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Treatment and management options for sustainable winery wastewater reuse
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posted on 01.03.2017by Mosse, Kim Patricia May
Winery Wastewater (WWW) is produced globally, and its treatment and management are of significant concern worldwide. Whilst it is difficult to accurately assess the volume of WWW produced globally, it is estimated that 5-9 billion litres of WWW are produced annually in Australia alone. The composition of the WWW is highly variable, which makes treatment and management difficult, and potentially quite expensive. Given that many wineries in Australia are quite small, low cost treatment options are preferable, and one such low-cost method is land disposal. Land disposal has the added benefit of conserving valuable water resources, which is particularly important in many wine regions facing water shortages; however, it is important that this practice is carefully monitored to ensure that long-term damage is not sustained by receiving soils. To date, there is minimal information in the scientific literature describing WWW composition, and effects on biological systems in reuse situations are also poorly understood. The work presented in this thesis was based on a multidisciplinary approach, and considered a range of questions pertaining to the characterisation of WWW and its effects on biological systems under simulated reuse conditions. In this thesis, I present the results of a study in which I considered WWW treatment processes, composition and reuse opportunities in the context of existing knowledge. A review of the current literature revealed that WWW is extremely variable in nature varying on both spatial and temporal scales. This presents a key difficulty in performing research in the area, and it is therefore relatively common for lab-scale research to use a synthetic WWW to ensure consistence and repeatability. Whilst there is considerable research focusing on WWW treatment options, the majority of these do not consider the specific nature of the treated end-product, with information on organic molecules being particularly limited. Depending on the ultimate fate of the treated water, the composition can be extremely important, especially where reuse is intended. Characterisation work focussed on both soluble and particulate materials in WWW samples collected from five wineries located in southeastern Australia, each utilising a different treatment process. Analytical techniques focussed on characterisation of both influent and effluent waters at the molecular level. The treatment processes all resulted in considerable reduction of all compound classes considered (alkanes, alkenes, fatty acid methyl esters, lignin derivatives, polyphenols and sterols in the particulate analysis; fatty acids, phenols, polyphenols and sugars in the soluble analysis), although certain recalcitrant molecules (mostly phenolics) appeared to persist through the treatment processes, which may pose problems from a reuse perspective. In addition, some treatment processes appeared to be net producers of fatty acids, which were likely to be of microbial origin. Because corresponding influent and effluent samples were collected at the same time, and it was not possible to track them through the treatment systems, the samples cannot be considered to be matched, and conclusions are therefore indicative only. Taken together, the detailed characterisation of the organic composition of WWWs provides new insights into the compounds present both pre- and post- treatment, which may be of significant benefit when considering reuse opportunities. Irrigation of plants using WWW is a key disposal method used by a large number of wineries, However, the effect of the WWW on the crop is hard to predict, due to the high variability of WWW between wineries and over time. Simple tests such as bioassays can therefore be very useful; for WWW, very few such bioassays have been developed, and none for cereals or grasses (which are commonly grown on WWW land disposal sites). Consequently, a glasshouse study was conducted in which I investigated the effects of different dilutions of a semi-synthetic WWW on the growth and germination of four common cereal and grass species (barley, millet, lucerne and phalaris). The wastewater caused a significant delay in the germination of lucerne, millet and phalaris, although overall germination success of all species was not affected. Vegetative growth was significantly reduced in all species, with millet being the most severely affected. Importantly, the germination index of barley correlated very highly (r2 = 0.99) with barley biomass (at the time of harvest), indicating that barley seed germination bioassays are a good predictor of plant growth, and therefore may be of use as a rapid bioassay for WWW toxicity. Impacts of WWW on soils were considered on both long- and short- term scales. Physicochemical and microbiological soil properties were compared between paired sites, one of which had a history of 30 years of winery waste application (both liquid and solid). The effects of a single application of untreated WWW were compared to equivalent application of treated WWW (sequencing batch reactor) and pure water to eliminate the effects of wetting alone. Long-term application of winery wastes was found to have significant impacts on many physicochemical properties including pH, EC, and cation concentrations; most parameters were elevated following winery waste application, although Al concentrations were decreased. Analysis of soils using 13C NMR revealed only slight differences in the nature of the carbon present at each of the paired sites. A short term WWW addition experiment was also undertaken at the site that had no history of WWW application; the single application of untreated winery wastewater was shown to increase soil respiration and inorganic nitrogen (both ammonium and nitrate) concentrations, and cause significant alteration to the microbial community structure, as determined by PLFA analysis. The treated wastewater application was much more similar to the control treatment, showing no differences to wetting alone for soil respiration and soil ammonium, and only a slight increase in soil nitrate. The comparison of soil properties at the two sites with different histories of WWW application, taken together with the results of the short term WWW addition experiment, suggest that application of WWW to soils has minimal impact upon soil physicochemical properties, although this is likely to be mediated by changes to the soil microbial community. Given that changes to the soil microbial community are likely to impact on the above-ground community, it is essential that this be carefully monitored. Further studies were conducted in California to consider the impacts of WWW irrigation of an established ‘Syrah’ vineyard using four simulated WWWs with varied salt composition to reflect industrial cleaning regimes, and a control. Briefly, the treatments simulated wineries utilising a sodium (Na) based cleaner; wineries utilising a potassium (K) based cleaner; wineries utilising a K based cleaner coupled with higher water use efficiency, resulting in a higher K concentration; and a treatment that combined the elevated K levels with the presence of wine, to consider the potential synergistic/antagonistic effects of the salts and organic matter. Soil salt concentrations increased consistently with the nature of the treatment applied, with K and Na treatments causing increased soil K and Na, respectively. Petiole concentrations of K and Na increased approximately three-fold and nine-fold in the K and Na treatments, respectively, in comparison with the water only control. Attributes related to berry and juice quality differed among treatments at both véraison (anthocyanin and juice K concentrations) and harvest (juice K, juice Na, total phenolics, berry weight, harvest weights), although the majority of these were slight, and therefore unlikely to have significant impact on wine quality. In general, the Na treatment appeared to have had the greatest impact on vine growth and juice quality. Based on the data collected after a single season, irrigation with WWW appears to have had minimal impact on established vines. Nonetheless, there is potential for greater impacts to occur over longer time periods due to the perennial nature of grapevines. Due to the difficulties in assessing the impacts of WWW application on root development in field situations, an in vitro tissue culture method was developed to focus on impacts of various WWW constituents on root development. This technique utilised a dual-layer media, the lower of which contained the compound of interest (i.e. NaCl, Na2SO4 and KCl). The method was tested on different salts relevant to WWW, using rootstocks of varying salt tolerances, and showed that NaCl resulted in significant root growth retardation, whereas Na2SO4 and KCl did not significantly impact upon root development. Whilst not as rapid as the barley seed bioassay described above, it nonetheless provides another small scale tool that may be further utilised in the future to explore the impacts of different WWW components on vine root development. Taken together, the work presented in this thesis shows that there are numerous components of WWW that must be considered when planning for land disposal or WWW reuse. The organic composition is complicated, and certain molecule types appear to persist through the majority of treatment processes, which means that there is potential for accumulation in the receiving environment. Both above- and below- ground biological systems are impacted upon following WWW application, and, whilst the magnitude of the impacts demonstrated here is variable, it is likely that any impacts will be magnified with longer periods of WWW application. Taken together, the data from this study has demonstrated that there is cause for concern when reusing WWW for irrigation purposes, and that all reuse operations should be carefully considered and monitored.