Josep M. Penya-Roja

Performance evaluation of a biotrickling filter treating a mixture of oxygenated VOCs during intermittent loading

Laboratory scale-studies on the biodegradation of a 1:1:1 weight mixture of three oxygenated volatile organic compounds (VOCs), ethanol, ethyl acetate, and methyl-ethyl ketone (MEK) in a biotrickling filter (BTF) were carried out using two identically sized columns, filled with different polypropylene rings. The performance of the BTFs was examined for a period of 10 months applying several operational strategies. Similar performance was obtained for both supports. Intermittent flow rate of trickling liquid was shown beneficial to improve the removal efficiency (RE). Continuous feeding of VOC resulted in an excessive accumulation of biomass so high pressure drop was developed in less than 20-30 d of operation. Intermittent VOC loading with night and weekend feed cut-off periods passing dry air, but without addition of water, was shown as a successful operational mode to control the thickness of the biofilm. In this case, operation at high inlet loads (ILs) was extended for more than 75 d maintaining high REs and low pressure drops. Outlet emission concentrations lower than 100 mg Cm(-3) were obtained for ILs up to 100 g Cm(-3)h(-1) working at 15s of empty bed residence time. The most easily biodegradable compounds ethanol and ethyl acetate were used primarily than MEK. After a 3-wk-starvation period, the system performance was almost restored since the first d of operation, being the removal of the less biodegradable compound, MEK, partially deteriorated.

Performance of a Pilot-Scale Biotrickling Filter in Controlling the Volatile Organic Compound Emissions in a Furniture Manufacturing Facility

Abstract A 0.75-m3 pilot-scale biotrickling filter was run for over 1 yr in a Spanish furniture company to evaluate its performance in the removal of volatile organic compounds (VOCs) contained in the emission of two different paint spray booths. The first one was an open front booth used to manually paint furniture, and the second focus was an automatically operated closed booth operated to paint pieces of furniture. In both cases, the VOC emissions were very irregular, with rapid and extreme fluctuations. The pilot plant was operated at an empty bed residence time (EBRT) ranging from 10 to 40 sec, and good removal efficiencies of VOCs were usually obtained. When a buffering activated carbon prefllter was installed, the system performance was improved considerably, so a much better compliance with legal constraints was reached. After different shutdowns in the factory, the period to recover the previous performance of the biotrickling reactor was minimal. A weekend dehydration strategy was developed and implemented to control the pressure drop associated with excessive biomass accumulation.

Hydrogen sulfide and odor removal by field-scale biotrickling filters: influence of seasonal variations of load and temperature.

Two biotrickling filters were set up at two wastewater treatment plants (WWTP) in The Netherlands to investigate their effectiveness for treatment of odorous waste gases from different sources. One biotrickling filter was installed at Nieuwe Waterweg WWTP in Hook of Holland to study the hydrogen sulfide removal from headworks waste air. The other reactor was installed at Harnaschpolder WWTP (treating wastewater of the city of The Hague) to remove mercaptans and other organic compounds (odor) coming from the emissions of the anaerobic tanks of the biological nutrient removal (BNR) activated sludge. The performance of both units showed a stable and highly efficient operation under seasonal variations of load and temperature over nearly one year of monitoring. The Nieuwe Waterweg unit achieved removals of up to 99%, corresponding to a maximum daily average elimination capacity (EC) of 55.8 g H2S/m3/h at an empty bed residence time (EBRT) as short as 8.5 s. Odor reduction at the Harnaschpolder unit was 95% at an EBRT of 18.9 s, with average outlet concentration lower than the objective value which was established as 1000 European Odor Units (OUE/m3).

Evaluation of a combined activated carbon prefilter and biotrickling filter system treating variable ethanol and ethyl acetate gaseous emissions.

The removal of a 1:1 by weight mixture of ethanol and ethyl acetate was studied in a gas phase biotrickling filter running under conditions that simulated industrial emissions from the flexographic sector, i.e. discontinuous loading (twelve hours per day and five days per week) and oscillating concentration of the inlet stream. Three sets of experimental conditions were tested in which empty‐bed residence time varied from 60 to 25 s (inlet loads from 50 to 90 g C m−3 h−1). The biotrickling filter reached a maximum elimination capacity of 48.5 g C m−3 h−1 (removal efficiency=68.9%) for an empty‐bed residence time of 40 s. A decrease in the residence time from 40 to 25 s adversely affected the elimination capacity (40.3 g C m−3 h−1, removal efficiency=46.6%). For the three tested residence times, outlet concentrations during pollutant feeding were above 100 mg C m−3 (EU legal limit for flexographic facilities). Then an activated carbon prefilter was installed to buffer the fluctuating concentration, enabling a more stable operation. The desorbed pollutant from the activated carbon during non‐feeding hours also served as an extra source of substrate, avoiding severe starvation. The use of the activated carbon prefilter with a volume 25 times lower than that of the bioreactor was shown to reach an average outlet emission concentration lower than 50 mg C m−3 operating the biotrickling filter at an empty‐bed residence time of 40 s, with a maximum elimination capacity of 59.6 g C m−3 h−1 (removal efficiency=92.0%).

Dynamic Mathematical Modelling of the Removal of Hydrophilic VOCs by Biotrickling Filters

A mathematical model for the simulation of the removal of hydrophilic compounds using biotrickling filtration was developed. The model takes into account that biotrickling filters operate by using an intermittent spraying pattern. During spraying periods, a mobile liquid phase was considered, while during non-spraying periods, a stagnant liquid phase was considered. The model was calibrated and validated with data from laboratory- and industrial-scale biotrickling filters. The laboratory experiments exhibited peaks of pollutants in the outlet of the biotrickling filter during spraying periods, while during non-spraying periods, near complete removal of the pollutant was achieved. The gaseous outlet emissions in the industrial biotrickling filter showed a buffered pattern; no peaks associated with spraying or with instantaneous variations of the flow rate or inlet emissions were observed. The model, which includes the prediction of the dissolved carbon in the water tank, has been proven as a very useful tool in identifying the governing processes of biotrickling filtration.

A Tool for Predicting the Dynamic Response of Biotrickling Filters for VOC Removal

This article presents the development of a MATLAB® computer program to simulate the performance of biotrickling filters. Since these filters behave differently during spraying and nonspraying cycles, the presented simulation tool is built on top of a mathematical description of each situation. The resulting variable-structure model is then used as the basis for simulation experiments. The model presented herein represents the first attempt to take into account the variable spraying pattern usually found in industrial installations. Overall, the software is flexible and easy to use, allowing the user to specify the emission concentration pattern, the gas concentration pattern, as well as the spraying cycle periods for up to two different emission patterns per day. The model is able to predict experimental data from a biotrickling filter treating isopropanol under intermittent conditions of loading and spraying. Simulation examples are then provided to study the effect of variable inlet concentrations and gas flow rates.