Treatment of Paint Spray Booth Off-Gases in a Fungal Biofilter

Biological processes, most notably biofilters and biotrickling filters, are increasingly used to remove and biodegrade a wide variety of volatile organic compounds (VOCs) present in gas streams emitted from industrial operations. In the research described herein, a laboratory-scale biofilter was operated for a period of more than 180 days to treat a waste gas comprised of a four-component VOC mixture representative of solvents present in off-gases emitted by painting operations. The biofilter, packed with a cubed polyurethane foam media and initially inoculated with a pure culture of the fungus Cladosporium sphaerospermum, was maintained under acidic conditions throughout the duration of the experiments. The system was supplied with a mixture of n-butyl acetate, methyl ethyl ketone, methyl propyl ketone, and toluene with influent concentrations of 124, 50.5, 174, and 44.6 mg?m?3, respectively. The biofilter’s empty bed residence time (EBRT) was varied from 2.0 min to 15 s. When the influent gas stream was properly humidified, the system exhibited stable long-term performance with an average total VOC removal greater than 98% even with an EBRT as low as 15 s. Under the loading condition tested, this corresponds to an average elimination capacity of 92 g?m?3?h?1. VOC concentration profiles measured along the height of the biofilter revealed a distinct VOC degradation pattern that was observed under all loading conditions tested. Although the column was initially inoculated with only Cladosporium sphaerospermum, several additional species of fungi tentatively identified as Penicillium brevicompactum, Exophiala jenselmei, Fusarium oxysporum, Fusarium nygamai, Talaromyces flavus, and Fonsecaea pedrosi were found growing attached to the packing medium by the end of experiment. Results demonstrate that fungal biofilters can consistently maintain high removal efficiency for paint VOC mixtures over extended periods of operation. The results also indicate that it would be difficult and likely unnecessary to maintain specific species in full-scale fungal biofilters treating paint spray booth emissions.     

Pharmaceutical wastewater treatment using an anaerobic/aerobic sequencing batch biofilter

The performance of a sequencing batch biofilter integrating anaerobic/aerobic conditions in one tank to treat a pharmaceutical wastewater effluent was studied. A pilot reactor, packed with a porous volcanic stone (puzzolane) was used in the study. The reactor operated as a sequencing batch biofilter, SBB, with reaction times varying for the anaerobic stage from 8 to 24 h and for the aerobic one from 4 to 12 h. The volume of exchange was from 16 to 88%. The pharmaceutical wastewater contained organic chemicals including phenols and o-nitroaniline, a concentration of organic matter that varied from 28,400 to 72,200 mg/L (as total COD), 280 to 605 mg N-NH4/L. and 430 to 650 mg SST/L. In order to acclimatize the microorganisms to the industrial wastewater, the organic load was increased stepwise from 1 to 7.7 kg COD/m3/d. The adequate time was obtained when the removal efficiency of COD reached 80%, or more. Maximal removal loads, associated to high removal efficiencies (95-97% as COD), varied from 4.6 to 5.7 kg COD/m3/d. Under these conditions color removal was 80% as Pt-Co units. Microtox analysis was performed to the wastewater and to the anaerobic and aerobic stages. It was observed that the aerobic stage was the responsible for wastewater detoxification. Results showed that the anaerobic/aerobic SBB was able to treat efficiently initial concentrations of the raw effluent up to 28,400 mg COD/L.     

Biotrickling Filtration for Control of Volatile Organic Compounds from Microelectronics Industry

This study investigated the transient and steady-state performance of a bench-scale biotrickling filter for the removal of an organic mixture (acetone, toluene, and trichloroethylene) typically emitted by the microelectronics industry. The microbial consortium consisting of seven bacterial strains that were fully acclimated prior to inoculation onto activated carbon media. Among the seven strains, the Pseudomonas and Sphingomonas strains appeared to be the major groups degrading toluene (>25?ppmv/h?108 cell) and trichloroethylene (>2.3?ppmv/h?108 cell), while Mycobacteria and Acetobacteriaceae strains were the primary decomposers of acetone (>90?ppmv/h?108 cell). The column performance was evaluated by examining its responses to the fluctuating influent total hydrocarbon concentrations, which varied from 850 to 2,400 ppmv. Excellent steady-state removal efficiencies greater than 95% were consistently observed, and system recovery was typically within two days after a significant increase in the inlet loading was experienced. The overall mass-transfer rate and the biokinetic constants were determined for each organic component. Mathematical simulations based on these parameters demonstrated that the removal of acetone was kinetically limiting, whereas the removals of toluene and trichloroethylene were at least partially mass-transfer limiting.     

Using Polyphosphate Buffering to Treat Phosphorus-Deficient Wastewater

The suitability of the anaerobic/aerobic process was investigated for treating phosphorus-deficient wastewaters with highly variable influent chemical oxygen demand (COD) loading patterns to produce consistently low effluent P levels. During laboratory-scale experiments, two sequencing batch reactors (SBRs), one anaerobic/aerobic (AnA) and the other completely aerobic (CA), received transient influent COD loading patterns that simulated (No. 1) daily COD loading fluctuations and (No. 2) low weekend COD loading, each for a period of approximately 6?months. The AnA SBR produced lower effluent soluble P concentrations than the CA SBR during loading pattern No. 1 (0.5 versus 1.2?mgP/L). During loading pattern No. 2, both SBRs allowed effluent acetate breakthrough, following the low weekend COD loading period, and the P removal in the AnA SBR gradually deteriorated. The AnA process has the potential to produce lower effluent P levels than the CA process during transient loading periods due to the P release and uptake characteristics associated with the polyphosphate-accumulating metabolism. Extended periods of low COD loading can however cause a loss of P removal.     

Removal of Methyl Isobutyl Ketone From Contaminated Air by Trickle-Bed Air Biofilter

A laboratory-scale trickle-bed air biofilter was evaluated for the removal of methyl isobutyl ketone (MIBK) from a waste gas stream. Six-millimeter (6?mm) Celite pellets (R-635) were used as the biological attachment medium. Effects of MIBK volumetric loading rates on removal efficiency, biofilter reacclimation, biomass growth, and removal kinetics were studied under three different operating conditions, namely, backwashing and two intermittent periods (off chemical—no MIBK input; and off flow-no flow input). Backwashing of the biofilter once a week with full-medium fluidization removed the excess biomass and attained stable long-term performance with over 99% removal efficiency for loading rates less than 3.26?kg chemical oxygen demand (COD)/m3?day. The two intermittent periods could also sustain high removal efficiency for loading rates up to 1.09?kg?COD/m3?day without any backwashing. The recovery time increased with an increase in loading rates. Furthermore, the intermittent operations required a longer time to recover than backwashing. The pseudo-first-order removal rate constant decreased with an increase in volumetric loading rate. The removal kinetics showed an apparent dependency on the experimental operating conditions.     

Fungal Biofiltration of Toluene on Ceramic Rings

Fungal biofilters attain higher toluene elimination rates compared to bacterial systems. However, strong mycelia growth can cause clogging. In the present work, toluene biofiltration with the fungus Paecilomyces variotii CBS 115145 was tested with two rigid packing materials that allow high mycelia growth. The reactor had two 4.25?L sections, each packed with ceramic Raschig rings differing in water retention capacity and internal porosity. After optimizing nutrient solution delivery, an overall maximum elimination capacity of 245?g/m3/h was obtained. Higher elimination capacity (290?g/m3/h) was measured in the ceramic ring with lower water content, indicating the interest of such packing material for treating hydrophobic pollutants in fungal biofilters. Additional experiments with this support in a 2?L biofilter showed bacterial contamination, but the fungal activity was responsible for about 70% of the total removal. The support with less humidity showed greater aerial growth, which possibly improves removal efficiency by favoring the direct transfer of pollutants from the gas phase to the microorganism.     

Formation of Aerobic Granules with Domestic Sewage

The use of aerobic granules in wastewater treatment can reduce the land area that is needed for the treatment of sewage. Until now granulation has been mainly studied using artificial wastewater. Studying the possibility of forming aerobic granules on domestic sewage in a sequencing batch reactor was a logical step in the scaling-up process and development of this technology. Therefore, aerobic granulation was studied using presettled sewage as influent. After 20?days of operation at high chemical oxygen demand (COD) loading heterogeneous aerobic granular structures were observed, with a sludge volume index after 10?min settling of 38?mL?g?1 and an average diameter of 1.1?mm. Applying a high COD load was found to be a critical factor for the formation of aerobic granules on this type of influent. Therefore short cycle times and concentrated wastewater are preferred to form granules in a sequencing batch reactor when low strength wastewater is used. The nutrient removal was not optimized in this study.     

Transient Response of Flow-Direction-Switching Vapor-Phase Biofilters

Transient loading of vapor-phase biofilters may result in exceedence of the local reaction or mass transfer capacity of the inlet region. In such cases, higher concentrations of contaminants are carried deeper into the bed where there is less active biomass and, in some cases, breakthrough of contaminants may occur. Previous studies have demonstrated that periodic reversal of the flow direction results in improved transient-loading response. However, quantitative information on the extent of the benefit is lacking. Step function increases in toluene concentration were applied to unidirectional-flow and flow-direction-switching laboratory reactors operated in parallel. Contaminant concentration was monitored at several points along the packed beds. Relative to unidirectional mode of operation, periodic flow reversal produced a more uniform distribution of microbial reaction capacity along the length of the packed bed. Directional switching at a 12-h interval did not result in a loss of activity or removal capacity. Mass-removal rates under transient-loading conditions were similar in the first-half of both biofilters but, in the second-half of the units, significant removals were observed only in the flow-direction-switching biofilter. As a result, maximum mass-removal rates under transient-loading conditions were approximately twice as great for the flow-direction-switching biofilter relative to the conventional unidirectional-flow biofilter receiving similar mass loading.     

Removal of EATX from Waste Gases by a Trickle-Bed Air Biofilter

The trickle-bed air biofilter performance for treating mixtures of ethylacetate (EA), toluene (T), and xylene (X) volatile organic compounds (VOCs) was evaluated under different influent VOC loadings. The EA removal efficiencies were significantly higher than those for T and X, indicating that EA is a preferred substrate in the EATX waste gas. More than 80% removal efficiencies could be achieved under influent loadings below 77 g EA∕m3∕h, 8 g T∕m3∕h, and 10 g X∕m3∕h. The trickle-bed air biofilter appears efficient for controlling EATX emission with medium EA loadings and low TX loadings. The elimination capacities of EA, T, and X for a pure VOC feed were higher than for a mixed VOC feed and the differences increased with increased influent VOC loading.     

Empirical Model for Biofiltration of Toluene

In this study the toluene removal efficiency of a composted pine bark biofilter was determined at loading rates ranging from 9.04 to 54.21 g m?3 h?1, retention times of 0.25–3.0 min, and at various bed heights. Toluene removal efficiencies exceeding 90% were obtained when the biofilter was subjected to a gas retention time in excess of 0.32 min (19.2 s) and loading rates below 42 g m?3 h?1. The data obtained were used to develop an empirical model. The empirical model successfully described the overall removal efficiency with an R2 value of 0.98. The influence of oxygen concentration on the removal efficiency was also evaluated. Reduced biofilter performance was observed at oxygen concentrations below 5%. A wide range of microorganisms were isolated from the biofilter, which included Corynebacterium jeikeium A, Corynebacterium nitrilophilus, Micrococcus luteus, Pseudomonas mendocina, Sphingobacterium thalphophilum, and Turicella otitidis.     

Polyurethane Foam Medium for Biofiltration. II: Operation and Performance

A polyurethane foam medium with characteristics described in Part I of this paper was tested in a toluene degrading biofilter to demonstrate its ability to support an active biofilm and to study feasibility of a novel nutrient addition and biomass wasting strategy. A laboratory-scale biofilter was fed a model waste stream containing toluene for more than 300 days using empty bed residence times ranging from 1 to 4 min and toluene concentrations ranging from 50 to 200 parts per million by volume. Results reported herein demonstrate that a polyurethane foam medium with high porosity, suitable pore size, low density, and an ability to sorb water was able to remove over 99% of the influent toluene after implementation of a nutrient addition and biomass removal strategy. The strategy, made possible by use of the foam medium, overcame problems such as clogging, high head loss, moisture content control, and nutrient limitation that are often associated with conventional biofilter operation.     

Swine Wastewater Treatment Using Submerged Biofilm SBR Process: Enhancement of Performance by Internal Circulation through Sand Filter

Pollutants removal from swine wastewater by a submerged biofilm sequencing batch reactor (BSBR) with internal circulation of liquor through a sand filter was studied. The variation of nutrient removal efficiencies with changes in volumetric circulation ratios and rates were determined. The reactor was operated under the following conditions: One cycle per day, hydraulic retention time of 15 days, average NH4–N loading rate of 55?g?m?3?d?1, and without supplemental external carbon source. System performance was enhanced by conducting internal circulation of liquor through the sand filter. When compared with the performance of a single BSBR without sand filter, nitrogen and phosphorus removal efficiencies were found to increase by 18% and over 33%, respectively. With a circulation rate of 170?L?h?1?m?3, and duration of 22 h (circulation ratio of 0.9), TOC, NH4–N, and total soluble inorganic nitrogen (as NH4–N plus NOx–N) removal efficiencies of 73, 97.8, and 85.6%, respectively, were achieved. The enhancement of nitrogen removal was attributed to the occurrence of denitrification in the sand filter during circulation of liquor. The denitrification rate was proportional to the volumetric circulation ratio per day, resulting in an average 15% NOx–N removal in the sand filter. Also, it was found that continuous circulation during the entire reaction phases could be one way to achieve better performance.     

Mathematical Model of Biofiltration of VOCs: Effect of Nitrate Concentration and Backwashing

The affect of nitrate concentration and reactor backwashing on biofilter performance is evaluated using a dynamic mathematical model of the biodegradation process of volatile organic compounds in a trickle bed biofilter packed with uniform synthetic solids. Experimental observations from a bench-scale biofilter system treating ether were used to develop and validate the model. Experience acquired in biofiltration of volatile organic compounds has demonstrated that although these two factors—nitrate and backwashing—are secondary when organic packing material is used, they are essential when the packing media is synthetic. The operation of a synthetic media packed reactor requires the addition of nutrients necessary for biodegradation. Since nitrate was utilized as the nitrogen source in this system, it was included in the model as a limiting substrate (nutrient). A negative affect of excessive accumulation of biomass in the reactor on biofilter performance has also been observed in highly loaded synthetic media biofilters. This problem was solved by removing excessive biomass via full media fluidization and backwashing of the reactor. The affect of periodic backwashing was included in the model as a reduction in the biofilm thickness and a new approach to calculate the reactor specific surface area after backwashing. The unknown model parameters that correspond to nitrate limitations were estimated. The mathematical model was then used for simulation and analyses of the affect of these two factors on the biodegradation process.     

矿化垃圾处理渗滤液中有机污染物的GC-MS研究

以上海市老港填埋场中矿化垃圾反应床处理渗滤液为例,定性分析了该反应床进水和出水中有机污染物组分,同时半定量分析了该反应床对有机污染物的去除效果,分析结果显示:从宏观尺度上,矿化垃圾反应床很好的去除了渗滤液中的污染物质,渗滤液经过矿化垃圾反应床后,14种有机污染物得到完全去除,3种有机物的含量降低,产生1种新物质,邻苯二甲酸二辛酯在进水和出水中同时存在,从谱图上可以看出其出水浓度降低,在不同pH值萃取条件下,从进、出水谱图的对比中可以发现,进水中大部分有机污染物得到去除。     

Use of a Sequencing Batch Reactor for Nitrogen and Phosphorus Removal from Municipal Wastewater

In this study, a suspended growth sequencing batch reactor (SBR) and an attached cum suspended growth SBR were used to investigate the performance characteristics of nitrogen and phosphorus (NP) removal from municipal sewage. The effects of three controlling factors, namely batch loading rate, feed pattern (initial feed or step feed), and mixing/aeration ratio, on NP removal were investigated under nine different experimental conditions. Owing to a large number of possible combinations among the controlling factors and different experimental conditions, it is very difficult to enumerate all the available combinations experimentally. In view of this, the Taguchi method, a cost-effective technique for design of experiments, was exploited for estimating the optimal operating condition. This study also evaluated the difference between the suspended growth SBR and the attached cum suspended growth SBR. The total nitrogen (TN), total phosphorus (TP), total biochemical oxygen demand (TBOD)5, and suspended solids (SS) removal efficiencies were 90.2, 83.9, 98.6, and 93.0%, respectively, for the suspended growth SBR. The corresponding values for the attached cum suspended growth SBR were 92.6, 82.1, 98.3, and 93.1%, respectively. It was observed that the batch loading rate influenced the efficiencies in terms of TN removal. It was also noted that step feed and mixing/aeration ratio had significant impact on TP removal performance. The optimal operating condition for the suspended growth SBR system in terms of batch loading rate, feed pattern, and mixing/aeration ratio were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 1-to-1, respectively. The associated TN, TP, TBOD5, and SS removal efficiencies for the suspended growth SBR were 93.8, 98.2, 99.6, and 98.5%, respectively. The corresponding results for the attached cum suspended growth SBR system were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 3-to-1, respectively. Similarly, the corresponding removal efficiencies for the attached cum suspended growth SBR were 94.7, 97.8, 99.3, and 98.8%, respectively.     

Media-Induced Hydraulic Behavior and Performance of Upflow Biofilters

Laboratory studies were conducted to assess the influence of media-related factors such as porosity, specific surface, and pore size on hydraulic behavior and performance of upflow anaerobic biofilters (ABFs). Three 15-L upflow biofilters, each packed with different support media, were subject to identical synthetic protein-carbohydrate substrate with chemical oxygen demand (COD) concentrations ranging from 2,500 to 10,000 mg∕L, and hydraulic retention times from 15 to 30 hours, corresponding to organic loading rates (OLRs) varying from 2 to 16 g COD∕L∕d. Tracer studies were carried out to characterize hydraulic behavior of the biofilters containing media with and without biomass, designated as dirty-bed and clean-bed, respectively. The results indicate that hydraulic flow regimes in all biofilters were characterized by a plug-flow pattern with a large extent of dispersion under clean-bed conditions. The tracer response curve under dirty-bed conditions operating at an OLR of 16 g COD∕L∕d reflects more closely the response of a mixed-flow reactor than that of a plug-flow unit, which suggests that there is significant short-circuiting in the ABFs. Waste treatment performance indicates that the biofilter associated with media of the largest pore size and porosity consistently demonstrated the highest COD removal from 96% to 73% at loadings varying from 2 to 16 g COD∕L∕d. The same reactor exhibited the lowest magnitude of dispersion along with minimum dead space within the bed from the tracer analysis. This implies that the use of support media with larger pore size and porosity may reduce the extent of short-circuiting, leading to better waste treatment performance. Increasing the media specific surface at the expense of media porosity may result in lower treatment performance in upflow anaerobic biofilters.     

Effects of Sodium Chloride on the Performance of a Sequencing Batch Reactor

In this study, we investigated the effects of sodium chloride (concentrations ranging from 0?to?60?g/L) on the performance of sequencing batch reactors (SBRs) using a microbial culture developed from a domestic sewage treatment plant. The lab-scale SBRs were fed with synthetic wastewater (acetate as the organic substrate) containing either sodium chloride solution or seawater to ensure consistency in feed composition. It was found that sodium chloride concentrations of up to 10?g/L stimulated substrate removal. The organic removal efficiency decreased from 96%, when no sodium chloride was added, to 86% when 60?g/L of sodium chloride was introduced into the influent wastewater. Effluent turbidity increased significantly when the sodium chloride concentration in the wastewater was equal to or above 30?g/L even though the sludge volume index (SVI) decreased. The increase in effluent turbidity could be caused by the release of nondissolved cellular components due to plasmolysis of microorganisms as observed by scanning electron microscopy. Experiments involving seawater (with 20?g/L total dissolved solids) showed that organic removal efficiency improved from 87 to 95% while effluent turbidity and SVI values were lowered when the loading rate parameter (Li) was lowered from 0.6?to?0.3?mg total chemical oxygen demand (mg?VSS?day). Optical microscopy and scanning electron microscopy indicated morphological changes in the microbial population. From this study, it was concluded that microbial culture from domestic wastewater facilities could be acclimated in a SBR to treat wastewater containing sodium chloride concentrations of up to 60?g/L.     

Trickling Filter Nitrification Performance Characteristics and Potential of a Full-Scale Municipal Wastewater Treatment Facility

The trickling filter solids contact water pollution control facility for the city of Ames, Iowa has successfully nitrified wastewater with trickling filters for the past decade. Both first stage, carbonaceous biochemical oxygen demand removing trickling filters (TFs) and second stage, nitrifying TFs (NTFs) remove significant quantities of ammonia from the wastewater. Based on operating data from January 1999 through December 2001, the average specific ammonia removal rate for the TFs was 1.5×10?4?kg?N/(d?m2). Most probable number testing confirmed the presence of nitrifiers in the top media layer of both stages of trickling filters. An experiment was performed whereby flows to the TFs and NTFs were varied to test ammonia removal capabilities of the facility. During the experiment, the TFs removed an average of 2.4×10?4?kg?N/(d?m2) and the NTFs removed an average of 1.5×10?5?kg?N/(d?m2) due to low loading. Data collected during the study varied with operating conditions. It was compared to and used to calibrate NTF models. An empirical design model poorly fit the data, and a theoretically based model could not be calibrated well with apparent ammonia removal rates. A best-fit equation, dependent on hydraulic loading and influent ammonia concentration (adjusted for recirculation), was regressed directly to the data and is useful for describing nitrification in the Ames WPCF TFs.     

Effects of Biomass Growth on Gas Pressure Drop in Biofilters

The effects of biomass accumulation and distribution on air pressure losses in biofilters were experimentally studied. Two bench-scale biofilters, one packed with inert porous pellets (Nova Inert) and the other with wood chips, were operated under similar conditions with excess nutrients to treat an airstream containing methanol, at loading rates of 100–150 g methanol∕m3 bed∕h. Localized biomass accumulation in the biofilter beds was the key factor increasing the pressure drop, which was caused by local bed clogging due to biomass growth. The highest pressure drops in the beds (wood chips: 2,600 Pa∕m; Nova Inert: 550 Pa∕m) occurred in sections where there were high biomass levels with high water content. The pressure drop varied nonlinearly with the amount of accumulated biomass and the amount of methanol consumed. Sixfold higher pressure drops were measured in the wood chip biofilter than in the Nova Inert biofilter because of more biomass growth and bed compaction. A model, based on the Ergun equation, was developed to predict biomass-affected porosity and pressure drop as a function of the biomass concentration in a bed packed with spherical pellets. A comparison of the experimental and the predicted pressure drops showed that the model provided good estimates of biomass-affected porosity and pressure drop in the biofilter packed with spherical porous pellets with even biomass distribution.     

Field Measurements and Modeling of Two-Stage Biofilter that Treats Odorous Sulfur Air Emissions

Because the presence of hydrogen sulfide (H2S) and methyl mercaptan (MeSH) inhibits the removal of some organic reduced sulfur compounds (e.g., dimethyl sulfide, Me2S) in biofilters, a two-stage biofilter may be an appropriate method to treat a mixture of reduced sulfur compounds. This work studied the treatment of odorous air emissions [a mixture of H2S, MeSH, Me2S, and dimethyl disulfide (Me2S2)] using a two-stage biofilter. H2S had the highest overall removal efficiency (96%) followed by MeSH and Me2S (90 and 91% removal, respectively) and Me2S2 (81%). Most of the removal of H2S, MeSH, and Me2S2 occurred in the primary biofilter (72% H2S, 66% MeSH, and 52% Me2S2), while most of the Me2S removal occurred in the secondary biofilter (64% Me2S). A dynamic model that describes biofiltration was calibrated and validated to H2S and MeSH field data. This is the first time a model was evaluated with organic odor-causing sulfur compound data obtained from a biofilter packed with compost and wood chips. Model simulations showed that H2S removal in a lava rock packed biofilter would be better than in a similar biofilter packed with compost and wood chips.