Environmental impact of winemaking different
Winemaking wastewaters have different pollution coefficients. Basic information to improve the management of cellar treatments
A South African research took into exam the impact of different winemaking techniques on wastewaters, in order to design new and more efficient systems, dependent on the utilized technology, to treat them.
The research published by Bories and Sire distinguishes winemaking techniques between two main processes. Liquid-phase vinification is applied to white, rosé wines and to the thermovinification for red wines which entails the treatment of grapes/must through different phases: soft pressing, clarification and/or filtration.
Solid-phase vinification is the classic technique for red wine making, by means of pressing of must and marc mixed in fermentation tanks. Following the alcoholic fermentation, which can last up to a few weeks, the svinatura takes place, with the tank washing and, in some case, with one more pressing of fermented marc, which produces alcohol rich wastewaters.
During liquid-phase vinification the entity of wastewaters is function of the quantity of grapes involved in treatments, included the washing of machines destined to clarification and filtration. On the contrary, solid-phase vinification only generates wastewaters during the svinatura and pressing of fermented marc.
Therefore, liquid-phase vinification produces sugar free wastewaters: 70% of the chemical oxygen demand (COD) when must is treated and volumes depend on the daily quantity of grapes and represent 40 to 46% of the yearly volume of wastewaters during the first months of winemaking (September).
On the other hand, solid-phase vinification does not produce large quantities of wastewaters, which are mainly produced during decanting phases, and are characterized by a predominant presence of ethanol (<= 75% COD) and by intermittent flows during the second month of vinification (October), with less intensity (27.6% to 33.6%) and more distanced.
The specific pollution coefficients of liquid-phase vinification (5.18 to 6.04 kg COD/grape ton) are higher than the correspondent solid-phase vinification coefficients (3.82 kg COD/grape ton). The higher the percentage of liquid-phase vinifications in a cellar, the higher and earlier the maximum volume of wastewaters.
In cellars where different types of vinification are performed, wastewaters can be large at the beginning of the winemaking season, because of the polluting charge and number of contemporary processes. Thus, the environmental impact of liquid-phase vinification is severe if adequate countermeasures are not adopted. The main threats are an overload of biological systems because of the massive discharge of sugar rich wastewaters and an issue with unpleasant effluvia if these waters are ineffectively stocked, for instance in the case of impoundment.
Cellars which want to seriously reduce the environmental impact of winemaking should take into account the different polluting loads during the course of the whole grape harvest, and aim at introducing different disposal systems for a truly sustainable wastewater management and treatment.
A. Bories and Y. Sire; Impacts of Winemaking methods on Wastewaters and their treatment; 2010. SOUTH AFRICAN JOURNAL OF ENOLOGY AND VITICULTURE; 31 (1): 38-44