Performance evaluation and effect of biogas circulation rate of a bubble column for biological desulfurization.

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 H(2)S. A positive correlation between the biogas circulation rate and H(2)S removal rate was observed. Moreover, the increase in the circulation rate stimulated the O(2) mass transfer, eventually translating into an increase in sulfate production from the oxidation of H(2)S. 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 H(2)S was the rate-limiting step in the biological desulfurization in the reactor, indicating that the mass transfer efficiency of H(2)S needs to be improved to enhance the desulfurization performance.

Extraction of raw sewage sludge containing iron phosphate for phosphorus recovery.

The objective of the present study was to establish an alkali extraction technology for FePO(4)-containing sewage sludge obtained from a wastewater treatment system that includes phosphorous removal by iron electrolysis. By clarifying the extraction properties of phosphorous, organic matter, and inorganic matter, conditions for alkali extraction were optimized. As a result, it was suggested that unheated phosphorous extraction would be superior for FePO(4)-containing sewage sludge. And, extraction methods and sewage sludge properties were also compared, and the noteworthy result that extraction of metals can be suppressed to extremely low amounts with alkali extraction as compared with acid extraction was obtained. A new insight was also gained that, as compared with the use of incinerated ash reported in previous studies, alkali extraction was more efficient when raw sewage sludge was used.

Application of vibration milling for advanced wastewater treatment and excess sludge reduction.

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.

Effects of acute gamma-irradiation on community structure of the aquatic microbial microcosm.

To characterise indirect effects of ionising radiation on aquatic microbial communities, effects of acute gamma-irradiation were investigated in a microcosm consisting of populations of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.) as producer; a ciliate protozoan (Cyclidium glaucoma), rotifers (Lecane sp. and Philodina sp.) and an oligochaete (Aeolosoma hemprichi) as consumer; and more than four species of bacteria as decomposers. Population changes in the constituent organisms were observed over 160 days after irradiation. Prokaryotic community structure was also examined by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA. Principle response curve analysis revealed that the populations of the microcosm as a whole were not significantly affected at 100Gy while they were adversely affected at 500-5000Gy in a dose-dependent manner. However, some effects on each population, including each bacterial population detected by DGGE, did not depend on radiation doses, and some populations in the irradiated microcosm were larger than those of the control. These unexpected results are regarded as indirect effects through interspecies interactions, and possible mechanisms are proposed originating from population changes in other organisms co-existing in the microcosm. For example, some indirect effects on consumers and decomposers likely arose from interspecies competition within each trophic level. It is also likely that prey-predator relationships between producers and consumers caused some indirect effects on producers.

Continuous H2 and CH4 production from high-solid food waste in the two-stage thermophilic fermentation process with the recirculation of digester sludge.

A thermophilic two-stage fermentation process using 10% total solids (TS) food waste was tested at varying organic loading rates (OLRs). The system was configured to produce H(2) and CH(4) in conjugation with the chemical oxygen demand (COD), nitrogen removal, and adjustment of the pH by returning sludge as an alkali buffer from the sludge storage tank for denitrification. The pH in the H(2) fermentation reactor was maintained in the range of 5.4-5.7 using sludge recirculation (Q(r)/Q(i) ratio 1). The average H(2) (11.1l-H(2) l(-1)-fed d(-1)) and CH(4) (47.4l-CH(4) l(-1)-fed d(-1)) production rates were achieved at OLRs of 39 (H(2) fermentation reactor) and 4.16 gCOD l(-1)d(-1) (CH(4) fermentation reactor), respectively. These results suggest that long-term stability of the continuous two-stage process can be successfully achieved by recirculation of high-alkalinity sludge of 6.7-7.5 g l(-1) as CaCO(3), without any added external chemical buffer.

Effect of hydraulic retention time on the hydrogen yield and population of Clostridium in hydrogen fermentation of glucose.

The conversion of glucose to hydrogen was evaluated using continuous stirred tank reactor at pH 5.5 with various hydraulic retention times (HRT) at 30 degrees C. Furthermore, the population dynamics of hydrogen-producing bacteria was surveyed by fluorescence in-situ hybridization using probe Clost IV targeting the genus Clostridium based on 16S rRNA. It was clear that positive correlation was observed between the cells quantified with probe Clost IV and hydrogen yield of the respective sludge. The numbers of hydrogen-producing bacteria were decreased gradually with increasing HRT, were 9.2 x 10(8), 8.2 x 10(8), 2.8 x 10(8), and 6.2 x 10(7) cell/mL at HRT 6, 8, 12, and 14 h, respectively. The hydrogen yield was 1.4-1.5 mol H2/mol glucose at the optimum HRT range 6-8 h. It is considered that the percentage of the hydrogen-producing bacteria to total bacteria is useful parameter for evaluation of hydrogen production process.

Effects of acute gamma-irradiation on the aquatic microbial microcosm in comparison with chemicals.

Effects of acute gamma-irradiation were investigated in the aquatic microcosm consisting of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.) as producers; an oligochaete (Aeolosoma hemprichi), rotifers (Lecane sp. and Philodina sp.) and a ciliate protozoan (Cyclidium glaucoma) as consumers; and more than four species of bacteria as decomposers. At 100 Gy, populations were not affected in any taxa. At 500-5000 Gy, one or three taxa died out and populations of two or three taxa decreased over time, while that of Tolypothrix sp. increased. This Tolypothrix sp. increase was likely an indirect effect due to interspecies interactions. The principal response curve analysis revealed that the main trend of the effects was a dose-dependent population decrease. For a better understanding of radiation risks in aquatic microbial communities, effect doses of gamma-rays compared with copper, herbicides and detergents were evaluated using the radiochemoecological conceptual model and the effect index for microcosm.

Microbial diversity of anammox bacteria enriched from different types of seed sludge in an anaerobic continuous-feeding cultivation reactor.

Enrichment of anammox bacteria from three types of seed sludge, sewage, digester, and nitrification sludges, was conducted using a nonwoven fabric carrier for immobilizing the anammox bacteria, and the microbial diversity of the enriched anammox culture was investigated. About four months later, simultaneous removals of ammonium and nitrite, and production of a small amount of nitrate, which is unique to the anammox reaction, were observed in all 3 sludge reactors. Results of 16S rRNA gene analysis indicated that anammox bacteria were cultivated and diversified in each sludge type. Moreover, the microbial diversity of anammox bacteria was higher in the enriched culture from sewage sludge compared to the other two types of seed sludge. Bacillus sp. coexisted in the anammox culture cultivated from sewage sludge. These results suggest that differences in the anammox community in the enriched culture were caused by differences in the type of seed sludge.

Measuring the effectiveness of a pilot scale bioreactor for removing Microcystis in an outdoor pond system.

A pilot scale fluidized bed bioreactor to control the cyanobacterium, Microcystis, was tested in an outdoor experimental pond system (28 m3) over a 57 day period. The pond system was inoculated with a wild bloom of Microcystis, and the bioreactor was preinoculated with an oligochaete, Aeolosoma hemprichi, which is known to prey on colonial Microcystis. This and other Microcystis predators such as the rotifer, Philodina erythrophthalma were observed to colonize the bioreactor during the experiment. The bioreactor performance in removing Microcystis was estimated using a mathematical model and a multiple regression analysis of the chlorophyll-a concentration, which was a satisfactory surrogate for the Microcystis cell density in the ponds. The estimated specific decrease in chlorophyll-a concentration due to bioreactor treatment was 0.04 day-1, which was equal to the net removal of 4.3 x 10(11) Microcystis cells day(-1) from the treated pond.

Seasonal effect on N2O formation in nitrification in constructed wetlands.

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.

Identification of the bacterial community involved in methane-dependent denitrification in activated sludge using DNA stable-isotope probing.

Methane is used as an alternative carbon source in the denitrification of wastewater lacking organic carbon sources because it is nontoxic and may be efficiently produced by anaerobic biological processes. Methane-dependent denitrification (MDD) in the presence of oxygen requires the co-occurrence of methanotrophy and denitrification. Activated sludge was incubated with 13C-labeled methane in either a nitrate-containing medium or a nitrate-free medium. Then, bacterial and methanotrophic populations were analyzed by cloning analysis and terminal restriction fragment length polymorphism analysis targeting 16S rRNA gene and cloning analysis targeting pmoA genes. DNA-based stable-isotope probing (DNA-SIP) analysis of the 16S rRNA gene revealed an association of the Methylococcaceae and the Hyphomicrobiaceae in a MDD ecosystem. Furthermore, supplementation of nitrate stimulated methane consumption and the activity of methanotrophic populations (i.e. the stimulation of uncultivated relatives of distinct groups of the Methylococcaceae). In particular, uncultured type-X methanotrophs of Gammaproteobacteria were dominant when nitrate was added, i.e. in the MDD incubations. On the other hand, most methanotrophs (types I, II, and X methanotrophs) were found to have been labeled with 13C under nitrate-free conditions. This DNA-SIP study identifies key bacterial populations involved in a MDD ecosystem.

Nitrous oxide emission from polyculture constructed wetlands: effect of plant species.

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.

RNA microarray for estimating relative abundance of 16S rRNA in microbial communities.

We developed an RNA microarray protocol in which total RNA from a microbial community was attached to a slide glass, and rRNA was detected by fluorescently labeled oligonucleotide probes. The RNA microarray requires only 4 h for hybridization and enables double staining and estimating relative abundance of rRNA.

Effect of plant harvest on methane emission from two constructed wetlands designed for the treatment of wastewater.

The emission of methane from two constructed wetlands [a free water surface flow system (FWS) and a subsurface flow system (SF)], constructed for the treatment of waste water, was evaluated at different sites inhabited by reeds (Phragmites communis), to test the effects of plant harvest. High methane emission was recorded immediately after harvesting in both wetlands. Several days after harvesting, the emission decreased in the FWS but remained high in the SF. The variation was significantly influenced by temperature, with lower emission and higher dissolved CH(4) in water occurring at lower temperatures. Both the emission and concentration of dissolved CH(4) were also influenced significantly by water quality, wetland design, level of stalk butt left above the water level, etc. The methane flux was explained on the basis of rizhospheric methanogenic and methanotrophic microbial populations. FISH analysis indicated the presence of Type A and Type B methanotrophs in both wetlands, and the methane flux was directly influenced by the quantitative variation in methanogenic and methanotrophic bacteria in both wetlands.

Highly sensitive real-time PCR assay for quantification of toxic cyanobacteria based on microcystin synthetase A gene.

The presence of cyanobacterial bloom in water supply reservoirs can cause potential health hazards. In this study, we aimed at the quantification of microcystin-producing cyanobacteria based on the microcystin synthetase A (mcyA) gene using real-time PCR. To perform a highly sensitive real-time PCR assay, the novel primer MSR-2R was designed and a coprecipitation DNA extraction method was used in this study. Cyanobacterial cells could be collected efficiently by coprecipitation with other bacteria suspended in solution even in the case of low concentrations of cyanobacteria. The detection limit of the method was found to be 8.8 cells per reaction. When cyanobacterial growth was monitored in pure culture, the cell concentration determined by real-time PCR positively correlated with the cell concentration determined from direct microscopic count. Furthermore, we could detect and quantify the mcyA gene in lake water samples using real-time PCR. It was concluded that the quantification of the mcyA gene based on real-time PCR is a powerful tool for the rapid quantification of microcystin-producing cyanobacteria in environmental samples.

Identification of acetate- or methanol-assimilating bacteria under nitrate-reducing conditions by stable-isotope probing.

Stable-isotope probing (SIP) was used to identify acetate- or methanol-assimilating bacteria under nitrate-reducing conditions in activated sludge. A sludge sample obtained from wastewater treatment systems was incubated in a denitrifying batch reactor fed with synthetic wastewater containing [(13)C]acetate or [(13)C]methanol as the main carbon source and nitrate as the electron acceptor. We analyzed how growth of bacterial populations was stimulated by acetate or methanol as the external carbon source in nitrogen-removal systems. Most of the acetate- or methanol-assimilating bacteria identified by SIP have been known as denitrifiers in wastewater treatment systems. When acetate was used as the carbon source, 16S rRNA gene sequences retrieved from (13)C-labeled DNA were closely related to the 16S rRNA genes of Comamonadaceae (e.g., Comamonas and Acidovorax) and Rhodocyclaceae (e.g., Thauera and Dechloromonas) of the Betaproteobacteria, and Rhodobacteraceae (e.g., Paracoccus and Rhodobacter) of the Alphaproteobacteria. When methanol was used as the carbon source, 16S rRNA gene sequences retrieved from (13)C-DNA were affiliated with Methylophilaceae (e.g., Methylophilus, Methylobacillus, and Aminomonas) and Hyphomicrobiaceae. Rarefaction curves for clones retrieved from (13)C-DNA showed that the diversity levels for methanol-assimilating bacteria were considerably lower than those for acetate-assimilating bacteria. Furthermore, we characterized nitrite reductase genes (nirS and nirK) as functional marker genes for denitrifier communities in acetate- or methanol-assimilating populations and detected the nirS or nirK sequence related to that of some known pure cultures, such as Alcaligenes, Hyphomicrobium, and Thauera. However, most of the nirS or nirK sequences retrieved from (13)C-DNA were clustered in some unidentified groups. On the basis of 16S rRNA gene clone libraries retrieved from (13)C-DNA, these unidentified nir sequences might be identified by examining the nir gene in candidates for true denitrifiers (e.g., the families Comamonadaceae, Hyphomicrobiaceae, Methylophilaceae, and Rhodobacteraceae).

On site experiments of the slanted soil treatment systems for domestic gray water.

In order to make a breakthrough for the acute problem of water shortage in the world, the key words "decentralization and re-use" are very important for new sustainable sanitation systems that will be developed. Therefore, we focused on a new treatments system called "a slanted soil treatment system" which combines a biotoilet system with a domestic grey water treatment system. Because this system is a low cost and compact system, the system can be easily introduced to homes in urban areas or in the suburbs of cities in many developing countries. In this study, we performed on site experiments carried out on Shikoku Island, Japan, for several years. We obtained the following results. The slanted soil treatment system could remove organic pollutants and total nitrogen and total phosphorus in grey water effectively. Furthermore, the system performance became high in the case of the high concentration of the influent water. The nitrification reaction and denitrification reaction were speculated to exist due to aerobic zones and anaerobic zones present in the slanted soil treatment system. The slanted soil treatment system could perform for approximately 3 years with zero maintenance. The plug flow model of 1st order reaction kinetics could describe the reaction in the slanted soil treatment system. However, it is necessary to improve the system to maintain the performance in all seasons.

Long-term monitoring of the succession of a microbial community in activated sludge from a circulation flush toilet as a closed system.

The microbial diversity and community succession of a circulation flush toilet were investigated by terminal restriction fragment length polymorphism and cloning analyses. Clonal libraries of 16S rRNA gene on day 3 and day 127 were constructed. On day 3, 102 clones were sequenced; Proteobacteria and Bacteroidetes accounted for 27% and 45%, respectively. On day 127, Proteobacteria had increased to 43% and Bacteroidetes had decreased to 26% of a total of 100 clones. Terminal restriction fragment length polymorphism peaks were identified by in silico analysis of clone libraries. The relative abundances of Nitrosomonas increased from 1% to 6% with commencement of nitrification and denitrification. Similarly, the relative abundance of terminal restriction fragments generated from Xanthomonas increased from 3% to 10%. Therefore, these bacteria could play a prominent role in this process. To reveal the relationship between stability of the microbial community and performance of the system, microbial community succession was visualized by multidimensional scaling analysis. The microbial community structure changed markedly, particularly during the start-up period of the system. The plots then became stable after the start of nitrification and denitrification. This result suggests that the succession of microbial community structure had a correlation with the performance of the system.

Development of an advanced biological treatment system applied to the removal of nitrogen and phosphorus using the sludge ceramics.

To develop a method of forming lake sediment into sludge ceramics with porosity and good biological adhesion for use as a medium for microorganisms in wastewater treatment, a study of the effects of forming conditions was conducted by adjusting the water content of sludge and compounding some additives. By adjusting the water content of the raw material at the kneading/pelletizing step to 40-42% and adding 3% waste glass to the raw materials to make up for the lack of flux, a sludge ceramic with a density in terms of specific gravity of saturated surface dry aggregate of about 1400 kg m(-3) was formed. In addition, to develop a small-scale wastewater treatment system capable of removing nitrogen and phosphorus, a sludge ceramic was applied as a medium for biological filtration. The results indicated that the BOD removal nitrification rate were superior to those of conventional ceramic media, reached at 95.3% and 87.4%, respectively. The introduction of iron electrolysis resulted in high treatment performance achieving BOD levels of 10 mg L(-1) or less, T-N of 10 mg L(-1) or less and T-P of 1 mg L(-1) or less.

Effects of organophosphorous pesticides used in china on various mammalian cells.

Organophosphorous pesticides are currently widely used in China to help boost agricultural production. However, these pesticides pose various threats to organisms, including humans, and are thus a cause of concern. Five organophosphorous pesticides, monocrotophos, omethoate, parathion-methyl, phoxim and dichlorvos, were examined for their effects on mammalian cell lines to determine their potential impact on physiological functions in vivo. Results show an increased proliferation of MCF-7 cells treated with 0.2 microM monocrotophos or 0.4 microM omethoate, suggesting that these compounds can induce breast cancer cell proliferation at relatively low concentrations. Murine primary spleen cells markedly decreased in number starting at a pesticide concentration of 0.01 microM; no cytotoxicity was observed below 0.001 microM. BALB/c3T3 murine fibroblasts treated with 0.25 microM monocrotophos showed enhanced DNA synthesis, while those treated with the other pesticides showed results similar to that of the control. The different pesticides reduced the acetylcholinesterase (AChE) activity of the rat neuronal cell line PC12 in a dose-dependent manner up to 100 microM. Parathion-methyl and phoxim showed acute toxicity at 0.01 microM. Finally, phoxim and parathion-methyl significantly reduced the transepithelial electrical resistance (TEER) of human intestinal Caco-2 cells, indicating that these pesticides can disrupt the tight-junction permeability of cell monolayers. These in vitro assays, which are rapid, reproducible, simple and inexpensive, clearly show the effects of organophosphorous pesticides on mammalian cells and suggest the potential impact of these pesticides on organisms in vivo.