“…The MES allowed the legal discharge thresholds of 125 mg.L −1 of COD and 25 mg.L −1 of BOD 5 to be reached with a considerably shorter hydraulic retention time (0.5 day) than the gravel-containing control (3.4 days) [9]. In the treatment of pig slurry, the COD reduction reached 90% with METland compared to 81% with a lagoon containing a sand bed [10]. This process has also proven to be effective for nitrogen and phosphate treatment [11].…”