The treatment of waste-air containing mixed solvent using a biofilter 2. Treatment of waste-air containing ethanol and toluene in a biofilter

An experiment for five stages of a biofilter-run was performed to investigate the effect of hydrophilic ethanol and hydrophobic toluene on the biodegradation of hydrophobic toluene and hydrophilic ethanol, respectively, when waste-air containing toluene and ethanol was treated by a biofilter. Removal efficiencies of toluene and ethanol began to decrease when inlet load surpassed 90 g/m³/h and 100 g/m³/h consistent with maximum elimination capacities of toluene and ethanol, respectively. At the end of the biofilter-run, removal efficiencies for toluene and ethanol were decreased and maintained at 65% and 40%, respectively. The concentration of toluene at 1st sampling port was raised by factor of two in the 3rd stage of the biofilter run when the inlet load of ethanol co-feed was increased by 1.5 times, while the process conditions of toluene were maintained the same as those of the 2nd stage of biofilter-run. According to the result of Mohseni and Allen, it may be interpreted that removal efficiency of hydrophobic toluene was affected by the presence of hydrophilic ethanol when high load of hydrophobic toluene was applied like that of the 1st sampling port of the biofilter. However it was not the case when a low load of hydrophobic toluene was applied like those of the 2nd, 3rd and 4th sampling ports since hydrophobicity of toluene is much less that of α-pinene. Thus, it may be suggested that biodegradation of hydrophobic VOC was interfered by hydrophilic VOC dissolved in the biolayer and the degree of interference was proportional to the inlet load of hydrophobic VOC as well as that of hydrophilic VOC and was inversely proportional to the solubility of hydrophobic VOC. However, it was inferred that the existence of hydrophobic toluene from waste-air can hardly inversely hinder the removal of hydrophilic ethanol in the biofilter when timeevolutions of hydrophilic ethanol concentrations of this experiment were compared with those of the previous experiment of biofilter to treat waste-air containing ethanol only.     

生物沸石滤池深度处理造纸废水的挂膜实验

采用生物沸石滤池深度处理麦草制浆造纸废水,研究其挂膜启动过程,以及对有机物、SS的去除效果及影响因素。结果表明:在表面负荷为0.24m3·(m2·h)-1,有机负荷为0.144kgBOD·(m3·d)-1,水力停留时间为5h的条件下,对CODCr和SS的去除率分别为60%和90%。     

Effect of temperature on the performance of a biofilter inoculated withPseudomonas putida to treat waste-air containing ethanol

The microbes ofPseudomonas putida (KCTC1768) were fixed on the biofilter-packing media comprising an equivolume mixture of granular activated carbon (GAC) and compost, by recycling the liquid medium containing incubatedPseudomonas putida (KCTC1768). A biofilter experiment was performed to observe its transient behavior under the operating condition of 2,180 ppmv of ethanol-inlet concentration and 158 g/m³/h of ethanol-inlet load for the five consecutive temperature-stages of operation ranging from 25 °C to 40 °C. For the five temperaturestages of operation their removal efficiencies were measured and were compared with each other. The optimum operating temperature of the biofilter turned out to beca. 30 °C, which was consistent with the previous experimental result of Lim and Park. However, the optimum incubation-temperatures ofPseudomonas putida (KCTC1768) and the equivalent (i.e., NCIMB8858) were announced to be of 26 °C and 25 °C by Korea Collection for Type Cultures (KCTC) and National Collections of Industrial, Food and Marine Bacteria (NCIMB), respectively. It was also confirmed by the experiment in which the microbes were incubated in the same liquid medium as in the previous work of Lim and Park at temperature ranging from 20 °C to 40 °C and their growth rates were subsequently measured. Thus, the optimum operating temperature of a biofilter inoculated withPseudomonas putida (KCTC 1768) was proved to be 30 °C, which was higher than its optimum incubation-temperature byca. 5 °C     

Assessment of nitrification in groundwater filters for drinking water production by qPCR and activity measurement

In groundwater treatment for drinking water production, the causes of nitrification problems and the effectiveness of process optimization in rapid sand filters are often not clear. To assess both issues, the performance of a full-scale groundwater filter with nitrification problems and another filter with complete nitrification and pretreatment by subsurface aeration was monitored over nine months. Quantitative real-time polymerase chain reaction (qPCR) targeting the amoA gene of bacteria and archaea and activity measurements of ammonia oxidation were used to regularly evaluate water and filter sand samples. Results demonstrated that subsurface aeration stimulated the growth of ammonia-oxidizing prokaryotes (AOP) in the aquifer. Cell balances, using qPCR counts of AOP for each filter, showed that the inoculated AOP numbers from the aquifer were marginal compared with AOP numbers detected in the filter. Excessive washout of AOP was not observed and did not cause the nitrification problems. Ammonia-oxidizing archaea grew in both filters, but only in low numbers compared to bacteria. The cell-specific nitrification rate in the sand and backwash water samples was high for the subsurface aerated filter, but systematically much lower for the filter with nitrification problems. From this, we conclude that incomplete nitrification was caused by nutrient limitation.     

Biofilter in water and wastewater treatment

Biofilter is one of the most important separation processes that can be employed to remove organic pollutants from air, water, and wastewater. Even though, it has been used over a century, it is still difficult to explain theoretically all the biological processes occurring in a biofilter. In this paper, the fundamental of biological processes involved in the biofilter is critically reviewed together with the mathematical modeling approach. The important operating and design parameters are discussed in detail with the typical values used for different applications. The most important parameter which governs this process is the biomass attached to the medium. The relative merits of different methods adopted in the measurement of the biomass are discussed. The laboratory-and full-scale applications of the biofilter in water and wastewater treatment are also presented. Their performances in terms of specific pollutant removal are highlighted.     

Treatment of gas-phase methanol in conventional biofilters packed with lava rock

The performance of laboratory scale methanol-degrading biofilters packed with lava rock was checked during almost 1 yr under different conditions. The biomass concentration and biomass adaptation of the inoculum dramatically affected the start-up and the performance of the systems during the first stages of operation. A fast start-up was obtained when using concentrated and adapted inocula, while diluted or non-adapted inocula proved to be much less efficient. The performance of the reactor during long-term operation was significantly affected by the toxic load and moisture content of the gas. Critical loads between 120 and 280 g/m(3)h were reached during different phases of the study. The reactor had a high stability to EBRT changes when working at values between 48.0 and 91.1s, showing little or no negative effect when decreasing the EBRT. Hardly any difference was observed regarding performance when using either a downflow or upflow feed, although slightly better results were obtained when working in a downflow mode.     

油田污水的生物处理技术

分析了油田污水的状况及特点,介绍了目前应用于含油废水处理的各种生物处理方法,以及生物处理的原理。总结表明,高效原油降解菌和生物处理构筑物相结合的生物深度处理技术是国内油田污水处理技术发展的趋势。     

Application of a pore network model to a biofilter treating ethanol vapor

Pore volume clogging due to biomass growth from the biodegradation of volatile organic compounds and other pollutants has significant implications for biofilter operation. As the larger pores in the biofilter narrow and the smaller pores fill, airflow through the biofilter is restricted, and headloss increases. The biomass surface area available for contaminant biodegradation is reduced, resulting in diminished removal efficiencies. As biomass clogging increases, flow channeling may occur, further reducing treatment efficiency. Biofilter designers try to overcome the effect of biomass clogging by making beds larger to reduce loading, which is costly. Better insight into the phenomena that occur during biofilter clogging is, therefore, clearly needed. In this paper the effect of biomass accumulation on the removal efficiency and pressure drop of a bench-scale biofilter treating an air stream containing ethanol vapor was investigated using a pore network model. In the model, the biofilter pore structure is described by a cubic lattice of cylindrical pores of uniform length and varying diameters following an experimentally determined pore size distribution. The model assumes that at the pore level biomass growth depends on the oxygen diffusion in the biofilm and on oxygen-limited Monod-type kinetics. Unlike prior biofilter models, this model accounts in detail for phenomena that occur at the pore level, and for the impact of the pore network structure on biofilter behavior. It accounts for the biomass growth in the biofilter and its interaction with the airflow distribution, and explains its influence on the headloss and the ethanol removal efficiency.     

Mathematical modeling of granular activated carbon (GAC) biofiltration system

In this study, a mathematical model of a fixed bed Granular Activated Carbon (GAC) biofiltration system was developed to predict the organic removal efficiency of the filter. The model consists of bulk transportation, adsorption, utilization, and biodegradation of organics. The variation of the specific surface area due to biofilm growth and the effect of filter backwash were also included in the model. The intrapellet diffusion and the diffusion of substrate in the biofilm were described by linear driving force approximation (LDFA) method. Biodegradation of organics was described by Monod kinetics. Sips adsorption isotherm was used to analyze the initial adsorption equilibrium of the system. The model showed that the organic removal efficiency of the biofilter greatly depends on the parameters related to the biological activities such as the maximum rate of substrate utilization (k_max) and biomass yield (Y) coefficients. Parameters such as suspended cell concentration (X_s) and decay constant (K_d) had little effects on the model simulation results. The filter backwash also had no significant impact on the performance of the biofilter.