In this study, the microbial community in the anaerobic/oxic/anoxic (A/O/A) process combined with sludge ozonation and phosphorus recovery was characterized by using phosphorus uptake rate (PUR) analysis and PCR-cloning analysis. Despite effective phosphorus removal, PUR analysis indicated a lower activity of both polyphosphate-accumulating organisms (PAOs) and denitrifying PAOs (DNPAOs) than in other systems utilizing DNPAOs. This result suggested that endogenous denitrifying bacteria actively contributed to denitrification. The PCR-cloning analysis revealed that Bacteroidetes was most prominent in the process, followed by Betaproteobacteria and Alphaproteobacteria. For Bacteroidetes, most of the sequences obtained in this study were not closely related to isolates. On the other hand, for the Alphaproteobacteria, the genera Amaricoccus, Aminobacter, Hyphomicrobium, and Paracoccus, which have the ability both to accumulate poly-β-hydroxybutyrate (PHB) and to reduce nitrate to nitrite, were detected. For the Betaproteobacteria, which are major denitrifying bacteria in wastewater treatment systems, the genera Dechloromonas and Zoogloea, were identified. Organisms belonging to the family Comamonadaceae, some of which have been reported as being primary poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-degrading denitrifying bacteria, also existed in the system. Major PAOs/DNPAOs, Rhodocyclus-related PAOs and Actinobacterial PAOs, were not detected, suggesting that unknown PAOs/DNPAOs could have played an important role for phosphorus removal.
Seasonal variation in phosphorus release potential from bottom sediment and environmental factors affecting phosphorus mobilization in shallow eutrophic lakes, Lakes Nishiura and Kitaura in Japan, were investigated. At uplake sites, the fluxes were low and showed no seasonal variation. The Eh in the sediments at these sites was positive and in an oxidizing state, whereas sediments at other sites were in a reducing state. The oxidation/reduction states were not affected by the presence of DO in the boundary layer water. DO in the boundary layer only oxidized the surface of sediment layer and affected DIP release from the sediment. The oxidation of sediment was due to nitrate input from inflowing rivers. At mid-lake sites, where the DIP release flux was high, the Eh in sediments was increased by nitrate input. Nitrate, which is an electron acceptor in the boundary layer, diffused into the sediment and oxidized the sediment layer in contrast to the definitive oxidation attributed to DO. The DIP release flux decreased with increasing nitrate supply rates. The sediment record shows that the oxidation state was maintained by nitrate supply, which is affected by the decomposition rate of nitrate and strongly affects DIP release from lake sediments under anaerobic conditions.
This study is highlighted to investigate the characteristics of pollutant runoff and relationships between pollutant load and runoff in an urban area of Vientiane city, Lao PDR. Hong Thong catchment area was selected for sampling during wet and dry weather. As a result of the survey, mean concentration of SS was higher in rainy season, in contrast, COD, TN and TP were much higher in dry season possibly due to being associated with domestic wastewater, and attenuation by stormwater in rainy season. The mean total PAHs concentration value were 230.13, 132.83 and 143.72ng/L respectively for rainy season wet and dry periods, and dry season. Base on the composition of specific components, PAHs in Hong Thong catchment area was determined to be derived mainly from oil discharge rather than fuel combustion.
This research was carried out to investigate the feasibility of using dredged sediment (DS) as the additive of silt and clay for artificial tidal flats. A series of experiments conducted in the real seashore and in a tidal flat simulator demonstrated that DS could be used for artificial tidal flats. Furthermore, the tidal flat simulator experiment showed that the macrobenthos population increased with the DS addition. However, use of conditioners made of paper sludge and poly-aluminum chloride for DS granulation treatment was associated with a time lag in the growth of the macrobenthos: these agents may be released during the course of the experimental period. Possible reasons for the increased polychaete and gastropod abundances in the artificial tidal flats might be an increase in supplied organic matter and stimulated benthic microalgae growth due to the DS addition. Finally, a growth test was carried out for the short neck clam Ruditapes philippinarum, which showed that it can grow in artificial tidal flats to which DS has been added. Too much DS, however, may suppress its growth.
This study investigated the mechanism of the loss of Undaria pinnatifida beds in Ogatsu Bay, Japan. Wave heights at the outside of the bay were 1 to 2 m over the course of study. In the outer areas of the bay with high water velocities, more than 14.5 ± 3.4 cm sec -1, U. pinnatifida grew densely and sea urchins were scarce. However, in some outer areas with lower velocities, less than 7.8 ± 2.3 cm sec -1, U. pinnatifida grew sparsely where the aggregation of sea urchin was found. In contrast, in the inner areas of the bay with calm water having velocities of 2.4 to 4.6 cm sec-1, the density of sea urchin was high and the U. pinnatifida beds disappeared. These results indicated high water velocities in the outer bay areas prevent the grazing by sea urchins. Disappearance of U. pinnatifida in the inner bay areas seemed to be caused by the high grazing pressure of sea urchins in calm water velocity conditions. We also performed a U. pinnatifida restoration effort to reduce the effects of the grazing pressure by sea urchins in the barren grounds in the inner areas of the bay. Artificial buoyed reefs were designed to prevent the migration of sea urchins by being detached from the bottom and allowed the recovery of U. pinnatifida and other non-encrusting macroalgae. Although there were some losses of transplanted U. pinnatifida partly caused by the withering after the reproductive maturation period, Saccharina japonica and other macroalgae were naturally recruited and increased due to the inhibition of migration by sea urchins using the buoyed reefs. In contrast, the formation of barren community remained at the area grounded to the bottom allowing the migration of urchin in the inner bay. Overall, our restoration efforts using the artificial buoyed reef, although not ideal, resulted in the success of the recovery of macrolagal habitats in the sea urchin - dominated barren grounds by the reduction of grazing pressure of sea urchins.