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Effects of calcium on anaerobic acidogenic biofilms Huang, Jifei


Calcium has been found to be involved in formation and development of the bioflims for many species of bacteria, but effects of calcium on anaerobic bioflims for industrial application have rarely been reported. In this study, a mixed-culture of anaerobic bacterial bioflims were grown in lactose cultural medium with various calcium concentrations -- 1.2, 80, 100, 120, 170 and 230 mg/I. Specially designed CSTR reactors were used. The temperature and pH in the reactors were controlled at 35 °C and pH 4.5 for optimal growth of acidogenic bacteria. The influence of calcium on biofllm dry mass, total organic carbon, immobilized calcium concentration and bioflim specific activity were measured. The biofllm mass accumulation was increased by the presence of calcium in the growth medium when calcium concentration was not higher than 120 mg/I. Calcium accumulated in the bioflims increased in proportion to the calcium level in the feed. The bioflims for an increased input calcium concentration showed a trend of decrease in specific activity. The biofllms with a thickness of less than 0.5 mm had the highest specific activity. The optimum calcium concentration for the substrate consumption by the biofilms was 100 -120 mg/i. The bioflims transferred from higher calcium medium to lower calcium medium were more susceptible to sioughing from their support surfaces, indicating calcium’s role in the stability of the bioflim structure.

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