By ROSS WHITMORE, managing director, Winery Waste Solutions Ltd

Winery waste water treatment in New Zealand has now reached a new phase with the record crop in 2008 and another large increase in volume predicted for vintage 2009.

New Zealand, with its abundance of water and lax regulation regarding discharge of waste water, is faced with a need to improve on past performance.

Australia and California for example have for some time had more stringent requirements for discharge quality. New Zealand has the clean and green image but does its performance back this? 

Waste water is often seen as a difficult problem that costs money and adds no value to the bottle of wine produced, however it is inevitable that tougher regulations will be legislated and consumers will want to know that the wine they are drinking came from a sustainable winery process.

A rapid increase in winery size now means that what worked in the past may not work in the future. Council trade waste systems and ponds are stretched to capacity in some areas and spray irrigation systems will be overloading soils on existing sites. Winery waste water is difficult to treat because of its varying volumes, pH, BOD (biological oxygen demand) and TSS (total suspended solids) levels. 

Plant design is more complex to incorporate features that allow for all the variables. Vintage is a period of maximum flow so is the critical period. Sixty percent of the annual waste water flow can be discharged over a 4-6 week period. Any treatment system needs to cope with this peak flow and accordingly this adds substantial cost to any system.

Treatment is defined as discharge water that is low in BOD, TSS, nitrogen and phosphorus compared to the water that went into the system. Examples of this are BOD 50mg/l and TSS 30mg/l.

Land-based systems use the soil as a digester which is all right for small volumes but quickly overloads the soil when greater volumes are introduced. This leads to anaerobic digestion and the bad smell that many people find offensive. 

Residual salts (e.g. sodium) have not yet been an issue in New Zealand but overseas this is a big problem. With repeated discharges soil structure is eventually compromised, as is the underlying ground water.

Ponds can be used but again they are anaerobic and have the smell issue. They use a large amount of valuable land as they need to be big enough to allow plenty of time for the anaerobic process to work. Large aerators can reduce the smell but don’t contribute enough oxygen to reduce BOD levels quickly.

In response to these problems Winery Waste Solutions (WWS) Limited has developed a treatment system that significantly reduces BOD, TSS, N and P in winery waste water

Wineries now have the option to treat before dispersal as opposed to treatment by dispersal.

The WWS treatment plant allows users to meet regional council requirements with effective BOD and TSS reduction on a daily basis. Each plant is designed to treat the winery’s daily peak flow after consultation with the winery operators.

A dedicated research program has shown the WWS system can reduce a BOD of 5000mg/l to less than 100mg/l. The system is designed to handle peak vintage flows and operates at a reduced capacity when there are low or no flows. 

The system uses pre-screening to < 1mm, pH adjustment and then an aerobic process with an on-line sludge handling system. Resultant water can be used for irrigation and with further sanitation could be fully recycled.

A treatment system can be installed in phases over a period of years and this enables the winery to spread the capital cost. 

It is important when considering waste water treatment to focus on what end result you want so that equipment can be designed correctly and a program of installation can be planned. Often the consideration of plant purchase leads to the winery operators reassessing their water use and practices. Substantial reductions in water use are regularly made. This then means a smaller treatment plant can be installed.

Winery Waste Solutions Ltd recommends a planned approach to the difficult issue of waste water treatment and this is usually supported by regional councils who see progress being steadily made to improve our waterways.