Carolyn went to New Zealand to participate in a technical tour focussing on the management and re-use of treated winery wastewater, with particular reference to wine grape irrigation. She reports …

The Western Cape is experiencing one of its worst droughts to date. Urban users are currently limited to 105 L of water per person per day and water is a precious, scarce resource. Approximately three years of good rainfall is needed to recover from the drought. This implies that even if the 2018 winter rainfall is normal, the region will still feel the negative consequences for some time thereafter. Therefore, alternative sources of irrigation water for vineyards, e.g. using treated wastewaters, will become more important under the above-mentioned conditions or if climate change reduces long-term winter rainfall.

 

The geography and climate of New Zealand

New Zealand is an island country located approximately 2 200 km from Sydney in the south-western Pacific Ocean. It consists of two main islands, namely the North Island and the South Island separated by the Cook Strait. The climate is mostly temperate, with January and February being the warmest months and July the coldest. Most settled, lowland areas of the country have between 600 and 1 600 mm of rainfall. The west coast of the South Island has the highest rainfall, while the east coast of the South Island and interior basins are the driest.

 

Wineries visited in the Wairarapa region

The Wairarapa wine producing region, of which Martinborough is a sub-region, is a small grape producing region and produces 1% of New Zealand’s wine grape harvest. Martinborough Vineyard is a small winery in Martinborough where approximately 200 tonnes of grapes are crushed per year. Seventy percent of the grapes crushed at Martinborough Vineyard are Pinot noir. Most of the wastewater in the winery is generated by cleaning tanks and washing floors. The winery has stopped using sodium hydroxide (NaOH) as a cleaning agent. The wastewater is pumped through a course sieve and stored in two 3 000 L underground tanks. With the exception of pH adjustment, the wastewater does not undergo any further treatment. There are legal requirements with regard to discharge of wastewater to land, such as monitoring volumes automatically. Therefore, a resource consent has to be obtained from the regional council. In the resource consent there are general conditions, design standards and regulations concerning the management of environmental effects and monitoring. At Martinborough Vineyard, winery wastewater is used to irrigate windbreaks (Picture 1) rather than paddocks, because of the scarcity of land in the area. During vintage, the wastewater is almost irrigated directly to the windbreaks. In terms of water quality, the wastewater sodium adsorption ratio (SAR) and potassium adsorption ratio (PAR) is important. It should be noted that only one water quality sample is required during vintage. In the resource consent, the loading of nitrogen (N) and biological oxygen demand (BOD) is given in kg per hectare per year. Drip irrigation is used to irrigate the windbreaks and there have been no problems with clogging of drippers. Irrigation with wastewater may not continue if ponding occurs.

 

PICTURE 1. The windbreak on the right hand side where the winery wastewater at Martinborough Vineyard is irrigated. Note that during winter the irrigation line is stored on the vineyard irrigation line. The wastewater irrigation line is purple, as per convention to indicate wastewater.

 

Palliser Estate is a small winery in Martinborough where approximately 400 tonnes of grapes are crushed per year. Cultivars include Pinot noir, Riesling, Chardonnay, Sauvignon blanc and Pinot gris. Harvest is over by March or April. Most of the wastewater in the winery is generated by cleaning tanks. Storm water is kept separate from the wastewater. The winery has stopped using NaOH as a cleaning agent. Instead, sodium bicarbonate, metasilicate and citric acid are used. In the case of pH adjustment, citric acid would probably be used to neutralise it. The winery also tries to reduce water used for cleaning by using blasts of hot water to clean the tanks. The wastewater system works on a float system. The wastewater is kept in the first chamber and the water in the second chamber is clear. Solids are removed once per year from the tank. Wastewater is irrigated almost immediately to an area of land near a windbreak. According to their resource consent, the outflow of wastewater is monitored automatically. Soil analyses indicate that there is no accumulation of salts associated with the wastewater irrigation. This is probably due to the relatively high rainfall in the area. Grape skins are also composted (Picture 2) at Palliser Estate in Martinborough. The grape skins are mixed with straw, cow manure and rock phosphate. The addition of the rock phosphate lifts the pH of the material and encourages earthworms to inhabit it. The mixture is composted for eight months. Thereafter it is used as a nutritional supplement in vineyards where growth vigour is poor or where young grapevines are growing. The compost pile in Picture 2 is covered and the material itself lies on a pad, which allows for the collection of the leachate.

 

PICTURE 2. The compost pad at Palliser Estate in Martinborough.

 

Wineries visited in the Marlborough region

The winery at Pernod-Ricard Winemakers has sluices for wastewater to run into, where after it is collected in a very big tank (Picture 3). The wastewater is disposed of by the local council. Wastewater quality is monitored by an on-site laboratory that measures total soluble solids (TSS) and BOD. The company is very pro-active in terms of sustainability and a natural wetland planted with New Zealand indigenous vegetation was visited.

 

PICTURE 3. The wastewater collection tank at Pernod-Ricard Winemakers in Blenheim.

 

When Matua Winery near Blenheim planned to expand the capacity of their winery, they were required to reduce their environmental impact. This required an improved wastewater treatment system, which was built by Factor UTB. The system was completed in April 2016 and cost approximately R46 million. The winery wastewater is first treated at a balance tank with magnesium hydroxide [Mg(OH)2]. Liquid Mg(OH)2 buffers the pH quickly and the liquid is not as messy as powders. The water travels from the balance tank to the three wastewater tanks each having a capacity to contain 400 000 L of wastewater (Picture 4). Two of the tanks are used for wastewater treatment. The wastewater passes from the first tank to the second tank. The third tank is used for emergencies when too much wastewater is being produced to be contained in the first two tanks. The wastewater can also be further refined in the third tank if necessary. The wastewater moves into the irrigation tank and is used for irrigation of pine trees that are located 3.8 km from the treatment plant. The application of these irrigations did not seem to result in salt accumulation in the soil. Two soil samples are required per year at this specific winery, one in the pre- and one in the post-vintage period. Solids are passed onto a belt filter press. The thickened sludge (Picture 5) can be used as a soil conditioner.

 

PICTURE 4. One of the 6 m high and 400 000 L capacity wastewater tanks at Matua Winery near Blenheim.

 

PICTURE 5. The thickened sludge from the wastewater treatment. The sludge has a spongy texture.

 

At Cloudy Bay Winery, 5 000 tonnes of grapes are crushed per year. Sauvignon blanc, Pinot noir and Chardonnay are the cultivars focussed on. Their Sauvignon blanc is well known all around the world. The solids are removed from the wastewater and passes through three settling tanks (Picture 6). From the third settling tank, it is pumped into the main tank. Air is pumped into the main tank. The tank also has bacteria in it. The tank has a pH indicator so at any time one can ascertain what the wastewater pH is inside the main tank. Once per day, the water is pumped out and used for irrigation of woodlots planted with gum trees, indigenous vegetation and pastures. The local council visits the winery a couple of times per year. Water samples are taken regularly. Soil sampling is also done once per year and levels of elements in the soil have remained fairly constant. The winery also takes pro-active steps to minimise the amount of water used for the production of wine.

 

PICTURE 6. The three settling tanks and main wastewater tank at Cloudy Bay Winery near Blenheim.

 

At Allan Scott Family Winemakers, there were sluices evident in the winery. Winery wastewater is pumped through a spin separator (Picture 7). Grape skins were still evident even months after vintage. The wastewater is settled in tanks. At this winery, they use the wastewater for vineyard irrigation after harvest.

 

PICTURE 7. The spin separator used to remove solids from winery wastewater at Allan Scott Family Winemakers near Blenheim.

 

Closing remarks

In South Africa and New Zealand there is some level of legislation regarding irrigation with wastewater. In New Zealand specifically, one has to obtain a consent from the local council and irrigation with wastewaters is a very localised process with the local councils being involved, and responsible for monitoring of water quality during vintage. Winery wastewater treatment varied from almost nothing at smaller wineries to the sophisticated system at Matua in Blenheim. In New Zealand and South Africa, beneficial irrigation with wastewater is strived for. Although New Zealand has high rainfall, they anticipate water shortages in the future and, as such, showed a great deal of interest in using winery wastewater for vineyard irrigation. The BOD, rather than chemical oxygen demand (COD) as in South Africa, is an important criteria of water quality in the New Zealand wine industry. Elements of concern in winery wastewater for all countries are potassium (K) and sodium (Na). In New Zealand there is also an intense interest in N content of wastewaters. Making compost at wineries in New Zealand will still get a lot of attention in the future.

 

Acknowledgements

The South African Society for Enology and Viticulture (SASEV) for awarding the prize for the best article in 2014. Winetech for funding of the prize for best article in the SAJEV journal. Funding for the technical tour was also provided by the Local IWA Organising Committee. The ARC Infruitec-Nietvoorbij for the opportunity to undertake the technical tour. All my hosts in New Zealand who showed exceptional hospitality and showed such an interest in the South African wine industry.

 

– For more information, contact Carolyn Howell at howellc@arc.agric.za.

 

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