Study on discharge characteristics of fermentor and oak barrel washing wastewater from typical wineries in Ningxia, China.

Wine wastewater management is critical to the sustainable development of the wine industry. In this study, three wineries were selected with growing wine production scales of Ningxia. The number of fermentors and oak barrels washing wastewater were counted during the production period of 2019. The water quality was analyzed and finally the pollutant production was estimated. The results showed that fermentor (barrel) cleaning method greatly influences wastewater amount. The five-step method during fermentor washing stage produced more wastewater than direct high-pressure washing. However, high-temperature fumigation in the oak barrels washing stage can effectively reduce wastewater. The residue of grape juice in fermentors and oak barrels made the main pollutant of washing fermentor (barrel) wastewater COD, and the unit product of washing oak barrels' wastewater produced more COD than washing fermentor wastewater. COD production of washing fermentor wastewater per unit product was ranked as Winery C (412.5 g·kL) > Winery B (331.5 g·kL) > Winery A (33.6 g·kL), in oak barrels washing stage, Winery C (679.2 g·kL) > Winery A (507.2 g·kL) > Winery B (350 g·kL). The results showed that a good linear relationship between annual wastewater production and COD production of the winery (R is 0.9777 and 0.9934, respectively). Compared with the first-level standard of cleaner wine production, the production of fermentors and oak barrels washing wastewater in winery accounts for 11-18% of total wine production wastewater, while COD production accounts for 17-43% of total COD.