In this study, the collection of extracellular polymeric substances (EPS) as a powder form from unicellular Microcystis aeruginosa and water bloom was attempted to control the EPS concentration in the culture medium and to promote the colonyformation of unicellular M. aeruginosa. Then, the effects of EPS and divalent cation such as iron ion on the colony formation of M. aeruginosa were examined through the unialgal culture experiment. The results showed that EPS collected from unicellular M. aeruginosa possessed the hydroxyl groups and carboxyl groups on EPS, indicating the similar trend to other cyanobacterial species. The unialgal culture experiment showed that, at the iron ion concentration of 0.68 mg-Fe/L, EPS itself would not act as a binder for M. aeruginosa cells. However, the colony of M. aeruginosa was observed when EPS as well as high amount of iron ion (6.8 mg-Fe/L) were added into culture medium, and the colony density tended to be higher for culture medium with the EPS concentrations of 10 mg/L or less than that with the higher condition (EPS = 25 mg/L).
Sinanodonta woodiana is widely distributed throughout Chinese freshwaters and is an important economic pearl mollusk. In order to evaluate the application feasibility of S. woodiana as a Microcystis-blooming removal tool, a series of microcosm experiments were performed. First the 6-day feeding responses experiment was carried out with naturally blooming pond water and the bivalves in laboratory, which was lasted for 6 days. In this experiment, phytoplankton abundances and community structure were analyzed on 0-day and 6-day for both control and treatment microcosms; also, filtration rate, absorption efficiency, oxygen consumption rate and ammonia excretion rate of S. woodiana were measured on 0-day and 6-day and finally the scope for growth (SFG) value as a measure of metabolic energy balance for S. woodiana was calculated and compared. The results showed that Microcystis spp. of colony and unicell were reduced obviously on the 6-day; meanwhile, after six day's exposure to Microcystis-blooming pond water, the SFG value for S. woodiana increased. Furthermore, in the extended long-term grazing experiment, bivalves were fed with highly concentrated toxic Microcystis-blooming water and non-toxic Chlorella at the constant concentration (Chl.a=424.5 mg/m3) in two respective tanks for 12 days. No bivalve mortality was registered on both Chlorella group and blooming water group. In addition, SFGs were significantly higher for the blooming water group, compared with them for Chlorella group on 3-day, 6-day and 12-day. These results indicated that toxic Microcystis spp. in natural eutrophic water can be removed greatly by S. woodiana; moreover, the bivalves themselves have strong adaptation ability when they were exposed to toxic natural eutrophic water. Therefore, it can be inferred that there is high application feasibility of S. woodiana as a Microcystis-blooming controller in practice.
多くの途上国では水不足が深刻だが，政府の対応は不十分で，家庭レベルでの対応が不可欠である．本稿ではネパール国カトマンズ市を例に，家庭レベルでの対応策と，それに影響を与える社会経済要因を明らかにし，雑排水・雨水の潜在的利用可能量を推計した．世帯特性・水源・利用目的をアンケートで217世帯にて，用途別詳細水使用量をダイアリー法で32世帯にて調査した．結果，水道の給水時間が短い世帯ほど，多くの水源を複合使用し，世帯収入は水源選択の主要因であった．水使用量は平均36.9±11.1 L/人/日であり，低収入層は，風呂・洗濯水量を減らし，炊事・衛生等より生活に必須となる水量を確保していた．最低必要水量(50 L/人/日)を通年で満たすには水道では不足し，水再利用と10,000 L の雨水貯槽容量をもつ雨水利用が必要と計算された．
This study investgeted the effect of temperature, pH and vegetation on removal efficiency of zinc from mine water in aerobic constracted wetland mesocosm. During two month operation, the removal efficiency of zinc was sharply decreased from 92% to 52% in unvegetated wetland mesocosm and from 95% to 39% in vegetated, respectively. However, by maintaining neutral pH condition using limestone, pH in the unvegetated wetland gradually increased which followed by high zinc removal, revealing a good correlation of zinc removal with pH. It was obvious that zinc removal in vegetated wetland was lower than that in unvegetated. Despite presence of limestone, the removal of zinc decreased when temperature decreased. Adsorption experiments in batch and continuous system proved the effect of temparure and pH on zinc removal observed in aerobic wetland mesocosm. The result of speciation of zinc by sequential extraction suggested that zinc removed in aerobic wetland mesocosm was mainly consisted of exchangeable form. It was considered that because oxygen supplied from roots caused pH decline, the fraction of exchangeable form in vegetated wetland as well as amont of zinc removed was lowed compared with unvegetated wetland.
Continuous treatments of synthetic groundwater were conducted by using an in-situ denitrification and oxidation process, and measurements of water quality parameters such as nitrate, nitrite, DO, etc. were made over one year. In the in-situ process, hydrogen gas and oxygen gas were produced by using an electrolytic cell and were injected separately into a laboratory scale aquifer filled with glass beads. Experimental results demonstrated that stable denitrification and oxygenation of groundwater were achieved. During the initial phase of experiment, nitrite was accumulated in a hydrogen-injected zone; however, it was oxidized to nitrate in subsequent oxygen-injected zone. In addition, water quality parameters such as TOC, SS, turbidity and chromaticity were smaller in the effluent than influent, and no clogging problem was observed. From these results, we concluded that the present process has several superior performances in terms of stability, effluent water quality and simplicity in long-term operation.
In this study, the effect of the vegetation and subsurface water level on nitrogen removal was elucidated based on two years performance obtained in a real scale vertical flow constructed wetland consisting of five-stage treatment. Neither presence of the vegetation and half-saturated condition had significant positive effect on nitrogen removal in the first year operation. It needs one year operation to stabilize ammonification and nitrification process and presence of the vegetation offered a significant improvement of TN removal in the second year. Stimulation of nitrogen removal was significant at downstream treatment stage among five-stage, resulting in a high overall nitrogen removal in the second year operation. This tendency was obvious especially in the vegetated condition regardless of the subsurface water level, suggesting no significant effect of half-saturated condition. Based on the variation of annual nitrogen removal through five-stage treatment, potential mechanisms of effect of the vegetation and subsurface water level on nitrogen removal were discussed.
The aim of this study was to evaluate the sorption characteristics of cesium onto freshwater reservoir sediment. For this, batch sorption experiments using sediment collected from a fresh water reservoir were conducted for 27 combinations of water temperature (5, 20 and 35 °C), pH (5, 7 and 9) and EC (130, 160 and 190 μS/cm). In addition, the distribution of adsorbed Cs was examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the equilibrium sorption data of cesium onto reservoir sediment could be fairly-well described by both Langmuir and Freundlich isotherm models. The estimated isotherm parameters indicated that the impacts of water temperature, pH and EC on the sorption capacity of cesium were less obvious within the investigated ranges of these three variables. EDS mapping and elemental analysis of sediment after cesium sorption, together with the analysis by XRD, revealed that sorption of cesium on the reservoir sediment occurs mainly on its surface and the distribution of the adsorbed Cs on sediment was not uniform.
The authors developed a protocol to analyze 16S rRNA in supernatant of activated sludge by reverse transcription—polymerase chain reaction (RT-PCR), and monitored a cycle of a laboratory activated sludge sequencing batch reactor (SBR) with the developed method. When RT-PCR was performed with filtered activated sludge supernatant with 25 thermal cycles, products were obtained, and were confirmed to originate from RNA, not DNA. The supernatant of the SBR was analyzed by the developed method in combination with pyrosequencing. Some of the operational taxonomic units (OTUs) were observed to increase or decrease significantly, while others remained stable. It was thought that the fluctuation of the OTUs were specific phenomena. While the real meanings of the fluctuations of rRNA in the supernatant are not yet fully understood, the authors developed here a new approach to investigate microbial ecosystems in activated sludge.
The authors investigated the possibility to reduce aeration time in one of the cycles of sequencing batch activated sludge reactors. It is known that there are microorganisms in activated sludge which can store organic materials temporarily in such forms as polyhydroxyalkanoate (PHA). It was expected that removal of organic materials in the cycle with reduced aeration was supplemented by the microbial activities to store organic materials temporarily. The authors operated sequencing batch reactors with 6 cycles/day with synthetic wastewater, and reduced aeration in one of the cycles. Short-term experiments were conducted to see the effects of aeration reduction for one time, and long-term experiments were conducted to see the effect of long term implementation of operation with aeration reduction. In both experiments, removal of DOC was greater than 92%, and no significant adverse effect was observed. The more aeration was reduced, the more PHA was carried over to the following cycles. It was estimated that about 17% to 50 % of PHA was carried over to the cycles following the cycles in which aeration was reduced. The operation with one-cycle reduced aeration was successfully implemented in the experiments. There is a big room to explore wastewater treatment technologies in the direction to flexibly control energy consumption.