This study paid attention to Deiratonotus japonicus, and field surveys and laboratory experiments were carried out to make clear the relation between the habitat of D. japonicus and aquatic environment in the Kita. Based on these survey andexperimental results, influences to habitation of D.japonicus by the environmental condition in the Kita were discussed. Major conclusions in this study are as follows:(1) The density of D. japonicus decreases in the area over middle waterlevel, (2) D. japonicus inhabits the place where mean diameter of riverbed materials is the middle sized gravel, (3) Preference curve on three environment factors (salinity, riverbed materials and water level) is shown by the results of field surveys, (4) Preference of D. japonicus is examined by laboratory experiments, the results show that riverbed materials over the middle sized gravel seem to play a role as their hiding place and feeding area.

View full abstract

Yang (1999) revealed that fish home range is an essential factor to estimate theimportance of the coexistence of pools and rapids in river habitat. Minns' formula, which is defined for rivers and fish in North America, is one of the rare studies on fish home range. In this paper we examined the applicability of the formula to Japanese rivers and fish by using radio telemetry technique. We attacheda radio transmitter to dark chub, crucian carp, common carp, Japanese dace and pike gudgeon, and tracked their behavior in rivers. The observations support the importance of the coexistence of pools and rapids. Shelters during the flood periods are also indispensable for fish. Although they showed a similar home range size with Minns' formula during one to three days, they showed much larger home range for longer periods' observation. Usually they stay within Minns' home range but occasionally they trip a long distance to a nearby habitat.

View full abstract

In recent years, a social demand toward an ecological aspect of a coastal area is increasing. However, very little things have been known about the relationshipbetween an ecosystem and a coastal environment. The objective of the present study is to investigate the transition of algae community on artificial reefs afterconstruction, and the relationship between the development of algae on artificial reefs and the intensity of wave-induced current around artificial reefs will be discussed.

View full abstract

Kenaf is a ligneous and annual tropical plant with the quick growth, and as the trunk is wood-base, the utility form is considered almost equal to the wood. Kenaf can grow actively either hydroponically or in soils. As the kenaf grows in the vertical direction, yield point per unit area is high. The hydroponic culture was carried out using the water from a farm pond which was polluted with household drainage. The removal characteristics of the nutrient salt and growth densitywere measured. As the density was able to be set from low to high easily in the hydroponic culture, the growth density in the place of the closely planted reached from 70 to 100t/ha. The nitrogen removal ratio per unit area was 0.56g/m²/D in the average at summer, this value was higher than that of the general wetland system.
Next the open-field culture of the kenaf was carried out in various places, and the yield point per area was measured. At the same time, nutrient salts and EC, VS, etc.in the soil of the growth place were analyzed, andthe relation between the yield and such indexes were examined.

View full abstract

The Watarase reservoir is the maximum flatland rservoir in Japan, and is one of the main water resources of metropolitan area. But at this reservoir, musty odorproblem arises frequently by the eutrophication, and it becomes a serious problem in water usage. Though the reed field purification method is being tried as a purification countermeasure, it is also necessary to examine the other method. Kenaf is an annual tropical plant originated from Africa. It is known that kenaf can grow also in hydroculture and that the good activated carbon can be producedfrom the wood-base trunk which can be utilized for the removal of the musty odor. As a result, kenaf may be able to contribute to the water purification in the Watarase reservoir.
Then, the author carried out the purification experimentby the kenaf hydroculture system using the reservoir water, and characteristics of the purification were examined.
Next they tried to produce activated carbon for water treatment from the core of kenaf. It was found that good activated carbon which removes color and odor (2-MIB) as well as other activated carbons on the market can be produced from kenaf core. Information on the activated carbon was reported.

View full abstract

Risk assessment methodology to set remediation goals were studied for a contaminatedsite with multiple contaminants such as tetrachloroethylene (PCE), trichloroethylene (TCE), etc. The methodology comprises of four steps. First, remediationtechnologies are selected to decrease the contaminants. Second, the decreasing concentrations of the contaminants are predicted by using numerical simulation techniques. Third, total risks (a non-cancer hazard index, HI, and a cancer risk, Risk T) are calculated by using the predicted concentrations. Forth, remediation goals for the multiple contaminants are set as the total risk is under the acceptable risks (Hl<1 and Risk T<10^-5). In this study, the selected remediation technologies were pump & treat, natural attenuation, and combination of pump & treat and natural attenuation. The methodologies in this study could be applied to set remediation goals for thecontaminated site with multiple contaminants.

View full abstract

Leaching experiments of activated nuclides from neutron irradiated cement were conducted. Nuclides such as ⁶⁰Co, ¹³⁴Cs, and ¹⁵²Eu were detected in the irradiated cements, and ⁴¹Ca, ⁵⁵Fe, ¹³³Ba, and¹⁵⁴Eu were expected to exist in the irradiated cements. It was proved that ¹³⁴CS had being leached from the irradiated cement pastes for about one year. On the other hand, radioactivity concentration of ¹³⁴CS in liquid phase decreased, and it was thought because thedecay speed of ¹³⁴CS was larger than the leaching speed of ¹³⁴CS. ⁶⁰Co was not detected in liquid phase with γ ray-spectrometry, but ⁵⁹Co leached from the not irradiated cement pastes was detected with inductive coupled plasma mass spectrometry (ICP-MS). Ca is one of the main components of a cement, and it was found that Ca had large leachability. Although it is considered that radioactivity concentration of ⁴¹Ca in the irradiated cements and in the leached liquid phase was not high, we must assess the environmental effect of ⁴¹Ca carefully, because of its very long half-life (1.03×105 years).

View full abstract

Leaching tests of arsenic and coexistent substances (Al, Fe, Ca and organic matter) from sewage sludge were conducted at different pH values (1, 3, 5, 7, 9 and 11) using a batch reactor to clarify elution characteristics of arsenic from the sludge. Alkalization of sewage sludge to pH 11 eluted As more than 90 %, whereas the elution efficiency of As at pH 1 was about 50%. The amount of As eluted was correlated with that of Al, Fe and TOCunder the alkaline conditions. Arsenic in the sludge liquid phase was classified into four forms (arsenic, arsenious, monomethylarsonic and dimethylarsinic acids) and each concentration was determined using a HPLC-ICP-MS. The major forms were As (III) at pH 1, both As (III) and As (V) at pH 3 and As (V) at pH≥5 through the leaching tests for 24 hours. These formsalmost corresponded to those illustrated in the Eh-pH diagram of As at equilibrium state. On the other hand, through the leaching tests for 1 hour, the major forms were both As (III) and As (V) at pH 1 and As (V) at pH 9. Although As (III) was readily oxidized to As (V) in the region of As (V) at the equilibrium state, As (V) was insignificantly reduced to As (III) in that of As (III). These results suggested that arsenic existing as As (III) and As (V) in sewage sludge could be effectively eluted by adjusting sludge conditions to the pH and ORP in the region of As (V) at the equilibrium state.

View full abstract

Because MSW Incinerator fly ash have a lot of heavy metals, that is needed to treat by stabilizedtreatment. Large-scale Lysimeters were used to study many materials; two types of chemically treated fly ash, untreated fly ash and molten slag. We continued to research this experiment for about 5 years. On this report, Water quality characteristics of leachate from lysimeters were described. Leachate volume of each lysimeter had large difference, because of permeability and water-holding capacity. Because treated fly ash has much alkaline substance, pH value of leachate was high at early period. Most of leachate from mono filling lysimeters had high concentration lead (Pb) at theearly period.

View full abstract

Material recycling is one of the most important subjects for waste management. Recycling is realized by consumer's positive actions as well as administrator's act and producer's technical development. Now the used materials are recovered from such points as each supermarkets, local centers, waste stations and individual houses on several occasions. It has not been sufficiently searched what kind of recycling opportunity is popular among and convenient for consumers. So we make a questionnaire survey of recycling selections by students. The recycling ratios are cleared in terms of a sort of materials; such as used cans, glass bottles, PET bottles, plastic trays, clothes. and six kinds of paper, and the differences between single and plural households are also examined. Then we analyze the dependence relations between recycling actions and awareness of recycling terms, in order to make the structural diagrams by Interpretive Structural Modeling. The result is offered that single households' recycling action shows tendency to dependent on awareness, though plural households are in habit of doing recycle not related to awareness. The single household chose very limited opportunity of recycling, so some other new recovery way has to be offered. The education about recycling also may be effective to increase the recycling ratio of single households.

View full abstract

Wastewater treatment sludge contains a high percentage of nitrogen and releases a large amount of ammonia when it is composted. By mixing poly-e-caprolactone (PCL), a biodegradable plastic, inthe raw compost mixture of wastewater sludge, ammonia emissions were reduced drastically due to ammonia being neutralized with the acidic intermediates of PCL generated by the microbial degradation during the composting process. Since the start of PCL degradation is retarded in comparison with that of wastewater sludge, the odor ofammonia was remarkably reduced at the later stage of composting when the PCL was actively degraded, and the ammonia never emitted in that composting period. It was not possible, however, to suppress the ammonia odor completely at the earliest stage of composting, even if the PCL dosage was increased. Furthermore, the effect oftemperature on the reduction of ammonia odor was examined by varying composting temperature between 50°C and 60°C. It was found that the optimum PCL mixing ratio is approximately 7 with sludge with a value of 5 on a dry weight basis regardless of composting temperature.

View full abstract

As an effective utilization of waste stillage which will be banned from dumping into sea in the near future, the authors have studied and succeeded in making sosei paper by using waste stillage from shochu distilleries. This research is to develop sosei paper pots using sweet potato waste stillage (hereafter, SPWS) and waste newspaper as one of the resource recycling goods and to consider the weight and property of waste water after compressing samples (SPWS+waste newspaper). Further, this research is tried to compare the physical, mechanical and chemical properties of sosei paper pots and those of waste paper pots, and is applied to the growth test of the tomatoes in sosei paper pots.
Following results were obtained: 1) The method of making sosei paper pots by adding waste newspaper to SPWS was established. 2) After compressing samples, in the case of the sample whose ratio of waste newspaper to SPWS is 3%, more than 70% of the CODcr and T-N components can be removed from waste water. 3) In the case of the sample whose ratio of waste newspaper to SPWS is more than 3%, the suspended solids in waste water after compressing samples were much about the same as mechanical treatments. Therefore, waste water after compressing samples can be treated biologically. 4) A sosei paper pot is about 1/3 to 7/10 of a waste paper pot in length direction compression strength. It was clear that sosei paper pots and waste paper pots have the same strength of tensile and side direction compression when the ratio of waste newspaper to SPWS is 3%. 5) It was found that a sosei paper pot contains 6 to 10 times the amount of T-N, 10 to 13.6 times the amount of P2O5 and 5 to 7 times the amount of K₂O compared with a waste paper pot. 6) While plants became well rooted, the sosei paper pots held their shapes and the roots were not affected at all.
N. B. sosei paper (sosei means rebor)

View full abstract

A huge amount of dewatered cake is generated from water treatment processes in large-scaled construction work sites. Although the dewatered cake has been conventionally disposed as an industrial waste, its recycling becomes a big social concern, and the reuse of the dewatered cake is required. In this paper, we describe a past case in which the dewatered cake generated in the actual hydroelectric power plant expansion construction was recycled as a vegetative soil base. The dewatered cake, a single-grained structure of inorganic particles, was not suitable for the growth and development of vegetation. The improvement of physical and chemical properties of the dewatered cake was then required. The improvement of physical and chemical properties was achieved by mixing bark composts and fermented chicken manure composts with the dewatered cake and by aging them for 14 days. Mixing of such good organic composts improved directly soil in fertilizer aspect, served as a supply source of various microorganisms, expecting improvement effects to the physical properties by those metabolites. This improved soil caused neither germination disorder nor growth disorder to the vegetation, thus, it was shown that the dewatered cake was reusable as a vegetative soil base material with such a procedure.

View full abstract

In this study, solubilization of return sludge from secondary sedimentation tank (excess sludge) of wastewater treatment plant was investigated by passing the sludge through varying gaps (0.1-20 mm) between two high-speed rotary disks. The process was found to enhance the solubilization considerably. Significant decrease of particle size was observed after the first stage of the treatment. The solubilization rate of sludge, indexed as the ratio of DOC/TOC, increased considerably with the treatment time and it was observed that the greater solubilization could be achieved under the condition of higher sludge concentration. The solubilization remained high even though the gap between the two disks was increased to 20 mm. Furthermore, the possibility of improving the solubilization with only one disk was also investigated in this study. The results demonstrate the applicability of high-speed rotary disk process as an attractive novel process of excess sludge solubilization.

View full abstract

Influences of hydraulic retention time (HRT) and temperature on the methane fermentation of organic fraction of municipal solid waste (OFMSW) and the sludge from treated night soil (SNS) were investigated by using a semi-continuous flow, completely mixed reactor. The experiments were conducted with a constant influent flow at a total solid (TS) of 10% by changing HRT from 5 days to 30 days under mesophilic (35°C) and thermophilic (55°C) conditions, respectively. Both the mesophilic and the thermophilic digestion reactors were successfully operated even at a short HRT of 5 days. The results indicate that the most important advantages of thermophilic fermentation over mesophilic fermentation for treating a mixture of OFSMW and SNS are its high efficiencies in VS reduction and CODcr removal, especially in the hydrolysis. It is suggested that the applicable HRT for the high-solids thermophilic digestion could be shortened to 7.5 days at the least. The first-order reaction could be more appropriate for describing the degradation of OFMSW and SNS, and kinetic constants for TS, VS and total CODCr were summarized in a table.

View full abstract

Microbial population shift of anaerobic sludge consortia in response to temperature change was investigated by using 16S rRNA molecular approach such as FISH (fluorescent in situ hybridization), PCR-RFLPsequencing and T-RFLP (Terminal Restriction Fragment Length Polymorphism). A bench scale UASB reactor maintained at 35°C for a long time period was subjected to abrupt temperature increase to 55°C. The mesophilic granular sludge exhibited the optimum methanogenic activity, opposed to our anticipation, at above 40°C, while the thermophilic granular sludge possesses the optimum methanogenic activity at different temperatures for each different substrate: 55°C for propionate-, 60°C for acetate-, and 65°C for hydrogen-fed methanogenic activity.
FISH analysis using our newly developed oligoneucleotide probes, which are able to distinguish separately mesophilic and thermophilic acetate-utilizing methanogen, successfully provided an evidence that some extent of Methanosaeta thermophilia, thermophilic acetate-utilizing methanogen, is present a priori in the mesophilic sludge consortium that have never experienced a thermophilic condition in the past.
The T-RFLP patterns of archaeral clones' 16S rDNA reflected distinctly the time-series population shift from mesophilic acetate-utilizing methanogen (Methanosaeta concilii) to thermopilic acetate-utilizing methanogen (Methanosaeta thermophilia). The molecular approach methodology employed in this study proved to be powerful and useful tools to monitor the population dynamics of anaerobic sludge consortia for better understanding of anaerobic wastewater processes.

View full abstract

Chlorinated solvents such as tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants. A microbial mixed culture capable of dechlorinating PCE to ethylene and ethane was enriched in a fluidized-bed reactor using soil sediments, anaerobic sludges and activated sludges as inocula. DNA sequence analyses of 16S rDNA clones obtained from the mixed culture showed the existence of clones which have high similarity to 16S rDNA of Dehalococcoides ethenogenes 195. This result indicated a high possibility that a bacterium phylogenetically close to D. ethenogenes was responsible for complete dechlorination. Soil columns were inoculated with the enrichment culture and continuously fed with PCE and organic compounds. PCE (4 mg/L) was completely dechlorinated to ethylene within 5 h of HRT with 30 mg/L of ethanol, 30 mg/L of lactate, 60 mg/L of propionate or 50 mg/L of sucrose. Although dechlorination was slightly inhibited in the presence of sulfate (64 mg/L), complete dechlorination occurred at 12 h of HRT.

View full abstract

A field scale biostimulation experiment was carried out at a contaminated site in Chiba prefecture to degrade trichloroethylene (TCE) in groundwater. Methane was dissolved into pumped-up groundwater, and it was injected again into groundwater to stimulate the co-metabolism of TCE by indigenous methane-utilizing bacteria producing methane monooxygenase. Molecular analyses of bacterial populations in groundwater including methane-utilizer were performed to understand the biological process in detail and monitor bacteria developed from the view point of safety. The 16S rRNA gene (rDNA) based analyses, clone and terminal restriction fragment length polymorphism (T-RFLP) analyses, were applied. The clone analysis showed that two types of methane-utilizing bacteria that are phylogenetically close to each of Methylophilus group and Methylomonas methanica subgroup oxidized methane, and thus at least one of them degraded TCE during the biostimulation. Additionally no 16S rDNA clone from a bacterium which possibly causes a disease was not observed. The changes of whole bacterial communities including the methane-utilizing bacteria were successfully detected by T-RFLP analysis showing the effectiveness of the molecular method for the monitoring of the field scale biostimulation process.

View full abstract

River flow derived from groundwater water was estimated from EMMA (End-Members-Mixing-Analysis) to predict NO₃-N concentration in the river water in the agricultural region. To use EMMA, we assumed that river flow consisted of three components: forest river origin, shallow groundwater origin and deep groundwater origin. EMMA revealed that contribution ratio of the shallow groundwater contaminated by NO₃-N in the river flow increased up to 67% in early March. EMMA and Principal Components Analysis also revealed that the particulate matters, SS, PON, PP, Chl-a were strongly related to the contribution ratio of forest river origin. pH and DP in the river water were affected by the contribution ratio of the deep groundwater. The concentration of NO₃-N in the river water increased in winter, because the flow rate of the forest rivers decreased, whereas NO3-N load from the springwater from the upland fields leveled off in winter. Our investigation into the water quality of the river flowing through an agricultural and dairy area found that upland fields constantly discharged NO₃-N loads into the river, in contrast to the forest rivers, which irregularly discharged loads.

View full abstract

The amount of nitrogen fertilizer used in a Kikugawa basin tea plantation decreased from 110 kgN/10a in 1997 to 65 kgN/10a in 2000. However NO₃-N concentrations were over 30mg/l and pH values remained unchanged. So the residual NO₃-N and acid in groundwater were calculated to determine whether the amounts of fertilizer and neutralizer were adequate or not. As a result, the calculated NO₃-N concentration in groundwater from precipitation, evapotranspiration, infiltration, outflow, eluviation and fertilizer was in good agreement with the actual NO₃-N concentration in the wells. As the actual and calculated NO₃-N concentrations exceeded the 10 mg/l, environmental quality standard, it was necessary to reduce the amount of nitrogen fertilizer. Similarly residual acid was calculated from the amount of neutralizer such as calcite, dolomite and fertilizer. The amount of neutralizer was sufficient for neutralization but pH values in the wells remained low. Therefore, no neutralizers were thought to work and some rain water was thought to directly bring acidic substances and infiltrate into the underground.δ¹⁸O and δD values clarified that the conveyance from Oigawa river reduced NO₃-N concentrations in the Kikugawa basin.

View full abstract

For the plan, design, management of separate sewer system, the distributed model considered watershed characteristic is necessary. In this study, the parameter selection of the runoff and water quality model is examined using the measurement data that was observed with the separate sewer system. Then, the watershed characteristic of parameter is examined. To make clear watershed characteristics a simulation is analyzed by the same rainfall. As a result, it found the thing about which it is possible to set a parameter for runoff and water quality model that fitted in with each watershed. It was found that the model parameter was able to use for the plan, design, and management of the separate sewer system.

View full abstract

At present, percentage of sewered population in our country has reached 60%, and conversion into flushtoilet reached 79% of the total population when the domestic wastewater by the private sewerage system is also included. However, the achievement ratio of environmental quality standard item related to living environment is low, and achievement ratio of environmental quality standard and conditions of rivers is not much improved the past 10 years. It is said that the main reason for low achievement ratio of such environmental standard is caused by the domestic wastewater. Especially, the coliform group's environmental standard item achievement ratio is very low. At present, most of Japan's rivers has not achieved the standard value of the coliform group. Within class a river in Kyushu, there is not a single river that cleared the standard value either in the upstream or in the downstream. Therefore, it is necessary to improvement the achievement ratio of the environmental standard, that is to grasps the actual condition of the coliform group pollution and provide for countermeasure of the each every pollution source.
In this paper, measurement of coliform group number, fecal coliform group, fecal streptococci of Kiyotake river and the water quality survey was being carried out from upstream of Kiyotake river which flowed from Tano town, passing Kiyotake town to Miyazaki City in the lower reach. Following result was obtained. 1) The coliform group number of Kiyotake River seasonally fluctuated, and it was proven that the coliform group number in rainfall time were more abounding compared to the time of fair weather. 2) The coliform group number of Oka river which was the tributary for the Kiyotake river were very high, and it was proven that domestic wastewater is a cause for the coliform group pollution of the Oka river. 3) It is said that the low achievement ratio of such environmental standard is chiefly caused by domestic wastewater and does not satisfy the environmental standard value of the coliform group in present state of the river in Japan.

View full abstract

The pollution sources and dynamics of organophosphoric acid triesters (OPEs) in the Kurose River Basin were investigated and numerically simulated. In order to estimate the loads from various pollution sources quantitatively, the effluent OPEs concentrations were measured at small-scale wastewater treatment plant, sewage treatment plant and waste disposal sites. Several kinds of OPEs were detected in the effluents, the waters and sediments of the Kurose River, and the waters of its tributaries. It was indicated that the domestic wastewater was the dominant OPEs source for the basin. Using the population data corresponding to a few kinds of wastewater treatment types in a number of sub-basins, per-capita effluent values on OPEs and water discharge, the base flow rates, and the OPEs diminishing rates in the river determined by the field experiment, we developed a model for predicting OPEs in the Kurose River during the non-rainy periods. Then, we confirmed that the differences between the observed and predicted OPEs were within one order of magnitude in all cases.

View full abstract

The function of a test structure for the environmental restoration in enclosed sea area was assessed by several field investigations. The objective of the structure is to activate material cycle through the foodweb of marine organisms feeding on suspended solid. Dissolved oxygen concentration in the bottom of structure was lower than 3mg/l in summer, because a number of mussels on the porous concrete had consumed oxygen. The mussels also had an effect on decreasing suspended solid, and concentration of suspended solid in the structure wasrelatively lower than the outside due to their feeding activities. Amount of deposited seston varied with seasons. Thedeposited seston contained faeces and pseudofaeces of mussels, indicating that suspended solid was transferred by mussel filteration onto the bottom of structure. However, since few numbers of deposit feeder inhabited the bottomof structure, deposited seston have accumulated and caused deterioration of sediment quality. Some ideas for improvement of the structure were proposed in the discussion.

View full abstract

The authors proposed a new manhole model for preventing urban flooding by installing a flat guide-cover with holes onto the invert of a conventional manhole with right-angle pipes. In this study, under the condition of sudden blocking of water flow at a downstream pipe end, flow characteristics on the propagation of interfaces between free surface and pressurized flow in the downstream pipe and on the height of water body spouted through 5 holes at the flat guide-cover in the manhole were examined. The propagation speed of the interfaces in the downstream pipe with the new manhole model was smaller than that of the conventional manhole model. The water body spouted through the flat guide-cover did not reach a manhole cover.

View full abstract

The damage caused by the aging of sewage pipe systems has become one of the major rising problems in modern cities. The traditional method to search for damage points on sewage pipes is using cameras and eyes. But using these methods to check all the sewage pipes in the city will waste a lot of money and time. In this paper we performed a quantitative analysis on sewage pipe damages. Our study utilized the results of the sewer investigation in Tokyo. Based on this analysis, we proposed a quantification theory type II to describe the relationships between various factors that contribute to the damages of sewage pipe systems. Namely, we can use the factors, such as the pipe diameter, the number of years for laying, the kind of road and foundation, overburden, pipe's slope etc., to judge the sewage pipes if it has a corrosion, crack or breakage. As a result, our diagnosis model can be used to discriminate whether and to what extent an existing sewage pipe system is damaged.

View full abstract

Field research on hydraulic works, in 2000 at Pisac, one of the ancient Inca Remains, defined some of the characteristics. There are four kinds of hydraulic works, that is, channels for ritual, waterworks, drainage, and irrigation in the Inca civilization. The site had at least five canals for water works, more than two canals for irrigation, more than three drainage channels for agriculture, and no channels for ritual. Drainage for domestic wastewater is not found. No technical contrivance for health risk on waterworks existed at the site, so that social discipline with taboo might work for the risk. Their design skill was not excellent on hydraulic works, but high in construction technology. The structure of an irrigation channel indicates that water right may exist. The concept of sacred water was similar to other old civilizations.

View full abstract

Several physical and chemical treatment processes for endocrine disruptors removal from sewage effluent were studied with laboratory and pilot scale experiments. The treatment processes investigated were chlorination, coagulation-filtration, ozonation and granular activated carbon adsorption. Nonylphenol (NP) and human-origin estrogen were chosen as target compounds. Ozonation was found to be the most effective in removing endocrine disruptors compared to the other methods, although reduction of total organic carbon (TOC) was not significant. Estrogenic effects in residual TOC after ozonation were then determined using the yeast screen assay and the receptor-binding assay by fluorescence polarization method. The results showed that residual TOC had no estrogenic effects. Granular activated carbon (GAC) was also found to be an effective method for endocrine disruptors removal during the three-month period of operation. The performance of GAC beyond this period, however, has yet to be examined. Degradation of NP by chlorine was influenced by ammonia, TOC and contact time. High chlorine dosage was effective in removing estrogen in sewage effluents containing very low ammonia concentrations. More studies, however, are needed to address the carcinogenic or mutagenic byproducts which might be formed during chlorination. Coagulation-filtration process was found to remove only small amounts of NP and had small effect on estrogen removal.

View full abstract

Temporal change of quantity of DEHP emitted from PVC products in a sealed glass container was measured to estimate its emission rate.An equation that expressed DEHP emission quantity in a sealed container was derived and its validity was examined by comparison with the results of some experiments. The following conclusions were obtained.(1) Most of DEHP emitted from PVC products in a sealed glass container stuck to its inner wall. Therefore, DEHP emission quantity from PVC products can be approximately estimated by measuring the DEHP quantity on glass walls, and DEHP absorbed on the surface of tableware and food should be considered when DEHP intake is evaluated.(2) The derived equation could well explain the results of the experiments. Estimation of the initial emission ability of DEHP seems to be possible using the equation.(3) DEHP initial emission ability from PVC sheet increased with a rise of temperature, and the rate was about 5 times greater at 50°C than at 40°C under the conditions of this study. Because a great increase of the emission ability with a rise of temperature is also expected in the actual environment, temperature must be considered in cases of DEHP intake evaluation.

View full abstract

Fundamental performance of a novel sequencing batch reactor/bioelectrochemical filter (SBR/BEF) process which combined recirculating filtration and a biofilter with a multi-electrode system was investigated experimentally. In this process, the recirculating filtration passed through the sludge bed which comprising a stratified layer of activated sludge and porous carriers. Meanwhile the filtrate was introduced to BEF, in which the same porous carriers were immersed (fill rate 80%) and a multi-electrode system was inserted. The obtained results showed that an effective suspended solid (SS) removal could be achieved by using the sludge bed as filter. In addition, the endogenous denitrification proceeded in the bed but the rate was small. When the filtrate introduced to BEF, the hydrogen gas produced by electrolysis of water was directly utilized for denitrification. The denitrification rate in BEF was estimated to be around 0.036 mg-N/mg-SS·d at electric current density of 0.76 mA/cm². The SS concentration reduced below 1.0 mg/l in the treated water, and the total nitrogen removal efficiency exceeded 90% under the condition of 6.25 hr of one cycle time.

View full abstract

In this investigation, the feasibility of phosphorus removal and recovery using a laboratory prepared Ca-based sorbent containing relatively large pores was experimentally demonstrated. Obtained results from the column experiment showed that the removal was accompanied by a leaching of Ca and relatively high pH values at the beginning of the experiment due to the hydration of CaO. After that, the elution of Ca ceased and the pH values decreased gradually to finally stabilize between 8 and 7.5. It was suggested that phosphorous uptake by the sorbent was governed by both sorption and precipitation/crystallization phenomena. The sorption capacity slightly increased with an increase in the flow rate and was associated with the increasing amount of the dissolved calcium. Maximum removal capacity was equal to 30.5 mg-P/g-sorbent, corresponding to a quantity of treated water equivalent to 4000 bed volumes. Pore sizes of the sorbent were entirely shifted to lower values due to the formation of hydroxyapatite on the surface. Furthermore, more than 75% of the sorbed phosphate was recovered using a mechanical sieving of the sorbent. X-ray measurement and P₂O₅determination revealed that the recovered product was quantitatively and qualitatively similar to a phosphate mineral ore. The sorbent was efficiently reused for a second time. However, its removal capacity was severely degraded upon the third utilization, probably because most of its calcium content was consumed. From these results, it was concluded that the fabricated sorbent could be effective for phosphorus removal and recovery.

View full abstract

In “Clean Lake Suwa” which was the terminal treatment plant of the Suwa Lake river-basin sewerage facilities, the renewal to the advanced sewage treatment plant was examined from 1995. In the simultaneous precipitation process, Al/T-P mole ratio had to be made over 0.75 in order to do under discharge regulation T-P concentration 2mg·l^-1. And, it was anticipated that the Al/T-P mole ratio had to be done over 2 in order to do under desired value discharge T-P concentration 0.5 mg·l^-1 In the flocculant injection point, phosphorus elimination reaction rate is low. It was confirmed that the flocculant which intermingles with the return sludge was bringing about the effective phosphorus elimination reaction in aeration tank front stage. The anaerobic-aerobic activated sludge process applied to “Clean Lake Suwa” has not reached the phosphorus elimination performance of the goal. The shortening of SRT was attempted by the charge of the preliminary sedimentation basin sludge to the aeration tank. As a result, it was possible that it was improved, and effective SRT was able to be judged with under 8th. In addition, the phosphorus elution from the sludge was measured. Largest phosphorus elution amount of the simultaneous precipitation process sludge was 3.5mgP·gSS^-1. It was confirmed that the phosphorus elution amount was little. And, it was confirmed that Al which originates for the simultaneous precipitation process sludge affected phosphorus concentration in the supernatant by the anaerobic digestion process.

View full abstract

This study was investigated in order to develop recovery system of phosphate and ferric chloride from precoagulated sludge with ferric chloride. Experiments were conducted to clear the following points, Dextraction efficiency of phosphate from pre-coagulated sludge with ferric chloride by introducing H₂S gas into sludge, 2) recovery of phosphate from the supernatant after the extraction using Ca (OH) ₂, 3) simultaneous recovery of ferric chloride and H₂S from the residue after the extraction by adding HCl solution and 4) the mass balance of suspended solid, phosphorus, iron and sulfur in this total system. As the result of mass balance in this system, 40% of phosphate and 73.1% of ferric chloride from precoagulated sludge with ferric chloride and 47.2% of introduced H₂S gas were recovered at the optimum experimental condition.

View full abstract

Ferric and ferrous iron contents in an activated sludge were examined. Total iron in the sludge was 10mg/gMLSS and 60% of iron was accumulated as Fe (III). Iron oxidation occurred in the activated sludge, and the iron oxidation rate increased, when the initial iron concentration increased. Biological iron reduction also occurred in the activated sludge and the iron reducing rate could be described using the Monod equation. It was estimated that iron reducing bacteria utilize hydrogen. Sulfur oxidation and iron oxidation occurred simultaneously and they competed for oxygen. Iron oxidation and sulfur oxidation activities were almost the same. Sulfate reduction and iron reduction also occurred simultaneously. Iron reduction outcompeted with sulfate reduction for hydrogen and propionate like organic matter. On the other hand, sulfate reduction stimulated the iron reduction, since chemical reduction by produced sulfur occurred simultaneously. Denitrification suppressed iron reduction and sulfate reduction. These results were explained thermodynamically. Poly-P release was also suppressed under the anoxic conditions.

View full abstract

Batch and semi-batch systems were applied to investigate the fouling characterization of nanofiltration (NF) by colored organic matters, i. e. humic substances. A diluted kraft pulp water containing organic colored matter, with the pretreatment of ultrafiltration fractionation (UFF), was used as a synthetic raw water to examine the influence of apparent molecular weight distribution (AMWD) of colored organic matters on the fouling mechanism of NF membrane. Results show that the substances having MW10, 000-100, 000 in colored organic matters play an important role on the fouling of NF membrane. A mass of foulant was calculated by the model describing the mass of colored organic matters transference developed in this study. It is found that the amount of foulant much increases when the fractions of MW10, 000-1 00, 000 exist in colored water. The flux decline or the resistance increase was due to the increase in mass or percentage of the substances having MW10, 000-100, 000. If the substances can be appropriately removed coagulation or UF treatment system, NF fouling would be effectively controlled.

View full abstract

Previous works on Low Pressure Reverse Osmosis (LPRO) have shown that the rejection of organic compounds is mainly controlled by molecular weight and dissociation constant. This study demonstrates that the membrane ζ-potential also can be considered as a key factor for rejections of ionic salts and dissociated organic compounds. We measured the membrane ζ-potential by using a streaming potential method. In addition, effects of the ζ-potential on rejection properties of some dissociated organic compounds and an ionic salt were investigated. The results of experiments are as follows.(1) The low pressure reverse osmosis membrane was positively charged under the strong acidic condition, and negatively charged under the weak acidic and alkaline condition.(2) The zero-point of charge (zpc) values of LPRO membranes were found to be between pH 2.66 and 3.74 by the ζ-potential measurement.(3) The rejections of an ionic inorganic salt and dissociated organic compounds with low molecular weight changed with pH, depending not only on the plus or minus sign of membrane ζ-potential but also on the absolute ζ-potential value.(4) Organic compounds with high molecular weight such as Pentachlorophenol showed high rejection without depending on the membrane ζ-potential.

View full abstract