title: Effects of a saturated layer and recirculation on nitrogen treatment performances of a single stage Vertical Flow Constructed Wetland (VFCW).
abstract: Upgrades to enhance nitrogen removal were tested in a 2 year old pilot vertical flow constructed wetland in spring and summer periods. The effects of a saturated layer and of recirculation were tested in particular. Two pilots (L = 2 m, W = 1.25 m, H = 1.2 m), filled with expanded schist (Mayennite(®)), were designed with hydraulic saturated layers of 20 and 40 cm at the bottom. Each pilot was fed with raw domestic wastewater under field conditions according to a hydraulic load of 15-38 cm d(-1) (i.e. 158-401 g COD (chemical oxygen demand) m(-2) d(-1)) and to recirculation rates ranging from 0% up to 150%. The initial load during the first 2 years of operation resulted in an incomplete mineralized accumulated sludge leading to total suspended solids (TSS), COD and biochemical oxygen demand (BOD5) release. A 40 cm hydraulic saturated layer enabled an increase of 5-10% total nitrogen (TN) removal compared to a 20 cm saturated layer. Recirculation allowed the dilution of raw wastewater and enhanced nitrification in a single stage. A design of 1.8 m² pe(-1) (48 cm d(-1), 191 g COD m(-2) d(-1)) with a 40 cm saturated layer and 100% recirculation enabled the French standard D4 (35 mg TSS L(-1), 125 mg COD L(-1), 25 mg BOD5 L(-1)), nitrogen concentrations below 20 mg TKN (total Kjeldahl nitrogen) L(-1) and 50 mg TN L(-1), to be met.
authors.affiliation: Jean VOISIN SAS, Les Charmilles, 37360 Beaumont-la-Ronce, France; Ecole des Mines de Nantes, GEPEA UMR CNRS 6144, 4 rue Alfred Kastler, B.P. 20722 F-44307 Nantes Cedex 3, France E-mail: florent.chazarenc@mines-nantes.fr.
authors.forename: S
authors.initials: S
authors.lastname: Prigent
authors.forename: J
authors.initials: J
authors.lastname: Paing
authors.forename: Y
authors.initials: Y
authors.lastname: Andres
authors.forename: F
authors.initials: F
authors.lastname: Chazarenc
mesh_terms: D009584:Nitrogen / Q000737:chemistry*; D010865:Pilot Projects; D012722:Sewage; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D009584:Nitrogen