Japanese Journal of Water Treatment Biology

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Aquatic oligochaete fauna （Annelida, Clitellata） was studied in the wastewater treatment system of plum processing plant in Wakayama Prefecture, central Japan. Eight oligochaete species were found from the wastewater treatment plants, of which a rhyacodriline Monopylephorus rubroniveus which is new to Japan is redescribed on the basis of the present material. Mass occurrence of oligochaetes forming thick mats were found on the suspended pile fabric substances in the salty wastewater treatment tank. The oligochaete assemblages on the piles were largely dominated by M. rubroniveus accompanied by a small number of an enchytraeid Enchytraeus albidus sensu lato, and the average density of oligochaetes was accounted for 5.7?million individuals m^－2. Experimental study shows that M. rubroniveus is euryhaline species with high survival rates both in fresh- and seawaters. It is suggested that M. rubroniveus can reduce salt-containing organic waste in wastewater treatments.

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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.

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