Abstract: The present invention relates to biotrickling filter systems and the packing material employed in such systems, as well as, methods of using same to remove odour causing compounds from waste gas streams. The packing material for the biotrickling filter system includes a plurality of expanded glass granules. When used in a biotrickling filter system, the packing material is highly efficient at removing from waste gas streams hydrogen sulfide at high concentrations in low empty bed residence times.

Abstract: The present invention relates to biofilter systems and the biofilter media employed in such systems, as well as, methods of using same to remove odour causing compounds from waste gas streams. The biofilter media has a plurality of expanded glass granules. Each expanded glass granule has a coating thereon. The coating includes a bonding agent, an adsorptive agent, microorganisms and nutrients. When used in a biofilter system, the biofilter media is highly efficient at removing from waste gas streams hydrogen sulfide at high concentrations in low empty bed residence times.

Abstract: A combined process for the recovery of sulfur from an acid gas stream. The combined process includes both a Claus unit and a unit for treating the Claus tail gas with caustic to remove hydrogen sulfide therefrom and to biologically oxidize the hydrogen sulfide using certain types of sulfur bacteria to make elemental sulfur. The combined process provides for an exceptionally low concentration of hydrogen sulfide in the finally treated sweet gas.

Abstract: The invention relates to a method for purifying gases escaping from a gully hole (1), particularly escaping from a sewer (8) guided at the bottom (7) of the gully hole (1) by means of a biofilter that is arranged inside the gully hole (1) in such a manner that the gases flow through it before they leave the gully hole (1). The biofilter is mounted at such a distance to the sewer (8) that its temperature and moisture are substantially influenced by the waste water (17) present in the sewer (8).

Abstract: A biofiltration apparatus and method for reducing methyl bromide concentration in a volume of a gas are disclosed. The apparatus includes a housing and a substrate component located in the housing. The substrate component includes a population of methyl bromide degrading microorganisms. The housing receives a volume of contaminated gas, such as exhaust from a fumigation site, through a contaminated gas inlet. The contaminated gas is exposed to the methyl bromide degrading microorganisms where the methyl bromide is biodegraded. The filtered gas, or the gas with a reduced methyl bromide concentration, is then directed out of the housing. The apparatus may also include a contaminated gas load dampening device.

Abstract: A stable continuous method for producing ethanol from the anaerobic bacterial fermentation of a gaseous substrate containing at least one reducing gas involves culturing a fermentation bioreactor anaerobic, acetogenic bacteria in a liquid nutrient medium; supplying the gaseous substrate to the bioreactor; and manipulating the bacteria in the bioreactor by reducing the redox potential, or increasing the NAD(P)H TO NAD(P) ratio, in the fermentation broth after the bacteria achieves a steady state and stable cell concentration in the bioreactor. The free acetic acid concentration in the bioreactor is maintained at less than 5 g/L free acid. This method allows ethanol to be produced in the fermentation broth in the bioreactor at a productivity greater than 10 g/L per day. Both ethanol and acetate are produced in a ratio of ethanol to acetate ranging from 1:1 to 20:1.

Abstract: A system and method for the purification and biodeodorizing of a gas are disclosed. The system is highly adaptable and capable of operating in a variety of modes to tailor performance of the system to specific odor control applications. The scrubber stages of the system may each be maintained at different conditions to selectively promote bacterial activity that targets a variety of odorous constituents. The pH level of the irrigation fluid provided to each scrubber stage may be controlled.

Abstract: Disclosed herein is a method for treating odors in wastewater treatment bodies. The pH of the body is preferably established above about 6 and most preferably above about 7, usually by adding a base to the body. The oxidation reduction potential of the body is established at about ?300 mV or higher and more preferably about ?200 mV or higher, usually by adding an oxidizing agent such as oxygen or nitrates. After these conditions are established, sulfur oxidizing bacteria are added to the body. These preferably include Paracoccus denitrificans (formerly called Thiosphaera pantotropha) ATTC number 35,512. The sulfur oxidizing bacterial population should be established at levels of at least about 1×104 cfu/mL and more preferably at levels of 1×105 to 1×106 cfu/mL or higher. The increased ORP and pH levels make sulfate reduction thermodynamically unfavorable. Additionally, the presence of an alternative electron acceptor such as oxygen or nitrate allows the sulfur oxidizing bacteria to oxidize organic acids.

Abstract: A ventilation system is disclosed for an enclosure in which people live. The ventilation system comprises a first ducting means for ducting fresh air from outside to inside the enclosure and a second ducting means for ducting stale air. The second ducting means comprises a stale air inlet for receiving stale air containing carbon dioxide from inside the enclosure and an exhaust manifold having a first vent to exhaust air outside the enclosure and a second vent in fluid communication with the first ducting means to return clean air into the first ducting means. The ventilation system is further characterised in that it comprises catalysing means for catalysing hydration of carbon dioxide contained in at least a portion of the stale air into a solution of carbonate ions and hydrogen ions, and thereby removing carbon dioxide from said portion of the stale air and obtaining clean air. Evacuating means are also provided for evacuating the solution out of the ventilation system.

Abstract: A system for capturing and neutralizing HAP's (hazardous air pollutants) and VOC's (volatile organic compounds) at the source point by providing a closed loop remediation system which utilizes an air collection, treatment and control module containing a predetermined size bay of multiple interchangeable mini-biofilter cartridges that function to consume the pollutant and recirculate remediated air back to the source point of the pollutant. The system includes establishing a closed loop air system at a work station which generates and emits VOC's, capturing the VOC's in the air stream flow and transporting them directly into an adjacent biofilter module which contains selected microorganisms in mini-cartridges which biodegrade said VOC's and recirculates remediated air back to the source point of the pollutant.

Abstract: This invention pertains to a novel biotechnological process of solubilization and concentration of CO2 from emission exhausts or streams that could be coupled for further biochemical/chemical conversion. The biotechnological process occurs in novel reactors/devices employing immobilized biocatalysts enabling concentration and solubilization of emitted CO2 by allowing catalytic contacting with water spray. These novel reactors or devices could be coupled to other reactors/devices resulting in further biochemical/chemical conversion of the concentrated carbon dioxide.

Abstract: A method of heap leaching wherein a gaseous suspension which contains a microbial inoculum or nutrients is introduced into the heap.

Abstract: A system and process of bio-treatment for enhancing the efficiency of treating waste gas is disclosed. This technology relates to an application of a dust/grease filtering device, a two-way directionally gas inlet system, a bioaerosol removal device, and a cell immobilization technology, to a conventional bioreactor for treating waste gas. The dust/grease filtering device is formed by fillers which form pores being less than 100 mesh, in order to efficiently remove the majority of dust/grease existing in the waste gas, and reduce the pressure drop of the reactor. The two-way directionally gas inlet system can control the direction of the gas flowing into the bioreactor, in order to efficiently control the pressure drop, and the variation of pH value and the humidity in the reactor.

Abstract: Disclosed herein is a method for treating odors in wastewater treatment bodies. The pH of the body is preferably established above about 6 and most preferably above about 7, usually by adding a base to the body. The oxidation reduction potential of the body is established at about −300 mV or higher and more preferably about −200 mV or higher, usually by adding an oxidizing agent such as oxygen or nitrates. After these conditions are established, sulfur oxidizing bacteria are added to the body. These preferably include Paracoccus denitrificans (formerly called Thiosphaera pantotropha) ATTC number 35,512. The sulfur oxidizing bacterial population should be established at levels of at least about 1×104 cfu/mL and more preferably at levels of 1×105 to 1×106 cfu/mL or higher. The increased ORP and pH levels make sulfate reduction thermodynamically unfavorable.

Abstract: A method of removing pollutants from porous, solid materials uses a biomass loaded onto a support. The biomass is put into contact with a pollutant contaminated porous, solid material so that the bacterial biomass degrades the pollutant. The moisture level of the support and biomass are maintained at a level that optimizes pollutant removal and is a function of the relative solubility of the pollutant.

Abstract: A process and system are disclosed for the biofiltration of volatile organic compounds. The process involved recirculating contaminated effluent gas through a biofilter (1), the biofilter (1) having an inlet (20), outlet (15) and micro-organism laden filter media bed (3). The filter media bed additionally having moisture retaining properties. This process has been effective in removing high levels of VOCs from effluent gas streams and also in removing VOCs from an effluent gas stream where the VOC levels and/or volumes of effluent gas vary over time.

Abstract: The inventors have isolated lysophospholipases from Aspergillus (A. niger and A. oryzae) having molecular masses of about 68 kDa and amino acid sequences of 600-604 amino acid residues. The novel lysophospholipases have only a limited homology to known amino acid sequences. The inventors also isolated genes encoding the novel enzymes and cloned them into E. coli strains.

Abstract: The air in a room can be cleaned of ammonia by passing the air through green plants grown hydroponically. The air passes through a falling curtain of droplets of the hydroponic water, whereby the ammonia goes into solution in the water. Microbes colonised on the roots of the green plants break down the ammonia in the hydroponic water, and assimilate the nitrogen into the plant tissue.

Abstract: What is disclosed is a conditioning agent for the treatment of effluent and a process for preparing such a conditioning agent which includes a proportion of flocculating or precipitating agent containing polymers as well as a proportion of micro-organisms.

Abstract: A method of composting especially high protein waste which reduces noxious odor and assists in reducing pathogens by recirculating substantially only the air and gaseous product of the composting process through the composting materials which are separated by layers of absorbent chips.

Abstract: A multi-stage malodorous or noxious gas purification system comprises: purifiers for extracting unnecessary ingredients from gas including such unnecessary ingredients; a plurality of unitary purification tanks each having a filling space for filling the purifiers therein and an inlet opening and an exit opening for the gas to pass through the filling space; and at least one connecting member being gas-permeable and installed at the inlet opening or the exit opening of each unitary purification tank, for isolatedly connecting the plurality of unitary purification tanks, wherein two or more different kinds of the purifiers are used.

Abstract: The invention relates to a system for purifying exhaust gases, comprising at least two filter stages (1, 2, 3), including at least one filter stage (1) for purifying the exhaust gases from particulate and aerosol-containing substances, and at least one filter stage (2) in the form of a biological filter for purifying the exhaust gases from organic compounds, aerosols and other odor-intensive substances by means of microorganisms. The second filter stage comprises a mass transfer zone (9) in which the exhaust gases are transformed from the gas phase to the liquid phase by the atomization of wash water. The aim of the invention is to provide a simple and inexpensive system with which high purification rates can be achieved. To this end, at least one filter stage (1, 3) is configured as a spray tower or wet electric filter using wash water, and the system is provided with means for maintaining a constant temperature in the thermophilic temperature range of from 45° C. to 75° C.

Abstract: A method for treating an organic exhaust gas comprises the following steps. First, an organic exhaust gas containing a harmful substance is generated. Then, a treating liquid is provided. The organic exhaust gas is contacted with the treating liquid so as to dissolve the harmful substance into the treating liquid. Finally, bacteria are contacted with the treating gas containing the harmful substance so that the harmful substance is biochemically degraded.

Abstract: The present invention relates to a biological filter for the purification of waste gases comprising a bed of biologically active carrier material consisting of pith extracted from coconut husks, the bed being contained such that the waste gases are brought in contact with the said bed and removed from the bed at points spatially separated from the inlet points.

Abstract: A process is disclosed for purifying a gas stream containing a contaminant gas and an energetic gas. The process comprises the steps of: a) providing a bioreactor comprising:-a reaction chamber containing a solvent and a biocatalyst capable of catalyzing a transformation reaction of said contaminant gas dissolved in the solvent into ions. The process further comprises the step of b) extracting the contaminant gas from the gas stream, which extraction comprises feeding the gas stream in the reaction chamber and thereby allowing the contaminant gas to dissolve and transform into ions, yielding said energetic gas free of said contaminant gas and leaving a spent solvent containing said ions in solution. Then, in step c) the energetic gas and the spent solvent obtained in step b) are separately released from the reaction chamber. The process further comprises the steps of d) removing the ions from the spent solvent to recycle the solvent; and e) feeding the recycled solvent of step d) in the reaction chamber.

Abstract: A filter system for removing organic, odor-causing substances from air has a filter bed which includes porous, particulate, non-compostable material and microorganisms capable of digesting the odor-causing substances. The particulate material of the bed is preferably lava rock, pumice or sandstone. A method of filtering air which contains organic, odor-causing substances, such as exhaust air from a process of thermophilic bacterial digestion of organic waste matter, includes providing a filter bed of particulate, porous, non-compostable material, inoculating the filter bed with a culture of microorganisms and passing the air through the filter bed.

Abstract: Air laden with biodegradable volatile organic compounds is passed sequentially through a first filter bed containing a biologically inert filter media, a second filter bed containing a biologically active filter media, and a third filter bed containing a biologically inert filter media. Water is present in the biologically active filter media and the biologically inert filter media. Water that drains from the second filter bed is collected and supplied to the first filter bed. Water that drains from the third filter bed is collected and recirculated to the third filter bed.

Abstract: CO2 is separated from waste gases by known technical methods and stored in underground cavities. By additions to the CO2, according to the invention, of H2 or NH3, methanogenic bacteria, bacteria substrate, catalysators and/or inhibitors the CO2 is reduced during the underground storage to CH4. The storage is possible in aquifer, natural gas reservoirs or oil and/or gas generating rock formations. Due to the equal volumes of CO2 and CH4 the process is a closed cycle and of constant pressure. Natural gas becomes a renewable energy.

Abstract: A ventilation system is disclosed for an enclosure in which people live. The ventilation system comprises a first ducting means for ducting fresh air from outside to inside the enclosure and a second ducting means for ducting stale air. The second ducting means comprises a stale air inlet for receiving stale air containing carbon dioxide from inside the enclosure and an exhaust manifold having a first vent to exhaust air outside the enclosure and a second vent in fluid communication with the first ducting means to return clean air into the first ducting means. The ventilation system is further characterised in that it comprises catalysing means for catalysing hydration of carbon dioxide contained in at least a portion of the stale air into a solution of carbonate ions and hydrogen ions, and thereby removing carbon dioxide from said portion of the stale air and obtaining clean air. Evacuating means are also provided for evacuating the solution out of the ventilation system.

Abstract: The invention relates to a composition and method for controlling odors, the composition containing an activated lignin-derived complex containing a histosol compound, and optionally containing a hydrolytic enzyme, or at least one microorganism capable of providing the hydrolytic enzyme, or a combination of hydrolytic enzyme and at least one microorganism capable of providing the enzyme. The composition can be applied to holding tanks, portable toilets, pulp and paper mills, and other loci giving rise to noxious odors, in particular, to hydrogen sulfide emission.

Abstract: A process and apparatus are provided for reducing volatile organic compound content, e.g., benzene content, of a hydrocarbon-containing gas stream, e.g., a refinery waste vapor stream by contacting the stream, preferably in a single pass, with an aqueous liquid medium containing volatile organic compound-metabolizing microbes, e.g., Bacillus subtilis, under volatile organic compound-metabolizing conditions. A treated stream results which contains volatile organic compound metabolization products of volatile organic compounds, e.g., water and carbon dioxide, and substantially reduced volatile organic compound content.

Abstract: A novel stack application for improved carbon dioxide and particle removal/collection from flue gases produced during coal power-generation processes. Flue gas tangential inlet velocity is increased to subject upward-flowing flue gas in a stack to a centrifugal force, thereby propelling entrained solid particles and CO2 in the flue gas to the stack wall for collection. Collection efficiency is further improved by a cascading water film or algae-laden water film on the inside of the stack wall and on surfaces of an optional internally mounted vortex generator to eliminate the re-entrainment of small particles and for ease of transporting the captured particles in a slurry. The stack can also be utilized as a photochemical or a biological reactor to promote a photosynthesis reaction between carbon dioxide and algae-laden water to form carbohydrate substrates for carbon dioxide sequestration and utilization.

Abstract: A system and method for the accelerated decontamination of contaminated soil, vadose zone and/or groundwater is described. Contaminates are removed from soil and from the groundwater via heat injection through trenching or directionally drilled or horizontally drilled and installed delivery plumbing, pure oxygen injection through separate plumbing installed in the same manner as the plumbing used to deliver the heat, bioventing, sparging, and bioremediation, all through the oxygen delivery plumbing, and soil vapor extraction through vertical wells, all contained in one mobile treatment system. Contaminants are separated from the soil gas via filtration or oxidation. Residual contaminants in the vadose zone and/or the in the groundwater are subjected to volatilization by increased temperature via heat injection and/or oxidation via contaminant degrading microorganisms.

Abstract: A process is disclosed for purifying a gas stream containing a contaminant gas and an energetic gas. The process comprises the steps of: a) providing a bioreactor comprising:—a reaction chamber filled with a solvent containing a biocatalyst capable of catalyzing a transformation reaction of said contaminant gas dissolved in the solvent into ions. The process further comprises the step of b) extracting the contaminant gas from the gas stream, which extraction comprises feeding the gas stream in the reaction chamber and thereby allowing the contaminant gas to dissolve and transform into ions, yielding said energetic gas free of said contaminant gas and leaving a spent solvent containing said ions in solution. Then, in step c) the energetic gas and the spent solvent obtained in step b) are separately released from the reaction chamber.

Abstract: The present invention relates to a fusion protein having enhanced in vivo activity of erythropoietin wherein a carboxy terminal peptide fragment of thrombopoietin is fused with the carboxy terminal of human erythropoietin. This fusion protein has highly enhanced in vivo half-life due to increased carbohydrate content without loss of the inherent activity of erythropoietin, and does not cause any antigenicity when applied to the human body.

Abstract: A garbage disposing device includes a treatment chamber used to decompose food wastes by a microorganism, intake passage, exhaust passage, and a return path extending from a diverging portion in the exhaust passage to the treatment chamber. An exhaust airflow adjuster is provided at the diverging portion. A control unit controls the exhaust airflow adjuster such that after water and ammonia in an air exhausted from said treatment chamber are adsorbed by a dehumidifier provided in the exhaust passage, a part of the air is returned to the treatment chamber through the return path, and the remaining air is exhausted to the outside through a deodorizer. As a result, a small deodorizer is available, and the garbage disposing device can be small-sized as a whole. In addition, it is possible to save energy used for the decomposing treatment of the food wastes.

Abstract: The present invention is waste treatment apparatus and process for diminishing the emission of malodorous off-gases during waste treatment. The apparatus typically includes a floatation panel formed from bonded foam particles that is adhered to a fabric layer. The present invention provides a reliable, cost-effective means by which to decrease the noxious odors generally associated with waste treatment.

Abstract: The present invention relates to a biological filter for the purification of waste gases comprising a bed of biologically active carrier material consisting of pith extracted from coconut husks, the bed being contained such that the waste gases are brought in contact with the said bed and removed from the bed at points spatially separated from the inlet points.

Abstract: It is biological deodorizing apparatus that has an inlet portion (1), a treating portion (2) and an outlet portion (3) in a series, and biologically deodorizes gas in said treating portion. Each of frames of said portions is composed of one or more rectangular hexahedron box-like frame units (6) constructed by connecting frame members (4) and joints (5). The treating portion is constructed containing cartridges (11) being set by several porous plastic sheets (10) in parallel with each other at a distance can be pulled out free in horizontal direction. The treating portion's blow-off surfaces (13) is connected to lower located blow-in surfaces (14) of the outlet portion in airtight condition, and open surfaces (15) are sealed with seal panels (16). Water is supplied to upper portion of said treating portion, and drained off through bottom portion.

Abstract: A cartridge for holding compost in a biofilter is substantially uniform in cross section perpendicular to the axis of the cartridge and has a sidewall formed with openings that are small enough to substantially retain the compost in the cartridge yet large enough to allow filaments of bacteria present in the compost to project through the openings. The cartridge is of cross-sectional form such that multiple cartridges can be placed side-by-side in an array with passages between each cartridge and adjacent cartridges.

Abstract: A biofilter apparatus includes at least one container having a height, length, and width containing a deep, low density, porous media within the container. An airflow apparatus is constructed and arranged to deliver a flow of air to be treated to the filter media. The airflow apparatus provides at least 37.5 cfm/ft2 with the porous media creating a backpressure of not more than about 10 inches of water. The media preferably consists of about 30-40% shredded tree bark particles, about 30-40% shredded wood, and about 30-40% composted wood sized such that 95% of the media will pass through a three inch screen and be retained by a 0.5 inch screen. A fluid mister may be provided in fluid communication with the flow of the air to be treated for introducing humidity to the air. The method for treating air via biofiltration utilizes the biofiltration apparatus discussed above and includes directing contaminated air into the container through the airflow apparatus and through the media at at least 37.

Abstract: A process is disclosed for the extraction, production and purification of carbon dioxide gas. The process may also be employed for the production of aqueous and/or organic solutions of bicarbonate ions using a precursor feed stream of gas containing carbon dioxide. The process consists of the countercurrent flushing of a packed tower-type bioreactor with gas containing carbon dioxide and a liquid solvent. The bioreactor contains carbonic anhydrase covalently bound to an inert inorganic support. The carbon dioxide of the gaseous phase diffuses into the liquid phase. The immobilized carbonic anhydrase catalyses the hydration of the carbon dioxide which forms hydrogen and bicarbonate ions. The solution of ions may be employed directly or, alternatively, subjected to an ion-exchange resin to immobilize the bicarbonate ions. The aqueous solution of hydrogen and bicarbonate ions may also be recirculated into a second identical bioreactor, wherein they are catalytically converted to water and carbon dioxide.

Abstract: The invention discloses a method for processing alkene-containing exhaust gas. It is a combination of ozonic and biological processes which mainly deal with exhaust gas mixtures having alkene-containing (C—C double bond) organic exhaust gas (such as alkene, acrylic acid) and other volatile organic compounds (such as ketone, alcohol, BTEX, and others). Since exhaust gas containing C—C double bond is difficult to dispose of, the method for processing exhaust gas presented in the invention utilizes ozone to completely decompose or transform the organic contaminants with C—C double bonds into intermediate products. The organic contaminant can then be treated in the biological process and converted into non-toxic substances. This method does not require large-sized biological process equipment, and the residual ozone is oxidized and degraded in the bio-filter.

Abstract: The inventors have isolated lysophospholipases from Aspergillus (A. niger and A. oryzae) having molecular masses of about 68 kDa and amino acid sequences of 600-604 amino acid residues. The novel lysophospholipases have only a limited homology to known amino acid sequences. The inventors also isolated genes encoding the novel enzymes and cloned them into E. coli strains.

Abstract: The present invention relates to an apparatus and a method removing contaminated gas by a biofilter resolving malodorous substance and volatile organic compounds, included in the waste gas generated from industrial and environmental facilities, into innoxious substances such as water, microorganism and carbon dioxide by means of microorganism

Abstract: A triphasic bioreactor for physico-chemically treating a gas is disclosed. The triphasic bioreactor comprises a reaction chamber with a liquid and biocatalysts in suspension in the liquid, for catalyzing a reaction between the gas and the liquid to obtain a treated gas and a solution containing a reaction product. A gas bubbling means is provided in the reaction chamber for bubbling the gas to be treated into the liquid thereby dissolving the gas into the liquid and increasing a pressure inside the reaction chamber. The bioreactor further comprises a liquid inlet in fluid communication with the reaction chamber for receiving the liquid and filling the reaction chamber, a liquid outlet in fluid communication with the reaction chamber for releasing the solution and a gas outlet in fluid communication with the reaction chamber to release the treated gas. The bioreactor further comprises a retention device to retain the biocatalysts in the reaction chamber.

Abstract: A system and a method for purifying a gaseous contaminated stream are provided. The system and method include a treatment solution that includes at least one non-pathogenic bacteria that digests at least a portion of contaminants contained in the contaminated stream.

Abstract: Biochemical decomposition of undesirable gaseous contaminants, including nitrogen oxides, VOC's, carbon monoxide and sulfur oxides, and malodorous contaminants, is achieved by passing a gas stream through a managed landfill providing microbiological activity capable of degrading the contaminants. Gases suitable for treatment include fuel combustor exhaust, landfill gases, putrescent gases and the like. The landfill functions as a biological reactor (bioreactor), where water is added if or as necessary to achieve concentrations between about 20% and about 65% by weight, and desired microbial contaminant abatement action. By a permeation of the polluted gas through the landfill, there is a consumption of polluting gases by microorganisms present in the landfill. The process enables increased combustion of fuels, such as landfill gases, whose energy values are currently wasted or are not available due to emissions problems.

Abstract: A process is described for the biological treatment of waste water containing ammonia, wherein the waste water is treated with sludge containing nitrifying bacteria in an aerated reactor, applying a sludge retention time in the reactor which favours nitrite-producing bacteria over nitrate-producing bacteria. The process is characterised by applying a hydraulic retention time in a continuously operated reactor, which is shorter than the sludge retention time as a result of part of the sludge being separated from the reactor effluent and being returned to the reactor. The performance of the nitrification is further improved by applying low oxygen and nitrite concentrations.

Abstract: Air laden with biodegradable volatile organic compounds is passed sequentially through a first filter bed containing a biologically inert filter media and a second filter bed containing a biologically active filter media. Water is present in the biologically active filter media and the biologically inert filter media. Water that drains from the second filter bed is collected and supplied to the first filter bed.