Showing papers on "Trickling filter published in 1996"

Environmental monitoring for linear alkylbenzene sulfonates, dialkyltetralin sulfonates and their biodegradation intermediates

Abstract: Concentrations of linear alkylbenzene sulfonates (LAS), dialkyltetralin sulfonates (DATS), and their biodegradation intermediates are reported for the influents and effluents of 10 U.S. domestic wastewater treatment plants as well as upstream and downstream river waters and sediments. Three types of treatment facilities in 10 U.S. states were sampled and analyzed. Removals were calculated based on initial concentrations of LAS and DATS. A derivatization electron capture/gas chromatography/mass spectrometry method was employed. Its increased sensitivity and selectivity permitted the determination of environmental levels of LAS, DATS, and their biodegradation intermediates at low micrograms per liter (ppb) concentrations. The removal from four activated sludge and five trickling filter wastewater treatment facilities averaged 99.5% and 82.9% for LAS and 99.1% and 97.3% for LAS intermediates, respectively, for the activated sludge and trickling filter facilities. In the same plants, percent removals for DATS averaged 95% and 63.2% and DATS intermediates 59.1% and 58.7%, respectively. The removals obtained by a rotating biological contactor were similar to those observed in the activated sludge wastewater treatment facilities.

Effect of activated carbon on the biological treatment of oil-water emulsions

Abstract: Waste water, derived from the reprocessing of used emulsions or suspensions, contains high concentrations of emulsified mineral oil and stabilizers, as well as different additives that are needed during the treatment process. Two stirred-tank reactors and two fixed-bed reactors were used to study the biodegradation of these waste-water compounds during two-stage biological treatment. The waste water was first proceesed in an activated sludge reactor to remove easily biodegradable substances. The effluent from the first stage was treated in three parallel operating reactors: an activated sludge tank containing different amounts of powdered activated carbon (PAC, between 0 and 2%), an upflow anaerobic fixed-bed reactor and an aerobic fixed-bed reactor (trickling filter). The results from the continuous treatment were compared with laboratory batch experiments. About 60% of the influent TOC was reduced by the first activated sludge treatment. The removal efficiency increased to about 70% by using a second activated sludge stage. This degradation was comparable to the maximum degree of degradation measured in laboratory batch experiments. PAC addition to the second activated sludge tank resulted in increased degradation rates. The removal efficiency increased to about 76% when 0.1% PAC was added and to 96% with 1% PAC. The removal efficiency decreased to 84% when the proportion of PAC was further increased to 2%. Variations in the amount of PAC addition per unit influent volume in the range of 50 and 200 mg/l had no significant effect on the TOC removal. Degradation models based on the MONOD-type equation were found to be in close correlation with the results obtained from batch experiments. However, the biological removal rates measured in batch experiments did not reflect the removal capacity determined in continuous operating treatment systems.

Chemico‐biological treatment of dairy wastewater

Abstract: Examines the treatability of highly polluted wastewater from a dairy factory prior to its final disposal into the public sewerage system. Physical treatment of the dairy waste via aeration, followed by settling, resulted in a 25 per cent chemical oxygen demand (COD) reduction and elimination of odours. Chemical treatment achieved almost 50 per cent removal of COD. The chemical‐biological process using activated sludge/trickling filter resulted in 64 per cent and 90 per cent removal of the volatile organic matter value respectively. However, the quality of the waste produced does not meet with the National Regulatory Standards for wastewater disposal into the sewerage system. Chemical‐biological treatment using an upflow anaerobic reactor succeeded in reducing the pollutional parameters to coincide with the limits of the Egyptian Law 93/1962 and produces biogas as a source of energy at a rate of 0.39m3/kg COD removed.

Evaluation of presence of THM in chlorinated wastewater and selected removal techniques

Abstract: This paper investigates the presence of THM's in wastewater in and from various types of treatment plants and evaluates the efficiency of selected techniques for THM removal. Activated Sludge, Trickling Filters, and Rotating Biological Contactors, are the main processes in the two treatment plant systems that are considered for the purpose of this study. Samples of wastewater were collected from various points such as before chlorination, and after chlorination and in the effluent channel and analyzed for THM's using Gas Chromatography. The results have shown that chlorination process contributes significantly to THM formation. Chloroform removal efficiency were excellent by air stripping using either mechanical or diffused aeration (98%) and by using Activated Carbon as adsorber, which has achieved similar efficiency.

Comparison between Three Secondary Effluents in Tertiary High Rate Filtration

Abstract: The study of filtration of three secondary effluents (activated sludge, rotating biological contactor, and trickling filter) is presented. It was found that filter effluent does not exceed, in average, 3 NTU for all the conditions studied. Activated sludge effluent has longer runs (6 to 27 h) than trickling filter (4 to 9 h) and rotating biological contactor (1 to 5.5 h). Best removals were achieved when treating trickling filter effluent (64%) compared to rotating biological contactor (51%) and activated sludge (55%). In all cases, the end of the run was caused by head loss rather than turbidity. Results showed that the behavior of each effluent varies widely under the same filtration and backwashing conditions and support the need for more experimental work to be conducted.

Experiment utförda på en nitrifierande biobädd 1995

Abstract: A number of experiments was conducted on a pilot scale nitrifying trickling filter during 1995. The experiments aimed for better knowledge of the flow-dependent fast dynamics, and the slow bacterial dynamics. The residence time distribution was investigated by a number of impulse response experiments where dissolved LiCl was added to the influent. The experiments showed that the amount of water in the trickling filter is almost independent of the flow through the plant, and corresponds to a liquid film thickness of approximately 0.5 mm. The residence time distribution can be approximated by a model with four or five identical and ideally continuously stirred tanks. Based on the results of the impulse response experiments the plant is modelled by four continuously stirred tank reactors in series, where the nitrification in each tank is described by a physically derived nonlinear expression. Data from a few step response experiments, where the ammonium concentration in the influent was raised from a low constant level to a high constant level at a constant flow through the plant, was compared to model simulations. The comparisons showed that the fast dynamics in the biofilm can be neglected in comparison to the dynamics caused by the mixing in the bulk and the residence time distribution. Implicitly, this means that the response time for the active nitrifying bacteria to changes in ammonium concentration is less than a few minutes, also when the ammonium load has been very low for a long time. An experiment, where the flow was stochastically varied around an operating point during one day, showed that the simple model derived sufficiently well describe the fast dynamics of nitrifying trickling filter also when the flow changes. When the ammonium concentration in the effluent is low, a model where the nitrification rate is assumed constant is not sufficient. The slow dynamics that depend on the growth and decay of the active nitrifying bacteria was investigated by a three months long step response experiment, where the ammonium concentration in the influent first was held at a high level (not full nitrification) for approximately one month and then at a low level (approximately 50% of the nitrifying capacity) for one month, and finally at the same high level as before for one more month. In spite of several practical problems, the experiment indicated that it takes one to two weeks for the concentration of active bacteria in the biofilm to increase to a new higher concentration after the raise in influent ammonium concentration. The corresponding increase in nitrification rate is approximately 20%. The two periods of the same high influent ammonium concentration was during periods with different water temperature. Comparisons of the nitrification rate between the two periods indicated a stronger dependency on the temperature than has earlier been observed. The standard temperature dependency of the maximum growth rate for nitrifying bacteria that are used for laboratory scale experiments may well apply also for this large scale process. During periods of the experiment the ammonium sensors were not working. Therefore the possibility to determine the influent ammonium concentration based on the flow into the plant was investigated. Both black box models and a physically based model was fitted to data. The investigation showed that with a good model of the influent flow to the plant it may be possible to predict the ammonium concentration with quite good accuracy. The trickling filter was flooded weekly for a couple of hours for predator control. An investigation of the nitrification rate before and after the floodings showed no short term effects of the flooding. When the pilot plant was taken out of operation at the end of the year the uppermost meter of the plant was investigated. It was observed that the biofilm thickness was approximately 0.5mm and no bare surfaces without biofilm could be observed.

Unsaturated flow phenomena in porous medium as in a trickling filter

Abstract: The relationship between substrate removal efficiency and dispersion characteristics of biological filters was investigated. Flow measurements were made using tap water and a synthetic feed solution. The importance of changes in fluid regime with regard to the simultaneous transport and reaction within the biological filter was demonstrated. The effect of drop formation and breakage of liquid jets on substrate utilization was shown.

ENGINEERING MODEL FOR FIXED-FILM BIOSCRUBBERS By Hanneke F. Ockeloen/ Thomas J. Overcamp,:Z and C. P. L. Grady Jr. 3

Abstract: The three basic types of biological treatment systems for the control of volatile organic compounds in air streams are the following: biofilters, in which microorganisms grow on a medium, such as soil, compost, peat, or mixtures of these materials with wood chips or polystyrene particles; suspended-growth bioscrubbers, in which microorganisms are suspended in a liquid; and fixed-film bioscrubbers, in which microorganisms are attached to a packing material. Design and application of biological treatment methods for air pollution control are difficult because only limited experimental data and few theoretical models are available. This paper utilizes an engineering simulation model of a fixed-film bioscrubber to investigate the applicability, removal efficiency, operational parameters, and design requirements for gaseous waste streams. Model results indicate that the removal efficiencies can be increased by increasing the column height, decreasing the superficial gas velocity or the superficial liquid velocity, or by treating the liquid prior to recirculation to the absorber. High removal efficiencies can be obtained for compounds with relatively low values of the Henry's Law coefficient with either cocurrent or countercurrent operation. However, as the Henry's Law coefficient increases, the removal efficiency decreases and high removal efficiencies can be obtained only with cocurrent flow. Cocurrent operation is usually more efficient because stripping does not occur at the top of the column. Physical, chemical, and biological scrubbing methods can be used to control pollutants in waste gases. Physical absorp­ tion transfers the waste components of the gas stream into a liquid. Prior to reuse, the liquid must be regenerated or treated to remove the contaminant. One approach is to use chemical reagents to neutralize acidic or alkaline pollutants or to oxidize pollutants. Alternatively, biological processes often can be used to mineralize organic compounds, allowing the liquid to be recirculated. Such biological treatment may be more eco­ nomical than conventional physical or chemical treatment. Despite successes of biological treatment systems in a num­ ber of air-pollution control applications, only limited experi­ mental data and few theoretical models are available, making design difficult. This paper presents an engineering model for fixed-film bioscrubbers to predict the removal efficiency, op­ erational parameters, and design requirements for various gas­ eous pollutants. The bioscrubber modeled in this paper is a combination of a packed adsorption tower in chemical engi­ neering and a high-rate trickling filter or roughing filter used in wastewater treatment. Generally, there is direct recirculation of the liquid from the bottom to the top of the tower. Simu­ lations were conducted to determine the important factors gov­ erning bioscrubber performance. The results offer guidance for the future development of this technology. BACKGROUND In aerobic biological treatment of waste gases, the pollutants are degraded by appropriate microorganisms to form carbon dioxide, water, and cell material. There are three basic types of biological treatment systems: biofilters, suspended-growth bioscrubbers, and fixed-film bioscrubbers. In a biofilter, the polluted gas passes through a moist, biologically active ma­ terial, such as soil, compost, peat, or mixtures of these materials