Effect of pH on the performance of an acidic biotrickling filter for simultaneous removal of HS and siloxane from biogas.

Acidic biotrickling filters (BTF) can be used for simultaneous removal of hydrogen sulfide (HS) and siloxane from biogas. In this study, the performance of a BTF under different acidic pH conditions was investigated. The removal profile of HS showed that 90% of HS removal was achieved during the first 0.4 m of BTF height with down-flow biogas. Decamethylcyclopentasiloxane (D5) removal decreased from 34.5% to 15.6% when the pH increased from 0.88 to 3.98. Furthermore, the high partition coefficient of D5 obtained in under higher pH condition was attributed to the higher total ionic strength resulting from the addition of sodium hydroxide solution and mineral medium. The linear increase in D5 removal with the mass transfer coefficient (k) indicated that the acidic recycling liquid accelerated the mass transfer of D5 in the BTF. Therefore, the lower partition coefficient and higher k under acidic pH conditions lead to the efficient removal of D5. However, the highly acidic pH 0.9 blocked mass transfer of HS and O gases to the recycling liquid. Low sulfur oxidation activity and low Acidithiobacillus sp. content also deteriorated the biodegradation of HS. Operating the BTF at pH 1.2 was optimal for simultaneously removing HS and siloxane.