Masaaki Hosomi

Simultaneous determination of total nitrogen and total phosphorus in freshwater samples using persulfate digestion

The accuracy and precision of total nitrogen (T‐N) and total phosphorus (T‐P) determinations in freshwater samples by the simultaneous digestion method using an oxidizing reagent solution of NaOH‐K2S2O8 were assessed. Detection limits based on the blank test of nitrogen and phosphorus were 0.02 mgN/1 and 0.001 mgP/1, respectively. This simultaneous digestion method gave not only a high recovery and reproducibility over a wide range of various nitrogen and/or phosphorus compounds of known nitrogen and phosphorus compositions, but also high recoveries of nitrogen and phosphorus from standard reference materials, such as orchard leaves, pond sediment and chlorella. No significant difference was found between the determinations of T‐N and T‐P in freshwater samples by this method and those determined by the standard methods of T‐N and T‐P, respectively. This method should be useful for the routine analysis of T‐N and T‐P in freshwater samples containing particulate material and samples of low T‐N and/or T‐P co...

Significance of a low oxygen layer for a Daphnia population in Lake Yunoko, Japan

Population dynamics and vertical migration of Daphnia longispina in Lake Yunoko were studied. The Daphnia population was small in spring and early summer, probably because of high predation pressure by fish. The population grew in midsummer, when thermal stratification developed and the dissolved oxygen became very low in the deeper layer of the hypolimnion. In this season, adults of D. longispina concentrated in the daytime near the lake bottom, where fish were absent because of the anoxic conditions, but ascended at night to the upper layer of the hypolimnion, where food was most abundant. The low oxygen layer near the bottom kept out the predators and protected Daphnia from predation, and consequently contributed to the built-up of its population. However, the low oxygen layer was unfavorable for reproduction of Daphnia, as reflected in the low egg ratio and high percentage of males in the population. The population decreased in the fall, when thermal stratification disappeared and predation pressure seemed to increase.

Release of phosphorus from lake sediments

Abstract The relationship between the content of various forms of phosphorus in lakesediments and the amount of phosphorus released under aerobic and anaerobic conditions was studied. Total phosphorus content in the sediment of Lake Kasumigaura was highest at the 0–5 cm surface layer and decreased with depth. The constant value below 15 cm was consistent with the decrease of iron-bound phosphorus conent (FeP). The amount of phosphorus released from the sediments was proportional to the decrease of FeP under both aerobic and anaerobic conditions. Under anaerobic conditions, 90% of the FeP initially held in the sediments was released in 55 days. Using dialysis apparatus, maximum growth yield of algae was shown to be linearly dependent on the amount of phosphorus released under aerobic conditions.

The effects of temperature on anaerobic filter treatment for low‐strength organic wastewater

Abstract The effects of water temperature and HRT on treatment efficiency in the anaerobic filter process were examined based on laboratory‐scale experiments. The treatment efficiency of the anaerobic filter process was affected by water temperature and HRT. The dependency of the first‐order rate constant in the specific substrate removal process on water temperature was shown by the activation energy in Arrhenius plotting and temperature coefficient, which were 23,500 cal·mole−1 and 1.515 with BOD and 16,600 cal·mole−1 and 1.105 with TOC.

Effects of the circulation ratio on the treatment of artificial domestic wastewater using the anaerobic‐aerobic circulation filter process

Abstract The effects of the circulation ratio on nitrogen removal of low‐strength artificial domestic wastewater using the anaerobic‐aerobic circulation filter(AACF) process was investigated. Both anaerobic and aerobic filter tanks were packed with synthetic string‐like packing material. The nitrification reaction in the aerobic filter was performed efficiently at all circulation ratios: 1,2, and 4, and the nitrification rate was more than 90%. The amount of nitrogen removed per day in the anaerobic filter tank was highest at a circulation ratio of 4. The nitrogen removal rate at a circulation ratio of 4 was 75%.