Many water quality conservation measures have been implemented in agricultural areas to reduce pollutant loading. We investigated agricultural drainage canals in three paddy-field districts around Lake Biwa. In this paper, we focus on nitrogen (N) and organic carbon (C) released from the sediments in the drainage canals. We collected sediment cores and conducted an incubation experiment. We measured temporal change in concentrations of N and organic C in the overlying water of the sediments. As a result, we found that the nitrogen is released mainly as inorganic nitrogen (ammonium N). Ammonium N flux for each sediment sampled from St. 1, St. 2 and St. 3 was 24, 13, and 41 mg N/m²/d, respectively. Nitrogen was released from the sediments mainly in an inorganic state. The C/N ratio of the sediments was about 10 and almost constant during the incubation period. It is suggested that the fraction of organic decomposed in the sediments was small during the incubation experiment.

View full abstract

Objectives of this study are to comprehend the removal characteristics of dissolved organic matter (DOM) and disinfection by-products formation potential (DBPsFP) in the upper layer, which has active microbial activities, of soil aquifer treatment for wastewater reuse. Three columns, in which sand was packed with the height of 5, 10 and 30 cm, respectively, were set, and wastewater effluent was continuously discharged. Dissolved organic carbon (DOC) and DBPsFP were measured in the influent and effluent from the columns. 22.4% of DOC was removed only at the 5 cm thick layer from the surface, and the removal efficiency increased to 40.1% by the 30 cm infiltration. Therefore, it was cleared that DOM was actively removed by the upper layer infiltration, and most DOM removal was attributed to biodegradation. It was found that the removal characteristics of each DBPs precursor by biodegradation in the upper layer were different. Chloroform FP and dibromochloromethane FP were also reduced by biodegradation in the 30 cm infiltration (removal ratio was 34.4 and 29.2%, respectively); meanwhile, bromodichloromethane FP did not decrease.

View full abstract

Anammox, anaerobic ammonium oxidation with nitrite, is recognized as a unique and novel nitrogen metabolic pathway for ammonia-rich wastewater treatment compared with conventional nitrification and denitrification system mainly due to cost saving. However, the enrichment culture of marine anammox bacteria (MAB) and its potential nitrogen removal capacity, so far, have not been well studied. The present study described the effects of shortening hydraulic retention time (HRT) and increasing nitrogen concentration in a medium on the nitrogen removal performance in the MAB culture using upflow column bioreactors in which non-woven fabric was installed as biomass carrier and the change of the nitrogen removal performance was continuously monitored. The results showed that in reactor-I, nitrogen removal rate (NRR) of 1.1 kg-N/m³/d was attained as a maximum value when the nitrogen loading rate (NLR) was 1.3 kg-N/m³/d at 740 mg-N/L total influent nitrogen concentration and 18 h HRT. As for reactor-II, a maximum NRR of 6.33 kg-N/m³/d was attained when the NLR was 10.08 kg-N/m³/d at 210 mg-N/L total influent nitrogen concentration and 0.5 h HRT. These results indicate that shortening HRT is an easy way to achieve high-rate nitrogen removal performance in the MAB culture.

View full abstract

This study evaluated the performance of a novel treatment system consisting of an upflow anaerobic sludge blanket (UASB) and a downflow hanging sponge (DHS) for the treatment of industrial wastewater containing 8% ethylene glycol and 2% propylene glycol discharged from a rubber production unit. The system achieved high COD removal (91 ± 4.3%) and methane recovery (82 ± 20%) at an organic loading rate of 8.5 kg-COD/(m³•day). The UASB allowed an organic loading rate of 14 kg-COD/(m³•day) with a constant hydraulic retention time of 24 h. The COD of DHS effluent was 370 ± 250 mg-COD/L during the entire experimental period. Thus, the proposed system could be applicable for treating industrial wastewater containing ethylene glycol. Massively parallel 16S rRNA gene sequencing elucidated the microbial community structure of the UASB. The dominant family Pelobacteriaceae could mainly degrade the organic compounds of ethylene glycol and decomposed products of ethanol. In Archaea, the hydrogenotrophic methanogen family Methanobacteriaceae was predominant in UASB granular sludge.

View full abstract

The variation of water quality arising from the hydrolysis of aluminum in the acidified river was evaluated by field investigations and multivariate analyses. Field investigations were conducted in Matsu River, a typical example of an acidified river in Japan, which receives inflow of acid mine drainage from the abandoned Nishiazuma sulfur mine. The results of the investigation of the acidified river basin indicated that the loading of aluminum ions decreased at the upper to middle reaches of the river because aluminum was precipitated onto the riverbed. Additionally, an increase in pH was inhibited by consumption of the alkali component through hydrolysis of aluminum ions. Multivariate analysis of the metal ion concentrations and water level in the middle reaches of the river was conducted using the data from intensive field investigations. Two processes including dilution by inflows of rainfall and snowmelt, and hydrolysis of Al, influenced the variation in the water quality of the river. Therefore, the pH behavior could be attributed not only to dilution but also to the hydrolysis of aluminum acting as a pH buffer in an acidified river containing excess aluminum.

View full abstract

Enzymatic hydrolysis is an essential step in the fermentative H₂ production process of lignocellulosic biomass to convert cellulose and hemicellulose into fermentable sugars. The waste from disposable wooden chopsticks (DWC) was represented as wood waste and investigated in this study. In order to optimize the condition of the enzymatic hydrolysis of alkaline pretreated DWC, response surface methodology is an efficient experimental tool used to determine the optimal conditions of numerous variables. In the present study, cellulase dosage, β-glucosidase dosage, Tween 80, and hydrolysis time, were found to have a significant effect on enzymatic hydrolysis based on the Plackett-Burman design. These factors were subsequently investigated on the optimal levels by a central composite design, which was determined at 36 FPU/g pretreated DWC of cellulase, 53 CBU/g pretreated DWC of β-glucosidase, and 0.4 g/g pretreated DWC of Tween 80 for 105 h. Under optimal conditions, glucose and reducing sugar yields were 121.7 and 435.8 mg/g pretreated DWC, respectively. Furthermore, enzymatic hydrolysate was applied as a substrate for fermentative H₂ production and obtained a yield of 27 mL H₂/g pretreated DWC by an anaerobic mixed culture.

View full abstract

Groundwater is often contaminated by ammonium and nitrate, causing problems in developing countries such as Thailand and Nepal. Therefore, development of new methods for removing contaminants from groundwater is necessary. In this study, we investigated the effectiveness of a new treatment system for simultaneous removal of ammonium and nitrate by anaerobic ammonium oxidation (ANAMMOX) and hydrogenotrophic denitrification. Enriched ANAMMOX sludge was cultivated under two conditions (20 mL/min hydrogen gas flow rate to investigate the effectiveness of ANAMMOX and hydrogenotrophic denitrification; and 60 mL/min hydrogen gas flow rate to examine the effect of the presence of nitrite on the activities of both microbes). Simultaneous removal of ammonium and nitrate was successfully detected using the former condition, and 95% of ammonium and 90% of nitrate were successfully removed. Additionally, the maximum nitrogen removal rate was 0.25 kg-N/m³/d, and 89% of the total dissolved nitrogen was removed. Using the latter condition, increases in nitrite removal were observed only during the supply of hydrogen gas. These results showed that a hydrogenotrophic denitrifier coexisted with ANAMMOX bacteria in our enriched sludge and that ANAMMOX and hydrogenotrophic denitrification removed ammonium and nitrate simultaneously. Therefore, this method may represent a novel efficient technique for the removal of contaminants from groundwater.

View full abstract

The release of radiocesium from the Fukushima Dai-ichi Nuclear Power Plant caused environmental contamination. We analyzed sources, behavior, and temporal trends of radiocesium by 1-year monitoring in an urban river, the Ohori River. The concentrations of ¹³⁷Cs in both particulate and dissolved phases decreased to ~ 16% within 1 year. The partition coefficient in dry weather was estimated to be 3.2 × 10⁴ L/kg. ¹³⁷Cs concentrations in the particulate phase were higher during wet weather than during dry weather on the basis of both suspended solids (SS) weight and liquid volume. The ratios of ¹³⁷Cs concentration to deposited ¹³⁷Cs in the Ohori River (e.g., composite: 0.26 m²/kg-SS in June - July 2012) were higher than those in the Abukuma River, probably because of differences in land use. Source analysis by a chemical mass balance method showed that 22% of ¹³⁷Cs came from river water in dry weather, 39% from river sediments, and 39% from road dust highlighting urban surface deposits such as road dust as major sources of ¹³⁷Cs in the river water even 2 years after the accident, and that the wash-off of these deposits increased the ¹³⁷Cs concentration in the river during wet weather.

View full abstract