Biofilter

Other than the biofilter and culture chambers, recirculating systems typically also employ one or more settling chambers or mechanical filters to remove soHds such as unconsumed feed, feces, and mats of bacteria that slough from the bio filter into the water. Each recirculating system requires a mechanical means of moving water from component to component. That usually means mechanical pumping, though air-lifts can also be used. 

Of course the presence of a Hquid phase of hydrocarbon in a soil gives rise to vapor contamination in the vadose zone above the water table. This can be treated by vacuum extraction, and the passage of the exhaust gases through a biofilter (see above) can be a cheap and effective way of destroying the contaminant permanently. 

Air. Biofilters are an effective way of dealing with air from industrial processes that use halogenated solvents such chloromethane, dichioromethane, chloroethane, 1,2-dichloroethane and vinyl chloride, that support aerobic growth (26). Both compost-based dry systems and trickling filter wet systems are in use. Similar filters could be incorporated into pump-and-treat operations. 

Yang, Yonghua and Eric R. Allen, Biofiltration Control of Hydrogen Sulfide. 2. Kinetics, Biofilter Performance, and Maintenance, yAWA. vol. 44, p. 1315. 

The basic biofilter process steps involved are shown in Fig. 25-17 and are as follows ... 

Design and Construction The capacity and efficiency of biofilter operation are a direc t function of active surface area, filter void... 

Raw Gas Preconditioning In order to ensure the required destruction efficiency and continued biofilter life, the raw gas stream must be adjusted to a preselected range of particulate loading, temperature, and humidification before the gas can be safely introduced into the biofilter. 

In terms of an economic determination, gas temperature adjustment is often the most important cost factor in determining whether to use a biofilter or a more conventional system. If the process gas stream is at an extremely high temperature (-i-I00° C), the cost of cooling the inlet gas stream might favor more conventional methods for odor control such as thermal oxidation. 

The filter media should have buffering capacity in order to maintain a pH of at least 3. This is especially a concern when inorganic compounds are targeted for reduction by the biofilter. 

Kinetics The capacity and efficiency of biofilter operation is a function of active surface area, filter void space, target removal efficiency, gas species, gas concentration, and gas flow rate. A simphfied theoretical model described by S.P.P. Ottengraf et al. is schematically represented by in Fig. 25-18. The mass balance made around the hq-uid-phase biolayer can be described as follows ... 

One of the hsted assumptions for Ottengraf s kinetic model was that no gas-phase interactions occur between different chemical species (the ideal-gas assumption). Under ac tual operating conditions, gas-phase interactions can either have a negative or positive impact on biofilter operation. These interactions include ... 

Based upon the above-mentioned species interactions, pilot-scale testing is generally recommended to accurately size a biofilter bed for a multicomponent waste gas stream. 

Many compounds can cause problems in pollutant-control equipment. Particulate matter, liquids, or solids in the waste stream can plug the adsorber beds, heat-recovery beds in regenerative thermal incinerator systems and biofilters. Conventional filtration systems are used to remove particulate matter before or after the process. 

Generally, adsorption, absorption, and biofilter units require more space than compact incinerators and condensers. If the plant room is restricted, a local roof-mounted system may be the best alternative. However, roof structural reinforcement may be required even for small and lightweight units. Consideration must be given to the effects of noise and vibration. Small adsorption systems, such as adsorption canisters, require an additional central regeneration unit on site, or they must be regenerated or disposed of off site. A central regeneration unit may require long runs of costly ductwork." ... 

Styrene-degrading bacteria from full-scale and experimental biofilters were exposed to [ HJstyrene, and analysis of fatty acids was used to distinguish the bacterial flora of the two systems (Alexandrino et al. 2001). 

Alexandrine M, C Knief, A Lipski (2001) Stable-isotope based labeling of styrene-degrading microorganisms in biofilters. Appl Environ Microbiol 67 4796-4804. 

Quinones, lipid-soluble substances involved in electron transport, can also be used as biomarkers. Lipski et al. (155) u.sed quinone analyses, physiological tests, and fatty acid profiles to differentiate Gram-negative non-fermentative bacteria isolated from biofilters. Quinone type was found to be an efficient method to group isolates prior to the analysis of results from the physiological tests. The detection of quinones appears to be restricted to the discrimination of isolated colonies and has limited potential to the analysis of mixed populations. 

A. Lipski, S. Klatte, B. Bendinger, and K. Altendorf, Differentiation of gram-negative, non-fermentative bacteria isolated from biofilters on the basis of fatty acid composition, quinone system, and physiological reaction profile, Appl. Environ. Microbiol. 58 2060 (1992). 

Biofilters. Microbial stripping columns are used to treat air or liquid emissions. 

The use of an attached growth aerobic biofilm reactor to treat leachate is relatively new. Past studies on anaerobic biofilters showed excellent organic removal up to 90%, and the retention time needed to treat high-strength effluent was between 3 and 5 d. The use of aerobic biofilters using... 

The aerobic biofilter used in the study had a capacity of 10 L. The reactor was packed to 60% of the empty bed volume with Cosmo ball media. The biofilter was seeded with active innoculum taken from an active aerated lagoon of a nearby landfill leachate treatment. Fresh raw leachate was used as feed to the reactor at a rate of 5 L/d over 24h. The loading rates applied to the bioreactor were between 1.6 and 22.2 kg COD/m3d. Initial studies were conducted as a batch process lasting for a period of 24 d. Thereafter, the biofilter was fed continuously for a total period of 240 d. 

Biofilters—Processes in which contaminants are biodegraded in a fixed-film bioreactor, typically consisting of a bed of high surface area filter media, such as GAC, that acts as a support matrix for a thin film consisting of microbes that are acclimated to the biodegradation of MTBE or other contaminants. 

Polymer Labs. PLRP-S A 0.1% TFA in water B ACN UV 350 nm OTC in water, biofilter sand, sediment, trout tissues Dilution with acidic buffer containing EDTA, cleanup with Polymeric SPE cartridge DL = 0.04 ppm (trout) 0.03 ppm (biofilter sand) 1 ppm (sediment), 0.003 ppm (water) Rec = 82-108% [48]... 

Cmz A, Buitron G (2001) Biodegradation of disperse blue 79 using sequenced anaerobic/ aerobic biofilters. Water Sci Technol 44(4) 159-166... 

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