South Africa Wine Technical Yearbook 2025

JANUARY/FEBRUARY

Winery wastewater irrigation (Part 1): Annual dynamics of volumes and quality at two wineries By Reckson Mulidzi & Carolyn Howell

Abstract In wineries, the composition and volume of their wastewater changes throughout the year. The quality thereof is usually at its worst when vintage operations are dominated by the production of red wines. Taking the above-mentioned into consideration, the objective of the study was to investigate the annual dynamics of winery wastewater (WWW) quality and volumes at: (i) an existing grazing paddock at a winery near Rawsonville where WWW has been disposed of for many years and (ii) a new paddock at a winery near Stellenbosch where no WWW had previously been Introduction Increasing wine production over the last two decades has necessitated wine-producing countries to find sustainable winery wastewater (WWW) management practices that address environmental concerns. The use and availability of WWW for irrigation has increased globally and the disposal of wastewater is governed by stringent legislation. Most wineries in South Africa dispose of their wastewater through land application. This is carried out by irrigating small areas of cultivated pasture with the wastewater or ponding, with the former being the more general practice. The use of WWW for wine grape production is increasing, and it is therefore important to understand the environmental implication of such a practice. Where wineries use sodium (Na + ) -based cleaning detergents such as sodium hydroxide, the WWW will contain high levels of Na + . The current trend to replace sodium hydroxide with potassium (K + ) -based cleaning detergents in cellars may increase K + levels in the WWW. In terms of the General Authorisations for legislated limits for irrigation using wastewater in South Africa, most South African wineries would not qualify to discharge their untreated WWW into natural water resources. Where the disposal of winery wastewater is through land application, the following requirements, as stipulated in the General Authorisations, must be met (Table 1).

applied. The study was conducted over two and a half years. Although the quality and volume of WWW varied between the two wineries, WWW contained high levels of potassium (K+) for both wineries, whereas the sodium (Na+) levels were only high at the winery near Rawsonville. The study showed that WWW did not always comply with national legislation in terms of chemical oxygen demand (COD) and pH throughout the study period, while some prominent spikes for non-compliance for sodium adsorption ratio (SAR) and electrical conductivity (EC) were observed for both wineries. TABLE 1. General Authorisations for legislated limits for chemical oxygen demand (COD), faecal coliforms, pH, electrical conductivity (EC) and sodium adsorption ratio (SAR) for irrigation using wastewater in South Africa. Parameter Maximum irrigation volume allowed (m 3 /day) <50 <500 <2 000 COD (mg/L) 5 000 400 75 Faecal coliforms (per 100 mL) 1 000 000 100 000 1 000 pH 6 - 9 6 - 9 5.5 - 9.5 EC (mS/m) 200 200 70 - 150 SAR <5 <5 Other criteria apply The composition of WWW changes throughout the year. The large variability in volume and quality of WWW is associated with different practices that occur during different times of the year. Winery wastewater quality is usually at its worst when vintage operations are dominated by the production of red wines. High pollution loads from July to November are associated with bottling of white wines, putting red wines to barrel and filtering of the previous year’s red wines. In the Southern Hemisphere, harvest is from the end of January until beginning of April. Winery wastewater produced during harvest will contain higher levels of chemical oxygen demand (COD) and salts than wastewater produced outside the harvest period. Levels of COD and salts in WWW fluctuate according to winery operations, and reach a maximum when grapes

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TECHNICAL YEARBOOK 2025