Octamethylcyclotetrasiloxane removal using an isolated bacterial strain in the biotrickling filter

• Sewage sludge was taken from an organic silicon manufacturer.
• A strain involved in degrading D4 was isolated and identified as Phyllobacterium myrsinacearum.
• A higher removal efficiency and elimination capacity than previous literature reports was obtained.
• The metabolites of D4 were identified.
• The D4 degradation pathways and mechanism were proposed.

Octamethylcyclotetrasiloxane (D4) is a volatile organosilicon compound present in biogas derived from widely using industrial and consumer products. Due to being harmful to many organisms at very low concentrations and forming SiO2 deposits during biogas combustion, the degradation of D4 was investigated. The D4-degrading culture was taken from the effluent of an organic silicon manufacturer. The isolation and the purification were performed. The isolated bacterial strain was inoculated in a biotrickling filter. The effects of the pH, the D4 inlet concentration, the empty bed residence time (EBRT), and the liquid flowrate on the removal performance of D4 were investigated. It is shown that the optimum pH for D4 degradation was 4.0–6.0. The max removal efficiency (RE) of D4 of 60.2% and the max elimination capacity (EC) of 165.4 mg m−3 h−1 were obtained. The main metabolic products consist of HOSiMe2OH, HOSiMe2OSiMe2OH, Me3SiO(CO)2OSiMe3, , and Si(OH)4. The degradation pathways and mechanism for D4 degradation by Phyllobacterium myrsinacearum were proposed.