Thursday, 10 September 2015 06:58

Membrane Bioreactors

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MBR units placed into custom built concrete tank. MBR units placed into custom built concrete tank.

The rapid growth in New Zealand’s wine industry has left local regulators playing catch-up throughout much of the country.

Environmental discharge standards for wineries are now being tightened to the point where many operators who could previously operate without even needing a resource consent for discharge of wastewater now need to look seriously at their options to minimise the environmental impact of this part of the operation.

Membrane Bioreactors (MBRs) offer treatment of wastewater from wineries to an extremely high level.  A membrane bioreactor is a biological wastewater treatment system that incorporates a microfiltration membrane (typically a 0.1-micron low-pressure filter) on the discharge to remove virtually all suspended solids, bacteria, and protozoa from wastewater.   

As well as directly cleaning up the wastewater discharge by filtering out these contaminants, the fact that this system retains 100% of the bacteria that are used for reducing the organic and nutrient loading of the wastewater means that typically three times as much organic loading can also be removed in a given size wastewater treatment plant by using the membranes.  

Due to the extremely high level of treatment achieved, membrane bioreactors can produce water that can be discharged to surface water such as a creek or injected into vineyard drip irrigation systems without causing blockage from solids or biological slime in the pipe network (as most other systems will do).

The level of biological treatment and pathogen removal achieved also means that membrane bioreactors are the only type of winery wastewater treatment plant in New Zealand that is commonly approved for treating mixed winery wastewater and human sewage (such as from an on-site restaurant or tasting rooms). 

This can provide huge benefits for large rural facilities that are not able to connect to a council sewerage scheme.

The removal of pathogens, solids, and dissolved sugars make the treated wastewater suitable for a wide range of reuses around the premises.  Uses in New Zealand for MBR treated winery wastewater (some mixed with sewage prior to treatment) include:

• Reuse for vineyard irrigation

• Landscape irrigation for native re-vegetation projects

• Discharge to surface water (which is not limited by weather or harvest cycles like land application can be)

• Landscape and lawn spray irrigation outside tasting room and winery restaurant

In areas such as Marlborough where water is becoming a very limited resource, councils are now accounting for landscape irrigation and deducting this from the winery or vineyard’s water allocation – therefore turning this highly treated wastewater into a valuable resource.

Furthermore in areas such as Hawke’s Bay where many of the wineries and vineyards are located over an unconfined aquifer, treatment to this level ensures that any wastewater applied to land does not compromise the quality of the region’s existing groundwater resource.

A significant driver of the change towards using MBR systems is the fact that the cost of installing the plants has now become competitive with (or in some cases better than) traditional systems.  

For instance, the cost of the membrane modules themselves to an end user in New Zealand has dropped by approximately 70% over the last 10 years.

Some wineries in New Zealand who have been feeding their membrane bioreactor systems a mix of restaurant sewage and winery wastewater for over seven years regularly achieve treated water quality of less than 1 E.Coli bacteria per hundred mL – down from millions in the feed, and around 1mg/L Biochemical Oxygen Demand (BOD5, a measure of sugars and ethanol in the water) – down from over 5,000mg/L in the raw wastewater. 

As the New Zealand wine industry moves towards a more sustainable future, this now well-proven technology is shaping up to be a cornerstone for ensuring the integrity of our pure clean image.

As an example of the growing adoption of this technology, Apex Environmental has recently installed the largest winery MBR in New Zealand, which will give the winery in question the cleanest wastewater discharge of any winery in Marlborough.   Many more are set to follow.

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