Showing papers on "Trickling filter published in 1994"

Biological vapor‐phase treatment using biofilter and biotrickling filter reactors: Practical operating regimes

Abstract: The biological treatment of volatile organic compounds (VOCs) and air toxics has received increased attention in recent years. Biotreatment of airborne contaminants offers an inexpensive alternative to conventional air treatment technologies such as carbon adsorption and incineration. Most biological air treatment technologies commercially available are fixed-film systems that rely on growth of a biofilm layer on an inert organic support such as compost or peat (biofilters), or an inorganic support such as ceramic or plastic (biotrickling filters). If designed properly, these systems combine the advantages of high biomass concentration with high specific surface area for mass transfer. At economically viable vapor residence times (1 to 1.5 minutes), biofilters can be used for treating vapor streams containing up to approximately 1500 [mu]g/L of readily biodegradable compounds. Biotrickling filters may offer greater performance than biofilters at high contaminant loadings, possibly due to higher internal biomass concentrations. Both systems are best suited for treating vapor streams containing one or two major compounds. If designed properly, biofilters are especially well suited for treating streams that vary in concentration from minute to minute. 11 refs., 8 figs.

The existence of a biological equilibrium in a trickling filter for waste gas purification.

Abstract: Clogging is a well-known phenomenon in the application of a biological trickling filter for both waste gas and wastewater treatment. Nevertheless, no such observations or even significant changes in pressure drop have ever been recorded during the long-term processing of a waste gas containing dichloromethane (DCM) as a sole carbon source. To obtain more information about this phenomenon, a detailed investigation into the carbon balance of this system has been performed. During a period of operation of about 200 days the rate of DCM elimination and the overall rate of CO, production in a continuously operating filter were therefore recorded daily, thus allowing an evaluation of the overall conversion process. Furthermore pseudo-steady-state measurements were carried out on a regular basis. These experiments reveal more detailed information on the actual DCM conversion by Hyphornicrobiurn GJ21 within the biofilm. The combined results of the experiments described in this article show that on an overall basis a so-called biological equilibrium, i.e., a situation of no net biomass accumulation, is obtained in the course of time. It appeared that the overall rate of CO, production slowly increased until, after some 200 days, it finally counterbalanced the conversion rate of DCM on a molar basis. As opposed to this result, all pseudo-steady-state experiments indicated that about 60% of the eliminated primary carbon source is converted into biomass. This is in good agreement with results from microkinetic experiments. Based on these results and evaluation of the experimental data, it is concluded that interactions between several microbial populations are involved in this biological equilibrium. These interactions include both biomass growth and biomass degradation. 0 1994 John Wiley & Sons, Inc.

Design and performance of a trickling air biofilter for chlorobenzene and o-dichlorobenzene vapors.

Abstract: From contaminated industrial sludge, two stable multistrain microbial enrichments (consortia) that were capable of rapidly utilizing chlorobenzene and o-dichlorobenzene, respectively, were obtained. These consortia were characterized as to their species composition, tolerance range, and activity maxima in order to establish and maintain the required operational parameters during their use in biofilters for the removal of chlorobenzene contaminants from air. The consortia were immobilized on a porous perlite support packed into filter columns. Metered airstreams containing the contaminant vapors were partially humidified and passed through these columns. The vapor concentrations prior to and after biofiltration were measured by gas chromatography. Liquid was circulated concurrently with the air, and the device was operated in the trickling air biofilter mode. The experimental arrangement allowed the independent variation of liquid flow, airflow, and solvent vapor concentrations. Bench-scale trickling air biofilters removed monochlorobenzene, o-dichlorobenzene, and their mixtures at rates of up to 300 g of solvent vapor h(-1) m(-3) filter volume. High liquid recirculation rates and automated pH control were critical for stable filtration performance. When the accumulating NaCl was periodically diluted, the trickling air biofilters continued to remove chlorobenzenes for several months with no loss of activity. The demonstrated high performance and stability of the described trickling air biofilters favor their use in industrial-scale air pollution control.

The influence of NaCl on the degradation rate of dichloromethane by Hyphomicrobium sp

Abstract: The degradation of dichloromethane by the pure strainHyphomicrobium GJ21 and by an enrichment culture, isolated from a continuously operating biological trickling filter system, as well as the corresponding growth rates of these organisms were investigated in several batch experiments. By fitting the experimental data to generally accepted theoretical expressions for microbial growth, the maximum growth rates were determined. The effect of NaCl was investigated at salt concentrations varying from 0 to 1000 mM. Furthermore the dichloromethane degradation was investigated separately in experiments in which a high initial biomass concentration was applied. The results show that microbial growth is strongly inhibited by increased NaCl concentrations (50% reduction of μmax at 200–250 mM NaCl), while a certain degree of adaptation has taken place within an operational system eliminating dichloromethane. A critical NaCl concentration for growth of 600 mM was found for the microbial culture isolated from an operational trickling filter, while a value of 375 mM was found for the pure cultureHyphomicrobium GJ21. The substrate degradation appears to be much less susceptible to inhibition by NaCl. Even at 800 mM NaCl relatively high substrate degradation rates are still observed, although this process is again dependent on the NaCl concentration. Here the substrate elimination is due to the maintenance requirements of the microorganisms. The inhibition of the dichloromethane elimination was also investigated in a laboratory scale trickling filter. The results of these experiments confirmed those obtained in the batch experiments. At NaCl concentrations exceeding 600 mM a considerable elimination of dichloromethane was still observed for during several months of operation. These observations indicate that the inhibition of microbial growth offers a significant control parameter against excessive biomass growth in biological trickling filters for waste gas treatment.

Growth and macronutrient removal of water hyacinth in a small secondary sewage treatment plant

Abstract: Studies have been made of the growth characteristics of water hyacinth, Eichhornia crassipes (Mart.) Solms, and its ability to remove N, P and K, in a secondary settling pond of a small secondary sewage treatment plant serving both the academic and residential blocks of the Swire Marine Laboratory, University of Hong Kong. The treatment plant consists of, in series, a primary settling tank, a trickling filter compartment and a secondary settling pond from which part of the treated wastewater is recycled to the primary settling tank while the remaining effluent (1 to 2 m3 daily) mixes with and hence is diluted by the outflowing seawater from the aquarium system of the Swire Marine Laboratory before discharge to the sea. Samples of wastewater have been taken regularly from the primary sedimentation pond, the outflow of the trickling filter, the secondary settling pond and the effluent of the treatment plant (before mixing with aquarium outflow) since January, 1992. Physical, chemical and biological characteristics of the samples have been determined and are typical of secondary effluents, with a mean pH of about 7.5, total solids 1200 mg L−1, suspended solids 45 mg L−1, conductivity 2000 μS cm−1, salinity 1 ppt, dissolved oxygen 2 mg L−1, BOD5 45 mg L−1, Kjeldahl-N 30 mg L−1, NH4,-N 25 mg L−1, NO3-N 4 mg L−1, total P 10 mg L−1, K 35 mg L−1 and total coliforms of less than 105 colonies 100 ml−1. Water hyacinth plants have been stocked in the secondary settling pond as an integral part of the treatment plant so as to improve the quality of, as well as to retrieving and recycling nutrient elements from, the wastewater. The plants are periodically harvested to maintain an active growing crop. The growth rate, standing crop biomass, tissue nutrient composition, nutrient storage and accumulation rate of two growth cycles, one from February 25 to March 18 (mean temperature 17.6°C) and the other from 22 April to 12 May (24.8°C) are reported. The water hyacinth assumed a relatively high standing crop biomass of 10 kg m−2 (5 to 6 t DM ha−1), and growth rates of 48 and 225 g m−2 day−1, respectively, for the first and second growth period. Nutrient storage capacities were relatively high, at about 20, 7.5 and 16.5 g m−2 for N, P and K, respectively. The nutrient composition was very high, reaching 5.42% for N, 1.97 for P, and 4.57 for K. Both the stem and lamina accumulated high levels of N, while the petiole had the highest level of P and K. Apart from nutrient removal, the water hyacinth also helped to decrease the suspended solids, BOD5 value and total coliforms of the wastewater. It is concluded that water hyacinth improves the quality of wastewater in such small-scale sewage treatment plants and it is recommended that frequent harvests of water hyacinth would increase the treatment efficiency, especially during the active growing season with high temperatures coupled with intense solar radiation.

Oxygen utilization of trickling filter biofilms

Abstract: In-situ oxygen consumption rate (OCR) observations for trickling filter biofilms under different hydraulic, substrate loading, and oxygen availability operating conditions are presented. OCRs were determined for sucrose- and dextrin-based synthetic feedstocks by growing biofilms on a 1.2-m deep section of 60° cross-flow media that was enclosed within a reactor vessel, sealing the reactor vessel to outside air entry, and observing the time rate of decrease in the reactor’s oxygen partial pressure. The results indicate that OCRs increased proportionately with increasing influent substrate concentrations for the 40 to 120 mg/L SCOD range, increased slightly or remained relatively constant with increasing influent substrate concentrations for the 120 to 200 mg/L SCOD range, increased slightly with increasing DO saturation condition for the 7.4 to 10.1 mg/L range, were affected by oxygen availability for influent substrate concentrations throughout the 70 to 175 mg/L SCOD range, increased with increasing hydraulic application rate from 2.4 to 4.9 m³/m²-h, and were slightly greater than predicted by currently acknowledged models. Other observations include the following measured OCRs were at least three times greater than those estimated from clean media oxygen-transfer testing; without liquid and feedstock application, biofilms consumed oxygen at 80–104% of their usual rate; and maximum biofilm oxygen consumption was ≈680 mg/m²-h.

Modelling the dynamics of a trickling filter for waste water treatment

Abstract: This study concerns the dynamics of the nitrifying efficiency of a trickling filter for waste water treatment. In a novel approach, based on minimum plant area usage, a filter will be placed after the secondary sedimentation tanks with recirculation to the activated sludge process stage. The objective of the trickling filter model is to describe the growth of the nitrifying bacteria Nitrosomonas and Nitrobacter in the bio-film. A steady state mass-balance model for the substrates in the film based on Monod kinetics has been formulated. The dynamics of the filter, or the "memory", is described by a division of the film in four volume fractions, Nitrosomonas, Nitrobacter, inert (non-active) material and water. These fractions are calculated at different depths of the film as well as for various layers of the filter structure. Data from a pilot plant at Rya treatment plant in Gothenburg, Sweden, have provided the necessary feedback for calculating model parameters, verifying assumptions etc. A shooting and matching routine in the NAG Fortran library is used for the solution of the model equations. Simulations performed so far have indicated that it can take days and even weeks for changes in the bacteria populations to take place. This means that the working point for the proposed full scale filter at the plant should track the past history of the filter. >

Mechanical ventilation system to capture gases released from wastewater passing through rock media trickling filters

Abstract: A trickling filter for treating and purifying wastewater, including a bed of filter media adapted to receive and support aerobic bacteria for reacting with the wastewater, and rotating radial areas for distributing the wastewater over the surface face area of the bed of filter media. Drainage blocks for collecting treated wastewater and reacted air are disposed below the bed of filter media collection channels for collecting air and treated wastewater from the drainage blocks. Air-discharge ducts are connected to the collection channels for discharging the reacted air to a scrubber, and water-discharge ducts are connected to the collection channels for discharging the treated wastewater from the filter. Fans create a negative air-pressure flow through the filter media collection channels, vent pipes, and the air-discharge ducts to draw the reacted air to a scrubber for filtering the reacted air.

Biological waste gas treatment

Abstract: Publisher Summary Biological waste gas treatment systems combine physical (gas/liquid or gas/solid mass transfer) and biological processes (biodegradation/biotransformation). The potential field of application is very broad because inorganic as well as volatile organic compounds (VOC) can be removed from waste gases by these techniques. Three types of conventional biological waste gas treatment systems are distinguished: bio-filters, trickling filters, and bio-scrubbers. They differ by the presence or absence of a mobile liquid phase and the type of biology (bioflocs or biofilms). Non-conventional systems such as the solvent vector bioreactor and the membrane reactor are investigated on lab or pilot scale. Organic sulfur degrading microorganisms were isolated from soil samples. Different operational characteristics were determined. The isolated cultures were used to construct a bio-filter to eliminate methyl sulfides from waste gases. From the experiments it became clear that the filter has to be inoculated otherwise the performance is low.

Process for improving wastewater clean up in trickling filter units

Abstract: To improve the clean up efficiency in biological wastewater (effluent) clean up in trickling filter units, it is proposed to enrich the wastewater with technical-grade oxygen prior to entry into the trickling filter 13. Preferably, the technical-grade oxygen is incorporated into the wastewater via perforated gas-introduction tubes 5 in a prepurification vessel 4 upstream of the trickling filter 13. In this manner, toxic wastewater constituents, in particular hydrogen sulphide, can be oxidised even before entry of the wastewater into the trickling filter 13. Thus the risk of some of the biomass colonising the trickling filter 13 dying off because of the pollution of the wastewater with toxic substances is reliably averted. Moreover, odour pollution due to spraying fouled wastewater over the trickling filter packing material 15 by means of a spraying rake 14 is avoided.

Treatment plant for wastewater

Abstract: In a treatment plant for wastewater, there are provided, in a shared housing 2, a chamber 3 for a trickling filter 4, a final clarification tank 10 and, separated from these by a wall 15, a pump chamber 5. In the final clarification tank 10 which is disposed immediately under the chamber 3 for the trickling filter 4, there is provided a pump 25 from which there departs a line 26 which leads to a digestion chamber which is connected upstream of the trickling filter 4. From the final clarification tank 10 wastewater flows through an overflow 17 in the wall 15 into the pump chamber 5. In the pump chamber 5 there is provided a pump 28 from which a line 29 departs which leads to a soil filter chamber. In this line 29 is provided a three-way valve 30 from which a pipe branch 31 departs which ends above the trickling filter 4.

Nitrification in Single-Stage Trickling Filters

Abstract: An assessment of nitrification of municipal wastewater in trickling filters was performed using operating data from wastewater treatment facilities currently in operation. A survey of trickling filter use in the United States, found twenty-seven plants accomplishing some degree of nitrification. Of the twenty-seven plants ten were identified as having operating data sufficient for further analysis. Although most of the plants evaluated were not designed as single-stage systems they all provided sufficient data to evaluate trickling filter performance as a single-stage system. The evaluated plants were generally meeting their permit requirements, including ammonia-nitrogen limits when applied. Analysis of the data compared favorably with the BOD loading rates suggested by the EPA Process Design Manual for Nitrogen Control.

Nitrification of ammonia polluted air in trickling filters

Abstract: The macro-kinetic behavior of a 12 dm3 nitrifying biotrickling filter and micro-kinetic behavior of 2 mm nitrifying aggregates from a fluidized bed reactor were investigated. Micro-kinetics were studied with micro-electrodes for O, pH, NH4+, and NO3-. The tip diams. of .apprx.2 mm allow a sufficient spatial resoln. at negligible substrate consumption. The goal is to understand macro-kinetics in terms of the local kinetics in a nitrifying biofilm to optimize trickling filter design. [on SciFinder (R)]

Tertiary nitrification of wastewater in trickling filters

Abstract: This study was designed to investigate, at laboratory and pilot scale, the effects of various loading and climatic factors on the nitrification perfon-nance of four media, and to undertake a comparative assessment of the media. The media used were blast furnace slag and three random plastic media: Flocor RS, Etapak 160 and a new medium, Etapak 210. Laboratory experiments using pure cultures of Nitrosomonas europaea have determined the effect on nitrification of temperature, pH and substrate, BOD and inhibitor concentrations. Optimal values have been resolved for the temperature and pH and halfsaturation constants for the substrate and inhibition are calculated for pure culture conditions. The presence of glucose and glutamic acid has been shown to have a beneficial effect on nitrification, although this observation could not be adequately explained. Pilot scale research, conducted over a two year period, has provided an accurate representation of a nitrifying trickling filter by using effluent from Cranfield STW in filters exposed to the full climadc variation. Data obtained from these filters have indicated the superior performance of the blast furnace slag media due mostly to its ability to maintain a large active bacterial Population without excessive accumulation. Results have been used to support or challenge previous publications, and to generate a set of desion curves. Conclusions from this research have been used in the design of a full scale nitrifying trickling filter which has been constructed at Cranfield STW, early data from which are 4: 5 presented.