Abstract
In batch-type treatment of starch wastewater by Aspergillus niger pellets, effects of nitrogen compounds and pH of the wastewater on the treatment efficiency were examined. The degradation of starch reached 75-85% with the treatment for 15 days, when the wastewater contained 10, 000mg/l TOC (25 g/l starch) and 5-1, 060 mg/l ammonia nitrogen (NH4-N) . In these experiments, the NH4-N added to concentrations of 5-53 mg/l was completely consumed with the 3th days. These results indicate that the pellet activity to degrade starch was maintained during the treatment even in the nitrogen insufficient wastewater, suggesting the utilization of cellular nitrogen pool. These results suggest that the nitrogen was recycled to maintain the pellet activity. On the other hand, the removal of TOC increased from 27 to 73% with the increase in the NH4-N concentration. At lower concentrations of NH4-N, other TOC components such as glucose and organic acids were accumulated in the treated wastewater. Changes in the starch degradation and the TOC removal were hardly observed when the initial pH was adjusted to ranges from 2.0 to 7.0. At the initial pHs of 3.0-7.0, the pellet state was kept over the treatment time. Since lower pH would be apt to repress bacterial contamination in the fungal treatment reactor, to control wastewater pH at 3.0 was shown to be desirable for both the effective degradation of starch and the maintenance of pellet state.
