The possible emission of sulfuric acid mists from a laboratory scale, counter-current packed bed tower operated with a caustic scrubbing solution was studied. Acid mists were applied through a local exhaust hood. The emissions from the packed bed tower were monitored in three different categories of gas flow rate as well as three liquid flow rates, while other influencing parameters were kept almost constant. Air sampling and sulfuric acid measurement were carried out iso-kinetically using USEPA method 8. The acid mists were measured by the barium-thorin titration method. According to the results when the gas flow rate increased from 10 L/s to 30 L/s, the average removal efficiency increased significantly (p < 0.001) from 76.8 ± 1.8% to 85.7 ± 1.2%. Analysis of covariance method followed by Tukey post-hoc test of 92 tests did not show a significant change in removal efficiency between liquid flow rates of 1.5, 2.5 and 3.5 L/min (p = 0.811). On the other hand, with fixed pressure loss across the tower, by increasing the liquid/gas (L/G) mass ratio, the average removal efficiency decreased significantly (p = 0.001) from 89.9% at L/G of <2 to 83.1% at L/G of 2–3 and further to 80.2% at L/G of >3, respectively. L/G of 2–3 was recommended for designing purposes of a packed tower for sulfuric acid mists and vapors removal from contaminated air stream.

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With increasing concerns about industrial gas contaminants and the growing demand for durable and sustainable technologies, attentions have been gradually shifted to biological air pollution controls. The ability of Pseudomonas putida PTCC 1694 (bacteria) and Pleurotus ostreatus IRAN 1781C (fungus) to treat contaminated gas stream with toluene and its biological degradation was compared under similar operating conditions. For this purpose, a biofilter on the laboratory scale was designed and constructed and the tests were carried out in two stages. The first stage, bacterial testing, lasted 20 days and the second stage, fungal testing, lasted 16 days. Inlet loading rates (IL) for bacterial and fungal biofilters were 21.62 ± 6.04 and 26.24 ± 7.35 g/m 3 h respectively. In general, fungal biofilter showed a higher elimination capacity (EC) than bacterial biofilter (18.1 ± 6.98 vs 13.7 ± 4.7 g/m 3 h). However, the pressure drop in the fungal biofilter was higher than the bacterial biofilter (1.26 ± 0.3 vs 1 ± 0.3 mm water), which was probably due to the growth of the mycelium. Fungal biofiltration showed a better performance in the removal of toluene from the air stream.

Biomanipulation is reliable method for treating volatile organic compounds (VOCs) in polluted air. The performances of two biofilters in the removal of toluene vapors from air stream were compared. Two identical biofilters designed in parallel configuration were operated in lab-scale for 20 days; one of them was filled by sterilized media (compost and wood charcoal 2:1 v/v) and another was filled by the same media inoculated with Pseudomonas putida PTCC 1694, as a native strain. Moreover, batch tests were performed to determine the biodegradation rate of toluene. The results showed that, in comparison with the sterilized BF (89% vs 58%), the inoculated BF could effectively eliminate toluene from air stream. The pressure drop across the inoculated BF and the sterilized BF were 0.66±0.28 and 0.47±0.27 mm water respectively. The batch test results showed that loss of toluene in the control bottles was greater than the blanks. Based on the experimental results, inoculated BFs can effectively treat toluene vapors from gaseous streams.

Biomanipulation is reliable method for treating volatile organic compounds (VOCs) in polluted air. The performances of two biofilters in the removal of toluene vapors from air stream were compared. Two identical biofilters designed in parallel configuration were operated in lab-scale for 20 days; one of them was filled by sterilized media (compost and wood charcoal 2:1 v/v) and another was filled by the same media inoculated with Pseudomonas putida PTCC 1694, as a native strain. Moreover, batch tests were performed to determine the biodegradation rate of toluene. The results showed that, in comparison with the sterilized BF (89% vs 58%), the inoculated BF could effectively eliminate toluene from air stream. The pressure drop across the inoculated BF and the sterilized BF were 0.66±0.28 and 0.47±0.27 mm water respectively. The batch test results showed that loss of toluene in the control bottles was greater than the blanks. Based on the experimental results, inoculated BFs can effectively treat toluene vapors from gaseous streams.