Water is an important topic in the world of wine. Protecting and conserving resources is of utmost concern so water is often looked at from the standpoint of usage and treatment of wastewater. Water quality is also critically important in food and beverage production. The conditions of the water must be suitable for the purpose it serves.
Throughout the winemaking process, water serves many functions; it’s used as a tool, to clean and sanitize, and as an additive or processing aid to make/prepare additions. Clean, potable water for use in wine production is typically sourced from a municipal (tap), a rural water district, or a well. However, there are some considerations beyond drinking water standards (set by the EPA) when it comes it’s use for winemaking. In production settings, the term process water defines water used for a variety of functions; rinsing, cooling, product water, or transport. Process water is generally treated in some manner to best fit the application. In winemaking, both water hardness and chlorination need consideration.
Water contains minerals (specifically calcium and magnesium) along with other alkali metals that lead to water hardness (Table 1). At a level over 120 mg/L measured as calcium carbonate, a given water source is considered hard. Hardness in water can cause issues with respect to cleaning and sanitation because it reduces the effectiveness of detergents (especially bicarbonates). Hardness also causes scale or deposits on equipment and can be a culprit in premature filter clogging. Water hardness is especially problematic in conditions that are alkaline (pH >7) and/or increased temperature. These deposits are unsightly and lead to other organic debris build up that make cleaning more difficult. High mineral content in water can also decrease the effectiveness of ozone.
To combat the issue of water hardness, water testing and subsequent use of water softening or conditioning systems can be employed. Water from different sources will have different composition, so testing prior to implementing a treatment system is imperative to ensure the best results. Water softening systems typically utilize ion exchange to remove positively charged calcium and magnesium from the water by use of an ion exchange resin that exchanges the calcium and magnesium ions in the water with the positively charged sodium ions on the resin. This results in an increase of the salinity of the water. As an alternative to sodium, potassium resin can be used. This results in an increase of the potassium content of the water.
As an alternative to softening, water conditioners or non-salt based systems are available on the market. Some methods will also soften (remove calcium and magnesium) but others do not. For those that don’t the instead affect the behavior of the minerals in a way to inhibit their precipitation and build up. Examples of methods to condition water are reverse osmosis (RO), chelation or various forms of technology using electricity.
Water treatment facilities routinely use chlorine (up to 4 mg/L) to control harmful human pathogens in municipal water. It may be added as elemental chlorine gas (Cl2), sodium hypochlorite solution (NaOCl), also known as bleach, or solid calcium hypochlorite Ca(OCl)2. Alternately, it is added as monochloramine (NH₂Cl) or chlorine dioxide(ClO2)*. Chlorination is extremely useful in the production of safe drinking water however, the recommendation in the winery is to avoid the use of all chlorine based products and this should include the process water for all cellar work.
Chlorine has been eradicated from the winery due to its contribution to the formation 2,4,6-tricholoranisole (TCA), a compound responsible for cork taint. Mold growth in corks or on other wood sources coming in to contact with chlorine results in production of TCA by the mold. The fault is a musty, dusty, or wet cardboard-like odor with a very low sensory threshold.
Dechlorination is an important step to consider for process water used for cleaning and sanitation, for all additions, and preparations of yeast and bacteria. Activated carbon filters are the primary way to dechlorinate water for process uses. The carbon works by adsorption, which through the activation process gains a very large surface area. The carbon also can react with chlorine to produce chloride ions. There is a contact time interval for the treatment and if a water source was treated with chloramine, this takes more time to dechlorinate. As with water hardness, testing of the water is the first step to formulating a means to treat the water source properly for the best result.
*The use of chlorine dioxide has not been linked to TCA production because chlorine is not involved in any of its reaction pathways. It is considered an alternative to chlorine based products.
Butzke, C. 2010. Chlorine Use in the Winery. Purdue Extension. www.extension.purdue.edu/extmedia/FS/FS-50-W.pdf
CBTECH. 2018. The Science behind Activated Carbon Water Filters. www.carbonblocktech.com/the-science-behind-activated-carbon-water-filters/
PennState Extension. 2018. Hard Water and Water Softening. https://extension.psu.edu/hard-water-and-water-softening
University of Minnesota Water Resources Center. Water Softener Alternatives (Water Conditioners, Non-salt-based. Systems). www.wrc.umn.edu/sites/wrc.umn.edu/files/residential_water_softening_alternatives_fact_sheet-_finalchedit.pdf
University of California Davis Extension Viticulture and Enology. Common Chemical Reagents: Chlorine Dioxide. https://wineserver.ucdavis.edu/industry-info/enology/methods-and-techniques/common-chemical-reagents/chlorine-dioxide
Zoecklein, B. 2011. Fermentation Considerations for the 2011 Season. In Enology Notes # 159. www.apps.fst.vt.edu/extension/enology/downloads/EnologyNotes159.pdf