Packing Media Research Articles

Effect of Water Content on Biofilter Performance

In this work, the effect of water content on biofilter performance is discussed. The inlet air humidity and media water content are two important parameters that affect biofilter performance. Using a laboratory scale biofilter unit, the effect of water content on toluene removal is studied. Water content of the packing media (peat) is varied and its effect on the removal efficiency was observed. Experimental data show that the biofilter media performed efficiently when the water content was around 50%. A good agreement between the model predictions and the experimental data was observed when experimentally obtained toluene removal efficiencies at various water contents were compared with the theoretical model predictions. Using the experimental data, correlations for biofilm surface area as a function of water content and porosity have been developed. These correlations can be useful in designing large-scale biofilter systems.

A honeycomb-tube packing medium and its application to column flotation

We address problems in the development of large-scale flotation columns that use short cylinders. As a starting point, we investigated the packing medium to identify a highly efficient internal packing for the flotation column. The chosen packing was a honeycomb structure with an aperture diameter of 80 mm, a web thickness of 0.80 mm, a film height of 1000 mm, packed into a 400 mm diameter space, which completely filled the vessel at optimal cost. The column consisted of a modular ring of single-hole hexagonal honeycomb tube packing made from atactic polyproplene (PP-R). The packing was tested in a cyclonic, static micro-bubble flotation column. Computational fluid dynamic modeling was used to analyze the flotation fluid in a honeycomb tube packed flotation column. Our results show that the fluid axial movement was maximized and that the transverse fluid velocities were zero in the vicinity of axial flow. Using the honeycomb tube packing for copper sulfide flotation we observed that the average concentration in the product was increased to 25.41%, from an average feed concentration of 0.729%, with an average recovery of 92.92%. The demands of on-site industrial production were met.

Evaluation of different packing media for anoxic H2S control in biogas

This paper presents the experimental results obtained during the operation of two biotrickling filters packed with 6.7 L of commercially available plastic fibres and lava rocks, respectively. The biotrickling filters were tested under similar operating conditions for hydrogen sulphide (H2S) removal from biogas under anoxic conditions, in order to determine the influence of biogas flow rate and H2S concentration on the process performance and to facilitate process modelling. The biogas flow rate was adjusted to between 25 and 75 L/h, while the input H2S concentration was varied between 500 and 1500 ppmv. The process performance was evaluated by two simultaneous system responses, namely the H2S removal efficiency and H2S loading rate, which were subsequently described by a second‐order empirical model and an interaction model, respectively. Good agreement between the experimental results, model prediction and simultaneous dual‐response simulation was obtained.

Kinetic evaluation of the psychrophylic anaerobic digestion of synthetic domestic sewage using an upflow filter

A study of the anaerobic digestion process of synthetic domestic sewage (total COD: 705 mg/L) was carried out. The digestion was conducted in an upflow anaerobic filter with corrugated plastic rings as packing media at psychrophilic temperature (15–17 °C). For HRTs of between 10.0 and 17.1 h, the total COD removal efficiency was almost constant and independent on the HRT, achieving an average value of around 80%. However, when the HRT decreased from 7.0 to 3.2 h the efficiency diminished from 77% to 65%. This decrease in removal efficiency was parallel to the increase in the VFA/Alkalinity ratio for this HRT range. The flow pattern observed in the reactor studied was intermediate between plug-flow and CSTR systems, although the plug-flow was predominant. It can also be observed that Young and McCarty’s model almost coincided with the CSTR model, when the biodegradable COD was used for fitting the data. The Manariotis equation allowed a better fit of the experimental data (total COD removal efficiency with influent substrate concentration and HRT) than the Young model. The methane yield coefficient obtained was 0.15 L CH 4/g COD consumed.

Ammonium nitrogen removal characteristics of zeolite media in a Biological Aerated Filter (BAF) for the treatment of textile wastewater

The main objective of this study is to evaluate ammonium nitrogen removal characteristics of zeolite media in Biological Aerated Filter (BAF) process for treatment of textile wastewater. Several biofilters were conducted to compare the performance of natural zeolite with sand and granular activated carbon (GAC) as packing media. The removal of NH 4 +-N on the BAF reactor packed with natural zeolite media was more efficient than that with sand and GAC. After biofilm was well developed on the surface of zeolite media, the removal of NH 4 +-N by ion exchange, nitrification, and biological synthesis was estimated as 35.1%, 40.2%, and 22.3%, respectively. The natural zeolite pretreated with heat and HCl solution showed higher ammonium removal efficiency than that with NaOH solution. No significant difference on ammonium adsorption capacity was observed when nature zeolite was neither pretreated by heat nor hydrochloric acid solution. This study shows that natural zeolites has the feasibility to be chosen as a useful media in BAF process for the treatment of textile wastewater.

Biological Perchlorate Reduction in Packed Bed Reactors Using Elemental Sulfur

Sulfur-utilizing perchlorate (ClO4-)-reducing bacteria were enriched from a denitrifying wastewater seed with elemental sulfur (S0) as an electron donor. The enrichment was composed of a diverse microbial community, with the majority identified as members of the phylum Proteobacteria. Cultures were inoculated into bench-scale packed bed reactors (PBR) with S0 and crushed oyster shell packing media. High ClO4-concentrations (5-8 mg/L) were reduced to < 0.5 mg/L at an empty bed contact time (EBCT) of 13 h. Low C1O4- concentrations (60-120 microg/L), more typical of contaminated groundwater sites, were reduced to < 4 microg/L at an EBCT of 7.5 h. PBR performance decreased when effluent recirculation was applied or when smaller S0 particle sizes were used, indicating that mass transfer of ClO4- to the attached biofilm was not the limiting mechanism in this process, and that biofilm acclimation and growth were key factors in overall reactor performance. The presence of nitrate (6.5 mg N/L) inhibited ClO4- reduction. The microbial community composition was found to change with ClO4- availability from a majority of Beta-Proteobacteria near the influent end of the reactor to primarily sulfur-oxidizing bacteria near the effluent end of the reactor.

Effects of adsorptive properties of biofilter packing materials on toluene removal

Various adsorptive materials, including granular activated carbon (GAC) and ground tire rubber (GTR), were mixed with compost in biofilters used for treating gaseous toluene, and the effects of the mixtures on the stability of biofilter performance were investigated. A transient loading test demonstrated that a sudden increase in inlet toluene loading was effectively attenuated in the compost/GAC biofilter, which was the most significant advantage of adding adsorptive materials to the biofilter packing media. Under steady conditions with inlet toluene loading rates of 18.8 and 37.5 g/m 3/h, both the compost and the compost/GAC biofilters achieved overall toluene removal efficiencies greater than 99%. In the compost/GAC mixture, however, biodegradation activity declined as the GAC mass fraction increased. Because of the low water-holding capacity of GTR, the compost/ground tire mixture did not show a significant improvement in toluene removal efficiency throughout the entire operational period. Furthermore, nitrogen limitations affected system performance in all the biofilters, but an external nitrogen supply resulted in the recovery of the toluene removal efficiency only in the compost biofilter during the test periods. Consequently, the introduction of excessive adsorptive materials was unfavorable for long-term performance, suggesting that the mass ratio of the adsorptive materials in such mixtures should be carefully selected to achieve high and steady biofilter performance.

High rate anaerobic filter with floating supports for the treatment of effluents from small-scale agro-food industries

The performance of four laboratory-scale upflow anaerobic filters (UAFs) of about 10 L effective volume packed with small buoying polyethylene media was investigated for the treatment of wastewater discharged from various small-scale agro-food industries with different composition and concentrations viz. synthetically prepared low strength (˜1.9 g CODt/L), fruit canning (˜10 g CODt/L), winery (˜20 g CODt/L) and cheese-dairy (˜30 g CODt/L) wastewaters. For the low strength wastewater, HRT was the limiting parameter with a minimum of 4 h corresponding to a maximum OLR of 12 g COD/L.d. For the high concentrated substrates, OLR was the limiting parameter, which was influenced by the nature of the substrates treated and not by the concentration of the substrates. Indeed, the UAF treating winery wastewater (20 g CODt/L) had reached the highest OLR of 27 g COD/L.d with 80% COD removal efficiency, while that of the other two reactors treating fruit canning and cheese-dairy wastewaters were comparatively lower (19 and 17 g COD/L.d respectively). At the end of the experiments, the total quantities of VSS inside the reactors were high (200–342 g), indicating that the low-density polyethylene support used in this study appears to be a good colonisation matrix to increase the quantity of biomass in the reactor. The packing medium had a dual role in the retention of the biomass that is entrapment of biomass within the support and filtration of the biomass in suspension to some extent. This result was confirmed by the specific biomass activity values, which were very close to that of suspended biomass. The efficiency of liquid mixing was good, even if the biomass matrix represented up to 70% of the reactor volume for the reactor fed with fruit canning wastewater.

Development of compact UASB/trickling filter systems for treating domestic wastewater in small communities in Brazil

The paper analyses the concept and performance of compact UASB/TF systems in relation to configuration, use of innovative packing media and operational conditions. For the conditions tested, the UASB/TF systems had consistently complied with the Brazilian discharge standard regarding to COD, BOD and TSS parameters. However, some enhancements are still necessary in order to increase nitrification in the process. The conditions to promote nitrification in shallow TF (packed bed up to 2.50 m height) seem to be compatible with the proposed simplification in the flowsheet, which is to operate the system without secondary clarifiers.

Degradation of pCBA by catalytic ozonation in natural water

The catalytic effect of commercially available ceramic Raschig rings versus stainless steel rings (known to be oxidant resistant) at different water qualities, for the decomposition of ozone and the hydroxyl radical formation have been investigated by using an ozone bubble column. Para-chlorobenzoic acid (pCBA) has been used as a model pollutant since it has been reported to be an ideal compound for ozone AOP studies because it displays slow reaction rates with ozone, but rapid oxidation kinetics with the OH radical. While the ozone was quite stable when the stainless steel rings were used as a packing media, the ceramic media enhanced the decomposition of the ozone. Nevertheless, the water quality was found to significantly affect the ozone stability. Indeed, in addition to high pH, both NOM and TIC lowered the ozone concentration in the system. When considering the degradation of pCBA, the ceramic packing rings, as high pH and NOM, increases its rate constant which is correlated to the higher decomposition of ozone and consequently to higher formation of hydroxyl radicals. In contrast, TIC decreased the degradation rate of pCBA even if it decomposes the ozone which is due to its scavenging effect.

Ethylbenzene,o-Xylene, and BTEX Removal bySphingomonas sp. D3K1 in Rock Wool-Compost Biofilters

Previously isolated Sphingomonas sp. D3K1 was biofilter (BF) inoculated into composite rock wool-compost packing media and biofiltration of single gas—ethylbenzene in BF1 and o-xylene in BF2—and mixed BTEX compounds in BF3 were investigated. At 62 s EBRT and feed flow rate of 0.14 m3/h, high removal efficiencies of 92.0 ± 2.8%, 92.0 ± 3.1%, and 89.2 ± 1.1% were achieved in BF1, BF2, and BF3, respectively. Decreasing the EBRT to 48 s resulted in lower elimination capacities of the three biofilters, while regular nutrient addition showed an increase in the attainable elimination capacities for ethylbenzene and o-xylene of BF1 and BF2, respectively. Maximum elimination capacities of 34.3 g-ethylbenzene/m3/h (BF1) and 38.6 g- o-xylene/m3/h (BF2) were obtained at 48 s EBRT. For BF3, the maximum elimination capacity was 32.9 g-BTEX/m3/h at 62 s EBRT. In the case of mixed BTEX biofilter, o-xylene showed the most significant decrease in the biodegradability when nutrient was insufficient in the system. Sphingomonas sp. D3K1 was more favorable to the removal of toluene when o-xylene was less than 10 g/m3/h, but shifted to benzene when the loading rate of o-xylene was higher than 10 g/m3/h.

Experimental and modeling investigations of a hybrid upflow anaerobic sludge-filter bed (UASFB) reactor

A 9.8-L hybrid UASFB reactor, in which the lower half was occupied by a sludge blanket and the upper half by small floating polyethylene media, was evaluated using wine distillery vinasse as substrate. The reactor was operated for a total period of 232 days at 33 + 1 degrees C. Continuous feeding of the reactor was started with an initial OLR of 2.9 g COD/L.d and then it was increased step wise to 19.5 g COD/L.d by increasing the feed COD, while maintaining a constant HRT (1.05 d). The reactor was equipped with a continuous internal recirculation system from top to the bottom at the rate of 9 L/h (upflow velocity = 0.83 m/h) upto day 159 and then it was reduced to about half on day 160 onwards. It was observed that the reduced recirculation rate did not affect the performance of the reactor with an average COD(t) and COD(s) removal efficiencies of 82 and 88%, respectively. A maximum gas production rate of 6.7 L CH(4)/L(reactor).d was achieved for the highest OLR applied. The specific activity analysis depicts that the activity of the attached biomass was more than 2 times higher than that of the granular sludge. The efficiency of liquid mixing was good through out this study. The packing medium had a dual role in the retention of the biomass inside the reactor: i.e. entrapment of biomass within the support and filtration of the granular biomass, preventing it from going out of the reactor. ADM1_10 model simulated well the dynamic evolutions of the main variables in the liquid as well as in the gas phases.

Study on the Performance of an Anoxic Biotrickling Filter for the Removal of Hydrogen Sulphide from Biogas

Abstract The paper presents aspects related to the performance of an anoxic biotrickling filter designed for hydrogen sulphide (H2S) removal from biogas. In this process, nitrate was supplied through a nutrient solution as an electron acceptor for anoxic growth of H2S-oxydizing microorganisms. The biotrickling filter's packing media consisted of a layer of plastic fibres over volcanic rocks in a ratio 0.78:1 by volume. The total volume of packing media was 0.014 m3. Several H2S loading rates (IL) were tested under continuous dynamic conditions, ranging between 20 and 550 g of H2S feed/(m3bed·day). Maximum process performance (&amp;gt;95%) was observed for IL ranging up to approximately 300 g of H2S feed/(m3bed·day). The degradation of hydrogen sulphide occurred with the formation of both sulphate and elemental sulphur, their formation ratio being dependent on H2S loading rate. Elemental sulphur was found to be the dominant degradation product, particularly at IL &amp;gt; 96.18 g of H2S feed/(m3bed·day). The use of two biotrickling filters in series was also tested, and a significant improvement in process performance was observed. This technology allows simple operation with low maintenance and has the potential for sulphur recovery.

Characterization of a Spherical Packing Medium for Biological Nitrogen Removal by Microelectrodes

A novel packing medium comprised of a spherical net-like shell, plastic stuffing, and a perforated hollow duct for biological reactors was investigated. In this study, we examined a biofilm process that employed the packing medium for combined aerobic carbonaceous substances removal, nitrification, and denitrification. As a result, we were able to obtain the average of nitrification, denitrification, as well as the chemical oxygen demand (COD) removal capacities, which correspond to 0.2 kg N/m3 · day, 0.3 kg N/m3 · day, and 5.56 kg/m3 · day, respectively. Moreover, the spatial concentration distribution of chemical species inside the packing medium was studied, using microelectrodes for dissolved oxygen, NH4+, NO3−, and redox potential. Clear evidence was found that aerobic/anoxic spatial stratification was formed inside the packing medium, and that due to microbial oxygen utilization, the aerobic zone was limited to a surface layer of 12 mm, which had a corresponding decrease in redox potentials from 157.4 mV to −99.5 mV. It was also found that nitrification dominated in the top 4 mm of the surface layer, whereas denitrification occurred in the deeper part of the packing medium. Furthermore, a gap zone only for aerobic heterotrophic oxidation was found to be present between nitrification and denitrification. This implied that a high C/N ratio could contribute to a decrease in the effective size of the packing medium. Based on the measured DO and NH4+ depth profiles under steady-state conditions, the effective diffusion coefficients of DO and NH4+ in the packing medium were calculated to be 0.0172 m2/day and 9.7 × 10−5m2/day, respectively. The turbulent diffusion of oxygen ensured the sufficient oxygen supply not only for aerobic carbon oxidation but for nitrification inside the packing medium as well.

Comparison of Shredded Tire Chips and Tire Crumbs as Packing Media in Trickling Filters

Abstract A five stage study was conducted using two trickling filters, one with shredded tire chips (12 to 50 mm) and the other with tire crumbs (1.5 to 6.5 mm) as packing media, and both landfill leachate and synthetically prepared leachate, to evaluate treatment performance. Due to increased surface area and sorption capacity, compared with other materials, a thick layer of biomass developed over the surface of tire chips and crumbs and sloughed off after approximately 21 days. Biochemical oxygen demand, chemical oxygen demand, and ammonia nitrogen removal were in the range of 81 to 96%, 76 to 90%, and 15 to 68%, respectively, under stable conditions. Organic removal and total dissolved solids reduction from the leachate were well correlated, with the exception of when biomass sloughing caused an increase in the organic content. The trickling filter with tire crumb media exhibited a more consistent organic removal throughout the experimental program. Tire chips, being readily available, could be a better alternative to crushed stone or gravel as a packing media in trickling filters. Tire crumbs appeared to be promising for small scale treatment systems.

Changes in the potential functional diversity of the bacterial community in biofilters

The bacterial community structure in a biofilter treating ethanol was investigated using community level physiological profiling. Laboratory scale biofilters of two sizes (5 or 11.5 cm internal diameter with 30 or 67 cm packed height, respectively) were packed with compost and a humidified airstream loaded with ethanol passed through them. Good removal efficiencies (82-100%) and elimination capacities (49-205 g ethanol m(-3) h(-1)) were observed in all units. Compost packing media samples were extracted and the community level physiological profiles assayed using Biolog Ecoplates. The community structure was found to be similar over a range of a few centimetres. No differences were observed between sample sizes of 0.5-1 and 6 g, and therefore, the smaller sample size (typical of that used in previous studies) is appropriate for use in the future. Two studies of parallel systems showed that the community structure diverged during the acclimation period (10 days) in one pair, but in another pair, no divergence was observed and a similar shift in community profile was observed in both units between 25 and 40 days of operation. Community level physiological profiling with Biolog Ecoplates is a useful method for detecting differences between and changes within the bacterial communities in biofilters.

Biological denitrification of reverse osmosis brine concentrates: I. Batch reactor and chemostat studies

A major technological concern with reverse osmosis in water purification, wastewater treatment, and water reclamation or recycling is the production of brine concentrates high in ammonia or nitrogen. This project addresses biological denitrification of reverse osmosis brine concentrates in a bioactive fluidized bed adsorber reactor (FBAR), accomplished in four stages. The first three stages are described in this paper, while the final stage is addressed in the companion paper (Ersever et al. 2007). The first stage optimized an FBAR to produce nitrified brine for subsequent denitrification studies. The second stage employed batch reactors to evaluate denitrification parameters such as temperature, pH, total dissolved solids, and carbon-to-nitrogen ratio. The specific denitrification rate was maximum at a temperature of 35 °C, pH of 8.0, and carbon-to-nitrogen ratio of 1.8. The third stage involved chemostats to determine Monod parameters under nitrate-, nitrite-, and carbon-limiting conditions. A biokinetic model was employed to simulate chemostat dynamics and to estimate the biological parameters. The final stage entailed FBAR denitrification experiments under different hydraulic retention times, nitrate concentrations, and packing media; simultaneous denitrification and sulfate reduction were addressed. A second FBAR used in series with the first achieved an overall sulfate reduction of 99%, and a biofilter effectively removed the hydrogen sulfide generated.

Evaluation of an aerobic submerged filter packed with volcanic scoria

An aerobic submerged filter (ASF) using volcanic scoria stones as packing media was evaluated. The wastewater used was a mixture of sewage with sugar to obtain organic matter concentrations between 28 and 3230 mg CODt/L, hydraulic rates up to 2.88 m 3/m 2 d and organic loading rates between 0.45 and 9.4 kg CODt/m 3 d. The system removed 80% of CODt as average for organic loading rates between 0.45 and 3 kg CODt/m 3 d and 54% at the higher rate (9.4 kg CODt/m 3 d). It was not necessary to backwash the filters, a negligible pressure drop and a good biomass attachment in the volcanic scoria stones was observed. Nitrification and organic matter biodegradation were carried out simultaneously with a nitrate production of 90% up to 1.7 kg CODt/m 3 d. Tracer studies revealed a completed mixed hydraulic pattern which was not affected by the presence of biomass.

Mass-Transfer Kinetics in a Shell Packing Material for Chromatography

A shell particle consists of a solid, nonporous core that is surrounded with a shell of a porous solid having essentially the same physicochemical properties as those of the conventional porous particles used as packing media in chromatography. The diameter of the solid core and the thickness of its shell or the external diameter of the particle characterizes the chromatographic properties of the packing material. The potential advantage of this particle structure would be the shorter average path length experienced by solute molecules during their diffusion across the particles of packing material when they are retained. Compounds having slow pore diffusion would exhibit higher efficiencies on columns packed with shell than with conventional, fully porous particles. Using columns packed with Halo, a new type of porous silica shell particles, we assess the gain achieved with this principle for peptides of moderate molecular weights and for small proteins.

Treatment of domestic wastewater using upflow anaerobic sludge blanket reactor

This paper presents the findings of the study on treatment of domestic wastewater using a laboratory scale Hybrid Upflow Anaerobic Sludge Blanket (HUASB) reactor. The reactor with a working volume of 5.9 L and plastic cut rings as packing media was operated at varying Hydraulic Retention Time (HRT) for a period of 110 days. While the COD removal varied from 75-86%, the BOD removal was in the range of 70-91%. Methane content in the biogas was 62±3%. VFA levels fluctuating between 100 and 186 mg/L (as acetate) did not pose operational problems such as souring of the reactor. During the treatment, nutrient levels exhibited an increasing trend. HUASB system could be designed with very short HRT of 3.3 hours, which will reduce the treatment cost significantly. It appears to be a promising alternative for the treatment of domestic wastewater in developing countries like India