Wine Cellar Waste

Winery waste water tends to be low in pH, low in nutrients and has a variable and often high organic load. The conductivity of the waste water is a function of chemicals used in the cellar and this too is variable.

The National Water Act of 1999 (Currently under review) currently makes a distinction between discharge to a water resource and disposal via kikuyu irrigation.

For both disposal routes emphasis is placed on sustainable reuse of the water. Irrigation is therefore a primary objective in the treatment of wine cellar waste water.

From our experience, removal of the waste water organic load is the most capital intensive. pH neutralization is relatively inexpensive and reduction of conductivity is best achieved by judicious use of chemicals in the cellar. Best possible cellar management can only partially reduce organic discharge.

Organic load in the waste water is analogous to sugar in coffee. It cannot be filtered out with conventional filtration. Like sugar it is biodegradable and can be removed successfully in a carefully designed biological environment. Typically wine cellar waste water has organic concentrations measured in COD units, and often in excess of 5 g/l. This is more than 5 times the concentration of domestic sewage which usually has a COD concentration of less than 1 g/l.

‘Out of sight’ spraying of waste water onto the land (most often on kikuyu pastures) initiates an underground and partial anaerobic cycle. Because the wine cellar waste water is low in pH and nutrients, organisms can only partially biodegrade pollutants in the water. A sub-surface, gelatinous bio-glue is formed that inhibits meaningful biodegradation. Eventually the pollutants move with the ground water flow and end up in the riverine catchment area. When this happens the water source is harmed for everyone.

All around us there are naturally occurring micro-organisms that will consume biodegrade and remove almost all the polluting particles present in wine cellar waste water. Unaided this natural cleansing process takes many years. The challenge is to create a friendly environment in which these natural micro-organisms can thrive. And this is what HWT does.

Each year we make small improvements in our treatment process and, in so doing, fine tune what nature does best. Our first treatment plants were constructed 1O years ago and, in the next pressing season, our treatment plants will process 2 million litres of water each day.

To produce 1 litre of wine requires between 2 and 8 litres of water, depending on how well the cellar is managed. For obvious reasons it is beneficial to bring water usage down.

Wine cellar waste water is cleansed in an engineered environment called a bioreactor. If the right conditions are in place – correct pH balance and sufficient nutrient ratios – then pollutants in the water are easily biodegraded by naturally occurring bacteria (biomass). For this reason lime dosing and the addition of nitrogen in controlled quantities is important. The Rotostab lime doser is a tried and tested unit that feeds lime and nutrients directly into an aerated bio-reactor. The biomass that grows is kept in a stable, contained environment. We have observed that by supplying sufficient oxygen, the biomass performs best under the massively varying conditions so typical of wine cellar waste water. For this reason we make use of a highly efficient diffuser dome and blower arrangement.

Once the pollutants have been removed, the water still requires further care. In the bioreactor mechanical processes subject the water to heat and compression. We therefore like to release the water into a constructed reed bed. In the reed bed, which is a diversity of wetland fynbos, the water is allowed a period of rest and revitalization. Our reed beds also provide important backup treatment capacity during peak flows. Waste water is an integral part of the water cycle that nourishes us all. If we interfere too negatively in the cycle we sell ourselves short. By honouring the water cycle everyone benefits – the micro-organisms, the soil, the crops, the people and their markets.