Winery wastewater irrigation (Part 1): Annual dynamics of volumes and quality at two wineries

by | Jan 1, 2025 | Technical, Viticulture research

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 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.

 

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.1 The use and availability of WWW for irrigation has increased globally and the disposal of wastewater is governed by stringent legislation.2 Most wineries in South Africa dispose of their wastewater through land application.3 This is carried out by irrigating small areas of cultivated pasture with the wastewater or ponding, with the former being the more general practice.4

The use of WWW for wine grape production is increasing, and it is therefore important to understand the environmental implication of such a practice.5 Where wineries use sodium (Na+) -based cleaning detergents such as sodium hydroxide,4 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.1

In terms of the General Authorisations6 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,6 must be met (Table 1).

 

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.6

Winery wastewater 1
 

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.7 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.8 Levels of COD and salts in WWW fluctuate according to winery operations, and reach a maximum when grapes are crushed.5 The lowest COD values in the WWW usually occur in December and January (pre-harvest) and June and July (mid-winter).9 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.10 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.

 

Winery wastewater 2

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.

 

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.11 The SAR of the wastewater was also calculated.

 

Results

 

Winery near Rawsonville

 

Chemical composition of WWW

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 study period, the Na+ was higher than 70 mg/L, i.e. the upper threshold for unrestricted use for sprinkler irrigation.12

The levels of calcium (Ca2+) and magnesium (Mg2+) in the WWW were substantially lower than the monovalent ions (Figure 2B). This was to be expected since chemicals containing Ca2+ and Mg2+ do not play a prominent role in winery processes. At these low levels, the bivalent ions would not have any negative effects on soils or crops. However, the Ca2+ and Mg2+ could have some positive effect on the water quality by reducing the SAR.

 

Sodium adsorption ratio (SAR): In 2011, the SAR of the WWW was frequently higher than 5, i.e. the legal limit for irrigation with wastewater as stipulated in the General Authorisations.6 During the remainder of the study period, the SAR was mostly equal to, or below the legal limit (Figure 2C). It should be noted that the wastewater SAR did not follow a distinct annual pattern that could be linked to specific activities in the winery.

 

Electrical conductivity (EC): The EC of the WWW was below the permissible limit of 2 dS/m, i.e. as stipulated in the General Authorisation for irrigation with wastewater,6 except for prominent spikes in January 2012 and June 2013 (Figure 2D). Similar to the SAR, the EC did not follow a distinct annual pattern that could be linked to specific winery activities.

 

Winery wastewater 3

FIGURE 2. Temporal variation in (A) K+ and Na+, (B) Ca2+ and Mg2+, (C) sodium adsorption ratio (SAR) and (D) electrical conductivity (EC) in wastewater from a winery near Rawsonville. Shaded columns indicate the harvest periods. Dashed lines indicate the Na+, SAR and EC thresholds for irrigation water.

 

Anions: Similar to the cations, the variation in levels of bicarbonate (HCO3), as well as sulphate (SO42-) and chloride (Cl), could not be related to a specific activity in the winery (Figure 3A & B). During February and March 2013, the level of Cl was above the recommended threshold of 150 mg/L for vineyard irrigation.13

 

Phosphorus (P): Since the levels of P were generally low throughout the study period (Figure 3B), land application of the WWW would not make a significant contribution to the P requirements of crops.

 

pH: With the exception of November and December 2011, the WWW pH was generally equal to or less than six, i.e. the lower limit for wastewater irrigation as stipulated in the General Authorisation6 (Figure 3C). Annually, the pH tended to be higher in winter than during the harvest period. Since the pH was below the legal requirement for disposal through land application during these periods, it was not suitable for irrigation of crops. Based on the foregoing, the experimental plots were irrigated with acidic water throughout most of the study period.

 

COD: Throughout the study period, the COD of the WWW was considerably higher than 400 mg/L, i.e. the upper limit for wastewater irrigation as stipulated in the General Authorisation6 (Figure 3D). Therefore, the WWW did not comply with the legislation for disposal through land application. Furthermore, the COD frequently exceeded 5 000 mg/L, i.e. the threshold above which wastewater may not be used for irrigation, or any other land application. Annually, the wastewater COD tended to peak during the harvest period (Figure 3D). This confirmed that the crushing and wine making generated wastewater with high COD.

 

Winery wastewater 4

FIGURE 3. Temporal variation in (A) HCO3 and SO42-, (B) Cl and P, (C) pH and (D) chemical oxygen demand (COD) in wastewater from a winery near Rawsonville. Shaded columns indicate the harvest periods. Dashed lines indicate Cl, pH and COD thresholds.

 

Rainfall and volumes of wastewater applied

Mean monthly rainfall was typical for a Mediterranean climate (Figure 4). However, the July rainfall was abnormally low in all the winters compared to the long-term average for Rawsonville (data not shown). Winter rainfall, i.e. from April to September, amounted to 380 mm, 420 mm and 685 mm in 2011, 2012 and 2013, respectively. During the harvest period from February until April, WWW irrigation amounts were substantially higher (Figure 5). During the peak period, in March, ca. 23 mm irrigation was applied per day. In December, the soil received only ca. 3 mm wastewater per day. The irrigation volumes also increased from mid-winter to reach a second peak in August when bottling occurred. Total irrigation applied from April to September, amounted to 1 475 mm, 2 600 mm and 3 285 mm in 2011, 2012 and 2013, respectively. Based on the foregoing, the soil received the highest irrigation plus rainfall in the winter of 2013, followed by 2012 and then 2011.

 

Winery wastewater 5

FIGURE 4. Mean monthly rainfall during the study period at a winery near Rawsonville.

 

Winery wastewater 6

FIGURE 5. Mean monthly wastewater applied during the study period at a winery near Rawsonville.

 

The application of WWW resulted in die-back of the grass on the irrigated area after only one month (Figure 6A). This could have been the result of oxygen depletion in the topsoil due to the high level of COD in the WWW. Most wineries that applied their WWW through land application do not measure how much wastewater they are applying, and their strategy is to irrigate an area until the plants die off and then move the sprinkler. The plants normally recover after three months. The soil also became totally waterlogged and the WWW ponded on the soil after irrigation was applied, particularly in winter. Due to the waterlogging, part of the water-soluble organic fraction of the WWW accumulated in the topsoil and in the ponded water on the soil (Figure 6B). The organic matter probably underwent anaerobic decomposition, which caused bad odours in the vicinity of the ponded water.

 

Winery wastewater 7

FIGURE 6. Waterlogging upon irrigation with wastewater caused (A) ponding and die-back of the grass, as well as (B) accumulation of organic matter on the surface of the Longlands soil form at a winery near Rawsonville.

 

Winery near Stellenbosch

 

Chemical composition of WWW

Basic cations: The wastewater contained high amounts of K+, but relatively low levels of Na+ (Figure 7A). This indicated that the winery probably used more K+ containing detergents than Na+-based ones. Most of the time, the Na+ was less than 70 mgL-1, i.e. the upper threshold for unrestricted use with sprinkler irrigation.12 The annual fluctuation in K+ and Na+ could not be related to specific seasonal activities in the winery, e.g. grape crushing or bottling. The levels of Ca2+ and Mg2+ in the WWW were lower than K+ and Na+ (Figure 7B).

 

SAR: Except in April and May 2011 (Figure 7C), the SAR of the WWW was well below 5, i.e. the legal limit as stipulated in the General Authorisation.6 This indicated that sodic soil conditions were unlikely to develop under the prevailing conditions. Similar to Na+, the wastewater SAR did not follow a distinct annual pattern that could be related to specific activities in the winery.

 

EC: Although the EC of the WWW was initially high (Figure 7D), it gradually declined and from January 2012 until the end of the study period, it was below, or equal to the legal limit of 2 dS/m, stipulated in the General Authorisation.6 This indicated that saline soil conditions were unlikely to develop under the prevailing conditions. It should be noted that the EC did not follow a distinct annual pattern that could be related to specific activities in the winery.

 

Winery wastewater 8

FIGURE 7. Temporal variation in (A) K+ and Na+, (B) Ca2+ and Mg2+, (C) sodium adsorption ratio (SAR) and (D) electrical conductivity (EC) in wastewater from a winery near Stellenbosch. Shaded columns indicate the harvest periods. Dashed lines indicate the Na+, SAR and EC thresholds.

 

Anions: The level of HCO3 in the WWW generally tended to decline over the study period (Figure 8A). However, the HCO3 content was relatively low during the harvest periods. Although irrigation with water containing high levels of HCO3 could affect soils, plants and irrigation equipment, there are no guidelines available.13 Given the high levels in the WWW (Figure 8A), negative effects could be expected over time if the water is used for irrigation. The level of SO42- in the wastewater was substantially lower than the HCO3 (Figure 8A). Except for some spikes following the harvest period in 2013, the variation in SO42- could not be related to a specific activity in the winery. Unlike the HCO3, the Cl tended to increase during the harvest periods (Figure 8B). The Cl levels in the WWW showed two distinct peaks where the permissible maximum norm of 150 mg/L for continuous irrigation of grapevines13 was exceeded. One of these peaks occurred in November 2011, whereas the second coincided with the harvest period in 2013 (Figure 8B).

 

P: The variation in P could not be related to a specific activity in the winery (Figure 8B). Since the levels of P in the WWW were generally low throughout the study period, land application of the WWW would not make a significant contribution to the P requirements of crops.

 

pH: Except during the harvest periods, the wastewater pH was within the legal requirement for wastewater irrigation as stipulated in the General Authorisations6 most of the time (Figure 8C). Based on the foregoing, the soil was irrigated with suitable water with regard to pH, except during the harvest periods when the wastewater became acidic.

 

COD: Annually, the wastewater COD tended to peak during the harvest period (Figure 8D). This confirmed that the crushing and wine making processes generated WWW containing high levels of COD. The COD of the WWW was considerably higher than 400 mg/L throughout the study period (Figure 8D). Furthermore, the COD frequently exceeded 5 000 mg/L, i.e. the threshold where wastewater may not be used for irrigation, or any other land application according to the National Water Act.6

 

Winery wastewater 9

FIGURE 8. Temporal variation in (A) HCO3 and SO42-, (B) Cl and P, (C) pH and (D) chemical oxygen demand (COD) in wastewater from a winery near Stellenbosch. Shaded columns indicate the harvest periods. Dashed lines indicate Cl, pH and COD thresholds.

 

Rainfall and volumes of wastewater applied

Mean monthly rainfall was typical for a Mediterranean climate (Figure 9). Similar to Rawsonville, the July rainfall was abnormally low in all the winters. Winter rainfall, i.e. from April to September, amounted to 325 mm, 500 mm and 590 mm in 2011, 2012 and 2013, respectively. As expected, WWW irrigation amounts increased from January until March (Figure 10). During the peak of the harvest period, in March, ca. 30 mm irrigation was applied per day. The irrigation volumes remained relatively high in winter and began to decline from October to a minimum in December when the soil received only ca. 1 mm wastewater per day. Total irrigation applied during winter, i.e. from April to September, amounted to 2 670 mm, 4 200 mm and 3 820 mm in 2011, 2012 and 2013, respectively. Based on the foregoing, the soil received the highest irrigation plus rainfall in the winter of 2012, followed by 2013 and then 2011.

 

Winery wastewater 10

FIGURE 9. Mean monthly rainfall during the study period at a winery near Stellenbosch.

 

Winery wastewater 11

FIGURE 10. Mean monthly wastewater applied during the study period at a winery near Stellenbosch.

 

Similar to Rawsonville, application of high volumes of winery wastewater caused die-back of the grass in the study plot (Figure 11).

 

Winery wastewater 12

FIGURE 11. Disposal of volumes of winery wastewater caused die-back of the grass in the plot at a winery near Stellenbosch.

 

Conclusions

It is important to note that this study represented the worst-case scenario, i.e. the WWW disposal was not carried out in a bigger paddock. The study focused on the real amount of WWW applied per week to the grazing paddocks and its direct environmental impact on a specific site. Consequently, high volumes of WWW were applied on a single plot, particularly in the harvest period and winter. The study confirmed that WWW from a winery near Rawsonville contained high levels of K+ and Na+, whereas WWW from a winery near Stellenbosch contained high levels of K+. These high levels of K+ and Na+ in the WWW reflected the cleaning detergents the specific winery used. Results confirm that WWW composition can vary substantially between wineries. The pH of the WWW tended to be below the legal limit. The study also confirmed that WWW did not comply with national legislations in terms of COD and pH.

 

Soil responses will be presented in the next two articles.

 

Acknowledgements
  • This article is an output of WRC Project K5/1881, entitled “The impact of wastewater irrigation by wineries on soils, crop growth and product quality”. This solicited project was initiated, funded and managed by the WRC. The project was co-funded by Winetech and ARC.
  • Goudini and Koelenhof wineries for their permission to work at their land and utilisation of their wastewater for research.
  • ARC for infrastructure and resources.
  • Staff of the Soil and Water Science division at ARC Infruitec-Nietvoorbij for their assistance, and in particular Mr. F. Baron for his dedicated technical support.

 

References
  1. Arienzo, M., Christen, E.W., Jayawardane, N.S. & Quayle, W.C., 2012. The relative effects of sodium and potassium on soil hydraulic conductivity and implications for winery wastewater management. Geoderma 173-174, 303-310.
  2. Arienzo, M., Christen, E.W., Quayle, W. & Kumar, A., 2009. A review of the fate of potassium in the soil-plant system after land application of wastewaters. Hazard. Mater. 164, 415-422.
  3. Van Schoor, L.H., 2001. A formula for the quantification and prioritization of negative environmental impacts in the wine industry. Wineland, 100-102.
  4. Mulidzi, A.R., 2001. Environmental impact of winery effluent in the Western and Northern Cape Provinces. M.Sc. Thesis, University of Pretoria, Private Bag X20, Hatfield, 0028.
  5. Laurenson, S., Bolan, N., Smith, E. & McCarthy, M., 2010. Winery wastewater irrigation: Effects of potassium and sodium on soil structure. CRD for Contamination Assessment and Remediation of the Environment. Technical Report no.19, 1-25.
  6. Department of Water Affairs, 2013. Revision of general authorizations in terms of Section 38 of the National Water Act, 1998 (Act No. 36 of 1998), No. 665. Government Gazette No. 36820, 6 September 2013. Dept. Water Affairs, Pretoria, South Africa, 3-31.
  7. Conradie, A., Sigge, G.O. & Cloete, T.E., 2014. Influence of winemaking practices on the characteristics of winery wastewater and the water usage of wineries. Afr. J. Enol. Vitic. 35, 10-18.
  8. Kumar, A. & Christen, E., 2009. Developing a systematic approach to winery wastewater management. Report CSL05/02. Final report to Grape and Wine Research and Development Corporation (CSIRO Land & Water Science Report Adelaide).
  9. Mulidzi, R., Laker, G. Wooldridge, J. & Van Schoor, L., 2009b. Composition of effluents from wineries in the Western and Northern Cape provinces (Part 2): Impacts on soil and the environment. Wynboer Technical Yearbook, 62-68.
  10. Mulidzi, R., Laker, G., Wooldridge, J. & Van Schoor, L., 2009a. Composition of effluents from wineries in the Western and Northern Cape provinces (Part 1): Seasonal variation and differences between wineries. Impacts on soil and the environment. Wynboer Technical Yearbook, 58-61.
  11. Clesceri, L.S., Greenberg, A.E. & Eaton, A.D., 1998. Standard methods for the examination of water and wastewater (20th ed). American Public Health Association, Washington DC.
  12. Ayers, R.S. & Westcot, D.W., 1994. Water quality for agriculture FAO Irrigation and Drainage Paper No 29. FAO, Rome.
  13. Howell, C. & Myburgh, P., 2013. Permissible element concentrations in water used for grapevine irrigation (Part 2) – Anions, trace elements and heavy metals. Wynboer Technical Yearbook, 59-61.

 

For more information, contact Reckson Mulidzi at mulidzir@arc.agric.za.

 

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