South Africa Wine Technical Yearbook 2025

FIGURE 1. Rain gauge with an attachment to catch the overflow for measuring the volume of wastewater applied to a replication plot at a winery near Rawsonville.

are crushed. The lowest COD values in the WWW usually occur in December and January (pre-harvest) and June and July (mid-winter). Peak periods of wastewater generation, as well as maximum levels of COD, tend to coincide with peak harvest periods. Variation in the period of high COD reflected local differences in harvest period. This variation also depends on the production period, as well as the unique style of winemaking of different wines. Taking above-mentioned into consideration, the objective of the study was to investigate the annual dynamics of WWW volumes and quality at two different wineries. Materials and methods Experimental sites The experiment was carried out over two and a half years at two different sites, namely (i) at a winery near Rawsonville in an existing cultivated pasture grazing paddock where WWW had been applied for over 15 years (-33.4137.7° 19.1920.3°) and (ii) at a winery near Stellenbosch in a newly cultivated pasture grazing paddock where no WWW had been applied before (-33.4958.6° 18.4759.9°). Both sites were in the centre of wide flat plains. The grazing paddocks were considered to be representative of WWW disposal through land application as practised by most wineries in South Africa. The winery near Rawsonville crushes ca . 22 000 tons of grapes annually, whereas the one near Stellenbosch crushes ca . 16 000 tons. Both wineries produce white and red wines. Trial layout At both sites, three 2 m x 3 m replication plots were demarcated. Rain gauges were installed at a height of 0.5 m

at each plot to measure the amount of WWW applied. A two-litre plastic bottle was attached to each rain gauge in the irrigation site to collect the overflow WWW when the rain gauge was full (Figure 1). Three rain gauges were also installed outside each paddock for measuring rainfall. Application of winery wastewater (WWW) to the soils At both sites, all WWW was disposed of through overhead sprinkler irrigation. The amount of WWW applied, as well as rainwater, were recorded on a weekly basis. Field measurements commenced on 1 March 2011 and were terminated on 30 November 2013. Wastewater sampling and analysis Winery wastewater samples were collected from the rain meters once a week and analysed for chemical composition. The COD of the WWW was measured using a portable spectrophotometer. The samples were also analysed by a commercial laboratory according to methods previously described. The SAR of the wastewater was also calculated. Results Basic cations: The WWW contained high concentrations of K + and Na + which could have a negative impact on the soil (Figure 2A). On average, K + levels in the WWW were substantially higher than the levels of Na + . This indicated that the winery probably used more K + -containing detergents than Na + -based ones. The annual fluctuation in K + and Na + could not be related to specific seasonal activities in the winery, e.g. grape crushing or bottling. However, almost throughout the Winery near Rawsonville Chemical composition of WWW

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TECHNICAL YEARBOOK 2025