Odor problem by algal bloom is one of new problems to be additionally removed from supplied water. The author has developed a biological process by gravel sand filtration to remove the odor. Here in this paper, application of a cermic membrane is tested in order to know whether it can support the biological activities as gravel sand can do. Experimental findings are as follows; 1) filtration speed of a lake water was about 1 m/day per membrane surface, 2) odor substance 2-methyl isoborneol was biologically removed more than 80%, 3) bacterial leak from the process was minimum because the pore of the membrane was less than 0.1μm, 4) chlorine consuming organics were biologically removed to a limitted extent in addition to the odor removal, 5) from the process, a species of bacteria wich can decompose fumic acid was isolated and identified.

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Biological treatment of gaseous hydrogen sulfide and ammmonia which were typical odoriferous pollutants was experimented. In this experiment, continuous vapor-liquid contact type bioreactors were used, and the influense of accumulation of several biological products in the liquid-phase was examined.
It is known that ammonium sulfate is accumulated in the liquid-phase of the bioreactor when the mixing gas of hydrogen sulfide and ammmonia is treated. In this experiment, ammonium sulfate inhibited the treatment of both hydrogen sulfide and ammonia. At the treatment of gaseous hydrogen sulfide, potassium sulfate also inhibited the increase of the oxidation activity in the reactor, but the inhibition could be reduced by addition of ferrous ion in the liquid-phase.
Furthermore, treatment of gaseous hydrogen sulfide was experimented using a batch-reactor. In this experiment, it was confirmed that the optimal pH was about 3 and the influence of sulfate ion was relatively low for the biological oxization of gaseous hydrogen sulfide. The activity of the hydrogen sulfide oxidation in the drain water of the continuous bioreactors was also measured. In the continuos bioreactors, it is defined that the activity exists both in the liquid-phase and the surface of packing materials of the reactor. The result of the batchreactor test shows that about 30% of the activity was occupied in the liquid-phase.

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A Phenol degrading bacterium, which could decompose TCE, was isolated and identified as Pseudomonas sp. KN1. The ability to degrade TCE was induced by addition of phenol. An enzyme responsible for TCE degradation was conjectured to be phenol hydroxylase (PH). A gene encoding PH was cloned from the chromosome DNA. Expression of the PH gene in Escherlchia coil DH5α was carried out by using pTrc100 as a vector. Although the gene cloned was expressed in the E. coil, phenol was oxidized only at a low rate. The degradation of TCE was not detected at all. A new plasmid vector, pRCL100, carrying the replicon of RSF1010 was constructed to use Pseudomonas sp.KN1 as a host. A higher activity of PH was observed when the PH gene was expressed under the control of the trc promoter in Pseudomonas sp. KN1. The TCE degradation was examined by using the genetically engineered Pseudomonas sp. KN1. TCE concentration in a vial was rapidly decreased when the bacterium engineered was inoculated, and the gene was expressed. The result showed that the gene encoding TCE degrading enzyme was the PH gene.

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Density currents which are developed by the difference of density between influent and effluent are a major cause of short circuits, instability and carry-over of suspended solids in sedimentation tanks. Numerical simulations of these currents were conducted based on finite element method in horizontal current sedimentation tanks. Simulated streamlines and density distribution are presented in animated computer graphics which showed very clearly dynamic behaviors of the currents. Stability of currents depended on the mean horizontal velocity which could be expressed as Froude Number (Fr²). If the value was high, the currents were stable and descened very soon to the bottom and the settling efficiency was excellent. If low, the currents were unstable, large areas of dead space were created at the both of the upper part of the inlet and the lower part of the outlet and the efficiency was very poor. Stability was improved as the density of influent became high. The analysis confirmed feasibility of the current design practices.

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An investigation is conducted to determine the dosage effects of the water treatment sludge produced in the back washing and the chemical precipitation process on the sewage treatment facility. In this experiment, HRT (4, 6 and 8hr) is varied for the raw sewage reactor. HRT and volumetric blending ratio (4 and 8 hr injection) are also varied for the blended reactor dosed with water treatment sludge and raw sewage. The effluent quality, the treatment efficiency and the bio-dynamic kinetics for two reactor systems are evaluated.
The results obtained indicate that the ranges of aluminium concentration in blended substrate are 10.8-11.3 mg/l, 5.4-5.7 mg/l for 4 hr and 8hr injections, respectively. It is also observed that both the treatment efficiency and the effluent concentration of the blended reactor system are not inferior to those of the raw sewage reactor system. It is further noted that kinetics suchlike the substrate removal rate (K), the specific maximum substrate removal rate (kmax) and Monod constant (Ks) determined from both the raw sewage reactor system and the blended one are 7.75 day^-1, 7.55 day^-1 for K and 4.0 day^-1, 4.8 day^-1 for kmax and 683 mg/l, 640 mg/l for Ks.

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Inner basin drainage at fully developed urban areas tend to be planned and installed with a large scale trunk sewer as the main flood control facility. It is of grave importance for such a case, operational policy could be vital thing from the viewpoint of risk analysis because artificially pumped drainage should be inevitable. Many existing policies have been presented and they seem to be effective in certain conditions with respect to hydrological and/or operational risk. But when and how effective these policies are depending on the magnitude of risk. This paper gives planning model of a pumping control policy for inner basin drainage. We focused on three types of policies; water-level, water-level and runoff, and hydrological forecast based operation. These can all be identified by dynamic programming. After then, the efficiency of these policies are investigated by numerical simulation. Then the strategy of making choice of policy is discussed with the given criteria of acceptable risk regarding monitoring and forecasting.

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Two bench-scale experiments were conducted to investigate effects of additional night soil load on wastewater treatment process. Run-1 was nitrificationdenitirification process with nitrified liquor recycle and Run-2 was anaerobic-anoxicoxic (A20) process with total recirculation ratio of 200%. From 0%V/V to 1.5%V/V of authentic collected night soil was mixed with synthetic wastewater and fed into the reactors. The experimental apparatus were set up in a temperature-controlled room (20°C), and polypopylene pellets were filled upto 30%V/V of oxic reactor in Run-2. In Run-1, effluent BOD was less than 20mg/L at 1.0%V/V night soil dose, but effluent COD_Mn occasionally exceeded 20mg/L. In Run-2, however, both BOD and COD_Mn remained less than 20mg/L at 1.5%V/V. COD_cr/TOC ratio in the effluent increased with additional night soil load, and, hence, was proposed as a parameter indicating bacterial ability to decompose refractory organics. From the result that COD_cr/TOC in the effluent from Run-2 was lower than COD_cr/TOC in Run-1, it was concluded that bacteria immobilized on polypropylene pellets obtained higher ability to decompose refractory organics in human excreta.

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Experiments on an upgraded RBC were conducted to investigate its removal efficiencies of NH₄-N, coliform group and coliphage in the municipal wastewater treatment. A bench scale RBC, made of stainless mesh media with 5 mm high surface protrusions, was fed with settled municipal wastewater tontaining 13-25 mg/l of NH₄-N and 40-75 mg/l of TOC at the hydraulic loading of 89 l/m²/d and 60 l/m²/d.
It was found that the nitrification effectively occurred at bulk liquid TOC concentration of less than 10 mg/l. The coliform group and coliphage were effectively adsorbed to the biofilm surface. The removal efficiency of coliform group and coliphage were more than 98% and 90%, respectively.

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A new method called “Thermophilic Oxic Process (TOP)” which completely decomposes the organic matter in high BOD wastewater was applied to treat food processing wastewater containing CODMN and BODE of approximately 28, 000 and 33, 000 mg/l, respectively. When the BOD loads ranged from 2 to 5 kgBOD. M^-3.d^-1, aeration rates ranged from 50 to 200 2. M^-3min^-1 and moisture content of absorbent ranged from 64-80 %, the temperature increased up to 50-65°C and the COD, BOD removal ratio was approximately 94 %. Meanwhile, no excess sludge was formed during 3 months of operation since the initiation of the experiment.

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Operational conditions, in solid-liquid separation, of a cross-flow type ultra membrane filtration system were examined to make clear the mechanism of water permeation. Activated sludge suspension was applied as a model sample, and a flat plate type module with different section areas and a tubular type module were used in the experiments.
In the both modules, the permeation flux is shown by the experimental equation obtained, which considers the effects of module pressure on membrane resistance (Rm) and applies the cake filtration to the resistance (Rcg) caused by cake-layer and/or gel-layer.
The effects of flow velocity to Rcg are evaluated more effectively by shear stress (τ₀) than flow velocity itself and Reynolds number. From the relationships between τ₀ and Rcg, the filtration is classified into 3 types as follows; 1) filtration with predominance of membrane filtration, 2) filtration with predominance of cake filtration, and 3) filtration with mixed effects of the both.
In the flat plate type module, at low MLSS concentrations, the filtration types 1) and 2) are observed and the critical values of τ₀ are around 500kPa. And at high MLSS concentration, the types 1) and 3) are observed and τ₀ of about 500 kPa is critical. On the other hand, in the tubular type module, only the types 1) and 2) are observed at low and high MLSS concentrations and the critical values of τ₀ are about 1000kPa in the both cases.

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Water quality characteristics of snowpack, snowmelt and stream during snowmelt period was investigated at the area of Mt.Gassan in Yamagata prefecture. Samples were collected in May 9-10, 1992. Ion concentration of snowpack was smaller than that of fresh snowfall and rainfall and its conductivity was 4-6 μS/cm. This indicates that ion in snowpack is linsed early in the snowmelt period. Top layer (0-5cm) of snowpack had high concentration of pollutants such as SS, COD, T-N and T-P. The loading potential of T-N and T-P in snowpack were 81-162 kg/km², 6.2-14.2 kg/km², respectively and these values were not small compared with annual loading of T-N and T-P from forest. Pollutants in snowpack contained quarts, feldspar, clay, alumi-silica mineral of spherical type and black organic matter. The particle size of pollutants in snowpack was getting small with the increase of snowpack depth. This indicates that a sieving of particles is occured in snowpack during snowmelt period.

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In Japan, acidification of stream and lake water has not been reported. However load of acid deposition in Japan is as much as northern Europe and north-eastern U. S. A., where acidification of lake water and decrease of fish population have occurred. In order to forecast the future change of Japanese surface water chemsitry, it is neccesary to study the neutralizing mechanism of acid deposition in watershed. Analytical results of hydrological and chemical surveys in two mountainous watersheds where streamwater chemistry has not been affected by human wastes suggest the following:(1) acid deposition is neutralized continuously during the percolation of precipitated water from ground-surface to aquifer.(2) Chemical weathering of primary minerals is an important mechanism of neutralizing acid deposition in watershed. These processes should be taken into account in the long-term forecasting of wafer chemistry.

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Two kinds of blue green algae, Phormidium tenue and Anabaena macrospora, were cultivated under bacteria-free condition in each laboratory test, and behaviors of excreted extracellular substances (by-products) were measured under light and dark conditions. Underlight condition, the number of algal cells were increased by approximately a hundredfold alongcultivation time, and DOC concentrations of cultures media remained relatively constant level during the logarithmic growth phase. As the cultures entered into the stationary phase, DOC began to accumulate. DOC excretion rates of P. tenue and A. macrospora were analyzed to 0.013, 0.048 mg DOC/mgPOC/day during the logarithmic phase, and 0.093, 0.078 mgDOC/mgPOC/day during the stationary phase, respectively. The rates during the stationary phase were about 2-7 times higher than those of the logarithmic phase. The ratios of carbon concentration of carbohydrates against total DOC was almost constant, whose value was 40% for P. tenue and 60% for A. macrospora during the overall incubation period. While, protein concentrations increased during the stationary phase, and then leveled. Under dark condition, DOC increased along by the progress of algal autolysis. It's DOC excretion rate was estimated to be 0.045mgDOC/mgPOC/day for P. tenue and 0.024 mgDOC/mgPOC/day for A. macrospora.

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Charcoal adsorbed 1.1mgNH₄-N/kg, and did not adsorb NO₂-N and PO₄-P. Oyster shell dissolved 12.22mgPO₄-P/kg in ten days, and did not adsorb NH₄-N, NO₂-N and NO₃-N. The dissolution rate of PO₄-P was decreased with time. Continuous purification of river water polluted slightly was studied with the use of reactors packed with charcoal and oyster shell on which microorganisms attached. At hydraulic retention times of 1 and 2 hours, TOC removal was over 50% in both reactors. Over 60% of NH₄-N was converted due to the nitrification and the assimilation by attached microorganisms. However, removal of nitrogen was not almost observed. PO₄-P removal was 10.2-86.7% at water tempertures of 15 and 8°C, depending upon the composition of the substrate. It could be expected that these reactors contribute to the decrease of PO₄-P loading into a reservoir in order to protect it from eutrophication.

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Water quality in lakes and reservoirs is usually predicted by ecological water quality models. The first step of the prediction is the identification of the ecological model based on the observed pollutant loads and water quality. But the estimated loads usually include estimation errors as it is difficult to estimate accurate pollutant loads. Therefore, the identified model is distorted even if the model reproduces the observed water quality. The future water quality predicted by this model is overestimated or underestimated.
In this paper, the prediction errors of the distorted ecological model are discussed based on the case study for Kojima Lake. The distorted model overestimates or underestimates the water quality according to the estimation errors of the pollutant loads used in the process of the calibration even if it can reproduce the observed water quality fairly well. The estimation errors of the least abundant nutrient loads greatly influence on the predicted water quality.

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Environmental monitoring wells should be allocated around the solid waste landfill site, to detect hazardous materials leakage from the site. The procedures, which was developed by combining the numerical simulation technique of material transport in the ground with the multi-objective systems design technique, was applied to obtain the optimum allocation of monitoring wells and their dependence on the available information added. The optimum wells network was also discussed under appropriate constraints.
The results obtained under the limits considered can be summarized as follows;
(1) The optimum wells network depends on the weighting factor for each attribute of the monitoring system. If larger weighting factor is given to the economy attribute, the monitoring network with smaller number of wells is likely to be selected as is easily expected.
(2) The optimum wells network does not depends largely on the variation of some environmental parameters. However, the increase of reliability in estimation of permeability coefficient and release concentration of hazardous material affected the wells network.
(3) Additional information to reduce the fuzziness in utility evaluation is more sensitive to optimum wells allocation than the information for the reduction of fuzziness in weighting factor evaluation.
(4) The procedures were successfully applied to obtain the optimum wells network under appropriate constraints; perfect detection of hazardous material leakage, wells allocation outside the landfill zone, existent wells usage and wells number limitation.

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Monitoring data for inhalation risk assessment of atmospheric Benzo (a) pyrene are evaluated by using linear multi-regression analysis. Macro-regression models using urban activities data and micro-regression models using road-side environmental data were developed. Inhalation health risk level was estimated by using linearized multistage model as mathematical extrapolation model. Values of the ratios of dose to VSD (Virtually Safe Dose) for 10^-6 for life time risk are in the range of 1.86 to 3.57. Sensitivity analysis show that the most dominant influensive parameter are the rate of number of cars registered in the city to the city area and paved road area in macro-regression model, and the concentration of suspended particles in micro-regression model.

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Biological nitrogen removal from supernatant of anaerobic digestion tank in night soil treatment plant in which two aeration tanks were connected in a line was studied. In the first aeration tank which was divided into four compartments the nitrified mixed water was recycled from the final compartment to the each compartment. TN removal rate was 65-90% in pH range above 7.2 at aeration tank 1. The critical C/N ratio varied with degree of nitrificatin.In the nitrite dominant plant, the ratio was calculated at 0.58 (g-TOC/g-TN), whether the sludge was counted or not. In the nitrate dominant plant, the ratio was calculated at 0.90 (g-TOC/g-TN) when the sludg was taken into the count, whereas the ratio calculated taking the water alon without sludge into the count was estimated at 0.77 (g-TOC/g-TN).

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The changes in adhesion strength and biological-and-physical properties of a denitrifying biofilm was investigated in the course of its development. The biofilm was experimentally established on the surface of the polyvinyl chloride plates which were placed in a rectangular open-channel reactor with effluent recycle. The adhesion strength was estimated on the basis of Newton equation by measuring biomass fragments detached from biofilm on which defined centrifugation forces were imposed. The adhesion strength was not uniformly distributed within biofilm, but had a tendency to increase with biofilm depth and with biofilm development. On 30th day the biofilm thickness increased up to about 3mm and, as a consequence, the adheion strengthnear the substratum interface attained a level in the order of 10² dyne·cm^-2, whereas that in the vicinity of biofilm surface was only of the order of 10⁰ dyne·cm^-2. The biofilm dry density did not remain constant throughout biofilm, having a tendency similar to that of the adhesion strength. A strong correlation was observed between the dry density and the content of extracellular biopolymer (ECP) of biofilm. It was suggested that the adhesion strength was affected explicitly by the ECP content, and rather implicitly by the dry density.

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Two identical scale of UASB reactors set at two different temperatures, i. e., at 55°C (Run 1) and at 65°C (Run 2), were used to investigate the effect of temperature on granulation and interaction of thermophilic anaerobes. When acetate was used a feed substrate to the reactors no granulation occurred in both experimental runs. Microscopic observation revealed that the predominant methanogen was Methanothrix in Run 1 while Methanobacterium existed to significant extent in Run 2. The acetate-utilizing methanogenic activities of these sludges increased with increasing temperature in the range from 55°C to 65°C. Because of the high hydrogenutilizing methanogenic activities of these acetate-grown sludges, it could be considered that the syntrophic association of acetate-oxidizing bacteria with hydrogenotrophic methanogens plays an important role for acetate-cleavage in thermophilic anaerobic sludge. Subsequently, the feed substrate was changed to the mixture of acetate and sucrose for the second experiment. Granules coated with filamentous bacteria and cocci-type bacteria were obtained in Run 1 and Run 2, respectively. Since the acetate-utilizing methanogenic activities of these granules were 4 to 5 times higher than those of the sludges cultivated on acetate only, these “coating bacteria” appeared to hold acetate consumers within the granules.

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The influence of loading rate on the content of extracellular biopolymer (ECP) and the methanogenic activity of granular sludge developed in a UASB reactor were investigated by varying the influent strength stepwise from 1.0 g COD·l^-1 to 5.0 g COD·I^-1 at a HRTof 12 h for a period of 150 days. The ECP yield along sludge bed varied with loading rate, ranging from 37 to 57mg ECP·gVSS^-1. The size of the granules increased with the increasing sludge loading. Granules having larger size tend to accumulate at lower portion of sludge bed and possessed higher amount of carbohydrate in ECP. The ratio of protein to carbohydrate in ECP increased with the sludge bed height in the range from 0.7 to 2.1. The carbohydrate content in ECP seemed to be more significantly responsible for granulation, rather than the ECP yield and the protein content in ECP.
The dependence of methanogenic activity on granule size was assessed using sludge taken from both lower and upper portions of sludge bed at each loading. Hydrogen-utilizing methanogenic activity decreased consistently with granule size. In contrast, granules with medium size (1mm-2.5mm) exhibited higher activity both from acetate and from propionate, rather than those of small size (0.5mm-1mm) and of larger size (>2.5mm). These results indicate that an excessive maturation of granule size (above 2.5mm) is not favorable owing to the prevalence of substrate diffusional limitation. A sludge loading larger than 0.45kgCOD·kgVSS^-1 caused a shift in morphology of the predominant acetoclastic methanogen, Methanothrix spp. from a long filament to a short one composed of only a few cells.

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The purposes of this study are to investigate the formation and accumulation of extra-cellular polymers (ECP) by hydrogen utilizing anaerobes under high hydrogen partial pressure conditions, which are found at bottom parts of UASB reactors. Two types of enrichment culture were obtained in which hydrogen gas was intermittently replenished as a substrate with and without sulfates. One of them is an enrichment culture of hydrogen utilizing methanogen (HUM) and the other is a mixed culture of HUM and hydrogen utilizing sulfate reducing bacteria (SRB). Effects of ammonium nitrogen and cysteine on ECP formation were investigated for each culture. A remarkable accumulation of ECP by HUM was observed at the beginning of a batch experiment. in which hydrogen gas and ammonium nitrogen were sufficiently added without cysteine. However, ECPs were not significantly accumulated in the other cases for the HUM culture and all the cases for SRB. Chemical analysis of the produced ECP suggests that ECP protein was more dominant than ECP carbohydrate. HUMs played a role in producing ECP under such a special condition as well as acid producing bacteria. The experimental results suggest that ECP formation from HUM might contribute to self-granulation of sludge in UASB reactors at the bottom where high hydrogen partial pressure was established. There is also a possibility that SRB had a negative effect on sludge granulation by suppressing ECP accumulation.

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The effect of adsorption and desorption in anaerobic biological activated carbon process was investigated. Phenol (100mg/L) was fed to lab-scale fluidized bed reactor as a single carbon source at iday of HRT. Influent phenol concentration was temporarily changed to 0 or 500mg/L for one or two days. Effluent phenol concentration was stable and methane activity was maintained during the changed period and about 5% of adsorbed phenol (100mg/gGAC) was desorbed. Physicochemical desorption test showed that about 10% of adsorbed phenol (100mg/gGAC) could be desorbed. And a substarte gradient model of three phases, namely, bulk liquid, biofilm and GAC, was suggested to explain some characteristics in BAC process which were observed in this study.

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Possibility of hydrogen recovery with a Teflon membrane unit and the effect of vacuum operation on start-up of anaerobic treatment processes were examined. Results of the experiment with a Teflon membrane unit suggested that it was difficult to take hydrogen effectively away from the process where the interspecies hydrogen transfer was established, and that it was the most important to develop a proper anaerobic bacterial population in the process for hydrogen recovery.
In vacuum operation experiments, three pressure conditions, namely 0.13, 0.5, and 1.0 atm were prepared. At 0.5 atm an unique bacterial population was established. It was independent from the interspecies hydrogen transfer. Little methane was produced in the reactor, while the sludge acclimated at 0.13 and 1.0 atm developed hydrogen-utilizing methanogen. It remained unknown why the reactor under 0.5 atm did developed such an unique bacterial population.

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Anaerobic degradation of various volatile chlorinated organic compounds was examined using a sewage sludge as a source of microorganisms. Tetrachloroethylene (PCE) was biotransformed to trichloroethylene (TCE), dichloroethylene isomers, and vinyl chloride by reductive dechlorination. The rate of dechlorination decreased as the number of chlorine in a molecule decreased. The depletion of PCE and TCE varied among sludges obtained from different sources. 1, 1, 1-Trichloroethane, carbon tetrachloride and chloroform were biotransformed more rapidly than PCE or TCE, and transformation pathways other than reductive dechlorination took place. In a sludge with low PCE-dechlorinating ability, addition of the substrate for methanogenic bacteria such as acetate stimulated the dechlorination of PCE, resulting in the formation of cis-1, 2-dichloroethylene (Cis). Studies with the selective methanogenic inhibitor BES suggested that this transformation did not take place as a co-metabolism of methanogens. Semi-continuous PCE-degrading cultures were operated using either methanol, acetate, n-butyrate or glucose as a primary carbon source. PCE was rapidly transformed to Cis in all cultures. On the other hand, the extent of Cis degradation was maximum in the glucose-fed culture. It was demonstrated that complete degradation of PCE to non-chlorinated compounds is possible under anaerobic conditions.

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