Abstract
Winemaking produces large volumes of poor quality water. The possibility to re-use this water for vineyard irrigation was investigated in a field trial. For this purpose, winery wastewater had to be diluted to chemical oxygen demand (COD) levels ranging between 100 and 3 000 mg/l. The relatively simple infrastructure and procedure required to dilute the winery wastewater in 15 m3 tanks are described. Analyses of the diluted winery wastewater confirmed that the COD concentrations were reasonably close to the target values. Furthermore, measuring COD concentrations in the irrigation water while it was being pumped from the tanks confirmed that the concentrations of diluted wastewater within the tanks were fairly homogeneous, and that effective mixing had taken place while tanks were being filled. The COD measurements were more reliable when the oxidation time was standardised at 2 h compared to shorter periods, irrespective of the level of COD in the water. After initial practical problems and sources of error were eliminated, the accuracy of treatment application obtained in terms of the target COD concentrations was acceptable.
Highlights
Wineries produce large volumes of wastewater, during the harvest period from February until March
This caused an overestimation of the chemical oxygen demand (COD) level in the stock dam, which in turn resulted in too low COD levels in the diluted water in the tanks, when low COD in the winery wastewater required sample volumes of 2 ml compared to the 0.2 ml required for the higher COD levels, i.e. > 1 500 mg/l
The relatively simple mix and distribution facility allowed dilution of large volumes of winery wastewater to a range of COD levels required for irrigating grapevines in a field trial
Summary
Wineries produce large volumes of wastewater, during the harvest period from February until March. Surveys have shown that soil chemical conditions deteriorated where grazing paddocks were irrigated with winery wastewater over a period of time (Mulidzi et al, 2009b). The sodium (Na) in the water could accumulate in the soil, which could have negative effects on the soil physical properties in the long run (Arienzo et al, 2009; Laurenson et al, 2012). This could be more pronounced in dry regions where winter rainfall is inadequate to leach accumulated salts from the soil. An alternative to the grazing paddocks would be to re-use diluted winery wastewater for irrigation of agricultural crops.
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