Packing Media Research Articles

Dynamic volume-averaged model of heat and mass transport within a compost biofilter: I. Model development.

Successful, long-term operation of a biofilter system depends on maintaining a suitable biofilm environment within a porous medium reactor. In this article a mathematical study was conducted of the spatial and temporal changes of biofilter performance due to interphase heat and mass transport. The method of volume averaging was used to spatially smooth the three-phase (solid, liquid, and gas) conservation equations over the biofilter domain. The packing medium was assumed to be inert, removing the solid phase mass continuity equation from the system. The finite element method was used to integrate the resulting nonlinear-coupled partial differential equations, tracking eight state variables: temperature, water vapor, dry air, liquid water, biofilm, gas and liquid phase organic pollutant, and nutrient densities, through time and space. A multiphase, gas and liquid flow model was adapted to the biofilter model from previous studies of unsaturated groundwater flow. Newton's method accelerated by an LU direct solver was used to iterate the model for solutions. Effects of packing media on performance were investigated to illustrate the utility of the model. The moisture dynamics and nutrient cycling are presented in Part II of this article.

Effect of Nitrogen Limitation on Performance of Toluene Degrading Biofilters

The literature reports conflicting observations regarding the need for nutrient addition to biofilters treating contaminated gases. Such conflicts are often based on quasi-steady-state performance data collected on biofilters operated under continuous loading conditions. In the studies described herein, the impact of nitrogen limitations on two toluene-fed biofilters was assessed over a 97-day period. The biofilters were packed with polyurethane foam medium and contained different initial levels of nitrate-nitrogen. Toluene and CO 2 concentration profiles were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (e.g., shock loads). Packing medium samples were periodically removed and analyzed to quantify changes in nitrate-nitrogen content over time. Data are presented which show that over long-time periods (several months), nutrient-induced kinetic limitations diminished biofilter performance during transient, unsteady-state conditions even when performance during normal steady loading was not adversely affected. Elemental analysis of biomass removed from the biofilters support nitrate-nitrogen and CO 2 concentration profile data and clearly illustrate how kinetically limited biofilters fail during shock loads even when there is an overall stoichiometric excess of nutrients.

Period biofilter operation for enhanced performance during unsteady-state loading conditions

In conventional biofilter operation, contaminated air is passed continuously through packed beds containing microbial consortia capable of contaminant biotransformation. This paper describes how biofilters can be designed and operated as controlled unsteady-state, periodic processes for the destruction of gas-phase contaminants. Such operation, previously limited to applications in wastewater treatment and soil remediation, increases an operator's ability to control the physiological state, "robustness," and spatial distribution of the microbial communities established within the biofilter and, thus, minimizes uncertainties that often accompany design and operation of biological systems. Results are presented from toluene degrading biofilters that used polyurethane foam packing medium. These studies demonstrate how controlled periodic operations can enhance contaminant removal during transient periods of elevated contaminant load.

Effects of adsorbent properties on zone spreading in expanded bed chromatography.

The mixing performance as well as the adsorption performance in expanded bed chromatography (EBC) was investigated by using various types of adsorption media (average particle size = 100-700 microm, density = 1100-1700 kg/m3, base matrix = hydroxyapatite, styrene-divinylbenzene, cross-linked agarose). The scale down study with 0.8 cm diameter columns was also attempted. Pulse response curves were measured with vitamin B12 as a tracer [Residence time distribution RTD experiments], and the HETP (height equivalent to a theoretical plate or plate height) values were calculated from the peak variance and the peak retention time. The HETP values for different types of packing media tested showed very similar values (0.5-1.0 cm), which did not depend on the flow-rate or the column diameter (0.8-2.6 cm). Dynamic binding capacity (DBC) values of lactic acid on a Dowex anion-exchange resin were determined from breakthrough curve (BTC) measurements for both EBC and fixed bed chromatography (FBC). The DBC values for EBC were similar to those for FBC. When the liquid feed contained insoluble particles (yeast cells) the degree of mixing increased. However, the contribution of the mixing to the total spreading of BTCs for EBC was usually small so that this increase in the mixing did not affect the adsorption performance or the DBC values significantly.

The Biofiltration of Indoor Air: Air Flux and Temperature Influences the Removal of Toluene, Ethylbenzene, and Xylene

An alternative approach to maintaining indoor air quality may be the biofiltration of air circulated within the space. A biofilter with living botanical matter as the packing medium reduced concentrations of toluene, ethylbenzene, and o-xylene concurrently present at parts per billion (volume) in indoor air. The greatest reduction in concentrations per pass was under the slowest influent air flux (0.025 m s(-1)); however, the maximum amount removed per unit time occurred under the most rapid flux (0.2 m s(-1)). There was little difference between the different compounds with removal capacities of between 1.3 and 2.4 micromol m(-3) biofilter s(-1) (between 0.5 and 0.9 g m(-3) biofilter h(-1)) depending on influent flux and temperature. Contrary to biofilters subjected to higher influent concentrations, the optimal temperatures for removal by this biofilter decreased to less than 20 degrees C at the most rapid flux for all three compounds. Microbial activity was decreased at these cooler temperatures suggesting the biofilter was not microbially limited but rather was limited by the availability of substrate. The cooler temperatures allowed greater partitioning of the VOCs into the water column which had a greater impact on removal than its reduction in microbial activity.

Evaluation of a Pilot‐Scale Bioscrubber for the Removal of Hydrogen Sulphide

AbstractThis technical note describes an investigation on the feasibility of using treated wastewater to support the operation of a fixed‐film bioscrubber for H2S removal. A laboratory‐scale fixed‐film bioscrubber was assembled using Thiobacillus bacteria which were isolated from a sample of raw sludge, cultured in the laboratory, and immobilised onto the scrubber's plastic packing media by an immersion method.

Polyurethane Foam Medium for Biofiltration. I: Characterization

Although biological treatment has been applied successfully to treat waste gases using conventional organic packing media such as compost, there is currently a need for further research on ways to optimize the medium selected. Use of a superior filter-bed medium could overcome or minimize many of the problems encountered in conventional biofilter operation (e.g., medium clogging, difficulty in control of moisture content, and nutrient limitation). In research described herein, polyurethane foam was manufactured and characterized to determine its suitability as a solid support medium for use in gas-phase biofilters. Part I of this paper describes studies conducted to determine the medium's porosity, pore size, head loss characteristics, density, sorption capacity, and chemical resistance. Results are presented that characterize the polyurethane foam medium's properties and suggest how it can be used effectively in treating gas-phase volatile organic compound contaminants. Part II of this paper describes studies conducted to determine the medium's ability to support an active biofilm and to study feasibility of a novel nutrient addition and biomass wasting strategy.

A bioscrubber for hydrogen sulphide removal

A study was carried out to investigate the feasibility of using treated wastewater effluent to support the operation of a fixed-film bioscrubber for odorous H2S removal. A laboratory scale fixed-film bioscrubber was set up using bacteria of the genus Thiobacillus. The bacteria were isolated from a sample of municipal sludge, cultured in the laboratory and immobilised onto the scrubber's plastic packing media by an immersion method. Series of experimental runs were carried out to determine the optimal operational conditions for the bioscrubber. Results indicated that for the gas retention times equal to or exceedingfive seconds, and with a H2S loading rate below 90 g-H2S/m3-hr, the bioscrubber could remove H2S and odour with efficiencies greater than 99%. The behaviour of the bio-scrubber under various operation scenarios arepresented and discussed in this paper.

Performance of periodically operated-gas phase biofilters during transient loading conditions

Most industrial processes and environmental remediation activities generate large volumes of air contaminated with volatile organic compounds (VOCs). In conventional biofilter operation, gaseous emissions contaminated with low concentrations of biodegradable VOCs are remediated by being passed continuously through packed beds. This paper describes how periodically operated biofilters can be designed as controlled, unsteady-state systems that destroy gas-phase contaminants. Periodic operation, previously limited to applications in wastewater treatment and soil remediation, increases an operator's ability to control the spatial distribution, physiological state, and “robustness” of the microbial communities established within a biofilter while minimizing uncertainties that often accompany design and operation of biological systems. Results are presented from toluene degrading biofilters that used a novel polyurethane foam packing medium. These studies demonstrate how controlled periodic operations can enhance contaminant removal during transient periods of elevated contaminant load.

Design and performance of a fibrous bed bioreactor for odor treatment.

Biological processes have become popular for odor treatment. In this study, a novel fibrous bed bioreactor was applied for treatment of odorous gas. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of microorganisms selected from activated sludge was immobilized. The first stage of this work comprised a preliminary study that aimed at investigating the feasibility of the fibrous bed bioreactor for treatment of odorous volatile fatty acids (VFAs). In this stage, the performance of a fibrous bed bioreactor at increasing mass loadings ranging from 9.7 to 104.2 g/(m3.h) was studied. VFA removal efficiencies above 90% were achieved at mass loadings up to 50.3 g/(m3.h). At a mass loading of 104.2 g/(m3.h), removal efficiency was found to be 87.7%. In the second stage of the work, the process was scaled up with design and operational considerations, namely, packing medium, process condition, and configuration selections. A trickling biofilter with synthetic fibrous packing medium was selected. It was operated under countercurrent flow of gas and liquid streams. The effects of inlet concentration and empty bed retention time on bioreactor performance were studied. The bioreactor was effective in treating odorous VFAs at mass loadings up to 32 g/(m3.h), at which VFAs started to accumulate in the recirculation liquid, indicating that the biofilm was unable to degrade all the VFAs introduced. Although VFAs accumulated in the liquid phase, the removal efficiency remained above 99%, implying that the biochemical reaction rate, rather than gas-to-liquid mass transfer rate, was the limiting factor of this process. The bioreactor was stable for long-term operation; no clogging and degeneration of the packing medium was observed during the 4-mo operation.

Post-mortem examination and analysis of anaerobic filters

This paper presents post-mortem examination and analysis of downflow (DAF) and upflow anaerobic filter (UAF) operated under similar sets of operating and environmental conditions but varying organic loads for more than 20 months. It can be observed from performance studies of these filters that the COD removal, methane gas production and COD methanisation do not differ significantly at 95% confidence level. However, the post-mortem analysis revealed that considerable filter volumes (42% in DAF and 49% in UAF) were occupied by retained biomass leading to significant reduction in operating HRT (hydraulic retention time) towards the end of the study period. Retained biomass (suspended as well as retained in packing media) in the filter was observed to have considerable black, brown-black and brown granular solid fractions. The brown granules were spongy in nature. The deposition of sludge solids in DAF packing media was observed to be uneven as compared to UAF. Solids were simply held-up or retained in the packing media. Solids retained in DAF packing media were mostly composed of black granules (3–5 mm in size) whereas solids retained in UAF packing media were brown-black granules (2–3 mm in size). The retained granular solids in DAF packing media appeared to be more compact as compared to that in UAF. The estimated concentration of retained solids in DAF packing media was 76.39 g TS/L that was significantly higher than that in UAF (69.91 g TS/L).

Deodorization of contaminated air by immobilized microbes

Biological removal of odorous volatile fatty acids (VFAs) in the gas stream of a trickling biofilter was studied. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of microorganisms selected from activated sludge was immobilized. The bioreactor was operated under counter‐current flow of gas and liquid streams. Odorous VFA, butyric and valeric acids were introduced into the bioreactor at various inlet concentrations and flow rates. The effects of inlet VFA concentration and gas empty bed retention time (EBRT) on bioreactor performance were investigated. The effect of inlet concentration was studied by increasing the gaseous VFA concentrations at fixed EBRTs of 90, 60, 45 and 30 s. While the effect of EBRT was investigated by increasing the gas superficial velocity or shortening EBRT, at different inlet VFA concentrations of 0.08, 0.2, 0.4 and 0.7 g/m3. The bioreactor was effective in treating odorous VFA at mass loadings up to 32 g/m3/h, at which VFA started to accumulate in the recirculation liquid indicating the biofilm was unable to degrade all the VFA introduced. Although VFA accumulated in the liquid phase, the removal efficiency remained above 99%, it implies the biochemical reaction rate rather than gas‐to‐liquid mass transfer rate was the rate limiting step of this process. The bioreactor was stable for long‐term operation; relatively low and steady pressure drop, no clogging and degeneration of the packing medium occurred during the 4‐month period studied.

Hydrodynamics and particle collection in turbulent bed contactor

AbstractPerforated spheres with 10% and 25% free area, oblate spheroids and the conventional plain spheres were tested as packing medium in a Turbulent Bed Contactor (TBC). Hydrodynamics and particle collection experiments were carried out in a column having 0.264 m diameter, at 3 static bed heights and several gas and liquid flow rates. Alumina (1.5 to 5.5 μm) was used as test powder for particle collection experiments. The higher efficiency of particle collection, the lower bed expansions and the higher fluidization velocities of perforated spheres, indicates that this packing type is suitable as contacting medium for particle collection in TBCs.

Canning Process that Diminishes Paralytic Shellfish Poison in Naturally Contaminated Mussels (Mytilus galloprovincialis)

Changes in toxin profile and total toxicity levels of paralytic shellfish poison (PSP)-containing mussels were monitored during the standard canning process of pickled mussels and mussels in brine using mouse bioassays and high-performance liquid chromatography. Detoxification percentages for canned mussel meat exceeded 50% of initial toxicity. Total toxicity reduction did not fully correspond to toxin destruction, which was due to the loss of PSP to cooking water and packing media of the canned product. Significant differences in detoxification percentages were due to changes in toxin profile during heat treatment in packing media. Toxin conversion phenomena should be determined to validate detoxification procedures in the canning industry.

Specific biogas production and role of packing medium in the treatment of rubber thread manufacturing industry wastewater

Wastewater from three rubber thread manufacturing industries collected from three different sampling points was characterised. The acidic wastewater (pH = 3.6 to 4.7) contains high levels of COD, BOD, nitrogen and zinc. The average COD:N:P ratio was 100:3.8:0.4 whereas the BOD:N:P ratio was 100:4.5:0.4 with more than sufficient amounts of N and P for anaerobic digestion using the up-flow anaerobic filter. The specific biogas yield ranged between 0.250 to 0.069 l CH4/g COD added when the organic loading rate was altered from 2.0 to 14.0 g COD/l/d respectively. The biogas production rate and the biogas yield rate increased from 8.2 to 42.7 l/d and 0.97 to 1.50 l CH4/l/d respectively, for the same organic loading rate. The N and P utilised ranged between 1.53 to 1.20 and 0.3 to 0.26 mg per 100 mg COD consumed respectively when the organic loading rate was increased from 2.0 to 14.0 g COD/l/d. The optimum COD:N:P ratio obtained for steady state operation of the up-flow anaerobic filter in this study for the rubber thread manufacturing wastewater was 100:1.3:0.3. Attached biomass was responsible for the removal of more than 70% of the COD in the wastewater when PU foam was used as the packing media.

Domoic Acid Levels of Naturally Contaminated Scallops as Affected by Canning

ABSTRACTChanges in domoic acid levels of toxic scallops (Pecten maximus) were monitored during the standard canning processes of pickled scallops and scallops in brine after 60 and 180 days of frozen storage. The concentration of domoic acid in whole scallops decreased by 43% after 180 days of frozen storage, the decrease being mostly in the hepatopancreas. No significant destruction of domoic acid was observed during the canning process but the transfer of toxin to packing media exceeded 30% of total toxin content in the canned product.

Henry's constants and mass transfer coefficients of halogenated organic pollutants in an air stripping packed column

Both Henry's constants and volumetric mass transfer coefficients (KLa) of eight priority chlorinated organic compounds including 1,1-dichloroethene, methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, and 1,4-dichlorobenzene in an air stripping packed column were investigated in this study. The liquid and gas phase EPICS (Equilibrium Partition in Closed System) and direct calculating methods were applied to determine the Henry's constants of VOCs. The interference of co-solute on Henry's constants was also investigated. Experimental results indicated that decrease in Henry's constants of VOCs was observed in the presence of humic acid but no apparent effect on Henry's constants was detected when there was NaCl and surfactant in solution. Four different configurations of packing media including Intalox Saddle, Super Intalox Saddle, Telleret, and Hedgehog made of polypropylene were respectively packed in the air stripping tower and investigated in the study. The dependence of hydraulic loading, air-water ratio, and configurations of packing media on mass transfer coefficients of VOCs was discussed.

Tomato pulp quality from transgenic fruits with reduced polygalacturonase (PG)

The physico-chemical and sensory properties of tomato pulps (i.e. diced tomatoes with 30% tomato juice as packing medium), prepared from transgenic tomato ( Lycopersicon esculentum) fruits with reduced levels of polygalacturonase (PG) activity due to the expression of a PG antisense gene, were evaluated. The application of genetic modification yields products that have improved viscosity (40–60%), colour (30–40%) and many sensory attributes in comparison with their conventional counterparts.

Application of packed scrubbers for air emissions control in municipal wastewater treatment plants

AbstractThe process air emissions from municipal wastewater treatment plants primarily consist of hydrogen sulfide gas, along with other organo‐sulfur compounds, and some trace quantities of volatile organic compounds, and some trace quantities of volatile organic compounds (VOC). Various Federal and/or State Regulations require monitoring, and control of these emissions down to some specified levels.At the Deer Island Wastewater Treatment Plant of the Massacbusetts Water Resources Authority (MWRA), air containing hydrogen sulfide is collected and treated in several emission control systems. These systems consist of wet scrubbers which facilitate destruction of hydrogen sulfide gas and the related odor by continuously contacting the collected air counter‐currently with a strong oxidizing solution of sodium hypochlorite.This paper reviews the performance of a typical scrubber in light of the theory of absorption followed by chemical reaction. Based on an analysis of a set of test data, it has been concluded that when the concentration of hydrogen sulfide at a scrubber inlet exceeds 25 ppm, the scrubber becomes mass transfer limited. This can lead to the incomplete oxidation of hydrogen sulfide gas. Unreacted H2S eventually can exit the scrubber while partially oxidized H2S, in the form of elemental sulfur, can deposit on, and eventually foul, the packing media. Measures taken to overcome such a situation have also been reported.

Effect of Packing Media on the Oxidation of Canned Tuna Lipids. Antioxidant Effectiveness of Extra Virgin Olive Oil

The effectiveness of packing media differing in the content of natural antioxidants has been tested on lipid oxidation occurring during tuna canning. Extra virgin olive oil, having a high content in natural polyphenols, and other filling media lacking phenols (refined olive oil, refined soybean oil, and brine) were selected. The three oils also showed different quantities of tocopherols, the highest amount being detected in refined soybean oil. Different rates of oxidation were observed among the four media after thermal processing and storage of tuna cans; extra virgin olive oil showed a potential antioxidant activity on fish lipids. The verified antioxidant ability may be attributed to the solubilization of hydrophilic phenols into the water−muscle interface. The phenolic composition from extra virgin olive oil studied by reversed-phase HPLC showed a marked change after fish processing, thus suggesting phenol decompositions and strong interactions between oil phenols and fish muscle components. The aqueous environment built by brine made fish lipids more prone to oxidation, presumably due to the accumulation of unsaturated fatty acids at the oil−water interface. Keywords: Antioxidants; fish lipid oxidation; canning; packing medium (extra virgin olive oil, refined olive oil, soybean oil, brine); phenols