Rapid expansion of the wine industry in rural California during the past three decades has created environmental contamination problems related to hillslope vineyard runoff and erosion as well as winery wastewater treatment and disposal. The effects of field slope, cover and surface roughness on rainfall runoff, infiltration and erosion were determined at two sites near Kirkland Ranch Road in southern Napa County, California using a portable rainfall simulator. Significant correlations (at the 95% confidence level) between the physical characteristics of slope, cover, and surface roughness, with total infiltration, runoff, sediment discharge, and average sediment concentration were obtained. The extent of soil cracking, a physical characteristic not directly measured, also affected analysis of the rainfall-runoff-erosion process. Average cumulative runoff and cumulative sediment discharge from site A was 87% and 242% greater, respectively, than that at site B. This difference was linked to the greater cover, extent of soil cracking and bulk density at site B than at site A. Field slopes within the range of 4-16%, while a statistically significant factor affecting soil losses, had only a minor impact on the total amount of soil loss. The extent of soil cover was the dominant factor limiting soil loss when soil cracking was not present.
Winery wastewater is often stored and “treated” in aerated ponds and disposed via post-harvest vineyard irrigation, however, little research has been directed towards onsite treatment and potential for downstream contamination. Winery wastewater is extremely variable in quality and discharge volume throughout the year depending on the winery operations underway at any particular time. After characterizing the wastewater at a 2 million case/yr winery, 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 is evaluated. Winery wastewater flowrates ranged from 80 to 170 m3/d at organic loads of 600 to 45,000 mg COD/L (Chemical Oxygen Demand per Liter). Average removal rates of 98% and 97% COD and Total Suspended Solids (TSS), respectively, were obtained using the subsurface-flow constructed wetland combined with an up-flowing sand prefilter loaded at variable rates as great as 1,640 kg COD/ha-d (hectar per day), or 8 times the recommended value. The system also appeared to be effective at removing the limited nitrogen (78.2 %) in the wastewater, sulfide (98.5 %), ortho-phosphate (63.3 %), volatile fatty acids (99.9 %), phenols (100 %), tannins and lignins (77.9 %), settleable solids and neutralizing pH of the high-strength acidic winery wastewater. Concerns remain, however, about increasing Total Dissolved Solids (TDS) (salinity) and boron (B) concentrations of the wastewater following treatment. Moderately high TDS and B concentrations will require careful vineyard irrigation management when reusing the treated wastewater.
Departments of LAWR-Hydrology and Biological & Agricultural Engineering, UC Davis, Davis, CA 95616. Phone: (530) 752-3243. E-mail: megrismer@ucdavis.edu