Artificial wetland performances in the purification efficiency of hydrocarbon wastewater

An artificial wetland planted with Typha latifolia was fed during a 360-day experiment with a reconstituted hydrocarbon wastewater (60 ppm, 850 A/day). Concentrations and chemical composition were periodically monitored. The operation efficiency was studied together with the accumulation in sediment and the bacterial development. The apparent effluent concentration was below 8 mg/L and the decrease in hydrocarbon concentration raised 90%. pH ranged between 6.9 and 8 and Total Suspended Solids (TSS) were below 10 mg/L. Hydrocarbon amount accumulated in sediment was estimated to be less than 10% of the input amount. We observed a high development of aerobic heterotrophic bacteria (10 super(6) bac/mL) and hydrocarbon-utilizing bacteria (10 super(5) bac/mL), which probably interacted with the plants for the biodegradation of hydrocarbon (in the saturated effluent fraction, normal alkane biodegradation amounted to approximatively 80%). A comparative system with floating plants (Lemma minor), named "control bed", was studied in parallel and showed lower performances.