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Three typical constructed wetlands (CWs) including Vertical Flow (VF), Free Water Surface (FWS), and Subsurface Flow (SF), and combined VF-SF-FWS constructed wetlands were investigated for the treatment of domestic wastewater with low C/N ratio. The performance of nutrient removal and the characteristics of greenhouse gas emissions, such as CH4 and N2O, from these CWs were compared. The results indicated that the four types of CWs had high removal efficiencies for organic matter and suspended solid (SS). The combined wetland also showed a comparatively good performance for nitrogen and phosphorus removal, and the removal efficiencies for total nitrogen (TN) and total phosphorus (TP) were 81.3% and 84.5%, respectively. The combined CWs had a comparative lower global warming potential. The FWS CW had the highest tendency to emit CH4 and led to a higher global warming potential among the four types of CWs, which was about 586 mg CO2/m2·h.

Nitrogen has been considered as one of important elements in domestic wastewater and resulted in frequent algal blooms over a wide range of water body. In this study, a dynamic system was constructed to simulate nitrogen transformation in reed constructed wetlands. The various nitrogen forms in the system were considered as the parameters. The effects of mineralization, nitrification, denitrification, plant uptake and plant decay were investigated. The overall performance of the model was validated with different data sets of parameters from the case study spanning 3 years. The results indicated a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for nitrogen removal performance in reed constructed wetland.

To evaluate the protective effect of the Three Gorges Dam Project (TGP) against flooding in the middle region of the Changjiang River basin, we applied an integrated watershed hydrological model using gauged daily precipitation data for 1998, when the second largest flood of the last century occurred in the basin. From the results simulated by applying the daily average discharge rate controlled by each of the upper limit values of 40,000, 45,000, 50,000, and 55,000 m 3 /s as the safety discharge in the downstream reach, we were unable to find any clear reduction effect on the water level during the flood period, not only in Dongting Lake, but also in the Changjiang mainstream, when the upper discharge limit exceeded 50,000 m 3 /s. When an upper discharge limit of 40,000 m 3 /s was used, although a flood protection effect was clearly exhibited in both the mainstream and the lake, the simulated storage volume of the TGP reservoir markedly exceeded the total flood control volume (221.5 × 10 8 m 3 ) at the inflow peak. These results suggest that the TGP would not work efficiently for decreasing flood damage in the Dongting Lake area in the event of another 1998-type flood without other countermeasures to control the increased water level in the lake.

This paper evaluates the potential for regional bioenergy recovery as electricity and heat by small-scale methane fermentation systems from organic waste matter generated from urban, industrial, and agricultural sectors. Biogas production functions of high-strength organic wastes are derived from data of implemented methane fermentation systems. The distributions of organic wastes from sewage, household, wholesale/retail, manufacturing, farming, and livestock activities in the Tokyo Bay region are calibrated into a disaggregated spatial database by compiling general activity statistics and emission intensity parameters using Geographic Information System (GIS). Three scenarios of organic matter circulation by co-digestion in sewage treatment plants (STPs) are designed and assessed. Surplus electricity and heat from methane fermentation systems are used for STP operations and household demand. The spatial database allows a preliminary examination for the suitability of locations for technology implementation from the aspects of bioenergy supply and balance. The results show that an additional 368,000–1,328,000 MW of electricity would be generated, and 1300–3600 TJ of heat could be used by households, reducing the annual emissions of CO 2 from fossil fuels by 307,000–798,000 t.

Constructed wetlands are considered to be important sources of nitrous oxide (N(2)O). In order to investigate the contribution of nitrification in N(2)O formation, some environmental factors, plant species and ammonia-oxidizing bacteria (AOB) in active layers have been compared. Vegetation cells indicated remarkable effect of seasons and different plant species on N(2)O emission and AOB amount. Nitrous oxide data showed large temporal and spatial fluctuations ranging 0-52.8 mg N(2)O m(-2)d(-1). Higher AOB amount and N(2)O flux rate were observed in the Zizania latifolia cell, reflecting high potential of global warming. Roles of plants as ecosystem engineers are summarized with rhizosphere oxygen release and organic matter transportation to affect nitrogen transformation. The Phragmites australis cell contributed to keeping high T-N removal performance and lower N(2)O emission. The distribution of AOB also supported this result. Statistical analysis showed several environmental parameters affecting the strength of observed greenhouse gases emission, such as water temperature, water level, TOC, plant species and plant cover.

Loss of nitrogen from the soil-plant system has raised environmental concern. This study assessed the fluxes of nitrous oxide (N2O) in the subsurface flow constructed wetlands (CWs). To better understand the mechanism of N2O emission, spatial distribution of ammonia-oxidizing bacteria (AOB) in four kinds of wetlands soil were compared. N2O emission data showed large temporal and spatial variation ranging from -5.5 to 32.7 mg N2O m(-2) d(-1). The highest N2O emission occurred in the cell planted with Phragmites australis and Zizania latifolia. Whereas, the lower emission rate were obtained in the cell planted with P. australis and Typha latifolia. These revealed that Z. latifolia stimulated the N2O emission. Transportation of more organic matter and oxygen for AOB growth may be the reason. The study of AOB also supported this result, indicating that the root structure of Z. latifolia was favored by AOB for N2O formation.

Wastewater and treatment processes have been regarded as large contributions to sources of methane (CH4). The flux rate of CH4 in constructed wetlands (CWs) was evaluated to test the influence of plant species. Methane emission data showed large temporal and spatial variation ranging from 0 to 16.76 g CH4 m−2 day−1. The highest CH4 flux rate was obtained in the Zizania latifolia systems and higher emission was found with higher influent load. The methanogenic and methanotrophic microbial populations were studied to clarify the mechanisms of CH4 emission. FISH analysis showed highest amounts of methanogens and methanotrophs in the Z. latifolia and Tytha latifolia systems. Linear regression between CH4 emission and environmental parameters showed that the regression lines were not forced to pass through the origin, and the slopes of the lines of different systems were allowed to vary between vegetation cover.

Methane (CH 4 ) and nitrous oxide (N 2 O) are important greenhouse gases, because of their contribution to the global greenhouse effect. The present study assessed emissions of N 2 O and CH 4 from constructed wetland microcosms, planted with Phragmites australis and Zizania latifolia , when treating wastewater under different biological oxygen demand (BOD) concentration conditions. The removal rate was 95% for BOD and more than 80% for COD in all three pollutant concentrations, both plants’ removal rates of pollutants were at almost the same level, and both were found to resist BOD concentrations as high as 200 mg L −1 . When BOD concentrations fell below 200 mg L −1 , the soil plant units reached an average of 80–92% T-N and T-P removal rates; however, as the concentrations increased to 200 mg mg L −1 or when during the initial phases of winter, the removal rates for T-N and T-P decreased to less than 70%. With NH 3 -N removal, the influences of BOD concentrations and air temperature were more obvious. When BOD concentrations increased to 100 mg L −1 after October, an obvious decrease in NH 3 -N removal was detected; almost no nitrification occurred beginning in December at BOD concentrations of 200 mg mg L −1 . N 2 O and CH 4 emissions showed obvious seasonal changes; higher emissions were observed with higher BOD concentrations, especially among Z. latifolia units. The enumeration of methane-oxidizing bacteria and methane-producing bacteria was also conducted to investigate their roles in impacting methane emissions and their relationships with plant species. The pollutant purification potentials of P. australis and Z. latifolia plant units during wastewater treatment of different pollutant concentrations occurred at almost the same levels. The nutrient outflow and methane flux were consistently higher with Z. latifolia units and higher concentrations of BOD. The more reductive status and higher biomass of methanogens may be the reason for the lower nitrification and higher CH 4 emissions observed with Z. latifolia units and higher concentration systems. The Z. latifolia root system is shallow, and the activity of methanotrophs is primarily confined to the upper portion of the soil. However, the root system of P. australis is deeper and can oxidize methane to a greater depth. This latter structure is more favorable as it is better for reducing methane emissions from P. australis soil plant systems.

An acoustic Doppler current profiler is used to characterize the river velocity against the morphology of the Yangtze River from Chonqing to the sea. High flow velocities occur in the Three Gorges section and lower velocities in the middle and lower reaches of the river. This is largely due to the change in river pattern from a high gradient deeply-cut valley to a flat fluvial plain. Flow velocities fluctuate in the middle Yangtze due to the presence of meander bends of different length. There are numerous smaller velocity fluctuations in the lower Yangtze channel that reflect multichannel pattern with numerous sand bars and a river morphology affected by bedrock outcrops. Water depths of 40-100 m occur in the Three Gorges valley but decrease to 15-40 m in the middle and lower Yangtze. At the Gezhou Reservoir, 30 km downstream of the Three Gorges damsite velocity drops to low (< 1.0 m s -1 ) 20 km reach. A second low velocity (

Variations of dissolved silicate (DSi) flux in the Yangtze River have caused great concern among scientists. Analysis of spatial and temporal variations of DSi indicates that the distribution of DSi concentration (DSiC) is closely related to the occurrence of bedrocks in the river cathchment. On average, the upper Yangtze River and Dongting and Poyang Lake of the middle Yangtze basin serve as the major DSi sinks, retaining 3.39 × 104 t y−1, 5.59 × 104 and 2.51 × 104 t y−1. The middle and low Yangtze River remains DSi sources, emitting 2.85 × 104 and 2.48 × 104 t y−1, respectively. Geochemical data at Datong hydrological station recorded the flux of nutrients entering into the sea during the flood season, i.e. 74% for DSi, 73% for DIN (Dissolved Inorganic Nitrate) and 68% DIP (Dissolved Inorganic Phosphate). The yearly DSiC and flux show a sharp decrease since 1950s. The mean DSiC was 109.47, 91.09, and 77.56 μmol l−1 in the 1960s, 1970s and 1980s, respectively. The mean DSi fluxes for the same time period were 2.72, 2.23, and 2.13 × 106 t. A PP (primary productivity) model estimates 3.14 × 105 t of DSi (13.08% of the annual mean flux entering into the sea) was fixated within the 162 reservoirs in 2002. On the other hand, DIN and DIP concentration and flux have increased greatly since the 1950s. Fertilizer application peaked after the 1980s can interpret these high DIN and DIP. A sharply decreasing DSi flux and quickly increasing DIN and DIP fluxes into the sea have enhanced eutrophication and caused frequent harmful algal blooms in coastal waters. On average, red-tide frequency was from 0.04 during 1933–1979 to 7.0 during 2000–2002. The Skeletonema costatum (siliceous alga), the red-tide-predominant species that is in positive proportion to DSi flux, decreased from 33% during the 1980s to 24% during 2000–2002. The present data evidence the increase of Prorocentrum dentatum (non-siliceous alga) from 12.5% in the 1980s to 36% in 2000–2002, which tends to be dominant species of the red tides off the Yangtze estuary. The number of big dams in the Yangtze River basin will double in the next 30–50 years. This will significantly influence the variations of nutrient fluxes in the river basin and estuary, in relation to health management of river-coast ecosystem.

We studied the influence of the water-soluble fraction (WSF) of diesel fuel oil on bacterial and photosynthetic producers and on carbon transfer to higher trophic organisms in an aquatic plankton ecosystem by means of a mesocosm experiment in the Yangtze estuary, China. In the oil-enriched mesocosm, average bacterial production increased 3.9 times compared with that in the control mesocosm. WSF addition also increased the abundance of bacterivorous heterotrophic nanoflagellates, but it decreased the abundance of other higher trophic organisms (micro- and mesozooplankton) due to the toxic effects of the WSF. The amount of carbon transfer from bacterial production to mesozooplankton was of nearly similar magnitude in the oil-enriched and control mesocosms, though bacterial production was much larger in the former. The relative reachable efficiency of bacterial production to mesozooplankton in the oil-enriched mesocosm was only about 36% of that in the control. This lower efficiency in the oil-enriched mesocosm was attributed to decreased mesozooplankton abundance rather than decreased abundance of trophic intermediates in microbial food webs. We found only a slight difference between photosynthetic production in the oil-enriched and control mesocosms. A complementary batch-incubation experiment showed that the WSF may have considerably decreased the photosynthetic activity of an algal assemblage, however, so the photosynthetic production in mesocosms was regulated by nutrient-limitation rather than by the toxic effect of WSF. The carbon transfer from photosynthetic production to mesozooplankton in the oil-enriched mesocosm was comparable to that in the control, though WSF addition decreased the abundance of mesozooplankton in the oil-enriched mesocosm. This may have resulted from the occurrence of the diatom Skeletonema costatum, which is much preferred by mesozooplankton (copepods) as prey, in the oil-enriched mesocosm, whereas the dinoflagellate Prorocentrum dentatum was overwhelmingly dominant in the control mesocosm.

A sea survey was conducted in May 2001 using CTD together with direct-reading current meter and water sampling to investigate the sediment dynamics off the Yangtze River mouth. Data obtained from five observational sites reveal density flows characterized by the halocline, thermocline and associated sharp current velocity gradients that prevail in the study area, especially at the freshwater plume front. The interaction of the Yangtze freshwater plume, littoral current and tidal current has generated these density flows. Particularly, the anomalous high speed (>140 cm s −1 ) current recorded at the freshwater plume front during the early flood stage leads to the resuspension of the sediment (SSC reaching 0.5 g l −1 ) off the river mouth during that time period. The suspended sediment flux measured at B2, the ideal site for recording frontal processes in the estuary, indicates the main trend of southward transport of fine-grained sediment up to 60 kg m −2 s −1 at early flood stage and 1.32 kg m −2 s −1 as net flux during two tidal periods. It is inferred that the density flow at the plume front plays key roles in dispersing the Yangtze fine suspended sediments southward during the non-flood season.

In this study, we identify climatic influences on summer monsoon inflow to the Three Gorges Dam (TGD) in the Yangtze River Basin and use indices of these influences to predict streamflow one season ahead. Summer monsoon streamflow at Yichang hydrological station (YHS) was analyzed for the period 1882–2003. Statistical analysis was used to develop a predictive model for summer streamflow using preceding climate variables. Linear correlation maps were constructed using 3-month ahead climate fields to identify regions that exhibit teleconnections with streamflow at Yichang. The analysis revealed regions in the eastern Indian and western Pacific Oceans that influence YHS streamflow. These regions and variables are consistent with those identified by previous studies of regional rainfall. In addition, snow cover in the Yangtze upland region provides predictive skill, likely due to snowmelt contributions to streamflow. A regression model for prediction using these indices provides a prediction R2 greater than 0.5, which is robust under the ‘leave one out’ cross-validation. A skillful prediction can provide guidance for water management in the Yangtze River Basin, e.g. the Three Gorges Dam and future projects for South-to-North water transfer. Copyright © 2006 Royal Meteorological Society

Concentrations of 31 particulate elements (Al, As, Ba, Ca, Cd, Ce, Co, Cr, Cs, Cu, Eu, Fe, Hf, La, Lu, Mg, Mn, Ni, P, Pb, Rb, Sb, Sc, Sm, Sr, Th, Ti, V, Y, Yb, and Zn) and 6 dissolved elements (Al, Cd, Cu, Fe, Mn, and Ni) in the Yangtze estuary were determined during the period from 1997 to 2002. The salinity increased monotonously, and suspended particulate matter (SPM) peaked initially and then decreased rapidly in the mixing zone, which lies between 121.5° E and 122.5° E. The elemental composition of SPM was almost constant throughout the estuary, except for an increase of P, Cd, Pb, Sr, Cu, Mg, Cr, Zn, Ni, Ca, and Ba at some stations on the continental shelf. On the other hand, dissolved metal concentrations changed as the salinity increased in the mixing zone: dissolved Cu was diluted conservatively, dissolved Cd and Ni were released from SPM, and dissolved (colloidal) Fe, Al, and Mn increased when SPM increased. By mixing experiments using unfiltered river water and seawater, the conservative mixing of dissolved Cu and the release of dissolved Cd and Ni from SPM were reproduced in the laboratory. Effective dissolved metal concentrations (including the metals released in the mixing zone) in the river were Al (330 nM), Cd (0.39 nM), Cu (23 nM), Fe (72 nM), Mn (8 nM), and Ni (7 nM), values significantly lower than the concentrations of particulate metals, that is, Al (880 μM), Cd (1.7 nM), Cu (300 nM), Fe (230 μM), Mn (5.5 μM), and Ni (240 nM). Riverine metals were transported to the sea mainly in particulate form. The metal input through the Yangtze River has not changed significantly since the 1980s, when previous investigations in the same area (U.S.–China joint cruises in 1980 and 1981, and France–China joint cruises in 1986) were conducted.

The objective of this study was to assess the feasibility of co-digesting food waste (FW) and de-oiled grease trap waste (GTW) to improve the biogas production. A lab-scale mesophilic digester (MD), a temperature-phased anaerobic digester (TPAD) and a TPAD with recycling (TPAD-R) were synchronously operated under mono-digestion (FW) and co-digestion (FW + de-oiled GTW). Co-digestion increased the biogas yield by 19% in the MD and TPAD-R, with a biogas yield of 0.60 L/g VS added. Specific methanogenic activity in the TPAD-R was much higher than that in the MD. In addition to methane, hydrogen at a yield of approximately 1 mol/mol hexose was produced in the TPAD-R. Alkalinity was consumed more in the co-digestion than in mono-digestion. Co-digestion resulted in more lipid accumulation in each digester. The MD favored the degradation of lipid and conversion of long-chain fatty acids more than the TPAD and TPAD-R.

Renewable energy recovery from submerged aquatic plants such as Egeria densa ( E. densa ) via continuous anaerobic digestion (AD) represents a bottleneck because of process instability. Here, a single-chamber membrane-free microbial electrolysis cell (MEC) equipped with a pair of Ti/RuO 2 mesh electrodes (i.e. the combined MEC-AD system) was implemented at different applied voltages (0–1.0 V) to evaluate the potential effects of bioelectrochemical stimulation on methane production and process stability of E. densa fermentation. The application of MEC effectively stabilized E. densa fermentation and upgraded overall process performance, especially solid matters removal. E. densa AD process was operated steadily throughout bioelectrochemical process without any signs of imbalance. The solubilization-removal of solid matters and methane conversion efficiency gradually increased with increasing applied voltage, with an average methane yield of approximately 248.2 ± 21.0 mL L −1 d −1 at 1.0 V. Whereas, the stability of the process became worse immediately once the external power was removed, with weaken solid matters removal along with methane output, evidencing the favorable and indispensable role in maintaining process stability. The stabilizing effect was further quantitatively demonstrated by statistical analysis using standard deviation (SD), coefficient of variance (CV) and box-plots. The syntrophic and win–win interactions between fermenting bacteria and electroactive bacteria might have contributed to the improved process stability and bioenergy recovery.

China has faced serious water problems as a result of economic growth and some development projects and it is widely thought that integrated management, including socio-economic factors in each basin unit, is effective. Hence, the target of this paper is to evaluate the structures of water demand and water pollutant discharge with socio-economic activities in the City of Chongqing, the main city upstream of the Three Gorges Dam. First we have developed a methodology for estimating water demand and water pollutants (carbon, nitrogen and phosphorus) based on an inter-industry analysis model, and then applied it to the City of Chongqing. As a result, we conclude that industry is the largest source of water demand and water pollutants in the City of Chongqing and accounts for more than 50% of the total of each. Water demand from agriculture, forestry and livestock accounts for 35% of the total, and about 20% of water pollutants are discharged from agriculture, forestry and livestock. Furthermore, water pollutants from households constitute more than 20% of the total in the City of Chongqing though water demand and wastewater account for less than 15% of each total. In addition, it becomes clear that about 20% of the water demand and water pollutant discharge in the City of Chongqing is caused by other provinces and foreign countries, with most of the demand and discharge being industrial.

The present study focuses on simulating sediment flux for 1998 big-flood with 60-year recurrent period in the Yangtze River catchment. On the basis of close correlation between discharge and sediment load recorded on the daily base of the past decades at a series of hydrological gauging stations located in the Yangtze River, the sediment rating curve of 1987/1988 was selected to simulate the annual and flood season sediment fluxes of 1998, when measured discharge was available in the most gauging stations. The result indicates that enormous sediment load was delivered downstream and to the estuary during the flood year. The simulated annual sediment flux was about 930 million-tonnes in the upper drainage basin, about 520 million-tonnes in the middle catchment and 720 million-tonnes in the lower drainage basin. These loads, respectively, approximate almost 1.9, 1.2, and 1.8 times those of the multiyearly sediment flux in the upper, middle and lower Yangtze catchments for the past decades. The result also indicates a unique pattern of sediment transport downstream through the drainage basin during the high flow season (early July to mid-September). While the upper Yangtze tributaries delivered about 580 million-tonnes of sediment downstream, the 3-Gorges valley added additional 270 million-tonnes. This totals about 850 million-tonnes that supplied the middle and lower Yangtze catchments, of which about 450 million-tonnes were silted in the middle catchments, immediately downstream of the exit of 3-Gorges. This amount is almost 6.5 times the normal flood season averaged over the last 50 years. High sediment load was also recorded in the river mouth area during the flood season, where 460 million-tonnes were delivered to the estuary and East China Sea, about 3.8 times that in a normal flood season. Intensifying human activity in the upper catchment is responsible for the large amount sediment sources delivered downstream and to the coastal region. q 2005 Elsevier B.V. All rights reserved.

In ammonia-oxidizing autotrophic bacteria, coenzymes such as NAD+ and NADP+ act as intermediates linking the electron transfer system in the cell membrane and the CO2- fixing Calvin cycle in the cytoplasm. The influence of these physiologically active substances on the growth of ammonia-oxidizing bacteria (AOB) and their nitrification ability was examined by adding a trace amount of NAD+ or NADP+ into a wastewater treatment system. In pure cultures of Nitrosomonas europaea IFO 14298, when NAD+ or NADP+ were added in the wastewater oxidation of ammonia increased comparing a control culture, and the strain grew 1.6-1.9 times faster than that of the control. Similarly, in activated sludge, both the rate of formation of NOx-N and the growth of AOB increased when NAD+ or NADP+ were added. Furthermore, ammonia monooxygenase-coding mRNA (amoA-mRNA), an estimate of ammonia oxidation activity, increased over time only in the presence of these physiologically active substances. When activated sludge previously exposed to NAD+ or NADP+ was used for new sewage, these desirable effects continued. The types of AOB affected by adding NAD+ or NADP+ were characterized using TaqI -based T-RFLP (terminal restriction fragment length polymorphism) of amoA-mRNA. The results indicated that AOB with fragment sizes of 219 bp and 491 bp were the active species in the NAD+ and NADP+-containing systems, respectively. These results suggest that the simple technique of adding a trace amount of NAD+ or NADP+ into activated sludge can result in increased nitrification and the selective growth of a particular AOB.

In order to determine material fluxes in rivers by non-contact methods, it is essential to estimate river discharge first. Although developed and optimized for open oceans, satellite radar altimetry has the potential to monitor variations in the levels of inland waters such as lakes and rivers. Making use of the concept of an ‘assumed reference point’, we converted TOPEX/Poseidon satellite altimetry data on water level variations in the Yangtze River (Changjiang) to ‘water level’ data. We also used ‘water level’ time-series data and in situ river discharge to establish a rating curve. By use of the rating curve, we converted data on ‘water level’ derived from 7 years (1993–99) of TOPEX/Poseidon data to actual river discharge. On the basis of statistical correlation between discharge and nutrient concentration data collected in 1987–88 and in 1998–99, we estimated the total amounts of freshwater and material fluxes transferred by the Yangtze River during the 1990s. The result reveals that an overall, but very slight, increase in freshwater and material fluxes occurred during the 1990s. Copyright © 2005 John Wiley & Sons, Ltd.

The measurement of river discharge is necessary for understanding many water-related issues. Traditionally, river discharge is estimated by measuring water stage and converting the measurement to discharge by using a stage-discharge rating curve. Our proposed method for the first time couples the measurement of water-surface width with river width-stage and stage-discharge rating curves by using very high-resolution satellite data. We used it to estimate the discharge in the Yangtze (Changjiang) River as a case study. The discharges estimated at four stations from five QuickBird-2 images matched the ground observation data very well, demonstrating that the proposed approach can be regarded as ancillary to traditional field measurement methods or other remote methods to estimate river discharge. Copyright (C) 2004 John Wiley Sons, Ltd.

The present study is aimed at clearly understanding the relationship among the arrangement of the gravel, the flow rate, and the porosity of the contact media, and the purification capability, which should be effective for a multi-natural type river restoration. Experimental studies were carried out by filling a linear circulation water passage (rated at a grade of 1/830, 30m long, 24cm wide, and 9cm deep, with a Stone type contact media or a net type contact media, whereby the biofilm attachment capability, the filling conditions and the flow rate were varied.The organic material removal capability differed depending upon the roughness coefficient of the flow passage; the greater the contact provided for the contact media, the higher the purification capability on contact with the biofilm; but it was found that the purification velocity would not improve, even when the amount of attached biofilm per unit contact media was increased to an extremely high level. This means that as the biofilm thickness increases, the porosity decreases so as to cause the decrease of the flow rate through the filled layer. In order to improve nitrification capability, it is necessary to establish the critical flow rate through the filled layer at above 5cm⋅s-1. On the other hand, for the nutrient removal (denitrification), it is important to have a greater amount of biofilm and to keep an anaerobic condition inside the biofilm. Therefore, it is important to make the proper combination of the rapids and pools in the biofilm processes in the rivers and streams.

The bacterial community structure in the Changjiang estuary was studied for comparison with future changes, related to the construction of the Three Gorges Dam. Population densities of bacteria in the surface water at station C1 estimated by CFU on marine agar plates and by DAPI direct count, were 2.8 x 10(4) ml(-1) and 4.2 x 10(5) ml(-1), respectively. Physicochemical properties of water, such as temperature and salinity, suggested that station C1 was affected by freshwater from the Changjiang River. Cluster analysis of the PCR-RFLP patterns obtained from 9 samples showed that the bacterial community structure at station C1 was different from the structure at the other stations. Bacterial diversity in the surface water at station C1 was studied based on the genotypes of the 250 clones of 16S rRNA, and on the phenotypes generated on Biolog GN plates for 70 isolates. Sequences of bacteria from two common marine groups, alpha- and gamma-Proteobacteria, were frequently observed. Some other divisions, including the beta-Proteobacteria, C/F/B group, low G+C gram positive, high G+C gram positive, chloroplasts, and relatives of Verrucomicrobia were also observed. The putative dominant species based on both genotype and phenotype analyses were close relatives of Alteromonas macleodii or Roseobacter spp. These results reflected the nutrient-rich environment at station C1.

China frequently experiences natural disasters, of which flooding is the most serious. How to monitor and control natural disasters, assess damage, and provide relief is the most urgent problem for the Chinese government and disaster experts. A national integrated system using remote sensing, geographic information systems, the Global Positioning System, and other technology for monitoring and evaluating flood disasters has been assembled and tried out for 3 years. The system has played an important role in flood mitigation during the trial and has become a key part of the flood management system at China's National Flood Control Headquarters. This paper presents an overview of the system and its use in China.

To better understand the underlying mechanisms for methane bioelectrosynthesis, a two-chamber MECs containing a carbon biocathode was developed and studied. Methane production substantially increased with increasing cathode potential. Considerable methane yield was achieved at a poised potential of -0.9 V (vs. Ag/AgCl), reaching 2.30±0.34 mL after 5 h of operation with a faradaic efficiency of 24.2±4.7%. Confirmatory tests done at 0.9 V by switching the type of flushed substrates (CO2/N2) or the electrical exposure modes (ON/OFF) demonstrated that cathode serving as an electron donor was the vital driving force for methanogenesis occurring at microbe-electrode surface. Fluorescence in situ hybridization reveled Methanobacteriaceae (particularly Methanobacterium) was the predominant methanogens, supporting the mechanisms of direct electron transfer between cell-electrode. Additionally, the analysis of scanning electron microscope confirmed that the multiple pathways of electron transfer, including direct cathode-to-cell, interspecies exchange and semi-conductive conduits all together ensured the successful electromethanogenesis process.

An effective way for restaurant grease trap waste (GTW) treatment to generate fuel oil and methane by the combination of physiological and biological processes was investigated. The heat-driven extraction could provide a high purity oil equivalent to an A-grade fuel oil of Japanese industrial standard with 81–93 wt% of extraction efficiency. A post-extracted residue was treated as an anaerobic digestion feedstock, and however, an inhibitory effect of long chain fatty acid (LCFA) was still a barrier for high-rate digestion. From the semi-continuous experiment fed with the residual sludge as a single substrate, it can be concluded that the continuous addition of calcium into the reactor contributed to reducing LCFA inhibition, resulting in the long-term stable operation over one year. Furthermore, the anaerobic reactor performed well with 70–80% of COD reduction and methane productivity under an organic loading rate up to 5.3 g-COD/L/d.

本研究では, 浚渫したへドロ上へのヨシ原の創出手法を確立するために, ヨシ種子の発芽特性及び「種子苗植栽手法」による凌深へドロ上での生育特性を把握し, ヨシ原創出の可能性について検討した. その結果, 発芽実験では, 発芽前に浸水状態で5℃5日間保存する「前低温処理」により塩分阻害を克服し得ること, 汽水産種子は淡水産種子より塩分耐性が高いことが確認された. 種子苗の生育実験では浚渫へドロ上に約80～90%の苗が植栽後定着し, 植栽場に砂を用いた系では, 土壌中の塩分濃度が1.3～2.0%でも自生しているヨシと生育, 生活環が植栽2年目で同程度となった. これらの結果より, 種子への工夫及び苗からの環境条件への馴化を行うことで, 種子苗植栽手法は浚渫へドロ上にもヨシ原の創出が可能であることが示唆された.

Nitrous oxide (N2O) is emitted from wastewater treatment processes. It is known as a greenhouse gas that contributes to global warming (over 200 times more per molecule than carbon dioxide) and to the destruction of the ozone layer. It is therefore of great importance to develop technology that can suppress N2O emission. The effects of an anoxic period on N2O emission and nitrogen removal were investigated in an actual domestic wastewater treatment plant. When operated with intermittent aeration, most of the N2O was emitted into the atmosphere during the aerobic period. N2O emission from the intermittent process was estimated to be 0.43–1.89 g N2O person−1 year−1. Maintaining a dissolved oxygen (DO) concentration of over 0.5 mg l−1 during the aerobic period resulted in the complete conversion of the influent NH4-N to NO3-N and a 60-min anoxic period was sufficient for denitrification to be completed. The findings show that an optimum combination of aerobic and anoxic conditions and their suitable control are very important for improving nitrogen removal efficiency and controlling N2O emission.

The developmental activities and utilizations of Japanese coastal seas have been increased recently. Consequently, the production of coastal fisheries, especially of those in enclosed seas, are considerably affected by artificial impacts such as reclamation from the sea and increased pollution load. The objective of this paper is to propose a new ecotechnological method to recover the polluted coastal environment by using an artificial beach system. An artificial beach (5 m × 10 m) was constructed in the Matsushima Bay facing the Pacific Sea, about 300 km northeast from Tokyo. The area was polluted by fishery production and untreated wastewaters from rural district. The major merits of this system are simplicity of the structure, energy-free operation, capability to use tidal current cycle effectively, and ease of maintenance. The results of field investigation indicated that rapid removals of turbidity, suspended solids, phosphorus and ammonium nitrogen by the artificial beach system were achieved. The removal rate of total organic carbon was high because of the retention of the particulate matters. These performances were related to physical and biological filtration through the artificial beach system. It suggests that restoration of polluted coastal area may be expected using this artificial beach system.

The water bodies of coastal area are extremely eutrophicated due to the receiving of excess nutrients, and the original ecosystem is seriously damaged. To restore water environment in coastal areas, it is necessary to understand the behavior of nutrients and availability for algaeand marine plants. From this point of view, the release of nutrients from sediments was studiedin Matsushima Bay. It was observed that in winter algal biofilm was formed on the surface ofmuds and nutrients were absorbed by the biofilm. The purpose of this study was to evaluate the effect of algal biofilm on the nutrient balance in Matsushima Bay. Results obtained from field surveys and laboratory experiments are summarized as follows.(1) Algal biofilm was composed of diatoms such as Navicula, Nitzschia and so on, and water qualities were improved, especially, concentrations of nutrients decreased significantly due to uptake of NOx-N and PO4-P.(2) The uptake rate of dissolved inorganic nitrogen (DIN) for algal biofilm on muds was expressed as a first-order function of DIN concentration of water, and the release rate of DIN was constant. The uptake and release rates of PO4-P were similar to those of DIN, but when PO4-P concentration of water was relatively low, PO4-P of pore water in sediment, which was not released usually, was absorbed by algal biofilm.(3) Mass balance model of nutrients was developed, and the behavior of nutrients was simulated using parameters from laboratory experiments. From the results of simulation, it was elucidated that the nitrogen load from the external was larger than that from the internal, and 70% of DIN and 90% of PO4-P from the influent were stocked in the sediment by the activity of algal biofilm.

A survey of nematodes in drinking water treated by an advanced water treatment plant with biological treatment and granular activated carbon filter bed has been conducted for one year. Some nematodes with average 5.3%survival were observed in all samples from drinking water and the densities of nematodes seasonally fluctuated. Three genera 4 species were detected, but only two genera often appeared in which Plectus was abundant and Rhabditis was lesser. There was no relationship between rainfall and the densities of nematodes in drinking water. It was found that water temperature has a strong influence on the densities of nematodes. The species of nematodes in drinking water were much less than those in the water resource, which indicated that nematodes from the water resource were able to be removed by the water treatment facilities. On the other hand, the densities of nematodes in drinking water were much more than those in the water resource especially in the warmer seasons. It was suggested that some species like Plectus were able to breed within some treatment facilities, probably within the GAC filter.

Biological desulfurization using a bubble column reactor was investigated in a continuous biogas treatment. Rapid biogas circulation between the digester and the bubble column for biological desulfurization was used to stimulate the gas–liquid mass transfer of H2S. A positive correlation between the biogas circulation rate and H2S removal rate was observed. Moreover, the increase in the circulation rate stimulated the O2 mass transfer, eventually translating into an increase in sulfate production from the oxidation of H2S. Throughout the continuous experiment, the reactor retained sufficient levels of sulfide-oxidizing bacteria. A comparison of the results of the continuous biogas treatment and batch tests suggests that the gas–liquid mass transfer rate of H2S was the rate-limiting step in the biological desulfurization in the reactor, indicating that the mass transfer efficiency of H2S needs to be improved to enhance the desulfurization performance.

As a new sludge reduction technology with a phosphorus removal mechanism, a vibration milling technology that uses iron balls have been applied to the wastewater treatment process. Three anaerobic–aerobic cyclic activated sludge processes: one without sludge disintegration; one disintegrated sludge by ozonation; and the other disintegrated sludge with the vibrating ball mill were compared. Ozonation achieved the best sludge reduction performance, but milling had the best phosphorus removal. This is because iron was mixed into the wastewater treatment tank due to abrasion of the iron balls, leading to settling of iron phosphates. Thus, the simple means of using iron balls as the medium in a vibrating ball mill can achieve both a sludge reduction of half and excellent phosphorus removal. Material balances in the processes were calculated and it was found that carbon components in disintegrated sludge were more resistant to biological treatment than nitrogen.

Messy Mountain Meandering Predicting the influence of climate on landscapes is sometimes straightforward; for example, river deposits might grow with increased rainfall because erosion rates and sediment transport increase. However, long-term tectonic processes complicate the geomorphic signatures of more gradual climate-related phenomena that reconfigure landscapes. By correlating a decades-long record of typhoon rainfall in Japan with digital elevation models, Stark et al. (p. 1497 ) show that climate directly influences the extent of river meandering. When expanded to a larger region of the western North Pacific, this analysis revealed a strong climatic imprint on the landscape of humid mountainous areas. The region-wide analysis also revealed that underlying bedrock strength, as opposed to tectonic uplift, acts as a secondary control.

Decentralized advanced wastewater treatment using adsorption and desorption process for recovery and recycling oriented phosphorus removal was developed. Adsorbent particles made of zirconium were set in a column, and it was installed as subsequent stage of BOD and nitrogen removal type Johkasou, a household domestic wastewater treatment facility. The water quality of the effluent of adsorption column in a number of experimental sites was monitored. The effluent phosphorus concentration was kept below 1 mg l−1 during 90 days at all the sites. Furthermore, over 80% of the sites achieved 1 mg l−1 of T-P during 200 days. This adsorbent was durable, and deterioration of the particles was not observed over a long duration. The adsorbent collected from each site was immersed in alkali solution to desorb phosphorus. Then the adsorbent was reactivated by soaking in acid solution. The reactivated adsorbent was reused and showed almost the same phosphorus adsorption capacity as a new one. Meanwhile, the desorbed phosphorus was recovered with high purity as trisodium phosphate by crystallization. It is proposed as a new decentralized system for recycling phosphorus that paves the way to high-purity recovery of finite phosphorus.

Abstract River discharge is traditionally acquired by measuring water stage and then converting the water stage to discharge by using a stage–discharge rating curve. The possibility of monitoring river discharge by satellite has not been adequately studied hitherto, because of the difficulty in making sufficiently precise measurements of the water surface. Since the successful launch of commercial satellites with very-high-resolution sensors, it has become possible to derive ground information from satellite data. To determine river discharge in a non-trapezoidal open channel, an efficient approach has been developed that uses mainly satellite data. The method, which focuses on the measurement of surface water width coupled with river width–stage and ȁremoteȁ stage–discharge rating curves, was applied to the Yangtze River (Changjiang) and an accurate estimate of river discharge was obtained. The method can be regarded as ancillary to traditional field measurement methods or other remote sensing m...

Although satellite radar altimetry was developed and optimized for open oceans, it has been used to monitor variations in the level of inland water-bodies such as lakes and rivers. Here, for the first time, we have further used the altimetry-derived variation of water level for estimating the fluctuation of water storage as an addition to the present in situ water storage estimation systems to be used in remote areas and in emergency situation such as in the events flooding monitoring and for studying the effect of climate change. Lake Dongting, the second largest lake in China, influenced frequently by flooding, was, therefore, chosen to demonstrate the potential of the technique. By using the concept of an "assumed reference point", we converted Topex/Poseidon satellite altimetry data on water level variations in Lake Dongting to "water level" data. The "water level" time-series data and in situ water storage were used to establish a rating curve. From the rating curve, we converted data on "water level" derived from seven years (1993-1999) of Topex/Poseidon data to actual water storage in Lake Dongting. The result reveals that the seasonal and annual fluctuations of water storage occurred during the 1990s with a more frequent flooding at the late 1990s' especially the flooding in whole catchment level in 1998 and 1999. The study supports the usefulness of satellite altimetry for dense and continuous monitoring of the temporal variations in water dynamic in moderate to large lakes.