Constructed wetland mesocosms for the treatment of diluted sugarcane molasses stillage from ethanol production using Pontederia sagittata

Sugarcane molasses stillage contains a very high concentration of organic matter and toxic/recalcitrant compounds. Its improper disposal has become a global problem and there is very scanty information about its treatment using phytotechnologies. This work aimed at evaluating the performance of subsurface flow constructed wetlands (SSF CWs) mesocosms planted with Pontederia sagittata and operating at two hydraulic retention times (HRTs), compared to an unplanted SSF CWs, for the treatment of diluted stillage subjected to no pre-treatment apart from an adjustment to pH 6.0. CWs were fed with very high surface COD loading rates (i.e. 47.26 and 94.83 g COD/m2 d). The planted CWs were able to remove COD in the range of 80.24–80.62%, BOD5 in the range of 82.20–87.31%, TKN in the range of 73.42–76.07%, nitrates from 56–58.74% and sulfates from 68.58–69.45%, depending on the HRT. Phosphate and potassium were not removed. It was concluded that this type of CWs is a feasible option for the treatment of diluted stillage.