Biodiversity and Water
Depending on the size of the vintage, between 700-1000 KL of winery wastewater are generated each year at Mills Reef Winery – a complex milieu of grape juice colloids, processing aids and cleaning residues. This considerable volume of wastewater presented a significant challenge - in its raw state it cannot be simply flushed down the nearest drain!
The decision was made to utilise it via recycling. Mills Reef Winery has a one-hectare woodlot of Australian blackwoods at the back of the property, and also significant plantings of avocado trees around two sides of the winery. Why not design a system where winery wastewater could be used to irrigate the blackwoods, and better still, take this a step further, and nurture the avocado trees?
Soil and water samples were sent off to an accredited laboratory for testing, as a starting point. Sprinkler systems were installed and two 20KL settling tanks positioned close to the blackwoods. Resource consent was sought and granted by Environment Bay of Plenty, who provide on-going guidance and support.
Wastewater now makes its way through a series of underground tanks and sumps, and finally arrives at the first of two 20KL settling tanks, where it remains for 24 hours before progressing through to the second tank for a further 24 hours. This two-step settling process ensures that only clear supernatant is discharged. Irrigation is timed to switch on around 2 am each morning and effectively empties the 2nd settling tank each day. The whole irrigation area has been divided into four zones, which are rotated so that each zone receives a discharge for a maximum of 7 days, then rested for 21 days to allow the soil to recover.
Samples are tested on a regular basis to ensure pH and BOD values remain within acceptable levels.
We now have:
• An ecologically-friendly system that recycles wastewater in a safe and controlled manner
• Reduction in town water usage, replaced by a self-sustaining irrigation system
• Contributed to conversion of carbon dioxide to oxygen through sustainable plantings