Narong Touch

Characteristics of electricity generation and biodegradation in tidal river sludge-used microbial fuel cells.

The electricity generation behavior of microbial fuel cell (MFC) using the sludge collected from the riverbank of a tidal river, and the biodegradation of the sludge by the electricity generation are evaluated. Although the maximum current density (150-300 mA/m(2)) was higher than that of MFC using freshwater sediment (30 mA/m(2)), the output current was greatly restricted by the mass transfer limitation. However, our results also indicate that placing the anode in different locations in the sludge could reduce the mass transfer limitation. After approximately 3 months, the removal efficiency of organic carbon was approximately 10%, demonstrated that MFC could also enhance the biodegradation of the sludge by nearly 10-fold comparing with the natural biodegradation. We also found that the biodegradation could be identified by the behavior of oxygen consumption of the sludge. Importantly, the oxygen consumption of the sludge became higher along with the electricity generation.

Loss on Ignition-Based Indices for Evaluating Organic Matter Characteristics of Littoral Sediments

Abstract Understanding organic matter characteristics ( e.g., amount and state) of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these characteristics are relatively expensive. This study attempted to evaluate the organic matter characteristics of littoral sediments by employing solely the loss on ignition (LOI) method, which is the most economical and accessible method in developing countries. Different types of sediments were first oven dried at 100 °C and then continuously burned at 200, 300, 400, 500, and 600 °C for 4 h at each temperature. The mass LOI at each temperature was calculated and compared with the 100 °C oven-dried weight. Our results suggested that the mass LOI across the temperature range of 200–300 °C (LOI 200–300 ):mass LOI at 600 °C (LOI 600 ) ratio (LOI 200–300 /LOI 600 ) could represent different types of sediments as well as the organic matter:organic C ratio. Compared with the sediments unaffected by wastewater, the sediments that were more influenced by the inflow of domestic wastewater had a higher LOI 200–300 /LOI 600 . Interestingly, LOI 200–300 /LOI 600 could also represent changes in the organic matter characteristics as a function of organic matter decomposition in sediments. In conclusion, the organic matter characteristics of littoral sediments could be evaluated using solely the LOI method, particularly with LOI 200–300 /LOI 600 .

Relaxing the formation of hypoxic bottom water with sediment microbial fuel cells

ABSTRACT The method of improving bottom water environment using industrial wastes to suppress diffusion substances from bottom sediment has recently captured the attention of many researchers. In this study, wastewater discharge-derived sediment was used to examine an alternative approach involving the use of sediment microbial fuel cells (SMFCs) in relaxing the formation of hypoxic bottom water, and removing reduced substances from sediment. Concentrations of dissolved oxygen (DO) and other ions were measured in overlying water and sediment pore water with and without the application of SMFCs. The results suggest that SMFCs can markedly reduce hydrogen sulfide and manganese ion concentrations in overlying water, and decrease the depletions of redox potential and DO concentration. In addition, SMFCs can dissolve ferric compounds in the sediment and thereby release the ferric ion available to fix phosphate in the sediment. Our results indicate that SMFCs can be used as an alternative method to relax the formation of hypoxic bottom water and to remove reduced substances from the sediment, thus improving the quality of both water and sediment environments.

Variation in properties of the sediment following electrokinetic treatments

ABSTRACT Many studies have reported variation in properties of the sediment within electrokinetic treatments (EKTs). However, we aim to reveal the variation in properties of the sediment following EKTs through laboratory experiments. We collected sewage-derived sediment from a littoral region, and passed it through a 2-mm sieve. We used a potentiostat to cause electrical current in EKT. We measured the sediment properties such as pH, redox potential (ORP), and hydrogen sulphide (H2S) concentration at the end of EKT and at 30 days following EKT. Results showed decreases in pH, increases in ORP, and decreases in H2S concentration at the end of EKT. Compared with the sediment without EKT, the decrease in ORP for the sediment within EKT was higher at 30 days following EKT. These suggest that anaerobic digestion of organic compounds occurs in the sediment following EKT, of which the oxidants produced by EKT serve as electron acceptors and organic compounds serve as electron donors. Furthermore, we found that EKT can remove H2S from the sediment and reduce H2S production in the sediment within EKT when compared to the case without EKT. These ensure that EKT can be used to remove H2S and control H2S production in the sediment.

MODELING THE SETTLING VELOCITY OF ORGANIC SETTLING MATTER WITH THE CONSIDERATION OF ORGANIC PROPERTIES

Estimating the settling velocity of organic settling matter (OSM) under the effects of organic properties is necessary for developing a pelagic-benthic coupled ecosystem model to evaluate the coastal environment, where OSM deposits on the sea bottom. In this study, laboratory experiments were performed with several materials, such as bentonite, OSM and suspended matter, using a particle distribution analyzer to reveal the effects of organic properties on the settling factors (e.g. effective density, fractal dimension). Prom the experimental results, it was found that the effective density of each material decreased in association with the increase in particle size from a certain size. Comparing these results to the organic properties of materials, it is evident that the organic properties, such as the absorption amount and the decomposition degree of organic matter, strongly affect the physical properties, such as the fractal dimension and the effective density. Furthermore, a model formula of the settling velocity, in which the effects of the organic properties are considered, has been suggested.

Improvement in benthic habitat environment via granulated coal ash in a water body exposed to wastewater discharge

The discharge of untreated wastewater into a water body strongly deteriorates the benthic habitat environment of bottom sediment. In this study, field experiments were conducted in the Fukuyama inner harbor (Hiroshima, Japan), which is exposed to large amounts of untreated domestic wastewater discharge. The water quality in this harbor is seriously deteriorated during the summer season, resulting in an aggravation of the marine biological environment. This study examines the improvement in benthic habitat environment at the bottom of the harbor via the use of granulated coal ash (GCA, a by-product of coal-fired electric power plants). In the field experiments, the pore water quality and benthic habitat quality (i.e., the abundance and species richness) in GCA, gravel, and sediment layers were observed over time. The experiment results suggest that both GCA and gravel provide a better habitat environment for benthos compared to the sediment. In addition, the species richness in GCA was higher than that in gravel, suggesting that benthos can more easily survive in GCA than in gravels. It appears that the absorptive ability of GCA can remove the reductants released from the anaerobic digestion of organic matter and that the dissolution of the chemical components of GCA is significant factors in creating the higher species richness in the GCA layer.

Nutrient salt removal by steel-making slag in sediment microbial fuel cells

ABSTRACT Applying sediment microbial fuel cells (SMFCs) into sediment can remediate the sediment; however, nutrient salts cannot be removed by SMFCs effectively. In this study, sediment mixed with steel-making slag is used a fuel in SMFCs for understanding the potential of steel-making slag in nutrient salt removal in SMFCs. To the best of our knowledge, no report related to the use of steel-making slag in SMFCs is found in the literature. The combination of SMFCs with steel-making slag is expected to make the individual efficiency of SMFCs and steel-making slag more reactive, and is another way to increase the benefit of using steel-making slag. Experimental results showed that steel-making slag was more effective for adsorbing nutrient salts in SMFCs. Interestingly, the combination of SMFCs with steel-making slag can increase the individual efficiency of SMFCs and steel-making slag.

Dissolution characteristics of granulated coal ash in different saline water conditions

Abstract Granulate coal ash (GCA) has been widely used for improving both sediment and water environments in littoral regions. Dissolved ions from GCA have been pointed out to play an important role in the improvements of sediment and water environments. As the dissolution characteristics of a material in solvent depend on the solvent characteristics, this study attempts to clarify the dissolution characteristics of GCA under different saline water conditions. This may provide useful information for practical uses of GCA in different water environments. The experimental results showed that GCA dissolved more with increasing salinity of solvent. This suggests that GCA is more active in saline water environment rather than freshwater environment. Interestingly, larger releases of calcium ions were confirmed when the solvent salinity was higher than 1000 mg/L. This was because the calcium ions of calcium silicate hydrate (C–S–H) present in GCA were replaced by the sodium ions present in solvent. The solubility of C–S–H present in GCA was low comparing with that of C–S–H gels. Only 40% of the total C–S–H were influenced by the high salinity concentration (higher than 1000 mg/L). Furthermore, a higher solubility of GCA was observed after combusting GCA. Our results suggest that GCA should be combusted at 200 °C prior to use for obtaining a higher performance in improving water and sediment environments.

Measurement of Sediment Retention in a Sandy Tidal Flat Based on Pressure Drop Model

Sediment can either play an important role in subsurface environments as a food source for bacteria or deteriorate the subsurface environments by its retention. Thus, understanding sediment retention is useful for designing the management of subsurface environments. The pressure drop model derived from the Kozeny–Carman model is experimentally verified by the seepage flow in sand beds. It was found that the water head in the sand bed under steady-state flow and variations of the water head corresponding to changes in the boundary water head could be reproduced by the pressure drop model. As the porosity of the sand bed is taken into account in the pressure drop model, the sediment retention can be predicted from variations of the porosity. Experimental results showed that the water head in the sand bed varied due to sediment retention. This ensured that variances in the porosity of the sand bed could be predicted, leading to the investigation onto sediment retention. A method based on the pressure drop model is proposed to measure temporal variations of the water head in a sandy tidal flat and river water head. From field experiments, the temporal variations of the water head in the tidal flat could be predicted when the porosity of the tidal flat was used. Conversely, it is expected that sediment retention in the tidal flat can be predicted based on the variations of the porosity, if the water head in the tidal flat is observed temporally.

MEASUREMENT OF MUD FLOC–SETTLING VELOCITY USING A LASER DIFFRACTION PARTICLE SIZE DISTRIBUTION ANALYZER

In-situ and laboratory measurements of particle setting velocity through different techniques, such as settling tubes and video systems, suffer from human and random sampling errors and lack of accuracy. The development of a method to improve the accuracy of the settling velocity measurements has been a challenge for researchers. We propose a method using a laser diffraction particle size distribution analyzer (Shimadzu, SALD-2000J) to estimate the particle settling velocity with increased accuracy. SALD-2000J measures continuously the average intensity of light scattered and the particle size distribution of mud flocs, which were used to estimate the particle settling velocities. The SALD-2000J method produced high accurate results saving both labor and time. The predicted settling velocity presented the same order of magnitude of those reported in previous studies. The settling velocity was used in the simulation of particle size distribution variation, producing a relative error of particle size distributions (obtained from SALD-2000J and the simulation) interior to 5%. The results suggested that the proposed method can be applied to the prediction of settling velocities of mud flocs and inorganic particles both in fresh and saline water environments.