器中,当进水COD和NH3-N分别约为1350和900 mg/L时,水力负荷为17.7～70.8 L/(m3.d),COD去除率可超过65%,氨氮的去除率可超过94%。粉煤灰的加入一定程度上降低了COD去除率,但有助于氨氮的去除。在二级矿化污泥生物反应器中(即C3～C1串联),水力负荷为35.4 L/(m3.d)的工况下,当COD、TOC、IC和NH3-N分别为1 500～2 500,500～900,1 200～1 600和1 200～1 450 mg/L时,出水可达到COD<300 mg/L,TOC<180 mg/L,IC<100 mg/L,NH3-N<5 mg/L。但是,矿化污泥生物反应器对渗滤液总氮的去除率较低,仅为20%左右。     

The styrene purification performance of biotrickling filter with toluene-styrene acclimatization under acidic conditions

The obvious disadvantages of biotrickling filters (BTFs) are the long start-up time and low removal efficiency (RE) when treating refractory hydrophobic volatile organic compounds (VOCs), which limits its industrial application. It is worthwhile to investigate how to reduce the start-up period of the BTF for treating hydrophobic VOCs. Here, we present the first study to evaluate the strategy of toluene induction combined with toluene-styrene synchronous acclimatization during start-up in a laboratory-scale BTF inoculated with activated sludge for styrene removal, as well as the effects of styrene inlet concentration (0.279 to 2.659 g·m^?3), empty bed residence time (EBRT) (i.e., 136, 90, 68, 45, 34 sec), humidity (7.7% to 88.9%), and pH (i.e., 4, 3, 2.5, 2) on the performance of the BTF system. The experiments were carried out under acidic conditions (pH 4.5) to make fungi dominant in the BTF. The start-up period for styrene in the BTF was shortened to about 28 days. A maximum elimination capacity (EC_max) of 126 g·m^?3·hr^?1 with an RE of 80% was attained when styrene inlet loading rate (ILR) was below 180 g·m^?3·hr^?1. The highest styrene RE(s) [of BTF] that could be achieved were 95% and 93.4%, respectively, for humidity of 7.7% and at pH 2. A single dominant fungal strain was isolated and identified as Candida palmioleophila strain MA-M11 based on the 26S ribosomal RNA gene. Overall, the styrene induction with the toluene-styrene synchronous acclimatization could markedly reduce the start-up period and enhance the RE of styrene. The BTF dominated by fungi exhibited good performance under low pH and humidity and great potential in treating styrene with higher inlet concentrations.

Implications: The application of the toluene induction combined with toluene-styrene synchronous acclimatization demonstrated to be a promising approach for the highly efficient removal of styrene. The toluene induction can accelerate biofilm formation, and the adaptability of microorganisms to styrene can be improved rapidly by the toluene-styrene synchronous acclimatization. The integrated application of two technologies can shorten the start-up period of biotrickling filters markedly and promote its industrial application.     

Characterization of Air Quality Problems in Five Finnish Indoor Ice Arenas

ABSTRACT

The air quality in five Finnish ice arenas with different volumes, ventilation systems, and resurfacer power sources (propane, gasoline, electric) was monitored during a usual training evening and a standardized, simulated ice hockey game. The measurements included continuous recording of carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO₂) concentrations, and sampling and analysis of volatile organic compounds (VOCs). Emissions from the ice resurfacers with combustion engines caused indoor air quality problems in all ice arenas. The highest 1-hour average CO and NO₂ concentrations ranged from 20 to 33 mg/m³ (17 to 29 ppm) and 270 to 7440 µg/m³ (0.14 to 3.96 ppm), respectively. The 3-hour total VOC concentrations ranged from 150 to 1200 µg/m³. The highest CO and VOC levels were measured in the arena in which a gasoline-fueled resurfacer was used. The highest NO₂ levels were measured in small ice arenas with propane-fueled ice resurfacers and insufficient ventilation.

In these arenas, the indoor NO₂ levels were about 100 times the levels measured in ambient outdoor air, and the highest 1-hour concentrations were about 20 times the national and World Health Organization (WHO) health-based air quality guidelines. The air quality was fully acceptable only in the arena with an electric resurfacer. The present study showed that the air quality problems of indoor ice arenas may vary with the fuel type of resurfacer and the volume and ventilation of arena building. It also confirmed that there are severe air quality problems in Finnish ice arenas similar to those previously described in North America.