Effects of Organic Nutrient Strength on the Purple Nonsulfur Bacterial Content and Metabolic Activity of Photosynthetic Sludge for Wastewater Treatment

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Changes in the purple nonsulfur bacterial content and metabolic activity of photosynthetic sludge in response to wastewater strength in a practical plant and in laboratory-scale batch reactors were investigated. Both plant and laboratory systems yielded large quantities of purple nonsulfur bacteria, as many as 10^7 viable cells・mg dry sludge^<-1>, when loaded with high biological oxygen demand (BOD) levels of eastewater containing acetate as a major BOD source. Experiments with laboratory reactors showed that the phototrophic bacteria could keep occurring in such large numbers at BOD-loading rates higher than 0.8kg BOD.kg dry sludge^<-1>・d^<-1>. The loading of high BOD wastewater also enhanced oxygen uptake activity with lower fatty acids used as substrates, as well as the enzyme activities of the tricarboxylic acid cycle of the sludge. However, there was no difference in the enzyme activities of the glyoxylate pathway between high BOD-loaded and low BOD-loaded sludges. The results obtained suggest that wastewater strength, especially a lower fatty acid concentration, is one of the most important factors affecting the viability and activity of purple nonsulfur bacteria in the photosynthetic sludge process.
1989-10-25