Winery wastewater: challenges and perspectives

The winery wastewater (WW) is a consequence of the wine production, generated from the numerous cleaning steps taken from the vintage, grape reception, must fermentation, wine stabilization, filtration and bottling. With this review, it is aimed to evaluate the composition of WW, its environmental consequences and solutions to mitigate its impact. Manny studies showed that the WW has low pH (3-4), high chemical oxygen demand (COD) ranging from 800 to 30000 mg O₂/L, well above the values of the Portuguese Decree Law nº 236/98, for wastewater discharge.

The high COD in combination with the presence of high content in polyphenols makes this type of wastewaters harmful for the environment. The consequences are measured in contamination to the water, soil, vegetation and air. Its low pH can affect the soil pH, color and electrical conductivity, reducing plant nutrients and the population of useful microbes.

For biodegradable fractions, biologic processes (aerobic or anaerobic) can be applied with the advantage of been cheap processes and remove large concentrations of organic carbon. However, biologic processes have difficulty in degradation of non-biodegradable organic matter and polyphenols, as well as the time required. Coagulation-flocculation-decantation (CFD) and advanced oxidation processes (AOPs) can be applied as complement to biologic processes with the advantage of faster removal of organic carbon and polyphenols, competitive costs and the sludge and water can be reused for fertilization and irrigation, respecting the principles of circular economy.