Conversion of chemical scrubbers to biotrickling filters for VOCs and H2S treatment at low contact times

Abstract

The purpose of this work was to evaluate the technical and economical feasibility of converting three in-series chemical scrubbers to biotrickling filters for the simultaneous removal at neutral pH of 10000 m 3 /h containing H 2 S and volatile organic compounds (VOCs) at a wastewater treatment plant (WWTP). The conversion was based on previous conversion protocols and mainly required of replacing the original packing material by a structured packing and recycle pumps, besides modifying the controls and operation of the reactors. Complete removal of H 2 S and VOCs on a routine basis was reached in a longer period of time compared to previous conversions reported. Under the conditions at the WWTP, i.e., a gas contact time of about 1.4 seconds per reactor and pH controlled between 6.5 and 6.8, inlet average concentrations below 10 ppm v of H 2 S and below 5 ppm v for VOCs were often completely degraded in the reactors. The first and second reactors played a major role in H 2 S removal. Long-term operation of the biotrickling filters proved the ability of the biotrickling filter to handle progressive load variations of H 2 S and VOCs. However, fast, sudden load changes often lead to reduced removal efficciencies. Odor removal showed average efficiencies above 80%. Limited outlet odor concentration was attributed to limited removal of VOCs, which was assessed through gas chromatographymass spectrometry of selected gas samples. The conversion showed as economically viable taking into account the theoretical consumption of chemicals needed for the absorption and oxidation of both H 2 S and VOCs.

Effect of the height‐to‐diameter ratio on the mass transfer and mixing performance of a biotrickling filter

“…Although lab‐scale BTFs are commonly provided with additional mechanical or magnetic stirring in the holding tank, this practice is quite difficult to implement in full‐scale BTFs as it would compromise the economic feasibility of the treatment technology. As a matter of fact, recent reports on air pollution control by means of full‐scale BTFs do not even consider the use of additional mechanical mixing in the holding tank . Under this scenario, knowledge of the parameters affecting the mass transfer and mixing performance of full‐scale BTFs become of paramount importance.…”

“…As a matter of fact, recent reports on air pollution control by means of full-scale BTFs do not even consider the use of additional mechanical mixing in the holding tank. [26][27][28] Under this scenario, knowledge of the parameters affecting the mass transfer and mixing performance of full-scale BTFs become of paramount importance. The results herein obtained showed that relatively short packed columns (1.8 ≤ H/D ≤ 3.2) will support higher mass transfer and mixing performance compared with tall columns (e.g.…”

Pilot-scale biofilter for the simultaneous removal of hydrogen sulphide and ammonia at a wastewater treatment plant

“…This scenario is common in wastewater treatment plants where the air stream has a higher concentration of hydrogen sulphide compared to ammonia [1,39]. There are several examples in the literature of full scale conversion of chemical scrubbers into biological systems for the treatment of gases in wastewater treatment plants [36,[54][55][56]. A convenient ten step protocol was developed by Deshusses and his coworkers as a general procedure for the conversion of chemical scrubbers to biofilters in WWTP [37,55].…”

“…For the microorganisms to operate at optimal performance, the pH of the biofilter in WWTP is typically maintained by washing the biofilter with chemicals or a buffered solution [19,23,36]. In an industrial scale biofilter, this leads to production of large volumes of leachate which contains ions like SO4 2-, NO2 -and NO3 -which needs to be measured and the leachate requires proper disposal [18,19,37].…”

Enhanced styrene removal in a two-phase partitioning bioreactor operated as a biotrickling filter: Towards full-scale applications

“…mg C m-3 ) progressively hindered the RE up to a value of 53% at an inlet concentration of 1100 mg m -3 (1014 mg C m -3 ).At this point it is important to stress that biological air treatment technologies are nowadays challenged by industrial end-users to improve the economic feasibility in terms of investment costs[23]. Thus, although an EBRT of 30 s is one of the shortest gas residence times yielding high and stable styrene REs in BTFs further optimization in terms of EBRT is still necessary to reduce the size of the BTF and, consequently, reduce the investment cost of the treatment technology[24].…”