BTEX degradation in a cold-climate wetland system

Area of Science:

• Environmental Engineering
• Wastewater Treatment
• Bioremediation

Background:

• Petroleum refineries generate wastewater containing benzene, toluene, ethylbenzene, and xylene (BTEX).
• Cold climates pose challenges for conventional biological treatment of BTEX-contaminated water.
• Subsurface vertical-flow wetlands offer a potential low-energy solution for BTEX remediation.

Purpose of the Study:

• To evaluate BTEX degradation rates in a pilot-scale subsurface vertical-flow wetland system under cold-climate conditions.
• To assess the impact of wetland sod and aeration on BTEX removal efficiency.
• To inform the design and operation of a full-scale remediation system.

Main Methods:

• Construction and operation of a 4-cell pilot-scale subsurface vertical-flow wetland.
• Application of nominal flow rates and testing of wetland sod and aeration.
• Calculation of areal rate constants (kA) using a three tanks in series (3TIS) model.
• Monitoring of BTEX concentrations to determine degradation rates.

Main Results:

• Mean kA values were 244 m/yr without sod or aeration, increasing to 356 m/yr with both enhancements.
• The full-scale system achieved permit compliance within one week of startup.
• Current operation at reduced hydraulic and mass loads yields a mean kA of approximately 350 m/yr.

Conclusions:

• Wetland sod and aeration significantly improve BTEX degradation in cold-climate subsurface vertical-flow wetlands.
• The technology is effective for achieving regulatory compliance in BTEX-contaminated wastewater.
• Optimized design and operation can lead to efficient and reliable remediation.