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Five bacterial strains (Chryseomonas luteola, Fusobactertum mortiferum, Enterobacter agglomerans, Klebsiella oxytoca and an unidentified Gram-negative rod) were grown on raw baker's yeast effluent to assess the influence of environmental factors on biodegradation processes. A 3x4x3 factorial design was used to determine the effects of time, pH and COD concentration, at four different temperatures. Total volatile fatty acid production was chosen as the most representative indicator of biodegradation. Results showed that the strains differed greatly in their ability to produce anaerobic digester intermediary metabolites, under defined environmental conditions. The study showed that the degradation of the complex compounds in baker's yeast effluent could be enhanced by changing environmental factors. The most positive responses were obtained at the higher COD concentrations (30 g l-1), the higher pH values (6.0), after 24 to 48h incubation time and at the higher temperatures (35°C). The most positive effect (+355.00) was found for Chryseomonas luteola at a 48h incubation time, COD concentration of 30 g l-1 pH of 6.0 and temperature of 357deg;C. The volatile fatty acid yields obtained by the strains differ from the statistical indications, but provide a valuable reference of the actual concentrations obtained during the experimented study. The factorial design represented the effects of environmental changes, while the quantitative TVFA data set gave experimental data. This study showed that the manipulation of various environmental factors in biologically controlled systems, such as anaerobic digesters, could further enhance the biodegradation efficiency of the microbial population in the raw effluent. [ABSTRACT FROM AUTHOR]

A Chryseomonas luteola strain was isolated from raw baker's yeast factory effluent as the dominant part of the microbial community and evaluated for its biodegradative activity, using the raw effluent as substrate. The strain was able to utilise the raw effluent and produce higher concentrations of energetically favourable metabolites and thereby, could contribute to the first degradation step in an anaerobic biological treatment process. A 3W4W3 factorial design indicated optimal degradation conditions in a specific environmental framework of 48 h incubation time, COD concentration of 30 g/l, pH of 6.0 and temperature of 35 deg. C. The C. luteola strain was thereafter used in a pre-degradation step followed by an anaerobic digestion step in a 5 1 laboratory-scale hybrid digester. With the use of the pre-degraded effluent, significant improvements were found in the overall anaerobic digestion performance. These included increased COD (>15%) and TVFA (>50%) removals, especially propionic acid (88%) removal, as well as higher biogas yields (18%). The results also showed a prominent improvement in fatty acid utilisation and methanogenesis. The pre-degradation step resulted in better process control and increased stability ofthe system, even at relatively high organic loading rates (10 kg COD/m3.d). When the raw effluent was not pre-treated (controlbioreactor), no improvement in bioreactor efficiency was observed. [ABSTRACT FROM AUTHOR]

The effect of ozonation on wine distillery wastewater was investigated firstly by monitoring the effect of ozonation on the composition of the wastewater and, secondly, by investigating its effect on the biodegradability of the wastewater. An average COD reduction of 271 mg COD.g O3 -1 was found for wastewater from a distillery pond system. Stable microbial populations, which are found in upflow anaerobic sludge blanket (UASB) granules, were used to determine the toxic effect of wastewater on microbial activity. Granule activity was measured in terms of the rate of biogas and methane production, as well as cumulative biogas volume. Low ozone doses (200 to 400 mg O3.L-1) increased granule activity in terms of biogas, methane production, and cumulative gas volumes. Distillery wastewater reduced the activity of granules, most likely due to the presence of polyphenols and other recalcitrant compounds in the distillery wastewater. [ABSTRACT FROM AUTHOR]