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Purpose: This study aimed at valorizing solid food waste containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Methods: Aurantiochytrium sp. L3W that produces DHA and EPA was cultivated on eight types of solid food waste: sake lees (SL), crown daisy, Japanese mustard spinach (JMS), soy sauce residue, lemon peel (LP), orange peel, grape skin, and Hiroshimana old pickle (HOP). The biomass mixture of the remaining food waste and strain L3W was analyzed for DHA and EPA. To characterize the types of food waste, the leachability of dissolved organic carbon (DOC) and dissolved nitrogen (DN) were compared. Results: The strain L3W grew on both pasteurized and unsterilized food waste such as SL and JMS. Elution of DOC and DN from the food waste might be a factor affecting the growth of strain L3W. However, the strain L3W might utilize solid-state organic compounds in JMS. Despite the unsterile conditions, the biomass mixture of SL contained both DHA and EPA, whereas DHA was found in the biomass mixtures of JMS, LP and HOP, thereby confirming the valorization of these types of solid food waste. Unsterile mass cultivation of the strain L3W using SL and HOP in a 200 L tank also produced a biomass mixture containing 12.6 mg-DHA/g and 0.217 mg-EPA/g. These DHA and EPA contents were 1500-times and 37-times higher, respectively, than that in commercial poultry feed, indicating that these mixtures could be used as an additive in poultry feed.

Biological wastewater treatment plants (WWTPs) produce large amounts of excess sludge. One approach to reduce sludge is treatment with ozone, which promotes sludge disintegration and solubilization...

Produced water generated in the recovery of crude oil contains oil and high concentrations of salts, organic matter, and suspended solids and must therefore be treated appropriately prior to disposal. Monolithic ceramic membranes have high oil removal rates and have the advantage of being compact, having a long life, and withstanding chemicals, heat, and high cleaning pressures. Membrane fouling, however, is a significant drawback to membrane filtration. Scrubbing using air bubbles generated by a diffuser is generally used to physically clean membranes. However, monolithic ceramic membranes cannot be scrubbed using air bubbles because their fluid channels are only a few millimeters wide. Membrane washing efficiency was therefore evaluated using fine bubbles smaller than the diameter of the channels. In dead-end filtration, flushing the membrane surface with air-microbubble water or air-ultra-fine bubble (UFB) water after backwashing and air-blowing (conventional cleaning) of the channels was more efficient than conventional cleaning. Flushing with UFB water was not influenced by changes in pH that changed the zeta potential of the UFB. Membrane fouling was suppressed in crossflow filtration by mixing UFB water with feed water. There was no significant change in the diameter of the oil droplets in the feed water before and after UFB mixing. The ZP of the oil droplets peaked at around -20 mV before UFB mixing. However, the peak shifted to around -25 to -29 mV after UFB mixing.

Esophageal cancer patients have a high frequency to coincide with head and neck (H&N) cancer. We have corporated together with Otorhinolaryngology, H&N Surgery, and Plastic surgery department doctors for the treatment of synchronous esophageal and H&N cancer patients. The aim of this study is to analyze the treatment results and prognosis of synchronous esophageal and H&N cancer patients. Methods From January 2014 to December 2019, 5 patients underwent concurrent surgical resection of synchronous esophageal and H&N cancer in our institution. We retrospectively reviewed the surgical outcomes and prognosis of these patients of synchronous esophageal and H&N cancer (HNEC group) and compared the results with 27 patients who had esophagectomy with 3 regional lymph node dissection during the same period (EC group). Results The location of H&N cancers were pharynx/tongue; 4/1, and clinical stage was all Stage IV. The clinical stage of esophageal cancers was Stage 0/I/II/III; 1/1/2/1. All patients underwent video-assisted thoracic esophagectomy. The surgical procedures concurrently performed for the H&N cancer were pharyngolaryngectomy with free jejunum transfer for 3 patients, wide tongue and mandibular segment resection with mandibular reconstruction in 1 patient, and mandibular transection with radial forearm flap reconstruction in 1 patient. There was no significant difference in the frequency of postoperative complication between 2 groups. HNEC group tend to have shorter recurrence free survival compared to EC group (p = 0.051). Conclusion H&N surgery with thoracotomy is a highly invasive surgery, however, it can be safely performed with local management. The risk of recurrence is high in H&N cancer patients, therefore it is important to move onto adjuvant therapy without delay. Paraenteral nutrition may be useful in management of these patients.

Deterioration of the sediment environment and benthic ecosystem is an undesirable effect of eutrophication, but little is known about the response of macrobenthic communities to eutrophication and their long-term recovery. In the present study, temporal changes in benthic ecological status, associated with reductions in anthropogenic impacts on a largest semi-enclosed sea in Japan, were determined using long-term monitoring data from water and sediment quality based on the multivariate AZTI Marine Biotic Index (M-AMBI), focusing on spatial differences in anthropogenic impacts. Several sub-areas were classified based on Chlorophyll a (Chl.a) concentrations in surface water during the 1980s. Chl.a concentrations decreased in all sub-areas except the sub-area with2 μg Chl.a L

Region-specific background Secchi depth (BSD) provides valuable information on light availability in aquatic ecosystems. We estimated BSD in two eutrophic bays located in central Japan, Tokyo Bay and Ise Bay. Estimates were based on monitoring data collected in the period 1981–2015. Reliable BSD estimates were obtained for 89–96% and 67–94% of the monitoring sites in Tokyo Bay and Ise Bay, respectively. Low BSD values were obtained in the innermost sectors of Tokyo Bay (around the Nakagawa, Arakawa and Sumidagawa estuaries) and Ise Bay (around the Shonaigawa, Kisogawa and Ibigawa estuaries). BSD was positively correlated with salinity in both bays, indicating that river-supplied substances, including tripton and/or colored dissolved organic matter, strongly influenced BSD values. Although the highest chlorophyll a concentrations were measured in the innermost sectors of both bays, the proportional contribution of phytoplankton to light attenuation was surprisingly low in comparison with other sectors of the two water bodies. In both bays, phytoplankton accounted for

In the Seto Inland Sea, Japan, chemical oxygen demand has increased over recent decades, while average dissolved oxygen concentrations in the bottom water have increased. In this study, we investigated responses of organic carbon (OC) in hypoxic sediment to changes of redox conditions using experimental columns containing sediment and overlying water. Surface sediment showed an increase in OC along with the change to an aerobic condition. Microbial community analysis showed a predominance of sulfur-oxidizing bacteria (SOB) such as Sulfurovum sp. in the sediment. This dominance could account for the increased OC. Additionally, the dissolved organic carbon (DOC) concentration in the overlying water increased. Further experiments using sandy sediment showed that biodegradation of Sulfurimonas denitrificans was associated with DOC release. These results show that a change in the sedimentary environment (increase in dissolved oxygen) increased the sedimentary OC and DOC of overlying water by stimulating certain autotrophic bacteria, especially the SOB.

Enclosed seas are suitable for bivalve farming due to high primary production, which provides food sources. The impact of oyster farming on the biological productivity of lower trophic levels was evaluated in Hiroshima Bay. The area-weighted mean primary production in the estuary (northeastern bay; NB) was 1.1 to 2.1 times higher than that of the offshore area (southwestern bay; SB) in all four seasons. In contrast, the area-weighted mean secondary production by net zooplankton in the NB was lower than that of the SB, except in August. The area-weighted mean secondary production by oysters in the NB was 2.2 to 2.8 times higher than that of the SB in all four seasons, and exhibited a similar spatial pattern to that of the primary production. The primary production was more efficiently utilized and transferred to secondary producers in the SB (16.7% on average) than in the NB (9.4% on average). This study provides guidance for oyster farming in Japan.

This study aims to reveal spatial distribution of hydrogen sulfide and sulfur species in marine sediments in Hiroshima Bay, Japan, by direct analyses using a combination of detection tubes and X-ray absorption fine structure spectroscopy. In summer and autumn, the hydrogen sulfide concentration ranged from

A total pollutant load control system (TPLCS) was implemented in the Seto Inland Sea in 1979 to reduce the water pollution and the frequency of red tides. We estimated primary production from 1981 to 2010 to determine the effects of reducing the nutrient loadings from the surrounding land. While primary production has decreased overall in the Seto Inland Sea in response to the TPLCS and the associated reductions in the total nitrogen (T-N) and phosphorus (T-P) loads from land since 1981, the reductions were limited to 4 of its 11 subareas. Primary production has increased in the Harima Nada but has been stable in the Bingo Nada subarea, reflecting the fact that the T-N and T-P stocks have not decreased in these subareas over the study years. The inconsistent responses of the 11 subareas suggest that the characteristics of each subarea should be considered when environmental management measures are established and implemented in the Seto Inland Sea. The controls on the nutrient loadings according to the TPLCS should be modified to permit better management of this semi-enclosed sea.

Ciona savignyi is an invertebrate filter feeder with an expanding invasive range in the world and a biofouling organism settling on artificial substrates such as fish net. In this study, we investigated the effect of body length and temperature on its filtration rate. As C. savignyi increased in size, filtration rate also increased. Optimal filtration occurred at a temperature of 24–25 °C. The effect of body length on filtration rate was expressed using an exponential function and the effect of temperature (15–27 °C) was calculated using a polynomial function. An equation to predict the filtration rate of C. savignyi was developed, by combining the terms for body length and temperature. The predicted filtration rates calculated using this power function showed good agreement with observed values. The filter-feeding ascidian, C. savignyi, is a biofouling organism that frequently grows on aquaculture structures. Using published data describing the numbers and weights of the cultured Japanese scallop (Mizuhopecten yessoensis) and of biofouling C. savignyi attached to pearl fishing nets in the Kugurizaka experimental fishing grounds, the filtration potential of both species was estimated as a case study. The results suggest that C. savignyi attached to the nets has the potential to negatively impact the growth of the Japanese scallop through competition for food.

Secchi depth has traditionally been used to assess the light transmittance of a water body and to indicate the degree of eutrophication. Anthropogenic eutrophication can decrease Secchi depth by increasing phytoplankton density. However, Secchi depth is determined not only by phytoplankton density but also by suspended particulate matter, chromophoric dissolved organic matter, and by the optical properties of the seawater itself. These latter factors contribute to a region-specific component of the Secchi depth that is independent of phytoplankton density. The present study aims to estimate this region-specific Secchi depth component, which we term the background Secchi depth (BSD). We compared measured Secchi depth for the past 10 years against BSD to understand the optical condition of extant water bodies and the limits of anthropogenic nutrient reduction as a method of increasing the Secchi depth. Our study analyzed 34 years of seasonal monitoring data across 124 sites in the Seto Inland Sea, Japan. BSD was obtained in 67% and 63% of the sites in the spring and summer, respectively, and 37% and 19% of the sites in autumn and winter. High turbulence during the autumn and winter caused unstable background light attenuation, making it difficult to determine an accurate BSD in many sites. BSD was positively correlated with salinity and water depth and could be estimated from these two parameters. Low BSD was observed near the shore and at shallow sites. Measured Secchi depths over 30% smaller than BSD were observed from 20% to 48% of the sites in 1981–1990, those observations were reduced to 4% to 9% of the sites in the past 10 years (2005–2014), indicating that the impact of eutrophication on light transmittance is not severe at present. Consequently, further reduction of anthropogenic nutrient loads will have a limited effect on Secchi depth in many areas. Moreover, we show the existence of a greater discrepancy between measured Secchi depth and BSD in warm seasons than in cold seasons. Similarly, the difference between measured Secchi depth and BSD was higher in geographically enclosed sub-basins than in other sub-basins.

Sludge ozonation, which promotes sludge disintegration and solubilization, is a promising technology for reducing waste sludge volume from biological wastewater treatment process. However, if this technology is to be widely adopted, reducing the energy consumption associated with ozone generation will be necessary. We used ultra-fine bubbles (UFBs) as ozone carriers to determine if their use could improve the efficiency of ozone treatment and reduce the ozone dose required. We used a spiral, liquid-type UFB generator, which can introduce UFBs directly into a sludge suspension. The death ratio of bacteria in sludge was used as an indicator of sludge reduction. The ozone requirement was reduced by UFBs. The ozone consumption required to achieve a death ratio of 80% was 15 mg-O3/g-MLSS in the sludge treated with ozone supplied by UFBs versus 25 and 45 mg-O3/g-MLSS in sludges treated with ozone supplied as a spiral, liquid-type microbubbles and by a diffuser, respectively. When mixing water ozonated with UFBs with sludge, the depth of the dead cell layer from the surface to the interior of the sludge floc was larger than that of ozonated water lacking UFBs at the same rate of ozone consumption. Ozone in UFBs kills bacteria inside the flocs. However, the fragmentation of sludge flocs by shear forces in the UFB generator made a larger contribution to the acceleration of bacterial death in sludge treated with ozone supplied by UFBs.

The model cationic molecule prodigiosin interacted with a polyamide/polysulfone composite reverse osmosis (RO) membrane, resulting in a reduction of the membrane permeation rate. Prodigiosin is an antibacterial agent produced by Serratia marcescens that is frequently isolated from activated sludge of domestic or industrial wastewater. Such molecules respectively secreted or leaked from live or dead cells are thought to affect membrane biofouling. In this study, a cell suspension containing prodigiosin-producing S. marcescens AS-1 wild-type or the non-producing AS-1ΔspnI strain was fed to the thin RO membrane to determine the occlusion ratio on the membrane. Cationic prodigiosin enhanced membrane biofouling by clogging the pores and enhanced the accumulation of the cake layer. The effects remarkably recovered the occlusion ratio after removing the cake layer by feeding with water. After temporary pressure relief, the occlusion ratios for AS-1 and AS-1ΔspnI were recovered to stable levels from approximately 70 to 49% and 23%, respectively. Zetapotential analysis supported the neutralization effects leading to the accumulation of bacterial cells under applied high pressure for RO membrane permeation.

Bacterial quorum sensing (QS) is one of the cell-to-cell communication systems. N-Acyl-homoserine lactones (AHLs) are the most common QS signals and responsible for biofilm formation in gram-negative bacteria. Inactivation of QS, also referred to as quorum quenching, has been regarded as a popular strategy to control membrane bioreactor (MBR) operations because biofouling in MBR wastewater treatment systems is often caused by biofilm formation. In the present study, 24 bacterial strains were isolated from the secondary effluent of a wastewater treatment plant and AHL productivity and biofilm formation were evaluated on 8 out of 24 isolates. The isolated 8 strains can produce AHLs that only possess a long (C8-C14) acyl side chain. The representative 3 strains were selected from these isolates based on the higher activity of biofilm formation. The AHL separation analysis with a thin layer chromatography clearly showed that N-octanoyl-L-homoserine lactone (C8-HSL) and N-hexanoyl-L-homoserine lactone (C6-HSL) existed in the secondary effluent sample, while no C6-HSL producing strain was isolated. C8-HSL was identified as the product of isolate No. 6. These results suggest that the secondary effluent probably contains various cell-to-cell signaling molecules derived not only from the inhabitants but also from the other microorganisms involved in the activated sludge for the biological pre-treatment. In this secondary effluent, AHL trapping techniques can be proposed as one of the acceptable strategies for the control of the QS systems because the remaining AHLs have relatively long acyl side chain and low concentrations.

A novel quantitative analysis method for cellulose fibre was developed to understand its behaviour in biological wastewater treatment and waste sludge processes. The method developed in this study was designed using Pseudomonas aeruginosa to remove it by dissolving all the organic components except cellulose from the sludge due to needing the solubilisation of bacteria occupied almost of sludge matrix and quantifying the amount of remaining cellulose. The results of this study indicated that a combined treatment process that employed 2,000 U/L protease, 2 M hydrogen peroxide, and 2 mM potassium hydroxide after pre-treatment for floc dispersion with an ultrasonic treatment at 26 W for 1 min resulted in a solubilisation of 96% of P. aeruginosa without losing the cellulose fibre. When it was applied to the cellulose fibre added in the sludge from a municipal wastewater treatment facility, 99.5% of the cellulose fibre was recovered by using the high-speed centrifuge.

A tertiary polyamide membrane was synthesized using N,N'-dimethyl-m-phenylenediamine. The durability of this membrane to chlorination by hypochlorite treatment followed by sodium hydroxide treatment was examined, and then deterioration mechanisms were proposed. The tertiary polyamide membrane demonstrated better durability to free chlorine than a conventional secondary polyamide one; however, the former was deteriorated by hypochlorite for 24 h at 2000 ppm of free chlorine below pH 7.5. The salt rejection and permeation performance of the membrane were almost unchanged, and the least chlorination of the active layer occurred during hypochlorite treatment at pH 10. These results indicated that hypochlorous acid rather than hypochlorite ion was the free chlorine species that induced membrane deterioration. The deterioration became severe as chlorination progressed, resulting in collapse of the active layer below pH 7.5. Chlorination and hydrolysis of the model tertiary amide N-methylbenzanilide and Fourier transfer infrared spectroscopy of a deteriorated membrane showed that chlorination of the tertiary polyamide occurred via direct chlorination of the benzene bound to the amidic nitrogen. Silver ion probing of the deteriorated membrane revealed that amide bond scission occurred in the active layer, which might be related to the electron deficiency of the amidic nitrogen caused by chlorination of its benzene ring.

Benthic invertebrates that inhabit the seafloor respond to anthropogenic and natural stresses, and are good indicators for assessing the benthic ecological status. We evaluated the ecosystem health of the Seto Inland Sea based on the multivariate AZTI Marine Biotic Index (M-AMBI), being its first application in a Japanese coastal sea with numerous endemic species. From the 415 locations studied, we were able to use M-AMBI in 384 sites (92.5% in all sites). The result revealed a statistically significant correlation among biotic indices including AMBI, M-AMBI, Richness, and H' (p 0.01). Most of the physico-chemical parameters of the sediment (water content, total organic carbon (TOC) content, sulfide content, mud content, and oxidation-reduction potential (ORP)) were significantly correlated with each other excluding sediment temperature. The M-AMBI was significantly correlated with physico-chemical variables including water content, TOC content, sulfide content, and ORP. We found that the sites classified into the organically enriched cluster, and having high contents of TOC, mud, and sulfide and negative ORP, corresponded with sites that had significantly low M-AMBI values (bad-poor ecological status). Conversely, sites in the unpolluted sandy cluster were assigned high M-AMBI values (high-good ecological status). Therefore, M-AMBI would be a useful biotic index in Japanese coasts due to the representation of the comprehensive sediment quality.

Reverse osmosis (RO) membrane technology is considered to be the premier process used for the purpose of seawater and brackish water desalination and water treatment of municipal and industrial wastewater for water reclamation and reuse. Membrane biofouling is a significant challenge in RO processes due to the interference of biofilm formed on the membrane surface on membrane performance. Thus, diverse areas of research are geared towards the understanding, prevention, and control of biofouling. Diagnosis of biofouling is difficult since no single microbial assay on the source water can accurately predict biofouling during the RO process. Biofouling evaluation methods of fouled membranes and collected biofoulants from the treatment processes are counterproductive when biofouling prevention is warranted. It is therefore important for the detection tests to be predictive enough taking into consideration the water quality characteristics of the source feed water, the properties of the RO membrane used for the water treatment, and the hydrodynamic properties during the RO process. This chapter provides an overview of biofouling tests most commonly used for detection of biofouling in the source feed water, and in the foulants and fouled membranes. It has a brief section on the use of flow cell units that can simulate hydrodynamic conditions in the RO plant with the ability to predict biofouling.

Certain metal ions accelerate deterioration of secondary polyamide reverse osmosis membranes during hypochlorite treatment. However, the mechanisms underlying this metal ion–mediated membrane deterioration have not been clarified. Here, we examined the deterioration of a secondary polyamide reverse osmosis membrane during hypochlorite treatment at various pHs by Ca2+, one of the most abundant ions in surface water. In the presence of Ca2+, accelerated membrane deterioration was observed after chlorination and hydrolysis treatment. In addition, the greater membrane deterioration was observed under neutral and alkaline conditions than under acidic conditions, suggesting that Ca2+ might accelerate hydrolysis rather than chlorination. X-ray photoelectron spectroscopy analysis confirmed that the Cl atomic concentration in the active layer was increased by hypochlorite treatment; however, the presence of Ca2+ did not enhance chlorination of the membrane. In addition, measurement of the water contact angle of the active layer of membranes treated by hypochlorite in the presence of Ca2+ showed a significant increase of wettability. Together, these results provided the evidence that Ca2+ increased hydrolysis rather than chlorination. Solid-state 13C nuclear magnetic resonance spectra of the membranes after hypochlorite treatment showed a signal attributed to the -C*-NH2 of phenylenediamine structures in the active layer, the intensity of which was increased in the presence of Ca2+, indicating that the presence of Ca2+ in hypochlorite treatment resulted in increased hydrolysis of the polyamide structure. In addition, evolved gas analysis–mass spectrometry analysis provided further evidence supporting the production of ions with an m/z of 108, which corresponds to phenylenediamine. Together, the present results showed that deterioration of polyamide membrane by hypochlorite is increased in the presence of Ca2+ via acceleration of hydrolysis but not of chlorination. Based on these findings, we proposed a mechanism for the accelerated degradation of polyamide membrane by Ca2+.

Thraustochytrids such as Aurantiochytrium are heterotrophic microorganisms that are known to produce valuable polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In this study, Aurantiochytrium sp. strain L3W was used to remove dissolved organic carbon (DOC) and dissolved nitrogen (DN) from bean-boiling (BB) and miso-processing (MP) wastewater and to simultaneously produce PUFAs. Strain L3W removed 52% of the DOC and 37% of the DN from sterilized BB wastewater and produced biomass that contained 137 mg/g of fatty acids (FAs), including 96.2 mg/g of DHA. Growth of strain L3W in sterilized MP wastewater resulted in the production of biomass containing 147.6 mg/g of FAs, including 97.8 mg/g of DHA, and removal of 47% of the DOC and 55% of the DN from the wastewater. The biomass of strain L3W was digestible by the enzymes extracted from the stomachs of rainbow trout. These results confirmed the potential for use of strain L3W to remove DOC and DN from food processing wastewater and to produce PUFAs. This study also provided the first evidence that the raw biomass of Aurantiochytrium sp. can be used as a fish feed additive.

The availability of steelmaking slag, an industrial by-product, was examined as a component of a basal medium for the creation and regeneration of shallow habitats in coastal ecosystems. We investigated nutrient dynamics in sediments prepared with slag and dredged materials by conducting a core incubation experiment for 379 days. Silica sand was used as the reference material. Although slag caused alkalization of pore water, the pH in the surface layer recovered within a few days. The use of slag had limited influence on the dissolved inorganic nitrogen content, but pore water phosphate concentrations were considerably suppressed in slag-based media, especially when the pH was high. Nutrient diffusion fluxes from slag- and sand-based sediment cores were comparable to those in natural coastal environments. After 379 days, more than 90 % of the nutrients remained in the top 5 cm of the cores. Moreover, the sustained release of nutrients from basal media prepared with slag may play an important role in sustaining the productivity of macrophytobenthic ecosystems, including seagrass meadows. The mesocosm-scale experiment we proposed could evaluate long-term variations of nutrient dynamics in the artificial basal media. Because of wide variations in chemical properties among the different types of slag and dredged materials, approaches similar to this study may be essential before any large-scale application to marine environments.

Accelerating effect of coexisting metal ions on the polyamide (PA) reverse osmosis membrane degradation by hypochlorite was evaluated. The acceleration mechanism by the metal ions was also examined. The acceleration of membrane degradation by hypochlorite was caused by all monovalent and divalent metal ions used in this study: Na+, K+, Ca2 +, Mg2 +, and Ba2 +. Potency of divalent metal ions in PA membrane degradation was shown since divalent ions in much lower concentration than the monovalent metal ions caused membrane degradation. Na+ did not accelerate the degradation of the PA membrane in concentrations less than 100 mM while Mg2 + and Ca2 + showed no threshold limits. Accelerated membrane degradation in the presence of both monovalent and divalent metal ions seemed to be influenced by the threshold limit of the monovalent ion within the concentration range of each of the ions present. Membrane degradation below the threshold limit is dominated by the divalent ion while above the threshold limit the monovalent ion dominated the degradation. The degradation mechanism of PA membranes with or without metal ions is the same. However, in the presence of the divalent ion, it possibly acts as a catalyst in the amide hydrolysis, leading to accelerated membrane degradation.

Steel slag and its granulated agglomerates, and the granulated agglomerates of ash from thermal power stations are reserved for and partially used in the construction of sand-alternatives (SAs) in coastal restoration and creation projects. These SAs contain CaO and leach calcium and alkalis that may affect biological activity of microorganisms colonizing surrounding sediments. We evaluated the chemical behavior of four SAs, namely, decarburized slag (DCSlag), dephosphorized slag (DPSlag), granulated agglomerates of DCSlag (GSlag), and granulated agglomerates of coal fly ash (GAsh) in coastal sediment and the impact of these SAs on bacterial community structure in the sediment. The SAs eluted calcium with a decrease in the surface calcium content in the sediment. The elution from slag and slag-based SA (DCSlag, DPSlag, and GSlag) continued for 8 weeks, whereas the elution from GAsh continued for 24 weeks. The different elution periods are explained by the depth of eluted calcium found in the SAs; 0.19 ± 0.07, 0.04 ± 0.02, 0.27 ± 0.12 and 2.4 ± 0.97 mm in DCSlag, DPSlag, GSlag and GAsh, respectively. After 1 year, the DGGE (Denaturing Gradient Gel Electrophoresis) profiles were different among all the SAs except for GSlag and GAsh. The taxon richness of bacterial communities was estimated by the number of DNA bands found in the sediment mixed with the SAs, and it was lower than that in the natural sediment. Physicochemical properties of the SA's have been shown to affect the bacterial community structure. On the other hand, the communities recovered to almost the same level as that in the natural sediment after 1 year. The long-term effects of chemicals eluted from the SAs on bacterial community structure would be limited or negligible.

In the recent years, steelmaking slag is attracting attention as suitable materials for restoration of estuary ecosystems. However, there is concern about solidification when the material is applied to create seagrass beds. In this study, dephosphorization slag (DePS) was immersed into seawater for 10 months to examine the solidification processes and its mechanisms to control the strength of solidification. The hypothesis in this study is that solidification could be alleviated by adding dredged soil to the DePS. After 5 months of immersion, the shear strength of the DePS increased from 1.8 to 5.0 kN/m2; however, its shear strength decreased significantly to 3 kN/m2 after 10 months. Furthermore, after 5 months, reddish color was observed on the surface of the DePS, whereas the color of the surface of the DePS turned black at 7 months under reducing condition with covering by mud. To validate the results, we carried out an additional study, in which the DePS was immersed in seawater, and the solidified DePS was subsequently treated with Na2S; the increase and decrease of the shear stress of DePS were reproduced. The solidified DePS before and after exposure to reducing conditions was also analyzed using a combination of microanalysis with an electron probe and Mossbauer spectroscopy. These analyses showed that the solidification was caused by the formation of bridges that composed of iron oxyhydroxides, whereas the subsequent embrittlement of the solidified DePS was attributed to changing in the chemical species of iron.