An electrolytic crystallization process for recovering and removing phosphate from a high-strength wastewaters such as livestock and industrial wastewaters was developed. In the process, phosphate crystallizes with calcium, magnesium and ammonium on the cathode surface because of a rapid increase in cathodic pH by electrolysis. The crystalline substance formed on the cathode surface was considered to be a mixture of hydroxyapatite (HAp) and magnesium ammonium phosphate (MAP). However, the MAP content of the crystalline substance was not very high. From the mass balance in the, electrolytic cell, magnesium phosphate could be simultaneously formed by electrolysis. In addition, a large amount of potassium was also included in the crystalline substance. The efficiency of the formation of the crystalline substance markedly depended on the kind of electrode material, electrode surface roughness and electrode arrangement.

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An A/O SBR fed with acetate as the sole carbon source was operated for 183 days to examine the dynamic behavior of Candidatus ‘Accumulibacter phosphatis’ (Accumulibacter) in activated sludge enhancing phosphate release activity due to an increase in pH from 7.0 to 8.2. The result obtained by real-time PCR analysis showed that the copy number of Accumulibacter gradually increased until 89 days after a lag period of around 60 days. After that, polyphosphate-accumulating organisms (PAOs) other than Accumulibacter probably proliferated, considering the dynamic change in phosphate release activity. Consequently, the significant acetate uptake by PAOs likely reduced the proliferation of glycogen-accumulating organisms at high pH.

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The on-site speciation analysis of inorganic arsenic at the μg · l^-1 level by anodic stripping voltammetry with a gold film microelectrode was described. As(III) was deposited on a gold film working electrode at -0.4 Vvs.Ag/AgCl for 5 min in 1.2 mol · l^-1 hydrochloric acid; the deposit was then anodically stripped in the potential range from -0.4 to 0.9 Vvs.Ag/AgCl at a scan rate of 5 V · s^-1. As(V) was chemically reduced to As(III) with sodium thiosulfate and the total inorganic arsenic was determined under the above voltammetric conditions. The original As(V) concentration in the sample was calculated by difference. The calibration curves prepared with As(III) and As(V) standard solutions were linear up to at least 20 μg · l^-1 and passed through the origin, with relative standard deviations of 2∼5% for 5 μg · l^-1 arsenic (n=5). The detection limits (3σ, n=10) of As(III) and As(V) for a deposition time of 5 min were 0.1 and 0.3 μg · l^-1, respectively. The proposed method was applied to the on-site speciation analysis of inorganic arsenic in groundwater in Saitama Prefecture. The time required for the on-site analysis was 20 min.

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Four years after the construction of an artificial tidal flat in Osaka Bay, Japan, the food web structure was analyzed using stable isotope ratios of nitrogen and carbon. The nitrogen stable isotope ratios (δ¹⁵N) ranged from 8.8±0.3‰ in Chondrus giganteus f. flabellatus (macroalga) to 15.2‰ in Repomucenus beniteguri (fish), whereas the carbon stable isotope ratios (δ¹³C) ranged from -18.6±0.2‰ in POM (particulate organic matter) to -10.5±1.1‰ in Ulva sp. (macroalga). The food web structure of the artificial tidal flat was estimated to be composed of three trophic levels. Moreover, it was thought that fishes inhabiting this ecosystem are dependent on POM and macroalgae (and/or benthic microalgae) for their carbon source, whereas crustaceans and mollusks are likely to be dependent on macroalgae (and/or benthic microalgae), not on POM. These results indicate that the food web structure of the artificial tidal flat resembles those of natural estuaries along the Japanese coasts. A temporal analysis of the food web structure of an artificial tidal flat and a comparison of such a structure to that of closely situated natural tidal flats using stable isotope analysis will contribute significantly to the evaluation of the structure and function of artificial tidal flats.

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