To manage these aspects and impacts efficiently and make provision for emergency situations, it is important for cellar managers to know what the potential impacts are, what the source of these impacts is and which management options may be followed to minimise the environmental risks.
POSSIBLE NEGATIVE ENVIRONMENTAL IMPACTS
The winemaking process is mainly divided into two periods generating different kinds of waste, namely the vintage period and the non-vintage period. During the harvest period, which ranges from 6 to 20 weeks, grapes are harvested and pressed while the juice is fermented into wine. During the non-vintage period other cellar activities take place, such as stabilisation, filtration, maturation, blending and bottling of wine. At larger cellars in particular there is not really a division between these two periods, since the processes associated with the non-vintage period take place throughout the year.
The various kinds of solid waste generated at a cellar during the harvest period, are skins, stems, pips and yeast. Stems, skins and pips are usually removed from white wine cultivars after pressing. From red wine cultivars they are removed only after fermentation of must to wine, particularly to extract colour pigments. Lees are the residues that remain in tanks once fermentation and removal of unfinished wine have taken place and consists of a mixture of wine, yeast and bacteria. During the post-vintage period, used sedimentation substances, such as bentonite and used filtration material, are generated and constitute a further source of unwanted solid waste. Usually stems, skins, pips and lees are heaped up and later worked into the vineyards.
Australian guidelines require skins, stems, pips and lees to be heaped on an impenetrable layer (such as cement or plastic) and covered against rain, so that organic acids cannot seap out and have a negative effect on soil and soil water before having broken down sufficiently to serve as compost. If no storage space has been provided for this, it should rather be used as animal feed. This waste, as well as used sedimentation substances (e.g. diotomatious earth and bentonite clay) and filtration material, must be stored temporarily before being removed to prevent bad odours in the adjacent vicinity. Used filtration material and bentonite should be made available for the recovery of alcohol or tartaric acid to prevent soil and water pollution (which occurs when these substances are exposed to the soil too quickly). From July to December the waste should be taken to a suitable dumping site (similar to Vissershok in South Africa) to be destroyed.
Must, wine and wastewater
Grapes from white and red cultivars differ in their chemical composition and the processes for making white and red wine also differ. Must is the liquid obtained when the grapes are pressed. Must composition reflects the composition of the specific cultivar, as well as the seasonal performance of the vines. The most important change in organic composition occurs during fermentation from must to wine. Sugars are used by yeasts and bacteria as the main source of carbon dioxide, with a drastic decline in sugar content. Anaerobic conditions give rise to the production of glycerol and ethanol, both of which are important components of wine. Malolactic fermentation of malic to lactic acid occurs naturally in red wine cultivars. Although this biochemical process may occur in some white wine cultivars, malolactic fermentation represents the biggest difference in the production of red and white wines. With regard to anorganic contents of wine, potassium (in the form of K-H-bitartrate) is the only element which changes during wine production. K-H-bitartrate occurs in both the must and the wine and precipitates against the sides of tanks and equipment during the cold stabilisation process. To dissolve these crystals, alkali products containing the hydroxy ion (OH) are used. The alkali products simultaneously serve as a means of removing red colour pigments. The most commonly used substance in South African cellars for the above is sodium hydroxide diluted to 5% (better known as caustic soda). Other products such as sodium metasilicate and sodium carbonate are also used at times. These chemicals react with water to release hydroxides (OH ions). The amount of OH ions released has a direct influence on the pH of the solution. The higher the pH, the more tartrate is removed. Sodium metasilicate generates more OH ions than sodium carbonate, resulting in pH values of 10-12 and 9-10 respectively. However, the pH of sodium hydroxide (5%) ranges between 12 and 13 and is therefore more effective in removing the tartrate. Once the tartrate has been removed, it is followed by a rinse of 5% citric or tartaric acid to neutralise the alkali. Washing water generated by this process is known as cellar wastewater, and the volumes thus generated, as well as the chemical composition, may entail huge environmental risks for nature. The Australian wine industry requires a wastewater audit which prescribes a monitoring programme, a specific sampling method and criteria for analyses.
To determine which environmental risks are posed by a specific cellar, cellars have to know how much wastewater is being produced as well as the pollution load thereof. Dr Chapman mentions that Australian cellars (the same probably applies to South African cellars) generate approximately 2 to 5 kilolitres of wastewater for each ton of grapes pressed. For large cellars, which generate wastewater throughout the entire year, approximately 50% of the wastewater is generated during the harvest period from February to April. Smaller cellars produce an even higher percentage of the annual volume during the harvest period. This wastewater may be high in organic carbon dioxide, relatively low in nitrogen and phosphor, and relatively high in salts and acids. In Australia, but also in South Africa, legislation requires cellars to follow a wastewater audit procedure. Since most cellars do not have a historic record of wastewater volume or quality, an intensive monitoring programme should be followed during the first 2 or more years. The monitoring programme should calculate, on an annual basis, the volume of wastewater, the normal variation in volume between key periods of wastewater production, the normal variation in chemical composition between key periods of wastewater production, as well as the potential environmental and social impacts of the recycling or disposal activities.
Once cellars have followed the initial intensive monitoring programme for 2 or more years, a routine monitoring programme should be followed to confirm the variation in wastewater volume and chemical composition. Furthermore cellars should monitor the impact of wastewater on soil, water resources, vegetation and health. In due course each cellar will then follow its own monitoring programme specific to the locality, associated with the method of purification and disposal.
A successful monitoring programme goes hand in hand with a thorough and representative sampling programme. In Australia cellars are recommended to take samples at the following six key stages:
Pre-harvest period: January to February
During this period bottling takes place and tanks are washed with sodium hydroxide. Other equipment is also washed to prepare for the harvest period.
Early harvest period: February to March
During this period wastewater generation increases drastically and reaches 40% of the maximum weekly rate measured at peak. White wine production dominates harvest activities.
Peak harvest period: March to May
This is when wastewater generation and harvest activities reach peak stadium.
Late harvest period: April to June
Wastewater generation decreases dramatically to 40% of the maximum weekly flow (at peak) and red wine production dominates harvest activities. Occasionally distillation of ethanol takes place.
Post-harvest period: May to September
During this period pre-fermentation activities come to a close and maximum usage of sodium hydroxide occurs.
No harvest period: June to December
Wastewater volume is at its minimum (less than 30% of the maximum weekly flow at peak) and wastewater quality depends on daily activities.
Recommended frequency of sampling differs for large (>20ML wastewater/annum) and smaller (<20ML wastewater/annum) cellars. Smaller cellars should take only one sample per period in each period, while large cellars should sample as follows:
- Pre-harvest period fortnightly
- Early harvest period weekly
- Peak harvest period weekly
- Late harvest period weekly
- Post-harvest period fortnightly
- No harvest period every 6 to 8 weeks
Sampling procedure for wastewater
- Most cellars store and/or pre-treat their wastewater to reuse it or to reduce extreme variations in composition prior to disposal. The Australian wine industry recommends the following procedure for taking representative wastewater samples:
- Sample the wastewater at the point where it is disposed into a catchment dam or onto grass at the depth where it will flow out.
- Take a composite sample (instead of a single sample) composed of equal quantities of at least 5 samples taken before the dam was filled.
- At least 1,5L wastewater must be sampled in a glass container and stored below 4C, or as suggested by the chemical laboratory doing the analysis.
- Sampling at times when the inflows are very low, or when stormwater has a diluting effect, should be avoided.
- Cellar activities at the time when sampling takes place should be noted down, especially when the total volume at the point of collection is dominated by one or two processes only.
- Keep records of all action taken.
Analysis of wastewater
In South Africa and abroad cellars are legally obliged to follow an environmental management programme and analyses have to be done by an accredited laboratory. The chemical composition of wastewater indicates whether the water has potential environmental and/or social impacts when it is released into nature. Table 1 below indicates the parameters that are important to monitor and which are regarded as the minimum for which analysis should be done in South Africa. Apart from these elements juice, wine and lees, which are also sources of organic carbon dioxide and anorganic components such as salts, acids and solids, may also end up in the waste stream during the harvest period and contaminate it even further.
Table 1. The most important parameters and risks of wastewater analysis.
- Total and dissolved solids Closing of soil pores Limited aeration of soil Limited flow of water through soil Closing of water purifier Formation of anaerobic sludge in catchment dams
- Organic carbon dioxide or biological oxygen demand (BOD) Reduction in oxygen content of water Bad odours at catchment dams
- Nitrogen (N) and phosphate (P) Eutrofication of water
- pH Acidification of soil
- Salt content (NaCI, KCI) Salination of soil and water
- Sodium (Na) Decomposition of soil structure with accompanying poor drainage Waterlogging conditions in soil Limited aeration of soil Compaction and hardening of soil Clogging of soil pores Soil erosion
- Sulphur (S) Bad odours in catchment dams
- COD (chemical oxygen demand) Reduction in oxygen content of water Bad odours at catchment dams
Legislation requires South African cellars to monitor the volume of water used in the cellar, as well as the quantity of wastewater, in order to obtain a water balance. Apart from the fact that large volumes of wastewater may result in waterlogging conditions and poor aeration of soil as well as bad odours, it also has other large scale financial implications. In Australia, where water is also a scarce commodity, cellars have to pay for each litre of water used, and if the water consumption in the cellar can be reduced, it will bring about a direct decrease in cost. Apart from this, it will also result in less wastewater being generated, which reduces the handling, storage, purification as well as irrigation cost. Each cellar has to do its own investigation concerning processes where water consumption may be reduced. The following are examples of how to reduce water consumption in the cellar with minimum cost and adjustment to main processes:
- Use brooms or pressure mops instead of rinsing floors with water
- Use high pressure hoses to reduce water volumes
- Separate stormwater from washing water
- Recycle stormwater to be used as washing water for cleaning floors
Design criteria for wastewater catchment dams
Catchment dams for cellar wastewater are usually designed by engineers. To do this efficiently, the engineer requires information about the volume and composition of the wastewater. The cellar management should ensure that the designer at least takes the following into account:
- The wastewater must be separated from the stormwater (rain water).
- Pipelines for conducting wastewater must be able to handle the maximum volume at any one time and must be made of quality material to prevent leakages.
- The catchment dams for wastewater must be able to handle the maximum volume of wastewater at any one time and enough space should be allowed for possible unexpected volumes of wastewater.
- Catchment dams should be large enough so that sufficient time may lapse for the solids to be deposited and so that the breaking down of organic matter may take place before the water is released or used for irrigation.
- Catchment dams should be situated in such a way that there is no contact with storm water.
- Irrigation systems must be designed to prevent leakages.
Cleaning of waste catchment dams
Wastewater dams, pipes and other equipment should be cleaned annually and large volumes of sludge are thus collected. In Australia, but also in South Africa, this sludge may only be applied to the soil once the chemical composition thereof has been determined, indicating that it may indeed be applied to a specific piece of land. If the sludge contains high concentrations of certain elements, it may influence the soil, water sources and plant peformance. An attempt should be made to conduct the cleaning operation in the summer months, so that breaking down can be more rapid, thus minimising bad odours.
Noise and air pollution
Noise from pumps, compressors, cooling apparatus and vehicles may cause distress to neighbours and gas leakages from refrigeration mechanisms may cause air pollution. For this reason Australia requires equipment or vehicle noise of which the noise exceeds 45 dB outside the cellar, to be used between 8am and 8pm only. Roads, trucks, tractors, pumps, compressors, refrigeration mechanisms and other equipment causing noise and/or air pollution should be monitored on a continuous basis and regular maintenance records should be kept.
For cellars, local and international, the most important environmental aspects which may impact negatively on the environment, are mainly wastewater and solid waste. Requirements from international markets regarding efficient management of these impacts are becoming more and more stringent and the South African wine industry cannot afford to fall behind in this regard. Since South Africa is still in the process of devising specific guidelines for the responsible management of possible environmental risks at wine cellars, it would make sense meanwhile to follow Australia’s guidelines, especially those which are applicable to South African conditions. International environmental management systems such as ISO 14001 are expected to become a requirement in the international markets within the next few years. The implementation of such an environmental management system takes months or even years. If this is required of a cellar at short notice, it will be difficult to implement if certain environmental issues have not already been addressed to some extent. It is therefore necessary for South African cellars and in their own interest to institute the required measures, eventually to comply with this system.