Effect of the organic loading rate in the stillage treatment in a constructed wetland with Canna Indica

Anaerobic processes have been used for the stillage treatment, although the effluent of these processes still has a remnant of organic matter measured as Chemical oxygen demand (COD) and Biochemical oxygen demand (BOD), which must be treated to reduce its environmental impact, and constructed wetlands are an opportunity to treat this effluent at low cost. In this study the effect of the organic loading rate (OLR) on the adaptation and growth of Canna Indica was evaluated in a horizontal subsurface flow constructed wetland for stillage treatment during 131 days. The wetland was operated at OLRs ranging 0.13 to 1.32 kg m-3 d-1, reaching average efficiencies about 87% for BOD and 70% for COD, depending on OLR, however efficiencies decreased for OLRs above 0.88 kg m-3 d-1. Canna Indica grew well in the wetland; the gradual increase in organic matter ensured the adaptation of plants. Height and growth of plants were more important near to the outlet of the wetland (zone 2), than near to the inlet (zone 1). This phenomenon is associated with the removal of organic matter and the increment in the bioavailability of organic matter and nutrients through the length of the wetland.