[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-227] Enhanced bioremediation of diesel-contaminated soil by microbial immobilization

Hsin-Yu Wu¹, Tzu-Hsin Lin¹, Ting-Yu Liang¹, Wen-Yi Yang², ○Yi-Tang Chang¹ (1. Deppartment of Microbiology, Soochow University (Taiwan), 2. Environmental Engineering Research Center, Sinotech Engineering Consultants (Taiwan))

Keywords:

bioaugmentation,total petroleum hydrocarbons,bioremediation,natural polymers,soil organic carbon

Conventional bioaugmentation is generally used to enhance the removal of total petroleum hydrocarbons (TPH) from diesel-contaminated soil. But this strategy faces significant challenges because the activity of TPH-biodegrading bacteria is limited by nutrient availability during bioremediation, thereby reducing the efficiency of TPH biodegradation. This study develops an alternative approach to enhance TPH biodegradation in the soil/water systems by using microbial immobilization. Biodegradable natural polymers, sodium alginate (SA) and chitosan (CS), are applied as beads to encapsulate TPH-biodegrading bacteria. 2.0% (w/v) SA-beads and 1.5% (w/v) CS-beads (~1 mm diameter) are selected for diesel-contaminated bioremediation in soil/water systems, optimized for mechanical stability and controlled microbial-release kinetics. their mechanical tolerance and microbial release rate. Batch experiments on 10% (w/v) TPH-contaminated soil for bioremediation show that the addition of both SA-beads and CS-beads significantly increases TPH biodegradation efficiency. The pseudo-first-order rates of TPH biodegradation for 28 days are ranked as follows: 2.0% SA-beads additives (0.0048 hr^-1) > 1.5% CS-beads additives (0.0044 hr^-1) > conventional bioaugmentation-biostimulation (0.0036 hr^-1) > biostimulation only (0.0018 hr^-1). Moreover, TPH biomineralization kept high removal in all treatments. Efficiencies of TPH biomineralization are ranked as follows: biostimulation only (91.67%) > conventional bioaugmentation-biostimulation (89.65%) > CS-beads additives (87.41%) > SA-beads additives (86.09%). Total bacterial numbers and TPH-biodegrading bacteria are continuously increased during all experiments. The genera Caulobacter (22.09%), Paenibacillus (9.76%-20.12%), Rhodococcus (11.97%-14.71%), Variovorax (12.29%), and Acinetobacter (10.38%-10.57%) are dominant and reported to biodegrade TPH or produce biosurfactants to increase TPH bioavailability. Microbial biodiversity in soil/water systems increases with the addition of SA-beads or CS-beads, as indicated by higher biodiversity indices (e.g., Chao1, ACE, and Richness). Beyond their efficiency in bioremediation, immobilized bead additives can also improve soil quality. Soil organic carbon (SOC) has significantly increased by 17.49-19.37% for 28-60 days due to residual SA or CS from fracture beads and enhanced microbial biomass. These findings confirm that microbial immobilization for soil bioremediation can enhance the efficiency of TPH biodegradation and improve soil quality by increasing microbial biodiversity and SOC content in treated diesel-contaminated soils. This study provides advanced bioremediation technology for petroleum-contaminated soils and offers a green and sustainable treatment process.