Performance assessment of Etueffont (France) lagooning treatment system: Report from a 16-year survey.

This study examined the lagooning treatment system of the Etueffont landfill (France) over a period of 16 years. Outflow concentrations in total suspended solids, biological oxygen demand (BOD) and trace metal elements largely met outflow standards and were on average of 5, 8 and 6 times lower than those observed at inflow, respectively. In 2000, however, high levels of BOD were observed in both the influent and effluent, exceeding the authorized outflow limits. At that time the lagooning ponds were subjected temporarily to organic pollution, coinciding with the arrival of the first leachates from a new cell. Though the chemical oxygen demand (COD) and total organic carbon in the influent exceeded authorized limits, overall values conformed to official standards with outflow exhibiting mean concentrations four times lower than those observed at inflow. The first period took place just after the arrival from the new cell of young leachates containing a very high level of COD (>10,000 mg L), causing an organic overload that led to a temporary dysfunctioning of the treatment installation lasting approximately two years. Additionally, the COD in the leachates fell below the strictest limits (125 mg L) at the end of monitoring (2005-2009). The initial nitrogen load brought in by the influent decreased progressively over time, evidence of continuous degradation. At the end of monitoring, regardless of the arriving inflow load, the discharge presented stable concentrations of approximately 30 mg L, appearing to indicate that the limits for nitrogen elimination. Total phosphorus elimination was optimal as the concentrations at outflow were minimal throughout most of monitoring, even though the phosphorus load at inflow was from two to thirty-five times greater. Thus, the findings show that landfill leachates in the methanogenic phase can be treated efficiently by lagooning without risk to the surrounding environment.