Solid-liquid separation and its type greatly affected the stability and performance of the anaerobic sequencing batch reactor (ASBR) for municipal sludge digestion. Flotation thickening occurred in mesophilic ASBR, while solid-liquid separation in thermophilic ASBR followed a gravity thickening. The HRT and cycle period as well as type of thickening were key parameters governing sludge thickenability and critical solids accumulation. Thickened sludge bed volume was a critical operating variable in the ASBR with gravity thickening, which had a poor performance because of loss of thickened solids, and sludge interface disruption or instability of sludge bed due to internal gas evolution. Cyclic mutual effect between thickened volume and gas production was serious in gravity thickening, whereas it was insignificant in flotation thickening.

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This paper considers the progressing salinization of Yizreal Valley in Israel ; a qualitative and quantitative analysis is made so that desirable irrigation strategy can be selected. Through the qualitative analysis, three relative and desirable strategies are planned, where the interrelationship between them is unclear. They are; l) Short-term benefit maximising strategy, 2) Water table level conserving strategy, and 3) Short-term yield maximising strategy. Future benefits including non-monetary values led by each strategy are quantified and systematically compared to one another by an adapted simulation model. As an effect, each is classified in monetary value of net present value and to non-monetary value of accumulated salt under root zone. As a result, the quantitative interrelationship of each strategy is derived, and the superiority of the short-term benefit-maximising-strategy was shown in terms of the monetary value. On the other hand, the superiority of the water-table-level conserving strategy was shown in terms of the non-monetary value. Leaving a comprehensive judgement order of superiority among strategies to decision makers, thresholds fluctuation to install drainage system, qualitative trade-off relationship between monetary and non-monetary benefit coupled with the interrelationship of each strategy along different values of some operational variables are presented.

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It has become concern that pesticides applied to agricultural lands may cause adverse effects to the environment and ecosystems. Therefore, it is important to predict both environmental fate and impact to organisms of pesticides. The fact of pesticide applications was investigated in both young seedling transplanting culture (YSTC) and direct seeding culture of paddy rice on non-tilled upland field (DSC). The environmental load (runoff amount of pesticides) was calculated by the mathematical model (PADDY). The risk to aquatic organisms (Carp and Daphnia) by runoff pesticides from paddy fields was evaluated by the ratio of predicted environmental concentration (PEC) and short term effect concentration (LC50). Application amount of pesticides in DSC was more than that in YSTC. However, on the contrary, the runoff amount in YSTC was same as that in DSC. As a result of calculating the ratios (PEC/LC50), it was estimated that the adverse effect to aquatic organisms was small by a short term exposure of pesticides.

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The acid neutralizing capacity of Lake Okenuma, a small, acidic softwater lake in Fukushima prefecture, was estimated in order to assess the impact of acid rain on this lake. Laboratry sediment-water microcosms experiment for Lake Okenuma was conducted 23 days incubation period to simulate sediments-water interactions. Nitrate consumption and cation exchange were found to be major acid neutralizing processes in the microcosms, whereas sulfate reduction did not play an important roll. However, the nitrate consumption rate was 350μeq/m²/day in the microcosms, one eighth the rate in other lakes with high alkalinity in Japan. Cation exchange capacities of the sediments and soils of the watershed were 750μ eq/100 g and 130μeq/100 g respectively, one or two order of magnitude smaller than those of other lakes with high alkalinity in Japan and acidified lakes in Canada. The sulfate reduction rate was estimated from sulfate profile in the epilimnetic sediments pore water obtained with in situ membrane sampler. The sulfate reduction rate was only 2μeq/m²/day and this result was consistent with that from the micro cosms experiment. These results indicate that Lake Okenuma is one of the lakes in Japan most susceptible to acid rain.

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Growth responses of fresh water cyanobacteria cultures of Microcystis and Oscillatoria to various organic compounds were studied. L-Lysine was shown to be a potent inhibitor of the growth of five species of Microcystis, i.e., M.ichthyoblabe TAC 110, M. aeruginosa TAC 192, M. novacekii TAC 65, M, viridis TAC 64 and M, wesenbergii TAC 52. L-Lysine inhibited specifically the growth of Microcystis cyanobacteria at low concentrations of 0.5 to 1 mg per liter added to the culture medium, while three amino acid could not block the growth of three species of Oscillatoria i.e., O. tennis 1001, O. limnetica NIES 36, and O. animalis NIES 206 even at a concentration of 50 mg per liter. L-Histidine as well as L-lysine also inhibited preferentially the growth of Microcystis cultures except for M, viridis TAC 64 though the inhibition by L-histidine was weaker than that by L-lysine. The growth inhibition was provoked when the amino acids were added at the beginning of growth period, while either L-lysine or L-histidine failed to block the growth when added during the logarithmic phase. In the mixed culture of M. novacekii TAC 65 with O. limnetica NIES 36, L-lysine or L-histidine added singly to the mixed culture inhibited preferentially the growth of M. novacekii TAC 65. The significance of the specific growth inhibition by L-lysine and L-histidine for Microcystis cyanobacteria was discussed from an ecological standpoint of the algal succession in Lake Kasumigaura.

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Some artificial surfactants are not sufficiently decomposed and remain in the water of seas, rivers and lakes. The influence of the artificial surfactants on the Polymorphic forms of calcium carbonate was experimentally examined. The calcium carbonate contained in the sediment of seas, rivers and lakes has three polymorphic forms: calcite, aragonite, and vaterite. Sodium dodecylbenzene sulf onate and sodium dodecyl sulfate promoted calcite formation in the presence of magnesium ions. The promoting effect was observed at the concentrations > 5 mg/L. Polyoxyethylene sorbitan monolaurate and sorbitan monolaurate facilitated vaterite formation in a magnesium-free solution at the concentrations > 10 mg/L. The known concentrations of these surfactants in the Japanese coastal seas, rivers and lakes are much smaller than the our observation. Therefore, it seems that surfactant effects on the polymorphic crystallization of calcium carbonate in these aqueous environments are very small.

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A variety of information pertaining to pesticide use in Cambodia were given by government officers and NGOs stuffs, and organochlorine compounds in fish collected from Phnom Penh and its suburb were analyzed in order to understand their status of pollution in the Cambodian waters. HCHs, CHLs, and DDTs were detected with low residue levels, while HCB and PCBs concentrations were less than the detection limits in most of the samples. Compared with data of fish from other areas in the world, organochlorine concentrations in Cambodian fish were apparently lower. The Cambodian daily intake of each organochlorine compound through eating fish was estimated to be much less than the threshold toxic level presented by FAQ-WHO. These results show that the extent of organochlorine contamination is still small in the Cambodian freshwater environments.

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Organochlorinated solvent has been widely used in industry as an organic solvent and a degreasing agent. Recently, this chemical has attached attention as an environmental pollutant not only in water but also in air. In the present study, we examined neurotoxicity of organochlorinated solvents such as chloroform, carbon tetrachloride, 1, 2-dichloroethane, 1, 1-dichloroethylene, 1, 1, 1-trichloroethane, trichloroethylene, and tetrachloroethylene using cultured C 6 glioma cells. Of the solvents examined, chloroform (5 mM), trichloroethylene (0.1 mM), and tetrachloroethylene (0.1 mM) showed a significant cytotoxicity after 8-hr exposure of the solvents to glioma cells. Induction of apoptosis evaluated as DNA ladders by chloroform at lower concentration (0.5 mM) was observed prior to the occurrence of mitochondorial dysfunction and morphological changes.

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