Numerical and experimental study on the biofiltration of toluene vapor

We have solved both steady state and transient problems on the biofiltration of toluene vapor. The effect of inlet toluene concentration and inlet gas-flow rate on the removal rate of toluene and the elimination capacity of a lab-scale biofilter has been investigated. In this study, the effectiveness factor was a function of pollutant concentration. The dynamic solutions show good agreement with experimental results. At an inlet toluene concentration of 100 ppm, the diffusion of toluene into biofilm was obviously a rate determining step. Above 200 ppm, however, biofilm already showed full activity. The steady-state simulation confirmed that the change of elimination capacity obtained by increasing only inlet toluene concentration was the same as that obtained by increasing only flow rate of contaminated air. The maximum possible performance is about 20 g/m³h with no addition of nutrients.     

Biofiltration potential of macroalgae for ammonium removal in outdoor tank shrimp wastewater recirculation system

Shrimp wastewater usually contain high amount of nitrogen that causes eutrophication, a phenomenon of algae bloom. It is harmful for shrimp growth and needs to be addressed if the objective is to improve water quality and make it suitable for shrimp growth. This paper addresses ammonium removal in tiger shrimp wastewater by using two macroalgae species: Ulva lactuca (U. lactuca) and Gracilaria edulis (G. edulis). To achieve this, an outdoor macroalgae with shrimp integrated system was developed. This integration was completed in two shrimp growth periods; 60 days and 120 days. The mean growth rates of G. edulis and U. lactuca were found as 4.0% day⁻¹ and 3.6% day⁻¹, respectively. The mean ammonium removal rates for G. edulis and U. lactuca were found to be 70% and 45%, respectively. Thus, both species are suitable as biofilter and their valuable biomass has a great commercial value. The potential applications of the findings include improvement of shrimp wastewater quality which will ultimately enhance shrimp and macroalgae productivity to meet growing demands of the market.     

Modelling and kinetic aspects of a BTEX contaminated air-treating biofilter

In this study, the overall performance of a biofilter was evaluated in terms of its elimination capacity by using 3-D mesh techniques. The overall results indicate that the agreement between experimental data and model predictions is excellent for benzene, toluene, ethylbenzene and o-xylene (BTEX). In this study, the maximum removal rate (r _max) values for BTEX were 0.0117, 0.0126, 0.0081 and 0.0146 g m^–3 h^–1, and the half-saturation constant (K_S ) values were calculated to be 0.269, 0.297, 0.156 and 0.394 g m^–3, respectively. For this system, the coefficients of determination (r ²) of BTEX compounds were greater than 0.97. The BTEX concentration profiles along the depth were also determined using a convection–diffusion reactor (CDR) model. The sums of squares of the errors (SSEs) of BTEX were 0.0078, 0.0059, 0.0129 and 0.0269, respectively, with r ² values greater than 0.99 for all four compounds at low concentrations.     

A new approach for using GIS to link infiltration BMPs to Groundwater Pollution Risk

ABSTRACT

This research analyzed the efficiency of the BMP Siting Tool developed by the US Environmental Protection Agency and the Grey-to-Green Decision Support Tool. Both tools were used in conjunction with ArcGIS 10.1 to obtain cartographic data illustrating suitable sites for bioswales and infiltration basins in Hillsborough County, Florida. The data were integrated with the Karst Aquifer Vulnerability Index (KAVI) groundwater vulnerability model. The BMP Siting Tool sited 2.80% of all bioswales and 27.89% of all infiltration basins above vulnerable areas identified by the KAVI. Alternatively, 21.66% of all bioswales and 9.62% of all infiltration basins sited by the Grey-to-Green Decision Support Tool were above vulnerable areas. The results of this analysis prompted the proposal of a supplemental framework unique to each tool’s weakness. The idea behind the supplemental framework is to determine the most suitable sites for stormwater BMPs by refining the current siting framework to better respect groundwater integrity.     

Using catalytic ozonation and biofiltration to decrease the formation of disinfection by-products

The effect of catalytic ozonation in a fluidized bed reactor (FBR) on the formation of individual disinfection by-products (DBPs) was investigated. A biofiltration column was used to evaluate the removal efficiency of biotreatment on DBP precursors. Dissolved organic carbon (DOC), simulated distribution system trihalomethanes (SDS THMs), and six simulated distribution system haloacetic acids (SDS HAA6) were monitored. The source water was polluted by domestic and agricultural effluents. Catalytic ozonation removed the concentration of DOC by 8.2-51.4% depending on the dosage of the catalyst. The decreases of SDS THMs and SDS HAA6 were 41.3-51.2% and 31.7-48.3%, respectively, under the same operating conditions. Biotreatment greatly improved the removal efficiency of DOC and decreased the formation of DBPs. Up to 81.7%, 76.1%, and 81.3% of DOC, SDS THMs precursors, and SDS HAA6 precursors were removed after the catalytic ozonation followed by biofiltration, respectively. The treatment processes also influenced the proportions of individual DBP species. The proportion of bromine-containing species from the SDS THMs and SDS HAA6 increased in water samples after being treated by biofiltration alone, ozonation alone, catalytic ozonation, and catalytic ozonation followed by biofiltration.     

Impact of support media in an integrated biofilter-submerged membrane system

The impact of a support material on an integrated biofilter-membrane system, simulating a difficult-to-treat surface water, was examined in terms of membrane fouling rate and water quality parameters. The support media in the membrane tanks did not generally affect any of the water quality parameters measured; however, there was an observable difference in the membrane fouling rates between the two processes with the support media system fouling at least two times slower than the non-support system. Total organic carbon (TOC) removals at around 60% were observed for two integrated biofilter-immersed membrane processes with the majority of the TOC removal occurring in the biofilters. One of the membrane tanks contained a support media (Process A) while the other did not (Process B). The feedwater contained humic acid (65% w/w) and readily biodegradable carbons (35% w/w) in the forms of acetic acid, formic acid and formaldehyde. The influent TOC values were between 3.35 and 3.94 mg/L. Acetate removals varied between 66 and 83%, while over 90% of the formate was removed and the formaldehyde was completely removed in the biofilters. There was a decrease in the UV absorbance values by over 70% for both processes.     

Biofiltration of xylene emissions: bioreactor response to variations in the pollutant inlet concentration and gas flow rate

In order to remove xylene vapors from an air stream, an upflow laboratory scale biofilter was operated for a period of 2 months. The experimental study consisted of two different phases: in the first phase, the biofilter was operated at various gas flow rates and the xylene inlet concentration was maintained at 1.39 g m⁻³. In the second phase, various inlet concentrations of the contaminant were tested at a constant gas flow rate of 0.4 m³ h⁻¹ corresponding to an empty bed residence time of 150 s. The biofilter response to steep and abrupt variations in the xylene inlet concentration and gas flow rate was examined. The results obtained revealed that the removal efficiency of the biofilter regained its high values (above 96%) in less than 24 h following the change to low concentrations and gas flow rate. Temperature measurements showed that the biofilter temperature strongly depends on the intensity of the microbial activity in the filter bed. The experimental mass ratio of carbon dioxide produced to the xylene removed was equal to 2.72 indicating that the contaminant was eliminated exclusively by aerobic biodegradation. These findings suggest that a follow up of the amount of carbon dioxide produced in the filter bed can be very helpful in monitoring the performance of the biofilter. For relatively small inlet loads of xylene, the contributions of the different sections of the biofilter to the removal efficiency of the contaminant and the carbon dioxide production were unevenly balanced but became more uniformly distributed for relatively high inlet loads.     

Evaluation of biodegradability of NOM after ozonation

The major purpose of this study was to develop a simple procedure to describe the kinetics of biodegradation of natural organic matter (NOM) in drinking water and to use this procedure to evaluate changes in the concentration of biodegradable organic matter during ozonation and biotreatment. The proposed approach quantitatively describes the formation and removal of rapidly and slowly biodegradable fractions of NOM. This study showed that, depending on source water, ozonation of NOM may result in either minimal formation of biodegradable organic carbon (BDOC), or the formation of predominantly rapidly biodegradable NOM, or in the formation of both rapidly and slowly biodegradable NOM. The kinetic data obtained in this study suggest that while conventional biofiltration processes are capable of removing the rapidly biodegradable fraction, slowly biodegradable organic matter would remain in the filter effluent and may cause bacterial regrowth in the distribution system. An addition of a small amount of easily biodegradable carbon ("stimulated" biodegradation) to ozonated water appears to be effective for the removal of slowly biodegradable organic matter.     

Impact of Support Media on the Biological Treatment of Ozonated Drinking Water

An extensive review of the technical literature was conducted in order to determine the advantages and disadvantages of the various media used for biological filtration of ozonated drinking water. Granular activated carbon (GAC) filters were found to be significantly more efficient than conventional filters such as sand and anthracite coal. The type of activated carbon also impacted the performance of biofilters; due to their greater adsorption capacity, microporous GACs were found to be better suited than macroporus GACs.     

A Study of the Biofiltration of High‐Loads of Toluene in Air: Carbon and Water Balances,Temperature Changes and Nitrogen Effect

Biodegradable atmospheric pollutants, released at low to moderate concentrations, can be removed by biofiltration. In this work, a laboratory‐scale compost‐based biofilter has been evaluated for the removal of high levels of toluene in air (～ 4.0 g.m^?3). By applying a variable nitrogen input in the irrigation solution, it was shown that the biodegradation extent can be controlled through the nutrient supply. The maximum elimination capacity achieved was 135 g.m^?3.h^?1, for a N‐concentration of 3.0 g of N.L^?1. A quantitative analysis of the bioreaction aspects (stoichiometry, temperature) led to the determination of the water flow rates associated with the toluene oxidation. Thus, it was estimated that some 530 to 800 g of water.day^?1 were lost at the bioreactor outlet, but were balanced by the irrigation system.