Treatment of high-strength winery wastewater using a subsurface-flow constructed wetland

Rapid expansion of the wine industry in rural California during the past three decades has created environmental contamination problems related to winery wastewater treatment and disposal. Often, winery wastewater is stored and treated in aerated ponds and disposed via postharvest vineyard irrigation; however, little research has been conducted on on-site treatment and its potential for downstream contamination. Throughout a given year, winery wastewater is extremely variable in quality and discharge volume. In addition to characterizing the wastewater, this study investigates the performance of a pilot-scale subsurface-flow constructed wetland (6.1-m long by 2.4-m wide by 1.2-m deep) in treating winery wastewater from a moderate-sized winery (2 million cases/a). Winery wastewater flowrates ranged from 80 to 170 m(3)/d at organic loads of 600 to 45 000 mg chemical oxygen demand (COD)/L. The study measured average removal rates of 98% for COD and 97% for total suspended solids using the subsurface-flow constructed wetland combined with an upflowing sand prefilter loaded at variable rates as great as 1640 kg COD/ha.d, or 8 times the recommended value. The system also seemed to be effective at neutralizing pH of the high-strength, acidic winery wastewater and at removing the limited nitrogen (78.2%) in the wastewater, in addition to sulfide (98.5%), ortho-phosphate (63.3%), volatile fatty acids (99.9%), phenols (100%), tannins and lignins (77.9%), and settleable solids.