Bioremediation of Silica Gel Contaminated with Total Petroleum Hydrocarbons: A Laboratory-Scale Study Using Non-Pathogenic Bacterial Consortia

Silica gel is extensively used as a desiccant for dehumidifying methane gas during natural gas treatment operations. Over time, the adsorbent becomes saturated with total petroleum hydrocarbons (TPHs), including saturated, unsaturated, and aromatic compounds, rendering it ineffective. This study presents a laboratory-scale bioremediation technology employing a consortium of non-pathogenic bacterial strains (Bacillus amyloliquefaciens, Bacillus pumilus, Bacillus subtilis, and Bacillus macerans) combined with a nutrient supplement to degrade TPH compounds adsorbed on silica gel granules. Three replicate experiments were conducted over 42 days with periodic aeration and partial water replacement every three days. The initial TPH concentration of 1309.06 mg/kg was reduced to 1.006 mg/kg after 42 days, corresponding to a removal efficiency of 99.92%. TPH degradation followed first-order kinetics (k = 0.192 day−1, R2 = 0.987, t1/2 = 3.6 days). Water adsorption capacity of the treated silica gel was 28% w/w compared to 35% w/w for virgin material, representing an 80% recovery of desiccant performance. These results demonstrate that biological remediation constitutes a cost-effective and environmentally sound alternative to landfill disposal of spent silica gel in the natural gas industry, with strong potential for industrial scale-up.