Contaminated storm-water discharge is a growing concern in the United States owing to a steady increase of harmful pollutants entering freshwater sources. This study remediated contaminated storm-water runoff from a bio-oil conversion facility through a simulated constructed wetland. A six-phase series of constructed wetlands was contaminated with varying dilution levels of bio-oil process water. The study concluded that there was a significant decrease in biological oxygen demand (BOD) and microtoxicity over a 10-day remediation cycle within the constructed wetlands for the lower levels of contaminated storm water. The higher levels of contamination changed very little in total volume of pollution. A comparative screening of the bacterial community within the wetlands during the contamination process showed a similar trend in species richness and composition for the first three phases of contamination. There was a shift in richness and diversity for the final three phases of contamination after 10 days. The constructed wetlands were successful at lowering BOD and toxicity levels and achieving permissible pH levels at dilutions higher than 500 times. When the concentrations of contaminated water were lower than 830 mL of contaminated bio-oil wastewater for every 240 liters of rainwater, the constructed wetlands were successful only at achieving permissible pH discharge levels. Better results for high-level contamination may be achievable with longer residence time in the wetlands.