Biodegradation of gas-phase styrene in a high-performance biotrickling filter using porous polyurethane foam as a packing medium

Methods Influence in Surface Area Result from Polyurethane Used as Support Media

We evaluated if different measurement methods influence the surface area results from a polyurethane sponge used as support media in biofilm reactors. The surface area values are normally used to characterize and present advantages from supported medias. However, the methodology to determine it is barely discussed. We compared two specific surface area methodologies: Brunauer-Emmett-Teller (BET) and analysis of images obtained by a scanning electron microscope (SEM). Specific surface area by BET was 93769.1 m2 m-3 (average); for SEM methodology, 10586.6 m2 m-3. The BET value was higher than expected in reality, and the SEM method result was more suitable and used as data input in a mathematical modeling.

Inorganic carbon limitation during nitrogen conversions in sponge-bed trickling filters for mainstream treatment of anaerobic effluent

Anaerobic sewage treatment is a proven technology in warm climate regions, and sponge-bed trickling filters (SBTFs) are an important post-treatment technology to remove residual organic carbon and nitrogen. Even though SBTFs can achieve a reasonably good effluent quality, further process optimization is hampered by a lack of mechanistic understanding of the factors influencing nitrogen removal, notably when it comes to mainstream anaerobically treated sewage. In this study, the factors that control the performance of SBTFs following anaerobic (i.e., UASB) reactors for sewage treatment were investigated. A demo-scale SBTF fed with anaerobically pre-treated sewage was monitored for 300 days, showing a median nitrification efficiency of 79% and a median total nitrogen removal efficiency of 26%. Heterotrophic denitrification was limited by the low organic carbon content of the anaerobic effluent. It was demonstrated that nitrification was impaired by a lack of inorganic carbon rather than by alkalinity limitation. To properly describe inorganic carbon limitation in models, bicarbonate was added as a state variable and sigmoidal kinetics were applied. The resulting model was able to capture the overall long-term experimental behaviour. There was no nitrite accumulation, which indicated that nitrite oxidizing bacteria were little or less affected by the inorganic carbon limitation. Overall, this study indicated the vital role of influent characteristics and operating conditions concerning nitrogen conversions in SBTFs treating anaerobic effluent, thus facilitating further process optimization.

Comparative evaluation on the utilization of applied electrical potential in a conductive granule packed biotrickling filter for continuous abatement of xylene: Performance, limitation, and microbial community

This study investigates the use of electrically conductive granules as packing material in biotrickling filter (BTF) systems as to provide insights on the specific microbial abundance and functions during the treatment of xylene-containing waste gas. In addition, the effect of applied potential on attached biofilm on conductive granules during xylene degradation was briefly investigated. During stable operation period, the conductive granules packed BTF achieved reactor performance of no less than 80% with a maximum EC of 137.7 g/m³ h. Under applied potential of 1V, the BTF system showed deterioration of xylene removal by ranging from 21 to 76%, which also affected the distribution and relative abundance of the major microorganisms such as Xanthobacter, Acidovorax, Rhodococcus, Hydrogenophaga, Arthrobacter, Brevundimonas, Pseudoxanthomonas, Devosia, Shinella, Sphingobium, Dokdonella, Pseudomonas and Bosea. The acclimation of applied potential led to the enrichment of autotrophic bacteria and strains, which are correlated to improved nitrogen cycling. In general, applying electrical potential is feasible to shape the microbiological structure of biofilms to selectively adjust their biochemical functions.

Degradation pathway and kinetic analysis for p-xylene removal by a novel Pandoraea sp. strain WL1 and its application in a biotrickling filter

In this study, a novel Pandoraea sp. strain WL1 capable of mineralizing p-xylene as sole carbon and energy source was isolated from the activated sludge of a pharmaceutical wastewater treatment plant. A nearly complete degradation of 16.6∼99.4 mg L(-1)p-xylene in the liquid-phase was achieved within 6∼18 h accompanied by 15.9∼56.3 mg dry cell weight (DCW)L(-1) for bacterial growth. A complete pathway for p-xylene degradation by strain WL1 was presented through identification of a major intermediate (p-toluic acid) and final products (2.193 gCO2 gp-xylene(-1) of CO₂ production and 0.215 g DCW gp-xylene(-1) of bacterial yield). Kinetics of bacterial growth and p-xylene degradation were evaluated using Haldane-Andrews model and pseudo first-order model, respectively. Furthermore, a biotrickling filter (BTF) was employed to evaluate the application of strain WL1 on the removal of gas-phase p-xylene under gas flow rates of 0.41∼1.98 m(3)h(-1) for inlet loading rates of 5∼248 gm(-3)h(-1). The BTF inoculated with strain WL1 proved to be robust against fluctuations of gas flow rates and inlet p-xylene concentrations. All the results obtained highlight the potential of strain WL1 for the treatment of p-xylene.

Evaluation of o-xylene and other volatile organic compounds removal using a xylene-acclimated biotrickling filter

In this study, performance evaluation for the gas-phase o-xylene removal using a xylene-acclimated biotrickling filter (BTF) was conducted. Substrate interactions during aerobic biodegradation of three poorly soluble compounds, both individually and in paired mixtures (namely, o-xylene and ethyl acetate, o-xylene and dichloromethane, which are common solvents used by pharmaceutical industry), were also investigated. Experimental results indicate that a maximum elimination capacity of 99.3 g x m(-3) x h(-1) (70% removal) was obtained at an o-xylene loading rate of 143.0 g x m(-3) x h(-1), while the top packing layer (one-third height of the three packing layers) only contributed about 13% to the total elimination capacity. Kinetic constants for o-xylene biodegradation and the pattern of o-xylene removal performance along the height of the BTF were obtained through the modified Michaelis-Menten kinetics and convection-diffusion reaction model, respectively. A reduction of removal efficiency in o-xylene (83.2-74.5% removal at a loading rate of 40.3 g x m(-3) x h(-1) for the total volatile organic compound (VOC) loading rate of 79 g x m(-3) x h(-1)) in the presence of ethyl acetate (100% removal) was observed, while enhanced o-xylene removal efficiency (71.6-78.6% removal at a loading rate of 45.1 g x m(-3) x h(-1) for the total VOC loading rate of 90 g x m(-3) x h(-1)) was achieved in the presence of dichloromethane (35.6% removal). This work shows that a BTF with xylene-acclimated microbial consortia has the ability to remove several poorly soluble compounds, which would advance the knowledge on the treatment of pharmaceutical VOC emissions.