The contribution of selected pesticides to the mutagen formation potential (MFP) of river waters was studied. The concentrations of the pesticides in river water samples were determined by means of a quadrupole GC-MS. Twelve out of 39 pesticides measured were detected in the water samples collected from Kotsuki River. Ames mutagenicity assays (preincubation method) using Salmonella typhimurium TA100 without metabolic activation by S9 mix (TA100-S9) were performed to measure the MFP. From all the samples collected, significant MFPs were detected. The maximum contribution of the pesticides to the MFP of the river water samples was 0.11%, indicating that the effect of the pesticides found in this study on the MFP of the river water samples is insignificant. The contribution of pesticide degradation products to the MFP of river waters should be investigated in order to see whether pesticide degradation products affect the MFP of river waters.

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Addition of coagulant to the activated sludge process is an effective method to remove phosphorus from wastewater. Recently, iron electrolysis method has been developed as a new methodology of addition of coagulant into the activated sludge process. Although this process has been applied to industrial wastewater treatment plants or small-scale domestic wastewater treatment plants, the phosphorus removal performance by iron electrolysis combined with full-scale activated sludge process has not been clear yet. The objective of this study is to investigate the phosphorus removal efficiency by iron electrolysis combined with the activated sludge process. The enhanced biological phosphorus removal took place and phosphorus removal efficiency was increased without iron addition because of the occurrence of anaerobic condition in the surveyed wastewater treatment plant. Phosphorus removal performance in the investigated wastewater treatment plant was improved by the iron electrolysis. Effluent phosphorus concentration was decreased below 1.0 mg/L with additional iron of Fe/P molar ratio 0.4. The theoretical weight of iron release agreed with the actual weight decrease of iron electrodes. The introduction of iron electrolysis to the activated sludge process could enhance the phosphorus removal efficiency without any effects on substrate removal performance and make the phosphorus removal to be stable and sustainable.

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The purpose of this study is to examine the allelopathic potential of emergent macrophytes in actual lakes or ponds. Water was collected around the roots of emergent macrophytes Phragmites australis, Carex dispalata and Typha domingensis vegetated on floating beds or areas without macrophytes in a pond every second month for a year, and examined by bioassay using Microcystis aeruginosa. The water at areas without macrophytes did not exhibit growth-inhibiting effect throughout the year, but almost all of the water collected at the floating beds with the emergent macrophytes had the effect when the macrophytes existed. These results showed an obvious tendency that the exhibition of the growth-inhibiting effect correlated with the existence of the emergent macrophytes. To confirm such effect observed in actual ponds, three kinds of macrophytes were cultured hydroponically in which the roots were submerged in water and their culture filtrates were collected. All of the culture filtrates showed allelopathically growth-inhibiting effect on M. aeruginosa. From the comparison between the bioassay results of the water in the pond and the culture filtrates, the growth-inhibiting effect shown by the water at the floating beds with the emergent macrophytes would be responsible for the allelopathic effect of the macrophytes.

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The objective of this study was to assess the biological safety and river health in an actual river and to clarify their relationship. In this study, "biological safety" meant safety level of contaminants in river water to aquatic creatures, which was evaluated by performing various bioassays. "River health" meant conditions of water quality and biodiversity from a viewpoint of benthic macroinvertebrate assemblages, which was desired by humans. At nine sites on the Sakawa River system (Japan), biological safety was evaluated as a toxicity score and bio-safety rank (BSR) using an algae growth inhibition test, a daphnia immobilization test, and a larval medaka assay. According to the result, the biological safety was found to be completely different among the sampling sites and the test species. River health was evaluated according to the Ministry of the Environment (MOE) of Japan water quality and biodiversity (taxa number) at the nine sites. According to the result, the number of taxa were found to be completely different among the sites. The results of the bioassays and macroinvertebrate collections were compared and indicated that the number of taxa and BSR described similar behavior when going downstream, although no clear correlation was found between BSR and MOE-water quality class. Therefore, biodiversity tended to deteriorate as the intensity of toxicity became more severe.

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Glyphosate herbicide was used as screening agent to be the sole source of phosphorus for the isolation of soil-born fungi of forest soil. Three fungal strains were able to grow consistently in the presence of glyphosate as the sole phosphorus source and were identified as Fusarium sp. strain FRP1, Scopulariopsis sp. strain FRP2 and Trichoderma sp. strain FRP3. On standard medium ten fungal strains were isolated and identified as Botrytis sp. strain FR1, Mucor sp. strain FR2, Acremonium sp. strain FR3, Trichoderma sp. strain FR4, Botrytis sp. strain FR5, Crysosporium sp. strain FR6, Scopulariopsis sp. strain FR7, Trichoderma sp. strain FR8, Botrytis sp. strain FR9 and Acremonium sp. strain FR10. Of the three screened fungal species, Scopulariopsis sp. strain FRP2 and Trichoderma sp. strain FRP3 were selected for further study because they had the highest ratio of growth diameter. The growth kinetics of Scopulariopsis sp. strain FRP2 and Trichoderma sp. strain FRP3 were also observed on broth Czapek medium containing glyphosate as the sole source of phosphorus. Synergetic interactions in vitro were examined on PDA. The synergetic interactions of Scopulariopsis sp. strain FRP2 and Trichoderma sp. strain FRP3 as mix culture showed antibiosis inhibition mode.

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Sediment remediation materials such as Mg and Ca were added to a microcosm (a mixed flask culture) consisting of bacteria, Cyclidium, Lecane, Philodina, Aeolosoma, Chlorella, Scenedesmus and Tolypothrix; and the respiration rate (R) and the production rate (P) were determined. The environmental impact risk assessment on aquatic ecosystem was conducted with the production/respiration ratio (P/R ratio) as the functional parameter and the succession of microbiota as the structural parameter in the flask-size microcosm system, in comparison with no addition system (control). The influence of each substance was different from each other, and being the sediment remediation materials, the risk of Mg was estimated as half of Ca. The m-NOEC (microcosm-NOEC) were estimated as less or equal to 10.0 mg/L Mg and as less or equal to 5.0 mg/L Ca with the P/R ratio as the functional parameter of the ecosystem.

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We investigated rhizoremediation using Phragmites australis (common reed) for fresh sediment contaminated with 4-n-butylphenol (4-n-BP). We collected P. australis plant, rhizosphere sediment, and unvegetated sediment samples from a natural pond and conducted degradation experiments using sediments spiked with 4-n-BP. 4-n-BP was rapidly removed from the rhizosphere sediment with P. australis plants, whereas 4-n-BP persisted in the unvegetated sediment without plants and in the autoclaved rhizosphere sediment with P. australis plants, suggesting that the accelerated 4-n-BP removal resulted largely from the biodegradation by rhizosphere bacteria rather than by adsorption and uptake by the plant. Four bacterial strains, Pseudomonas spp. TO-1, TO-2, TO-3, and TO-4, capable of utilizing 4-n-BP as a sole carbon source via a meta-cleavage pathway, were isolated from the rhizosphere sediment. These strains presumably contributed to the accelerated 4-n-BP removal from the rhizosphere sediment. Oxygen and organic compounds from the roots elevated both cell numbers and 4-n-BP-degrading activity of strain TO-4 (the only strain tested) in the rhizosphere sediment, leading to rapid 4-n-BP removal. The results suggest that rhizoremediation using P. australis can be applicable to remove 4-n-BP from the contaminated sediments.

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