Masters Degrees (Food Science)
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Browsing Masters Degrees (Food Science) by Subject "Anaerobic digestion"
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- ItemAnaerobic bioconversion of liquid and solid wastes from the winemaking process(Stellenbosch : Stellenbosch University, 2015-02) De Kock, Michelle; Sigge, G. O.; Britz, T. J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.ENGLISH ABSTRACT: South Africa is a developing country that relies on its agricultural sector as a main source of overall economic welfare. Development does not only give rise to new technology and new products but also results in increased amounts of liquid and solid waste. Generally, the production of wine is considered an environmentally friendly process, but significant amounts of natural resources and organic amendments are necessary, while generating large amounts of liquid and solid wastes. Anaerobic digestion (AD) is an attractive and proven treatment option for both liquid and solid wastes as valuable products and depollution can be obtained. AD of liquid waste results in an effluent and biogas, while anaerobic composting of solid waste results in an organic amendment, leachate and biogas. The overall objective of this study was to investigate the operational feasibility of the cotreatment of leachate produced during the anaerobic composting (AnC) of grape skins in an upflow anaerobic sludge blanket (UASB) reactor while treating winery wastewater. This first aim of this study was to investigate the efficiency of the anaerobic composting of grape skins. Laboratoryscaled digesters (1L) were utilised as anaerobic composting units. The most important operational parameters were identified (pH, moisture content and inoculum (size, ratio, composition)) in order to produce a pH stable, odour free compost in 21 days. Experimental studies highlighted the importance of shredding waste as well as the addition of calcium oxide and green waste to increase the initial pH of the composting mixture. After optimising a 50% (m.m-1) cow manure inoculum, lower inoculum concentrations (10, 15 and 25% (m.m-1)) were investigated to make the process more economically viable. A 10% (m.m-1) anaerobic compost (AC) inoculum was found to produce the most favourable results in terms of pH stabilisation and leachate generation. A 50% (m.m-1) moisture level performed the best by attaining a pH > 6.5 on day 6 and having the highest end pH (7.65) on day 21, while white and red grape skins in an equal ratio were found to generate a higher end pH. With all these optimum parameters in place (shredded waste, green waste, CaO, inoculum, moisture, grape skins), a compost with a final pH (7.09), moisture (58%), nitrogen (2.25%), phosphorous (0.22%) and potassium content (1.7%) was obtained. The optimised parameters were scaled-up (1:10) by using polyvinyl chloride anaerobic digesters (20 L) to suit the operational requirements of the AnC process and also produced a stable compost within 21 days. The second aim of this study was to investigate the combined anaerobic digestion of winery wastewater (WWW) and leachate obtained from the anaerobic composting of grape skins in an upflow anaerobic sludge blanket (UASB). This involved the operation of a 2.3 L laboratory-scale UASB reactor for 205 days. The reactor successfully co-treated WWW and leachate at ca. 8.5 kgCOD.m-3d-1 with a final chemical oxygen demand (COD) reduction of over 90%, a stable reactor effluent pH (7.61) and alkalinity (3 281 CaCO3 mg.L-1). This study showed the feasibility for the combined treatment of liquid and solid waste from the winemaking process. Although the legal limits for reactor effluent disposal onto land was not met, significant reduction in COD concentrations were achieved, whilst producing a soil amendment that could potentially result in cost savings for chemical fertilisers. The benefits related to using anaerobic bioconversion as a treatment option for liquid and solid waste could possibly be advantageous to the wine industry as an environmental control technology, by converting liquid and solid waste into valuable resources.
- ItemEnhancement of the biodegradability of grain distillery wastewater to improve upflow anaerobic sludge blanket reactor efficiency(Stellenbosch : University of Stellenbosch, 2007-12) Gie, Lowna-Marie; Sigge, G. O.; Britz, J. J.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science.The distillery industry generates large volumes of heavily polluted wastewater and thus effective wastewater treatment is essential. It has been reported that a chemical oxygen demand (COD) reduction of more than 90% can be achieved when wine distillery wastewater (WDWW) is treated in an upflow anaerobic sludge blanket (UASB) reactor. The first objective of this study was to investigate UASB treatment of WDWW and to try to enhance the efficiency by using ozonation treatments. Secondly, the impact of grain distillery wastewater (GDWW) on UASB granules was determined. The third objective was to determine whether ozonation and enzymatic treatment combinations might improve the biodegradability of GDWW and thus make GDWW more amenable to UASB treatment. It was found that UASB treatment combined with ozonation improved the WDWW treatment efficiency. When diluted WDWW (chemical oxygen demand COD = 4 000 mg.L-1) was ozonated (dose = 47 mg.L-1) in a 50 L venturi circulating contactor system, the COD reduction was 7%. When WDWW was treated in a laboratory-scale UASB reactor (substrate pH = 7.0, COD = 4 000 mg.L-1 and organic loading rate (OLR) = 4.0 kg COD.m-3.d-1), the COD reduction was 92%. When the UASB treatment was combined with either pre- or postozonation, the COD reduction was 94 and 96%, respectively. When UASB treatment was combined with pre- and post-ozonation, a COD reduction of 98% was achieved. The activity of the UASB granules was also found to improve over time, despite the addition of the ozonation treatment. It has been reported that operational problems occur when GDWW is treated in an UASB reactor as a result of the encapsulation of the granules. This was confirmed when granules from a full-scale UASB treating WDWW became encapsulated in a layer after being exposed to GDWW (COD = 4 000 mg.L-1) for 24 d. The results showed that the lipid content of the granules increased from 1.25 to 60.35 mg lipid.g-1 granule over the 24 d exposure period. Therefore, granules exposed to GDWW were encapsulated in a lipid-rich layer and as a result the contact between the GDWW and microbial consortium in the granules was reduced. The operational problems found during the industrial UASB treatment of GDWW were ascribed to the encapsulation of the granules. Combinations of ozonation (dose = 1 476 mg.L-1) generated in a 2 L bubble column and enzymatic treatments (1% FogFreeTM (FF) dosage and 2 d incubation at 35°C) were found to improve the biodegradability of GDWW. This improvement was in terms of lipid reduction in GDWW, granule activity and visual appearance of the encapsulating layer of the granules. The highest lipid reduction (90%), highest granule activity, lowest lipid content of the granules (3.74 ± 0.10 mg.g-1 granule) and best visual appearance were achieved in ozonated GDWW treated with 1% FF, followed by just ozonation. The higher lipid reduction and subsequent higher granule activity were ascribed to the reduction in lipids which resulted in the fact that fewer lipids were available to encapsulate the granules. As a result of the lipid reduction, the granule activity improved and the GDWW was made more amenable to UASB treatment. This study proved that UASB treatment combined with ozonation led to an enhancement of the treatment efficiency of WDWW. It was also found that the cause of the operational problems during UASB treatment of GDWW was as a result of the granules being encapsulated in a lipid-rich layer. It was established that treating GDWW prior to UASB treatment improved the biodegradability of GDWW. The data from the study showed that high lipid reduction in the GDWW directly led to better granule activity, lower granule lipid content and a thinner encapsulating layer. Based on the data from this study, it is recommended that GDWW be ozonated prior to other treatments because it can be done inline and the costs would be lower than that of enzymatic treatments.