Oportunities and challenges of using constructed wetlands for the treatment of high-strength distillery effluents: A review

Abstract

Distillery wastewater (DWW) is a highly polluted industrial effluent generated during the distillation step for the production of alcohol from some feedstocks such as sugarcane, corn, sugar beet, wheat, agave, etc. The aim of this review was to find out the current use of constructed wetlands (CWs) for DWW treatment and/or the challenges of using this technology for such effluent. It was found that CWs has been evaluated almost exclusively at laboratory and pilot-scale levels for DWW produced from sugarcane/agave for alcohol or alcoholic beverage production. India, Brazil and Mexico are the main countries where CWs have been studied for DWW treatment with anaerobic digestion, dilution with tap water and cooling-sedimentation-neutralization pretreatments. Chemical Oxygen Demand (COD) concentration in the reported studies varied from 1181 to 14,055 mg/L and organic loading rate (OLR), between 61.2 and 281 g COD/d.m2. The highest removal efficiencies were 95% - 96% in two types of conventional CWs treating DWW generated during an alcoholic beverage production in Mexico. It was found that the higher the hydraulic retention time (HRT), the higher the efficiency for COD removal. According to this review, it is possible to use CWs for the treatment of DWW with high removal efficiencies of pollutants such as COD, with high HRT in deeper systems (to avoid a greater surface area), coarse filter material and an adequate selection of plants.