Simazine and metolachlor removal by subsurface flow constructed wetlands

Area of Science:

• Environmental Engineering
• Water Quality Management
• Wetland Systems

Background:

• Container nursery runoff can contain harmful herbicides like simazine and metolachlor.
• Constructed wetlands offer a potential solution for treating agricultural and horticultural wastewater.
• Understanding factors influencing herbicide removal in wetlands is crucial for effective system design.

Purpose of the Study:

• To evaluate the effectiveness of subsurface flow constructed wetlands in removing simazine and metolachlor from nursery runoff.
• To determine the statistical significance of hydraulic flow rate, media depth, cell aspect ratio, and vegetation on herbicide removal.
• To optimize constructed wetland design for enhanced herbicide remediation.

Main Methods:

• Pilot-scale field study utilizing subsurface flow constructed wetlands.
• Analysis of variance (ANOVA) with the general linear model procedure was employed.
• Key factors investigated: hydraulic flow rate, media depth, cell aspect ratio, and presence of Scirpus validus.

Main Results:

• Vegetation and hydraulic flow rate were statistically significant factors (alpha = 0.05) affecting herbicide mass removal.
• Vegetated cells demonstrated higher removal rates for both simazine and metolachlor compared to non-vegetated cells.
• Reduced hydraulic loading rates significantly increased the percentage of herbicide mass removed, reaching up to 96%.

Conclusions:

• Subsurface flow constructed wetlands, particularly vegetated systems, are effective in removing simazine and metolachlor.
• Optimizing hydraulic loading rates is critical for maximizing herbicide removal efficiency.
• Media depth and cell aspect ratio did not significantly impact effluent herbicide concentrations in this study.