The average amount of water used in wine-making is reported to be in the range of 1,500 to 3,500 litres /tonne of grapes crushed. This is about 2.6 litres /litre of wine produced. Wineries without a bottling line use about 40% less water than the wineries that undertake bottling onsite. Competing pressures on the supply of fresh water, incidences of drought, and increasing limitations on disposal options have resulted in a greater need to treat wastewater to a quality suitable for recycle on these sites.
The wastewater produced is complex and can be relatively high in BOD (up to 8,000 mg/l) and suspended solids (up to 700 mg/l). Variations in the nature of the wastewater contaminants can be significant because of the seasonal nature of wine-making. The wastewater usually requires several stages of treatment, including primary solids removal and dissolved organics (BOD) removal. In some cases, conventional aerobic biological processes (eg activated sludge, extended aeration, sequencing batch reactor) can be used to achieve more than 90% removal of BOD. In recent years, the membrane bioreactor has emerged as a suitable process for treatment for recycle purposes. These aerobic processes have to be designed to perform well under peak season conditions, so a modular design with two process trains in parallel are used.
In the case of very high BOD levels, the use of anaerobic treatment (eg digesters, anaerobic lagoons) may be desirable. Anaerobic processes can remove about 70% to 90% of the BOD. Relative to aerobic processes, the anaerobic processes can better reduce the amount of sludge produced and have a lower power usage. However, they require larger sites and tend to have higher capex costs. In some cases, it may be necessary to follow these anaerobic processes with aerobic treatment to meet low BOD and TSS discharge limits.
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