title: French vertical-flow constructed wetland design: adaptations for tropical climates.
abstract: The French Outermost Regions are under tropical climate yet still have to comply with both French and EU regulations. French vertical-flow constructed wetland systems appear well adapted to the technical specifics of these regions but their adaptation to tropical climate requires new design guidelines to be defined (area needed, number of filters, type of plants, material to be used, etc.). A study was started in 2008, with backing from the national water authorities, to implement full-scale experimental sites and assess the impacts of local context on design and performances. This paper reports the monitoring results on three vertical-flow constructed wetlands fed directly with raw wastewater (known as the 'French system') in Mayotte and French Guiana. The plants, now in operation for between 1 and 6 years, range from 160 to 480 population equivalent (p.e.). Monitoring consisted of 28 daily composite flow samples in different seasons (dry season, rainy season) at the inlet and outlet of each filter. Performances are benchmarked against French mainland area standards from Irstea's database. Results show that performances are improved by warmer temperature for chemical oxygen demand (COD), suspended solids (SS) and total Kjeldahl nitrogen (TKN) and satisfy national quality objectives with a single stage of filters. Treatment plant footprint can thus be reduced as only two parallel filters are needed. Indeed, warm temperatures allow faster mineralization of the sludge deposit, making it possible to operate at similar rest and feeding period durations. Systems operated using one twin-filter stage can achieve over 90% COD, SS and TKN removal for a total surface of 0.8 m²/p.e.
authors.affiliation: Irstea, Freshwater Systems, Ecology and Pollutions Research Unit, 5 rue de la Doua - CS70077, 69626 Villeurbanne, France E-mail: pascal.molle@irstea.fr.
authors.forename: P
authors.initials: P
authors.lastname: Molle
authors.affiliation: Irstea, Freshwater Systems, Ecology and Pollutions Research Unit, 5 rue de la Doua - CS70077, 69626 Villeurbanne, France E-mail: pascal.molle@irstea.fr.
authors.forename: R Lombard
authors.initials: RL
authors.lastname: Latune
authors.affiliation: SIEAM, BP289, Mamoudzou 97600, France.
authors.forename: C
authors.initials: C
authors.lastname: Riegel
authors.affiliation: ETIAGE, 4 avenue des Plages, Rémire-Montjoly 97354, France.
authors.forename: G
authors.initials: G
authors.lastname: Lacombe
authors.affiliation: SINT, Chef Lieu, la Chapelle du Mont du Chat 73370, France.
authors.forename: D
authors.initials: D
authors.lastname: Esser
authors.affiliation: ODE Martinique, 7 avenue Condorcet, BP 32-97201 Fort de France Cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Mangeot
mesh_terms: D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D052918:Environmental Restoration and Remediation / Q000295:instrumentation / Q000379:methods*; D005602:France; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D011891:Rain; D012621:Seasons; D012722:Sewage / Q000032:analysis; D014329:Tropical Climate; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry*; D053833:Wetlands
chemical_list: D009584:Nitrogen; D012722:Sewage; D062065:Wastewater