Water legislation is one of the instruments that are used to streamline social behaviour towards water resources management. However, the pieces of water legislation in most of the developing countries, Tanzania in particular, have many weaknesses that affect their enforcement. This paper aims at presenting some of the weaknesses present in Tanzanian pieces of water legislation. The majority of the pieces of legislation are outdated and where fines are prescribed are too low to compensate for any damage caused. They are generally based on control and command principle rather than sustainable use of the resource. Community participation is generally neglected, as too much power is concentrated to the executives. Provisions protecting the quality and quantity of water resources are scattered in various government departments. Thus, in order to achieve sustainable water resources management there is a need of having comprehensive, cost effective and environmentally sound water legislation, which takes into account the existing weaknesses. There should be an autonomous regulatory organ with legal powers to enforce the laws and oversee environmental matters. Environmental impact assessment must become a statutory obligation for any planned projects so as to reduce their impacts to water resources and environment in general.

抄録全体を表示

Effects of C/N, C/S and S/N ratios on TOC and denitrification removal were examined in the sulfate reductionsulfur denitrification process using the two upflow biological filter reactors. High TOC and nitrogen removal ratio was obtained at C/N=2.2 and S/N=0.7 through the reactors. In the first reactor, sulfate reduction occurred predominantly. SRB mainly produced acetate at C/S=3.1. However, acetate was decomposed in the first reactor at C/S=1.6. In the second reactor, sulfur denitrification and heterotrophic denitrification occurred simultaneously. Sulfur denitrification occurred in the lower part of the reactor in S/N=0.7, and all sulfide produced in the first reactor was re-oxidized. On the other hand, sulfur denitrification also occurred in the upper part of the reactor in S/N=1.3, and 35 mg/gSS of sulfur granules were accumulated in the biofilm. The sulfur granules played an important role on denitrification. The activity of SDNB in the second reactor was about 3-4 times lower than the activity of DNB. When the S/N ratio increased, the activity of SDNB increased and those of DNB decreased. The number of SDNB was greater than those of DNB. The activity of SRB in the first reactor increased, when S/N ratio increased. SRB also grew in the anoxic second reactor, and the activity of SRB in the second reactor was relatively high. The sulfur cycle consist of sulfate reduction and sulfur denitrification in the second reactor might be established in the reactor.

抄録全体を表示

Liquid-solid two-phase fluidized bed type reactor was operated for struvite recovery for the purpose of developing the reactor that can be applied to wastewater having low PO₄-P concentrations. In area-wide sewage sludge treatment plant, the reactor was examined to recover struvite from thickener effluent, whose PO₄-P concentration was around 40 mg/L. When the thickener effluent was treated by the reactor without the addition of Mg²⁺, Ca²⁺ affected struvite recovery and the Ca contents of the recovery particles increased. In batch tests, it was confirmed that the condition where struvite precipitates prior to calcium phosphate in wastewater requires the condition of [Ca²⁺]/[Mg²⁺] < 0.25 in the influent. The inorganic SS flowing into the reactor was also found to affect the recovery in column tests. To prevent this effect by the inorganic SS, the reactor was operated without the influent of fine suspended solids in the wastewater from the melting furnace. The only influent processed was the thickener effluent, and MgCl₂ aq. was added using a magnesium resource. Consequently, the recovery rate improved to 62%. In the case that struvite is recovered from wastewater including low PO₄-P concentration, the recovery rate of struvite was affected by the coexistent substances in the influent. But if this effect was controlled, this reactor could recover struvite particles passably.

抄録全体を表示

UV disinfection is noted to have some problems, one of which is photoreactivation. Photoreactivation allows inactivated microorganisms to regain viability following UV disinfection. The objective of this study is to determine the susceptibility of enterohemorrhagic Escherichia coli (EHEC) O26, vancomycin resistant Enterococcus (VRE), and Pseudomonas aeruginosa to UV radiation and photoreactivation. The conclusions obtained in this study can be summarized as follows. EHEC O26 exhibited apparent inactivation under sunlight after photoreactivation following UV inactivation. VRE exhibited apparent photoreactivation. The dose of UV light required for 90% inactivation of VRE with and without photoreactivation was 10.9 and 24.2 mW sec/cm², respectively. P. aeruginosa exhibited apparent photoreactivation under fluorescent lamp and weak regrowth under dark conditions following UV inactivation. The dose of UV light required for 90% inactivation of P. aeruginosa with and without photoreactivation was 4.1 and 5.2 mW sec/cm², respectively.

抄録全体を表示

A program of cancer prevention, which aimed at identifying and minimizing human exposure to hazardous chemicals, requires the development of a rapid inexpensive screening assay as a complement to expensive long-term animal tests. Among thousands of hazardous chemicals to which humans are exposed, very few have been tested for genotoxicity. This report presents 255 chemicals (mutagens, non-mutagens, etc.) of a wide variety of chemical types which have been tested for genotoxicity, both in the Salmonella microsome test (Ames test) and in 8-hydroxyguanine (8-OH-Gua) assay, in order to detect carcinogens. Of the 255 chemicals tested, 83 chemicals (32.5%) were mutagenic in S. Typhimurium YG1041, YG1042, YG3003 and/or YG7108 strain, and 21 chemicals (8.2%) formed 8-OH-Gua in the rat hepatocytes oxidized DNA. These results may demonstrate the utility and limitation of both the Ames test and 8-OH-Gua assay in detecting chemicals likely to be toxic.

抄録全体を表示

This study describes the dye removal under the iron oxide(FeOOH) catalysed decomposition of hydrogen peroxide. FeOOH was selected as iron oxide. The effect of FeOOH concentration, H₂O₂ concentration, the presence of radical scavenger, and pH on the dye removal and the decomposition of hydrogen peroxide was investigated. The rate of H₂O₂ decomposition was obtained as a pseudo-first-order kinetics relative to FeOOH concentration. However, despite of the increased H₂O₂ decomposition rate, the dye removal rate was not proportional to FeOOH concentration because FeOOH surface plays a role of scavenging OH radical. The H₂O₂ decomposition by FeOOH at pH 7 was more significant than that at pH 3, suggesting the possibility for overcoming limitations of homogeneous Fenton reaction which occurs only in acidic condition. The mechanism for the dye removal under the iron oxide catalysed decomposition of hydrogen peroxide was suggested, based on the experimental results obtained in this study.

抄録全体を表示

There has been considerable interest in photocatalytic oxidation of recalcitrant contaminants using titanium dioxide (TiO₂) in recent years. A solar-driven, photocatalyzed detoxification system using TiO₂ was constructed, and this system was applied for the degradation of trichloroethylene (TCE) contaminated water. The results showed that, with both UV light illumination and TiO₂ present, TCE was more effectively degraded than with either UV or TiO₂ alone. A 50ppm of TCE could be completely degraded in 3 to 4 hours of solar light illumination. Photocatalytic degradation of TCE increased linearly with increasing sunlight intensity. The degradation of TCE also increased with increasing TiO₂ dose, however, the degradation efficiency reached a plateau over 0.2 wt% of TiO₂ dose. The mass balance study showed that about 80% of chloride was recovered as TCE degradation byproducts. Finally, the experiment was performed in order to examine the deactivation of TiO₂ due to the adsorption of TCE during consecutive runs, but no reduction in the activity of TiO₂ was observed after the deionized water regeneration.

抄録全体を表示

Effect of phenols on hydroxyl radical formation during ozonation was investigated, using spin trap ESR technique in batch system. Addition of methylphenols increased amounts of DMPO-OH. The enhancement effect was similar to the case in which the stopped flow equipment was used. In case of chlorophenols, amount of DMPO-OH was also enhanced but it decreased in a time and ozone-concentration dependent manner. In case of 20 µM ozone, DMPO-OH generation in batch and stopped flow system were almost the same, when the enhancing effect was calculated using the Y intercept obtained by extrapolating from elimination curves. However, in higher ozone concentration, enhancing effects of phenols in DMPO-OH formation were underestimated compared with that in stopped flow-system. In conclusion, batch system, in addition with stopped-flow system, would be also useful for analyzing enhancing effects of dissolved compounds on ozone reaction when they have moderate enhancing effects.

抄録全体を表示

Salt water from the sea flows up- and down-ward in tidal rivers due to tides. When mixing in a tidal river is relatively weak, a saltwater wedge is formed in it. The Kita river, the objective field in this study, located in eastern part of Kyushu island in Japan is in this state. When external forces work on an ecosystem, then changes might occur in response to them. The ecosystem in such a river is with more impact, because its aquatic zone in the tidal range is fragile and high in productivity. This study attempts to investigate the behavior of Deiratonotus japonicus, known as a rare species in the world, in association with saltwater wedge movement, to obtain relationships between water quality and hydraulic factors and to study the preferable environmental condition on the habitat of Deiratonotus japonicus. Based on field observations, the habitat of Deiratonotus japonicus has a distribution correlated to salinity and water temperature in the longitudinal direction, and riverbed materials and water surface elevation in the cross-section in the tidal range.

抄録全体を表示

The Hanshin Water Supply Authority (HWSA) has introduced effective wastewater treatment system to its New Amagasaki water treatment plant (WTP) with the objective of strengthening water quality management, dewatering process improvement, and cake volume reduction. As for the water quality management, turbidity particles including microorganisms in filter backwash water are separated by dissolved air floatation (DAF), and removed from the washwater reclamation system. The exhaust heat energy from the natural gas co-generation system installed into the WTP is used for heating sludge and drying dewatered cake. Heating sludge improves dewaterability and reduces power consumption. It is possible to extend re-utilization field of the cake by heating the dewatered cake into pelletized one, which leads to complete recycling; zero emission. Wastewater treatment system at the plant could reduce microbial risk and environmental load, while decreasing operation and maintenance cost by about 15%.

抄録全体を表示

A new method was developed using the carbon dioxide detected in the headspace of a batch reactor to determine the carbon source addition in the biological nutrient removal (BNR) process. The activated sludge used in this study was taken from the University of British Columbia (UBC) Wastewater Treatment Pilot Plant aerobic tanks undergoing simplified UCT process. Experiments showed that detectable changes of carbon dioxide concentration in the headspace reflected the acetate utilization in the anaerobic condition, i.e. the P release reaction. In the sodium acetate addition cases, the elapsed time (E Time) of carbon dioxide evolution rate changes was proportional to the amount of acetate added in solution. Results were successfully used to estimate the amount of acetate added in tests. This new methodology was also capable of estimating the amount of VFAs recovered from the thermophilic aerobic digestion (TAD) supernatant.This on-line “E Time” monitoring approach has the potential to optimize the carbon source addition in BNR processes.

抄録全体を表示

Tea field soils, and sediments of an irrigation pond and a tidal river, in which a variety of organic matter was supplied as energy sources, were collected. The activities of bacterial and fungal denitrifications in these samples were determined. Denitrifying fungi in all of these samples produced N₂O from nitrate and nitrite as a final product, whereas denitrifying bacteria produced N₂. Nitrous oxide produced by fungi was reduced to N₂ by bacteria. The fungal denitrification potentials were the highest in the submerged litter on the pond sediment, followed by the farmyard manure-amended soil, the inorganic fertilizer-amended soil, the litter-free pond sediment, and the tidal river sediment. The enrichments of denitrifying fungi in natural environments were related with the distributions of the organic material such as straws and litter. The contributions of fungal denitrification to total denitrification were large in soil environments, especially in the farmyard manure-amended soil, and were small in aquatic environments such as the sediments of pond and river. The pH in situ was not related with the fungal denitrification potentials.

抄録全体を表示

A research was made on phosphorus recovery conditions using a MAP (Magnesium Ammonium Phosphate) method and anaerobically digested desorption liquor (containing ammonia and phosphorus). A fluidized-bed phosphorus removal system was used as the reactor. The main objective of the research was to study the treatment performance, influent phosphorus load and MAP microcrystallization, and phosphorus recovery. One typical result of treatment performance was a treated water T-P of 26.6 mg/L and a phosphorus recovery of 81%, versus a raw water T-P of 142 mg/L. It was found that MAP microcrystallization increased and phosphorus recovery declined along higher influent phosphorus loads. In a case where the mean MAP particle size was 1.5 mm, the recovery was about 80% under an influent phosphorus load of 25 kg-P/m³/d, 60% under 40 kg-P/m³/d, and reaching a constant recovery rate of about 70 kg-P/m³/d at loads exceeding 100 kg-P/m³/d. The constant recovery rate was assumed as due to the limit in the growth rate of MAP particles. Study results indicated that effective phosphorus recovery using the fluidized-bed system could be achieved by maintaining the MAP particles in the reactor to be small (1 - 2 mm) so that they could be easily handled.

抄録全体を表示

This study describes the solubilization of excess sludge by high speed rotary disk process. The excess sludge from final sedimentation tank in wastewater treatment plant was used in this study. The experiments of sludge through the high speed rotary disk were carried out. The results indicated that it was possible to improve the solubilization of excess sludge by this treatment process. Significant decrease of particle size after first time treatment was observed. With the increase of recycle time of treatment, the solubilization was obviously improved. It was suggested that the solubilization of microorganisms due to the function of hydrolase from broken microbial cell was promoted .

抄録全体を表示

The existing method was improved to simulate the coagulation process. In this method, Smoluchowski discrete equation was directly solved using the fourth order Runge-Kutta method. Through incorporating five different collision results of two colliding particles in different or same sections into calculation process, the coagulation process was simulated exactly. This process avoids the complex conversion process and additional assumptions as the previous works. Mass balance was strictly realized during the whole process. Changes due to different fractal dimension D, shear rate G and different coagulation kernels were demonstrated. Finally, experimental study was used to check the simulation result.

抄録全体を表示

Three reactor set-ups were investigated, namely nitrification UCBR prior to coupling, coupled UCBR-packed bed system for nitrogen removal, and de-coupled recovering UCBR. Batch studies were conducted on the biofilm particles taken from the UCBR. A mathematical model was developed to estimate the growth kinetics of the biofilm autotrophic and heterotrophic bacteria. Heterotrophs was noted to accumulate on the nitrifying biofilm due to the effect of residual COD from the packed bed column during the coupled reactor phase. The growth of heterotrophs had affected the substrate removal rates, biofilm morphology, and growth kinetics of nitrifying bacteria. For example, µ_m of ammonium oxidizing bacteria decreased from 0.55 to 0.19 d^-1, while K_s increased from 1.42 to 3.34 mg N/L. This study demonstrated that µ_m and K_s of the nitrify bacteria changed with the type of substrate. Hence, growth kinetics would not be the same for nitrifying bacteria that is exposed to residual carbon in a coupled UCBR-packed bed system and a single UCBR that is fed on organic-carbon free substrate.

抄録全体を表示

Six Multi-Soil-Layering systems with combinations of two type of soils, Andisol (volcanic ash soil) and Entisol (granitic sandy soil), two particle size classes of zeolite, 1-3 and 3-5mm in diameter, and various hydraulic loading rates, 1 to 4 m³ m^-2 day^-1, were constructed and were compared for polluted river water treatment. Removal rates of BOD, T-N and T-P were 72.2 to 83.5 %, 22.4 to 50.5 %, and 51.9 to 66.8 %, respectively. Entisol was more efficient for T-N and T-P removal than Andisol. Zeolite of 1-3mm in diameter was more efficient for removal of all the pollutants than that of 3-5mm. These materials might contribute more effective contact of inlet water to the various components for purification in the MSL systems. Lower loading rate was more efficient for BOD and T-N removal. The loading rate of 2 m³ m^-2 day^-1 was the most efficient for T-P removal. However, differences in removal rates of these pollutants of river water among the MSL systems were small considering with the differences of hydraulic loading rates. The difference in BOD removal rates between MSL 1 and 6 was only 10 % against to 400 % difference in the loading rates between them. Although clogging was observed at the loading rate of 4 m³ m^-2 day^-1, the system was recovered after 2 months rest. These results indicated that higher loading rate, 4 m³ m^-2 day^-1, was more advantageous and practical for direct river water treatment.

抄録全体を表示

In this study, fillers (gravel and brick) of different surface areas were installed on both banks of two test channels so as to have the same capacity, and effects of differences in surface area and porosity of the streamside on aquatic biota and activity of the attached biofilm were investigated at downstream distance. The results showed that an increase in surface area and porosity causes change in the composition of microbial community, increasing the number of total bacteria and nitrifying bacteria and improving oxygen uptake activity. Although there was no evident difference found in the biofilm microfauna between the two test channels, a result was obtained that oxygen uptake rate by protozoa and metazoa evaluated by laboratory batch experiments quadruples farther downstream in the gravel-filled channel. Furthermore, it was clear, from the result that there observed many Physidae and Ephemeroptera that prey on deposits such as detritus precipitated in the interstices, that the amount and diversity of macrobenthos increased in the gravel-filled channel. These results suggest that surface area and porosity are extremely important factors in the detritus food chain constructed by settling and accumulation of particulate organic matter, and it is considered that controlling them can create a diverse aquatic biota.

抄録全体を表示

This study aimed to identify the origin of DOC loading, by which the extent of SUVA representing of humic content or aromaticity of natural organic matter, NOM concentration in lake, could be determined and the effect of hydraulics conditions on the dynamic behavior of SUVA in the Daecheong reservoir, Korea. The type of Daecheong reservoir was meso-stratified as the ratio of inflow rate to reservoir capacity, α, was under 10 but it was temporally classified into intermediate type during storm season by heavy rainfall. Over 90% of total DOC loading attributed to allochthonous sources in upstream and it concentrated in storm season. While, autochthonous DOC by production of algae in Daecheong reservoir appeared only in short period of algal bloom. And the proportion of autochthonous DOC to total organic carbon loading varied significantly depending on spatial locations but was not significant. The extent of SUVA in lake water depth was severely deteriorated by inflow rate and the location of intrusion of storm flows into lake layer during storm event because density of inflow storm water is usually heavier than that of the surface water. It has been found that SUVA in Daecheong reservoir strongly attributed to allochthonous DOC from upstream watershed.

抄録全体を表示

Presence of wastewater particles is often cited as the reason for failure of UV-irradiation to inactivate targeted organisms to desired level. However, till now there is no method to directly assess the inactivation of particle-associated indicator organisms after UV-irradiation. In this study, we tried to establish a method to identify viable bacteria within wastewater particles. This method was then used to distinguish between particle-associated viable and non-viable bacteria after UV-irradiation. The objective was to assess the fraction of particles of different sizes that are associated with coliform bacteria and to analyze the impact that these particles may have on the residual coliform concentration after UV-radiation. We found that fluorescent in-situ hybridization (FISH) in conjugation with Direct viable count can be effectively used for identification and counting of particle associated Enterobacteriaceae. The method can also successfully distinguish viable bacteria after UV-radiation. We found that only 2 percent of the total coliforms in the supernatant from the secondary clarifier of the Shibaura water treatment plant is associated with particles. Association of coliforms were maximum for the particle size ranging from 41-µm to 80-µm. It was also found that UV-radiation can effectively penetrate through most of the waste water particles.

抄録全体を表示

The scientists of Rajshahi University together with Research Group for Applied Geology (RGAG) and Asian Arsenic Network (AAN) of Japan suspect that groundwater of about 56 districts out of 64 districts are seriously contaminated with arsenic. There are 11 Million tubewells in Bangladesh out of which about 5 Million tubewells are highly arsenic contaminated. About 75 Million people of the affected districts are at risk and the total number of patients suffering from Arsenicosis are about 7000 and out of which about 200 persons already died. To give safe water to the peoples more investigations in the whole country is essential. The source of arsenic in groundwater of Bangladesh is as yet unknown. But it is now widely believed that the high arsenic levels in the groundwater in Bangladesh have a natural geological source which may be due to abstraction water from Quaternary confined and semi-confined alluvial or deltaic aquifers. Groundwater in Bangladesh from sandy alluvial deposits are considered to be arsenic free. It is essential to consider the groundwater occurrences, its distribution and geological and hydrogeological settings of the country for the mitigation of arsenic problem. To know the basic understanding of the source and mobility of arsenic it is essential to investigate the sampling depth and aquifer provenance. Present study will give some clue about the future action plan for the mitigation of the arsenic problem in Bangladesh. The result of investigation have been discussed. To save these huge population of the area all sorts of international help are essential. If precautionary measures against arsenic contamination are not taken immediately consequences like death of many people will be inevitable and massive. A awareness raising about the issue among the people should be the first step for precaution.

抄録全体を表示