Browsing by Author "Edwards, Richard Frederick"

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    Investigating the treatment optimisation of a pilot-scale Anaerobic Sequencing Batch Reactor (AnSBR) and partial characterisation of the winery wastewater using Near-infrared (NIR) spectroscopy
    (Stellenbosch : Stellenbosch Univesity, 2020-03) Edwards, Richard Frederick; Sigge, G. O.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Water is arguably the most vital natural resource on Earth. It is of critical importance to humans, plants, animals, environments as well as ecosystems. Agriculture is estimated to be responsible for the abstraction of approximately 66 – 70 % of the freshwater supply globally, with that number rising to 90 % in some countries. The wine industry in South Africa is responsible for producing large amounts of wastewater with 1.24 billion litres of wastewater generated in 2018. Winery wastewater is challenging to treat due to variable strength and seasonal compositional variation. Biological treatments are very effective for the removal of organic pollutants in winery wastewater. Anaerobic digestion is an example of a biological treatment that has been widely used for the treatment of winery wastewater. Anaerobic sequencing batch reactor (AnSBR) is a viable option for the treatment of winery wastewater. The technology is still under development and has not been used extensively in the wine industry. The advantages of the AnSBR include ease of changing operational parameters, can operate in batch or fed-batch mode; it efficiently removes chemical oxygen demand (COD) and generates biogas with a high methane percentage, that can potentially be reclaimed as a source of heat generation. Knowledge of the optimal conditions for pH, mixing intervals and feeding time of the AnSBR is limited and needs to be investigated. Two important parameters for the overall stability and performance of an AnSBR are COD and total suspended solids (TSS) concentrations. Determination of these parameters are however time-consuming and laborious. Near-infrared (NIR) spectroscopy is a rapid, non-destructive technique which makes use of the wavelength range of 780 – 2 500 nm. The first aim of this study was to investigate potential for the use of NIR to quantify and classify winery wastewater based on the COD and TSS concentration. Near-infrared spectroscopy was used in combination with multivariate data analysis (MDA) for the classification and quantification of COD and TSS in winery wastewater. Spectra were acquired using a benchtop FT-NIR (Büchi NIR-Flex N500) spectrophotometer with a wavelength range of 1 000 – 2 500 nm and a portable spectrophotometer with a wavelength range of 900 – 1 700 nm. The concentration of COD could be predicted with a RMSEP value of 893 mg.L-1, an error of 9.9 % compared to the range of the reference values, using PCR along with orthogonal signal correction (OSC). This was achieved using the wavelength range 2 060 – 2 340 nm on the benchtop instrument. The PCR model performed to a satisfactory degree to be used as a screening method to rapidly determine COD concentration of winery wastewater. The concentration of TSS could be predicted with a RMSEP of 136.94 mg.L-1 , an error of 5.72 %, using the benchtop instrument. The prediction model for TSS achieved a prediction performance that was almost comparable to the reference method, meaning it is suitable for screening purposes at the very least. Classification accuracies of 90.4 % (COD) & 100 % (TSS), 80.1 % (COD) & 95 % (TSS) could be achieved with the benchtop and handheld instruments respectively. Both the benchtop and the handheld instruments could classify winery wastewater based on their COD or TSS concentrations to a satisfactory degree. The above classification accuracies for the handheld instrument indicates that classification of winery wastewater, into low or high strength categories, may be possible for in-line monitoring of winery wastewater and screening via class, instead of quantification. The second aim of this study was to evaluate whether the AnSBR technology could successfully treat winery wastewater of varying quality and determine the optimal operational parameters for the reactor A pilot-scale AnSBR with a volume of 165 L was operated for 16 cycles treating winery wastewater. The cycle length was 24 h and the hydraulic retention time (HRT) was approximately 1.85 days. The reactor was initially seeded with 22 kg anaerobic granules. A central composite design (CCD) was performed to determine the optimal operational parameters. A mean COD reduction of 68.32 % (mean influent 5 852 mg.L-1 ) was achieved along with a mean polyphenol reduction of 53.35 % (mean influent 215 mg.L1 )(SAWIS, 2018) and a stable VFA:Alkalinity of 0.23 on average. The AnSBR technology could therefore feasibly be used to treat winery wastewater. The pH, feeding time and mixing interval were selected to determine the optimal operational parameters. The optimal values achieved were determined to be: pH 7.30; feed time 180.91 minutes and a mixing interval of 84.17 minutes. This study confirmed the optimal operational parameters previously obtained for treatment of synthetic winery wastewater with an AnSBR.