Futoshi Kurisu

Modelling glycogen storage and denitrification capability of microorganisms in enhanced biological phosphate removal processes

Some important aspects in the modelling of enhanced biological phosphate removal processes which are not considered in IAWQ Activated Sludge Model No. 2 are discussed and three submodels are proposed. When denitrification by polyphosphate accumulating organisms (PAOs) is introduced to the model, anoxic uptake of soluble orthophosphate, which is sometimes observed in the real world can be expressed. Appropriate values of stoichiometric and kinetic coefficients remain to be determined. Glycogen storage capability is another essential character of PAOs. By incorporating biochemical information obtained so far, the processes relating to glycogen storage can be modelled. The model implies very delicate kinetic characteristics of PAOs. A group of organisms, which can cause deterioration of phosphate removal and has been referred to as “G bacterium”, is characterized as glycogen accumulating non-poly-P organisms (GAOs). A preliminary model for GAO metabolism is proposed.

Microbial community analysis of thermophilic contact oxidation process by using ribosomal RNA approaches and the quinone profile method

Microbial community structure of a lab scale thermophilic aerobic wastewater treatment reactor was analyzed by a combination of culture-independent methods. Quinone profile method provides for chemical analysis of respiratory quinone molecular species, which corresponds to bacterial groups. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA partial sequences (PCR-DGGE) clarifies community changes at species level, as DGGE can separate DNA fragments of different sequences. Certain phvlogenetic groups of bacterial cells can be labeled by fluorescence in situ hybridization (FISH). Quinone profile showed a predominant presence of MK-7. PCR-DGGE revealed that constituents of the community were unchanged during the stable phase. FISH demonstrated the existence of the relatives of Bacillus lentus and B. thermocloacae in considerable proportions. The community was mainly composed of Bacillaceae, and obligate thermophilic and mesophilic Bacillus appeared in spite of the temperature fluctuation from 35 degrees C to 60 degrees C. The combination of these culture-independent methods revealed the community precisely enough to evaluate the reactor performance.

Evaluation of microbial regrowth potential by assimilable organic carbon in various reclaimed water and distribution systems

Microbial regrowth introduces several problems to the use of reclaimed water, such as health concerns, aesthetic deterioration, and biofouling. This study evaluated assimilable organic carbon (AOC), which is a part of the biodegradable organic matter promoting microbial growth, in water reclamation systems in Japan. The AOC concentration in the reclaimed water from various treatment processes ranged between 36 and 446 μg C/L (median 316 μg C/L). The AOC concentration in the reclaimed water from the plants equipped with ozonation was significantly higher - more than two times - than that in the reclaimed water from plants equipped with other processes. UV and chlorine also changed the AOC concentration slightly. Moreover, reverse osmosis produced reclaimed water with the lowest AOC content. Processes equipped with membrane filtration were effective in removing seed microorganisms that enter the distribution system. Microbial growth in reclaimed water distribution systems occurred when the total and free residual chlorine was lower than 0.36 and 0.09 mg/L, respectively. The AOC reduction occurred simultaneously with regrowth, which suggests that AOC could support microbial growth in reclaimed-water-distribution systems. As the residual chlorine is often depleted during distribution and storage, it is essential to control the AOC to suppress microbial growth.

Degradation of natural estrogen and identification of the metabolites produced by soil isolates of Rhodococcus sp. and Sphingomonas sp.

Five bacterial strains capable of utilizing 17beta-estradiol (E2) and estrone (E1) were isolated from soil samples. Using their morphological and physiological features and 16S rDNA sequences, we classified these isolates into two groups: Group A (Rhodococcus sp. strains ED6, ED7, and ED10) and Group B (Sphingomonas sp. strains ED8 and ED9). All isolates used E2 and E1 as the sole carbon sources and showed high E1 and E2 degradation activities. In all strains, more than 50% of 0.8 mg of E1 or E2 was degraded in 4 mL of inorganic medium over 24 h, and 90% was degraded over 120 h. By incubating the resting ED8 cells with E2 and the meta-cleavage inhibitor 3-chlorocatechol, we identified two metabolites, 4-hydroxyestrone (4-OH-E1) and 4-hydroxyestradiol (4-OH-E2), and confirmed their identity using authentic chemicals. The 4-OH-E1 and 4-OH-E2 compounds were assumed to be intermediate metabolites formed before meta-cleavage, as they were not identified in culture without 3-chlorocatechol. Degradation of E2 by strain ED8 can be initiated by hydroxylation of the C-4 position, followed by meta-cleavage of the benzene ring. When strains ED8 degraded E2, we further identified hydroxy-E2, keto-E1 and -E2, and an additional degradation product via mass spectrometry. The presence of these compounds implied degradation through a second pathway initiated through an attack of the saturated ring.

Predominance of ammonia-oxidizing archaea on granular activated carbon used in a full-scale advanced drinking water treatment plant.

Ozonation followed by granular activated carbon (GAC) is one of the advanced drinking water treatments. During GAC treatment, ammonia can be oxidized by ammonia-oxidizing microorganisms associated with GAC. However, there is little information on the abundance and diversity of ammonia-oxidizing microorganisms on GAC. In this study, the nitrification activity of GAC and the settlement of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in GAC were monitored at a new full-scale advanced drinking water treatment plant in Japan for 1 year after plant start-up. Prechlorination was implemented at the receiving well for the first 10 months of operation to treat ammonia in raw water. During this prechlorination period, levels of both AOA and AOB associated with GAC were below the quantification limit. After prechlorination was stopped, 10(5) copies g-dry(-1) of AOA amoA genes were detected within 3 weeks and the quantities ultimately reached 10(6)-10(7) copies g-dry(-1), while levels of AOB amoA genes still remained below the quantification limit. This observation indicates that AOA can settle in GAC rapidly without prechlorination. The nitrification activity of GAC increased concurrently with the settlement of AOA after prechlorination was stopped. Estimation of in situ cell-specific ammonia-oxidation activity for AOA on the assumption that only AOA and AOB determined can contribute to nitrification suggests that AOA may account for most of the ammonia-oxidation. However, further validation on AOB contribution is required.

Bacteriophages isolated from activated sludge processes and their polyvalency

In this study, bacteriophages were isolated from activated sludge and their host range was studied. Bacterial isolates were obtained from an activated sludge process treating urban sewage, and bacteriophages were obtained by plaque assay using the bacterial isolates obtained in this study as the host. Out of 15 bacteria isolated, 9 supported plaque formation. The host range test was conducted with a combination of 8 bacteriophage isolates and 9 bacterial isolates. All of the 8 bacteriophages tested were found to form plaques on more than 1 host, and 4 of them formed plaques on both gram-positive and gram-negative bacterial isolates. Three of the 8 bacteriophages failed to form plaques on their original bacterial host. The experimental result indicates that bacteriophages are an active part of the activated sludge microbial ecosystem, having a very close ecological relationship with their host bacteria.

Sorption behavior of heavy metal species by soakaway sediment receiving urban road runoff from residential and heavily trafficked areas.

Groundwater contamination by heavy metals from infiltration facilities receiving road runoff is of potential concern. In this study, sorption tests were conducted to evaluate the influence of the water quality of road runoff, especially dissolved organic matter (DOM), on the sorption of heavy metal species by soakaway sediment. Sequential batch tests were conducted to assess metal sorption by the soakaway sediment receiving road runoff from residential and heavily trafficked areas. Ni was adsorbed by the sediment, indicating that soakaway sediments function to prevent groundwater contamination by Ni. In contrast, Zn was released from the soakaway sediment in sorption tests using heavily trafficked road dust leachates. Ni, Cu, Zn, and dissolved organic carbon concentrations were higher in soakaway sediment leachates obtained by sorption tests using heavily trafficked road dust leachates than those using residential road dust leachates, suggesting traffic activities contaminate these pollutants. A large portion of Zn, released from the soakaway sediment, existed as stable complexes. DOM in road runoff possibly enhances the release of Zn from the sediments within infiltration facilities and might cause groundwater contamination.

Identification of putative benzene-degrading bacteria in methanogenic enrichment cultures

Anaerobic benzene-degrading enrichment cultures performing methanogenesis were obtained from non-contaminated lotus field soil. Stable isotope probing with 13C benzene was used to detect the bacteria that were involved in benzene degradation. Denaturing gradient gel electrophoresis (DGGE) of fractionated samples exhibited an obvious shift of some DGGE bands to a heavier DNA fraction. An almost full-length 16S rRNA gene sequence corresponding to the DGGE band, namely Hasda-A, was obtained by constructing a clone library of the heavier fraction. The Hasda-A sequence showed only 85.1% identity with the closest identified bacterium, Syntrophus gentianae. Hasda-A may be an important bacterium involved in the initial steps of benzene degradation under methanogenic conditions, as it was the most prominent bacterium that assimilated labeled benzene early in the process of benzene degradation. A primer set was designed to quantify the gene copies of Hasda-A by quantitative PCR. Hasda-A was present at a concentration of (3.5+/-0.8) x 10(6) copies/mL and represented 8.4% of gene copies among bacteria in the enrichment culture. The enrichment culture consisted of three dominant bacterial groups: Hasda-A and both aceticlastic and hydrogenotrophic methanogens. Methane is believed to be produced from benzene by the sequential degradation of benzene by fermenting bacteria, hydrogen-producing acetogens, and methanogens.

Potential mobility of heavy metals through coupled application of sequential extraction and isotopic exchange: Comparison of leaching tests applied to soil and soakaway sediment

Artificial infiltration facilities (AIFs) that enhance groundwater recharge and regulate urban runoff are going to be an integral element of the urban infrastructure. However, AIFs provide a sink which trap pollutants that are likely to cause groundwater contamination. The current study aimed first to examine the mobility characteristics of Cu, Zn, and Pb through soil and soakaway sediment using an integrated analytical approach for column leaching with artificial road runoff (ARR) and then to differentiate the sorption patterns among different samples, (i.e., surface soil, underlying soil, and soakaway sediments) using mass balances. In addition, the study compares metal retention and release under continuous and intermittent flow conditions. Column leaching experiments were conducted using batches for 10 and 30 d under continuous flow condition and for 20 d of intermittent leaching. Heavy metal content and partitioning in soil and sediment used in columns were well characterized before and after leaching experiments. The results showed that a gradual increase in pH and decrease in dissolved organic carbon had pronounced effect on the mobilization of heavy metals. Pb showed the highest retention compared to Cu and Zn which implies that metal complexes play a pivotal role in metal transport. Labile fractions were found to be trapped by the solid materials for retention and their high concentration in ARR is a major concern from the pollution point of view through infiltration facilities. Results obtained in this study predict the risk associated with the release of retained heavy metal under changing environmental conditions in AIFs.

Combined effects of EPS and HRT enhanced biofouling on a submerged and hybrid PAC-MF membrane bioreactor.

The goal of this study was to quantify and demonstrate the dynamic effects of hydraulic retention time (HRT), organic carbon and various components of extracellular polymeric substances (EPS) produced by microorganisms on the performance of submersed hollow-fiber microfiltration (MF) membrane in a hybrid powdered activated carbon (PAC)-MF membrane bioreactor (MBR). The reactors were operated continuously for 45 days to treat surface (river) water before and after pretreatment using a biofiltration unit. The real-time levels of organic carbon and the major components of EPS including five different carbohydrates (D(+) glucose and D(+) mannose, D(+) galactose, N-acetyl-D-galactosamine and D-galactose, oligosaccharides and L(-) fucose), proteins, and polysaccharides were quantified in the influent water, foulants, and in the bulk phases of different reactors. The presence of PAC extended the filtration cycle and enhanced the organic carbon adsorption and removal more than two fold. Biological filtration improved the filtrate quality and decreased membrane fouling. However, HRT influenced the length of the filtration cycle and had less effect on organic carbon and EPS component removal and/or biodegradation. The abundance of carbohydrates in the foulants on MF surfaces was more than 40 times higher than in the bulk phase, which demonstrates that the accumulation of carbohydrates on membrane surfaces contributed to the increase in transmembrane pressure significantly and PAC was not a potential adsorbent of carbohydrates. The abundance of N-acetyl-d-galactosamine and d-galactose was the highest in the foulants on membranes receiving biofilter-treated river water. Most of the biological fouling compounds were produced inside the reactors due to biodegradation. PAC inside the reactor enhanced the biodegradation of polysaccharides up to 97% and that of proteins by more than 95%. This real-time extensive and novel study demonstrates that the PAC-MF hybrid MBR is a sustainable technology for treating river water.