Developing a fundamental understanding of the microbiological treatment of winery wastewater
Abstract
The objective of this project was to develop a fundamental understanding of the microbial populations that exist in the treatment of winery wastewater. Winery wastewater treatment plants (WWTP) were surveyed across Australia, at different stages of wine processing, and from anaerobic and aerobic treatment and storage lagoons. Conventional and molecular microbiology data identified microbial communities and relationships with effluent chemistry and plant operations were extrapolated. Pre-vintage preparation, solids management in the winery, surge water management and nutrient dosing were found to be key to promoting a healthy microbial community, essential for efficient and effective wastewater treatment.
Summary
Biological treatment of winery wastewater is common, but it has been poorly understood and difficult to manage. This project aimed to provide industry with strategies to reduce these difficulties, making the process more efficient and effective. It was a collaborative project between the University of Adelaide Wine Microbiology and Biotechnology Laboratory, CSIRO Land and Water and JJC Engineering.
Thirty plants were surveyed for three consecutive vintages, providing each winery with a snapshot of what their treatment plant looked like from a microbiological point of view, improving the understanding of their treatment systems. So-called ’G-bacteria’ dominated many plants and were associated with poor settling and cloudy supernatant, which prompted a PhD project titled, 'Identity and Ecophysiology of Glycogen Accumulating Organisms (GAO) in winery wastewater treatment plants’ to be established to specifically target their dominance. Alysiosphaera europea, Gordonia amarae-like organisms, Zoogloea and Type 0041/0675 are all commonly observed in WWTP. Yeast also dominated WWW in many plants and were associated with poor solids management in the winery.
Additionally, four WWTP were frequently sampled and analysed over three years to develop an understanding of trends that occur at the start of vintage, during peak vintage and at quiescent periods, both in terms of the microbiology of wastewater treatment plants, and the chemistry of influents and effluents. Each plant displayed a unique microbial community and while the communities at three plants were very stable, one plant was very dynamic and regularly changed in response to environmental changes and contained many novel organisms. Each of the plants was treating wastes from wineries with different operations however they shared similar characteristics. Influents were characterised by high Ec, low pH, low nitrogen and phosphorus levels and very high COD, which was attributed to large concentrations of phenols, ethanol and tartaric acid.
The application of anaerobic digesters to treat winery wastewater is growing internationally however they are still rare in Australia. Anaerobic treatment offers significant environmental and economic benefits and we believe this to be the direction in which wineries should be moving. We investigated two plants to gain a snapshot of the organisms present and the environmental factors that influence the community structure. It was found that temperature, pH and phosphorus have the greatest impact on the community structure and microbiology revealed low methanogen populations, so there is scope to improve performance significantly.
In response to consultation with wineries, two additional studies were undertaken. One to assess any potential health hazard associated with working with lagoon water and a second to investigate the impact of common additives (charcoal, perlite, skim milk and bentonite) used in the winemaking process on an SBR.
Potentially toxic cyanobacteria were measured in storage lagoons. Levels were found to be very low, posing no health threat to plant operators. Toxin levels were well within the World Health Organization guidelines for irrigation water.
Scientific data confirmed empirical observations by plant operators that charcoal has a significant negative effect on SBRs. Charcoal released the phenolics, ethanol, sugars and organic acids it had stripped from wine and juice back into the SBR water, significantly increasing the COD load on plants and lowering the pH.