In this paper, we have examined the cycle of carbon, nitrogen and phosphorus on the basis of the measurement of nutrients and primary production from 1978 to 1983, to elucidate the mechanism of eutrophication in the northern area of Hiroshima Bay.
It became clear that the pollution of water and sediment in this sea area associated with high primary productivity which produced organic matter (270 tC d^-1) 15 times as much as the inflow of organic pollutants (as TOC). The contribution rates of inflow to the primary productivity for nitrogen and phosphorus were respectively 21 and 17%, and those of regeneration of nutrients from organic matter in the water column occupied 74 and 75%, respectively. The contribution rates of nutrients benthic fluxes to primary productivity were 5% for nitrogen and 8% for phosphorus. However, in summer, the nutrients release was equivalent to the influent. It was presumed that the turnover times of nitrogen and phosphorus were about 11 and 7 days respectively and the residence times were about 50 days, and that nitrogen and phosphorus were utilized the growth of phytoplankton repeatedly several times until these nutrients flowed out of this sea area.

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A three-phase fluidized bed was employed for a process of nitrification of ammonia nitrogen. In the experiments, the activated carbon BAC and cement ball (CB ball) were used as media. The evaluation method of the characteristics of biological treatment, which the authors had already proposed, was applied to the nitrification.
It was possible to utilize the evaluation method for the evaluation of the nitrification. Within the range of this experiment, nitrification was approximate to first-order reaction. Total nitrification rate was proportional to the product of total biofilm surface area and logarithmic average of driving force of ammonia nitrogen concentration. The characteristics value for the first-order reaction was obtained as k=0.17 m·d^-1 (at 30°C). There was no significant difference in the effects of media on the nitrification rate.
Ammonia nitrogen removal was affected by organic substances (phenol or glucose). Ammonia nitrogen removal rate became to about 1/10 under the inlet condition in which 0.91.8 mg·l^-1 ammonia nitrogen and 15.719.8 mg·l^-1 phenol coexist. Glucose led to almost no removal of ammonia nitrogen under the inlet condition of 7.217.9 mg·l^-1 ammonia nitrogen and 15 mg·l^-1 glucose.

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Trihalomethanes formation potential (THMFP) in wastewaters of Satsuma mandarin (Citrus Unshiu Marc.) cannery was the highest among food processing plants tested. Then, it was assumed that flavanones in Satsuma mandarin would be one of the main trihalomethanes precursors. In order to demonstrate the assumption, THMFP of flavanones and the flavanones (hesperetin and naringenin) in wastewaters were determined. And THMFP contribution ratio (THMFP calculated on the basis of the amounts of flavanones vs. THMFP in wastewaters) was estimated. The main results of the research were as follows.
1. Faavanones in Satsuma mandarin had more than 100μg·mgC^-1 of THMFP per carbon and were found in processing unit operation waters. Especially separating operation water was the main source of flavanones. But flavanones were not found out in water treated with activated sludge.
2. The range of THMFP contribution ratios for all processing unit operation waters was from 10% to 92%.

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A method was described for the sequential determination of eight elements (Zn, Pb, Cd, Ni, Mn, Fe, Cr and Cu) in industrial waste water by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The compromised operating conditions were established. Spectral intensity was reduced by the physical interference due to the change of mineral acids and salts concentration. In the determination of zinc, spectral interferences were observed in the presence of high concentration of copper, nickel, and iron at the Zn I 213.356nm line. However, at Zn I 213. 856nm line, the same net intensity for zinc was yielded regardless of these diverse elements. The lower limits of detection of eight elements obtained here were the lower values compared with the environmental quality criteria. Industrial waste waters were digested with HNO₃, HNO₃ -HCl, and HNO₃-HClO₄ followed by ICP-AES measurement. These results obtained (by three digestion methods) were almost consistent with each other. The result obtained by ICP-AES were in good agreement with those obtained by flame atomic absorption spectrometry. The ICP-AES was successfully applied to the sequential determination of eight elements in industrial waste water.

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