Masters Degrees (Microbiology)

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Browsing Masters Degrees (Microbiology) by Subject "Anaerobic bacteria -- Industrial applications"

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    Anaerobic digestion application in the treatment of gelatin-manufacturing effluent
    (Stellenbosch : Stellenbosch University, 2000-12) Lloyd, Magaretha Hester; Van der Merwe-Botha, M.; Britz, T. J.; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: A severely polluted industrial effluent is generated by the local gelatinmanufacturing industry. Due to increasingly stringent restrictions on discharge qualities enforced by the National Water Act of 1998 and National Environmental Management Act of 1998, as well as increasing trade-effluent charges implemented via the Local Municipal Bylaws, the industry is compelled to consider a system to pre-treat the polluted effluent. A study was undertaken to examine the viability of anaerobic treatment of the gelatin-manufacturing effluent, since the anaerobic digestion technology is well recognised for the high success rate in the treatment of high-strength, complex wastewaters. Various laboratory and pilot-scale studies were done, using different hybrid Upflow Anaerobic Sludge Blanket (UASB) and contact designs. Two mesophilic laboratory-scale hybrid UASB digester designs, fitted with polyethylene (AD-1) and polyurethane (AD-2), performed well at a hydraulic retention time (HRT) of 1.0 d. Chemical oxygen demand (COD) removal efficiencies of up to 90% (avg. 53%) for AD-1 and 83% (avg. 60%) for AD-2 at organic loading rates (OLR) of 9.56 and 4.62 kg COD.m-3.d-1, respectively, were obtained. High sulphate (S04) removal efficiencies of up to 96% (avg. 86%) for AD-1 and 98% (avg. 82%) for AD-2 were also achieved, respectively. A maximum total solid (TS) removal of 65% (avg. 25%) for AD-1 and 62% (avg. 28%) for AD-2 was reported. An average methane content of 80% (AD-1) and 79% (AD-2) with average methane yields per COD removed of 2.19 and 1.86 m3. kg CODremoved.df-o1r AD-1 and AD-2 were found, respectively. When the same digesters (AD-1 and AD-2) were combined in a muItiphase series configuration, a total COD removal efficiency of up to 97% (avg. 80%) at an OLR of 8.32 kg COD.m-3.d-1,was achieved. Excellent total S04 removals of 96% (avg. 69%) were accomplished. Up to 82% TS (avg. 29%) was also removed during this study and the biogas consisted of 89% methane (avg. 79%). For this multi-phase combination up to 92% volatile fatty acids (VFA) (avg. 48%) were removed, indicating possible selective phase separation of the respective fatty acid producing/utilising bacterial populations. The use of a laboratory-scale UASB bioreactor with recirculation, resulted in COD removal efficiencies of up to 96% (avg. 51%) at an HRT of 3.0 d, and 95% (avg. 54%) at a HRT of 1.0 d. Low performances were generally found, with average S04 and TS removals of 59% (max. 97%) and 26% (max. 67%), respectively at an HRT of 1.0 d. The biogas production was very low throughout the study (0.05 - 0.63 I,d-1 ). A pilot-scale UASB reactor (300 I) was constructed and performed satisfactory with a 58% average COD removal and maximum of 96%. S04 and TS removals up to 96% (avg. 44%) and 93% (avg. 63%), respectively, were obtained. The methane content of the biogas was 85%. The pilot-scale studies were conducted under actual field conditions, where various shock and organic loads had to be absorbed by the system. The pilot-scale contact configuration (300 I) did not perform satisfactory as a result of continuous blockages experienced in the feed and recirculation lines. Maximum COD, S04, VFA and TS removal efficiencies of 41% (avg. 27%), 62% (avg. 41%), 64% (avg. 27%) and 39% (avg. 21%), respectively, were obtained. The results of all the studies indicated acceptable COD removals with increasing OLR's. Indications of the presence of active methanogenic and sulphate-reducing bacterial populations were apparent throughout the studies. One possibility for the successful start-up and commissioning of the anaerobic reactors was the use of a well-adjusted biomass, which consisted of highly selected and adapted microbial consortium for the specific gelatinmanufacturing effluent. It was clear from this study that gelatin-manufacturing effluent can be treated successfully, especially with the use of the UASB design. A welldefined data base was constructed which could be of great value for further upscaling to a full-scale digester.