Removal of trichloroethylene (TCE) contaminated soil using a two-stage anaerobic-aerobic composting technique

Abstract

The effect of organic carbon addition on remediation of trichloroethylene (TCE) contaminated clay soil was investigated using a two stage anaerobic-aerobic composting system. TCE removal rate and processes involved were determined. Uncontaminated clay soil was treated with composting materials (dried cow manure, rice husk and cane molasses) to represent carbon based treatments (5%, 10% and 20% OC). All treatments were spiked with TCE at 1,000 mg TCE/kg DW and incubated under anaerobic and mesophillic condition (35°C) for 8 weeks followed by continuous aerobic condition for another 6 weeks. TCE dissipation, its metabolites and biogas composition were measured throughout the experimental period. Results show that TCE degradation depended upon the amount of organic carbon (OC) contained within the composting treatments/matrices. The highest TCE removal percentage (97%) and rate (75.06 μ Mole/kg DW/day) were obtained from a treatment of 10% OC composting matrices as compared to 87% and 27.75 μ Mole/kg DW/day for 20% OC, and 83% and 38.08 μ Mole/kg DW/day for soil control treatment. TCE removal rate was first order reaction kinetics. Highest degradation rate constant (k ₁ = 0.035 day^{− 1}) was also obtained from the 10% OC treatment, followed by 20% OC (k ₁ = 0.026 day^{− 1}) and 5% OC or soil control treatment (k ₁ = 0.023 day^{− 1}). The half-life was 20, 27 and 30 days, respectively. The overall results suggest that sequential two stages anaerobic-aerobic composting technique has potential for remediation of TCE in heavy texture soil, providing that easily biodegradable source of organic carbon is present.

Keywords:

• Trichloroethylene
• contaminated soil
• sequential composting
• anaerobic-aerobic
• bioremediation
• biodegradation

Acknowledgments

Major source of funding to this research is made possible by the Royal Thai Government.

Notes

^a Contains 56.99% clay, 9.85% silt and 33.17% sand particles distribution.

^b The mixture of dried cow manure, rice husk, and cane molasses solution (10%) at a ratio of 2:2:1 by volume.

^c Wet weight basis.

^a Overall composting condition = composting under Anaerobic condition for 8 weeks followed by Anaerobic condition for 6 weeks.

^b Production rate (μ Mole/day) = concentration produced (μ Mole)/production period (days).

^c Consumption rate (μ Mole/day) = concentration consumed (μ Mole)/consumption period (days).