Enrichment and Community Analysis of Acid-resistant Nitrifying Bacteria form Activated Sludge

Abstract

Using the returned sludge from the sewage treatment plant as seed sludge, the enrichment cultivation of acid-resistant nitrifying bacteria by the biofilm method and the flora were examined. The sludge by forming the biofilm in a moving-bed reactor containing 10% of PVA carrier using inorganic synthetic wastewater containing 40 to 100 mg/L of NH₄－N was accumulated. We initiated the process at pH 7, and in decrements of 0.2, lowered the pH to 3 over a period of 350 days and succeeded in accumulating a group of acid-resistant nitrifying bacteria. A nitrification rate of 0.18 kg－N/m³/d and a nitrification ratio of 99.9% were obtained at pH 3. As a result of analyzing the biofilm by 16S rDNA an amplicon sequence, we found that 14.5% of the 27428 reads were Nitrospira sp.