Nature based solutions applied to mature leachate treatment in the Latin American resource-poor environment

Some Latin American countries have implemented environmental policies which have enhanced a shift in domestic solid waste practices from open dumps to sanitary landfills, bringing about a serious challenge to the region in terms of leachate management both in the operation and the aftercare phases of landfills. This work looks at the viability of Nature based Solutions (NbS) in the Latin American resource-poor environment as a cost-efficient alternative for dealing with such a challenge. In particular, an experimental trial was carried out in order to evaluate the contaminants removal of four subsurface constructed wetlands at a pilot scale, for treating mature leachate with emphasis on nitrogen removal. The wetlands were set in two treatment lines: (1) a vertical flow wetland followed by a horizontal flow wetland and (2) two vertical flow wetlands in series. Each line was fed at a 173 L.d−1 rate of mature leachate. The wetlands were planted with a polyculture of the tropical plants Colocasia esculenta and Heliconia psittacorum in a random way and the support media used was composed of 3/8″ gravel and gross sand. Both treatment lines showed similar behaviours and it is important to highlight that ammoniacal nitrogen, that is the principal contaminant to treat, was significantly removed (40% approx.) considering the high loads the system was fed with (490 kg.d−1 TAN). It is considered that the removal mechanism of the ammoniacal nitrogen is a biological nitrification-denitrification process, due to the increase of nitrite and nitrate concentrations in the effluent, as well as the bicarbonate alkalinity consumption. These results suggest the system proposed as an NbS has promising potential for leachate treatment in Latin American countries. •Leachate treatment is a great a growing challenge in Latin America, since landfilling is expanding.•A pilot constructed treatment wetland, as NbS was assessed, showing a promising viability for dealing with mature leachate.•The NbS configuration which showed the best organic matter and nitrogen removals was the vertical-vertical flow wetland.