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.     

Bioconversion of Dimethylformamide in Biofilters

ABSTRACT

Bioconversion of dimethylformamide (DMF) was studied using two sets of three-stages-in-series biofilters, one packed with inoculated pig manure and the other with coconut fiber compost-based media. The two media were different in carbon/nitrogen (C/N) ratio and specific area. Tests were made to compare effects of different C/N ratio and specific area on the performance of the filter and on the variation of physicochemical properties of the media for treating DMF. DMF concentration in the influent air stream was in the range of 100 to 4,500 mg/m³. The gas retention time (GRT) in the first stages of both filters was 19 to 76 sec. The volumetric loading of DMF (L) to the first stages of both filters was 3 to 97 g DMF-N/m³.h (15.6 to 506 g DMF/m³.h). Results indicated that DMF was successively hydrolyzed to ammonia and nitrified to nitrite and nitrate or incorporated into microbial cell. Inlet portions of the media subjected to high DMF or ammonia loading varied greatly in pH due to insufficient buffering capacity. The middle portions of the media subjected to moderate ammonia loading were suitable for nitrification. The coconut fiber compost media with a higher initial C/ N ratio and porosity favored the elimination of DMF. For the media, DMF-N removal efficiencies of larger than 90% were obtained with L < 50 g DMF-N/m³.h and GRT > 23 sec. The pig manure compost media with a lower initial C/N ratio favored the nitrification reaction; its maximum capacity was 8.58 g NO₃ ^--N/m³.h.     

格式栲天然林水源涵养功能的研究

本文通过对三明莘口格式栲天然林与人工林的林冠层,林木植被层和林褥层及林下土壤层的持水量,土壤渗透性能差异等的研究。结果表明:格式栲天然林林分持水总量比格式持和楠木人工林分别增加 225.131t/ha 和 296.558t/ha;土壤稳渗值高达 8.09 mm/min,分别是格式栲和楠木人工林的3.3倍和25.3倍。格式栲天然林具有良好的水源涵养功能。     

A novel method to make regenerable core-shell calcium-based sorbents

A sorbent having a calcium oxide core and a clay shell was prepared and shown to be capable of reusable applications in absorption and desorption processes for carbon dioxide. The novelty of this sorbent is that only calcium carbonate and clay are used for its preparation with water as a binder. A two-step granulation procedure is used to get the core and then another step to coat the shell layer with the clay powder. A repeated wet-and-dry procedure probably makes the core porous yet strong enough to serve as a sorbent. The pellet is then calcined at 1200 degrees C for 2h to reach its final structure. The core-shell pellets have an overall diameter of 4.4mm with average shell thickness of 0.45 mm, crush load of 35 N and attrition index of 0.035 wt%/h. These results indicate that the pellets will probably be capable of withstanding the stress in future applications. Carbon dioxide absorption at or below 300 degrees C showed a maximum weight gain of 38% for our pellets. Finally, desorption in nitrogen at 800 degrees C can restore the pellet to its original state and hence it is ready for re-use as a sorbent.     

Use of waste rubber as concrete additive.

For resource reutilization, scrap tyres have long been investigated as an additive to concrete to form 'Rubcrete' for various applications and have shown promising results. However, the addition of rubber particles leads to the degradation of physical properties, particularly, the compressive strength of the concrete. In this study, a theoretical model was proposed to shed light on the mechanisms of decrease in compressive strength due to the addition of rubber particles as well as improvement in compressive strength through modification of particle surfaces. The literature suggests that the compressive strength can be improved by soaking the rubber particles in alkaline solution first to increase the inter-phase bonding between the rubber particles and cement. Instead, we discovered that the loss in compressive strength was due to local imperfections in the hydration of cement, induced by the addition of heterogeneous and hydrophobic rubber particles. Microscopic studies showed that the rubber particles disturbed the water transfer to create channels, which were prone to cracking and led to a loss in the compressive strength. Unexpectedly, no cracking was found along the surfaces of the rubber particles, indicating that the bonding strength between the rubber particles and cement phases was not the critical factor in determining the compressive strength. Therefore, a theoretical model was proposed to describe the water transfer in the Rubcrete specimens to explain the experimental data. In the model, the local water available for hydration (Q) is: Q = -A(slv)/6piv, where Q, A(slv), and v are mass flow rate (kg s(-1)), Hamaker constant (J), and dynamic viscosity (m2 s(-1)), respectively. By maximizing the quantity Q and, in turn, the Hamaker constant A(slv), the compressive strength could be improved. The Hamaker constant A(slv) for water film on rubber particle surfaces was smaller than that for the hydrated cement particles; the water transfer rate was lower in the presence of rubber particles because the Hamaker constant A(slv) for water film on rubber particle surfaces was smaller than that on the hydrated cement particles. Thus, the compressive strength of Rubcrete could be improved by increasing the Hamaker constant of the system. This was achieved by increasing the refractive indices of the solids (n(s)). The refractive indices of materials increase with increases in functional groups, such as OH and SH on the surface. The model provided a possible mechanism for the efficacy of treating rubber particles with NaOH in improving the compressive strength. By using NaOH solution treatment, an oxygen-containing OH group was formed on the rubber surface to increase the Hamaker constant of the system, leading to higher compressive strength. Based on this mechanism, a novel method for modification of the rubber particles was also proposed. In this process, the rubber particles were partially oxidized with hot air/steam in a fluidized bed reactor to produce the hydrophilic groups on the surface of the particles. Preliminary results obtained so far are promising in accordance with the theory.     

Health risk of aerosols and toxic metals from incense and joss paper burning

We report for the first time the distribution and hazard potential of aerosol and metals resulting from joss paper burning. Burning joss paper and incense is a traditional custom in many Oriental countries. Large amounts of air pollutants, including particles, polycyclic aromatic hydrocarbons, toxic metals and other gaseous pollutants, are released into the environment during the burning stage. Many investigations have reported on the emission of pollutants from the incense burning. However, no work has been reported until now on the analysis of the released pollutants apart from polycyclic aromatic hydrocarbons. In this study, a micro-orifice uniform-deposit impactor and inductively coupled plasma optical emission spectrometry were, respectively, used to collect aerosols and characterize the toxic metals from joss paper burning. We studied two types of particulate matter (PM): PM_2.5 that are particles with a diameter smaller than 2.5 μm and PM₁₀ that are particles with a diameter smaller than 10 μm. PM_2.5 are the most potentially toxic particles. Our results showed that PM_2.5 are the major component of the pollutants and that the PM_2.5 to PM₁₀ ratio ranged from 62 to 99%. The metals Na, Ca, Mg, Al and K were the main species in the aerosol and in the bottom ash.     

Study On the Hydraulic Characteristics of Taichung Harbour in Taiwan

For this study, field measurements of current profiles, buoy trajectories and the lag of two tidal stations were performed to explore the flow characteristics of Taichung Harbour. in order to distinguish the effects of wind drift current on circulation inside Taichung Harbour, field surveys during both summer and monsoon (winter) season were completed separately. the speed of the drift current was about 3.5% that of the, wind speed, based on the field data. the horizontal dispersion coefficients were close to Bowden's (1965) formula for the tidal current. the water temperature showed a two-layer profile, with the mixing thickness about 4 to 6 metres for the upper layer. the corresponding Richardson number was about 70. the tidal lag between the two tidal stations was 9.68 minutes. All the results agree well with the theoretical results.     

Factors influencing the preparation of supported iron oxide in fluidized-bed crystallization

Our previous work applied a novel supported iron oxyhydroxide (FeOOH) catalyst to effectively treat benzoic acid by hydrogen peroxide. The FeOOH catalyst was prepared via the oxidation of Fe2+ by H2O2 in the acidic condition using a fluidized-bed crystallization reactor. The major components coated on the surface were identified as amorphous FeOOH and gamma-FeOOH. In terms of the crystallization conditions of FeOOH, some parameters including the operational pH, superficial velocity, specific iron loading, and influent H2O2 concentration were investigated to quantify their effects on the crystallization efficiency. All these parameters were found to significantly influence the crystallization efficiency. Two types of FeOOH catalysts were synthesized: FeOOH I was prepared at pH 3.5, and FeOOH II was formed by aging FeOOH I at pH 13. The percentages of surface amorphous FeOOH reduced from 70% to 30% after aging. The FeOOH II catalyst presented a higher reactivity toward H2O2 but lower stoichiometric efficiency in oxidizing benzoic acid than FeOOH I, similar to the result of the commercial goethite. Therefore, it is concluded that the crystalline property significantly affects the performance of catalytic oxidation.