Circulation of fibrous microplastic (microfiber) in sewage and sewage sludge treatment processes.

The fate of microplastics (MPs) in the sewage treatment process has been investigated worldwide, and novel results have been reported; few studies have also clarified the fate of MPs in the sewage sludge treatment process. Although most MPs in sewage are transferred to sludge, some flow back from the sludge treatment process to the sewage treatment process. Therefore, throughout the sewage treatment plant, the removal rate of MPs may increase via a countermeasure during the sludge treatment process. In this study, samples obtained from sewage and sewage sludge treatments were used to degrade organic matter with hydrogen peroxide. Water sample particles were trapped on Ni filters with 20-µm-sized pores, dried at room temperature and then the MPs were detected and identified by FTIR microscopy. Note that sludge samples were treated with hydrogen peroxide and separated by specific gravity using NaI solution. The concentration of MPs per unit volume was then calculated and the MPs load was estimated using flow rates of water and sludge. Subsequently, we clarified the fate of MPs with sizes of 20 µm or greater in a sewage treatment plant. When the MPs load in the influent sewage is 100%, 12% of the MPs were found to return to the sewage treatment process via the sidestream of the sludge treatment process. Per this observation, it was made evident that MPs are in fact circulating throughout the sewage and sludge treatment processes. MPs in the sidestream mainly consisted of the effluent from the sludge concentration process, and most MPs were thought to be fibrous polyethylene terephthalate (fibrous MPs, i.e. microfibers [MFs]). The results show that MFs circulate throughout the sewage and sludge treatment processes, and for effectively increasing the removal rate of MPs, the removal of MFs proves correspondingly effective during the sludge treatment process.

Reduction of ozone dosage by using ozone in ultrafine bubbles to reduce sludge volume.

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.

Benthic quality assessment using M-AMBI in the Seto Inland Sea, Japan.

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.

Spatial distribution of hydrogen sulfide and sulfur species in coastal marine sediments Hiroshima Bay, 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 <0.1 to 4 mg-S L-1. In this study, only hydrogen sulfide was observed in autumn and at two stations in summer. In contrast, some earlier studies reported in all seasons in Hiroshima Bay the presence of acid volatile sulfide, which is used as a proxy of sulfide content. The sulfur species in sediments were mainly identified as sulfate, thiosulfate, elemental sulfur, and pyrite. Thiosulfate was a minor component compared to the other sulfur species. The formation of pyrite and sulfur derived from hydrogen sulfide oxidation played an important role in the scavenging of hydrogen sulfide.

Elastic and dynamical structural properties of La and Mn-doped SrTiO3 studied by neutron scattering and their relation with thermal conductivities.

The electron-doped SrTiO3 exhibits good thermoelectric properties, which makes this material a promising candidate of an n-type oxide thermoelectric device. Recent studies indicated that only a few percent co-doping of La and Mn in SrTiO3 substantially reduces the thermal conductivity, thereby greatly improving the thermoelectric figure of merit at room temperature. Our time-of-flight neutron scattering studies revealed that by doping both La and Mn into SrTiO3, the inelastic scattering spectrum shows a momentum-independent increase in the low-energy spectral weight approximately below 10 meV. The increase in the low-energy spectral weight exhibits a clear correlation with thermal conductivity. The correlation is attributed to dynamical and local structural fluctuations caused by the Jahn-Teller instability in Mn3+ ions coupled with the incipient ferroelectric nature of SrTiO3, as the origin of the low thermal conductivity.

Effect of ozonated water on the surface roughness of dental stone casts.

Infection control of dental stone cast is an important issue. Ozone is effective for disinfection against microorganisms and inactivation of viruses. However, there is little information regarding the use of ozone. We prepared 4 types of gypsum specimens and 3 types of disinfectants (4-5 ppm Ozonated water [OZW], 2% glutaraldehyde [GL], and 1% sodium hypochlorite [SH]). Gypsum specimens were immersed in each disinfectant for 5 and 10 min, and surface roughness was then examined using laser scanning microscopy. Surface microstructure was investigated using scanning electron microscopy. Immersion of gypsum specimens in SH, GL, and OZW increased the surface roughness to a maximum of 1.04, 0.37, and 0.30 µm, respectively, based on the difference between the average values of surface roughness before and after the disinfection procedure. The effects of OZW and GL were comparable. OZW is useful as a candidate for relatively safe disinfection of material for dental stone casts.

Water Reclamation Using a Ceramic Nanofiltration Membrane and Surface Flushing with Ozonated Water.

A new membrane fouling control technique using ozonated water flushing was evaluated for direct nanofiltration (NF) of secondary wastewater effluent using a ceramic NF membrane. Experiments were conducted at a permeate flux of 44 L/m²h to evaluate the ozonated water flushing technique for fouling mitigation. Surface flushing with clean water did not effectively remove foulants from the NF membrane. In contrast, surface flushing with ozonated water (4 mg/L dissolved ozone) could effectively remove most foulants to restore the membrane permeability. This surface flushing technique using ozonated water was able to limit the progression of fouling to 35% in transmembrane pressure increase over five filtration cycles. Results from this study also heighten the need for further development of ceramic NF membrane to ensure adequate removal of pharmaceuticals and personal care products (PPCPs) for water recycling applications. The ceramic NF membrane used in this study showed approximately 40% TOC rejection, and the rejection of PPCPs was generally low and highly variable. It is expected that the fouling mitigation technique developed here is even more important for ceramic NF membranes with smaller pore size and thus better PPCP rejection.

Strongly correlated oxides for energy harvesting.

We review recent advances in strongly correlated oxides as thermoelectric materials in pursuit of energy harvesting. We discuss two topics: one is the enhancement of the ordinary thermoelectric properties by controlling orbital degrees of freedom and orbital fluctuation not only in bulk but also at the interface of correlated oxides. The other topic is the use of new phenomena driven by spin-orbit coupling (SOC) of materials. In 5d electron oxides, we show some SOC-related transport phenomena, which potentially contribute to energy harvesting. We outline the current status and a future perspective of oxides as thermoelectric materials.

Optimum reaction ratio of coal fly ash to blast furnace cement for effective removal of hydrogen sulfide.

Reducing hydrogen sulfide concentration in eutrophic marine sediments is crucial to maintaining healthy aquatic ecosystems. Managing fly ash, 750 million tons of which is generated annually throughout the world, is another serious environmental problem. In this study, we develop an approach that addresses both these issues by mixing coal fly ash from coal-fired power plants with blast furnace cement to remediate eutrophic sediments. The purpose of this study is to optimize the mixing ratio of coal fly ash and blast furnace cement to improve the rate of hydrogen sulfide removal based on scientific evidence obtained by removal experiments and XAFS, XRD, BET, and SEM images. In the case of 10 mg-S L-1 of hydrogen sulfide, the highest removal rate of hydrogen sulfide was observed for 87 wt% of coal fly ash due to decreased competition of adsorption between sulfide and hydroxyl ions. Whereas regarding 100 mg-S L-1, the hydrogen sulfide removal rate was the highest for 95 wt% of coal fly ash. However, for both concentrations, the removal rate obtained by 87 wt% and 95 wt% were statistically insignificant. The crushing strength of the mixture was over 1.2 N mm-2 when the coal fly ash mixing ratio was less than 95 wt%. Consequently, the mixing ratio of coal fly ash was optimized at 87 wt% in terms of achieving both high hydrogen sulfide removal rate and sufficient crushing strength.

Spatial and temporal distributions of Secchi depths and chlorophyll a concentrations in the Suo Nada of the Seto Inland Sea, Japan, exposed to anthropogenic nutrient loading.

Thirty years of monitoring data were used to elucidate the spatial and temporal distributions of Secchi depths in the Suo Nada (Suo Sea) and to evaluate how chlorophyll a concentration and reductions of nutrient loading from the watershed affected those distributions. Secchi depths throughout the Suo Nada were positively correlated with water depths. The spatial and temporal variations of Secchi depths could be explained by variations of phytoplankton biomass in areas where the water depth exceeded 20m, but in areas shallower than 10m, other factors affecting light attenuation beside phytoplankton, which include suspended particulate matter and chromophoric dissolved organic matter, obscured relationships between phytoplankton biomass and Secchi depths. Phosphorus limited phytoplankton biomass in the Suo Nada. The main source of allochthonous phosphorus from the 1980s to the 1990s was the watershed. Because of significant reductions of nutrient loading from the watershed, the Pacific Ocean will most likely be the principal source of allochthonous phosphorus after around 2000, except in areas shallower than 10m.

Rapid novel test for the determination of biofouling potential on reverse osmosis membranes.

A novel method was proposed to determine biofouling potential by direct analysis of a reverse osmosis (RO) membrane through fluorescence intensity analysis of biofilm formed on the membrane surface, thereby incorporating fouling tendencies of both feedwater and membrane. Evaluation of the biofouling potential on the RO membrane was done by accelerated biofilm formation through soaking of membranes in high biofouling potential waters obtained by adding microorganisms and glucose in test waters. The biofilm formed on the soaked membrane was quantified by fluorescence intensity microplate analysis. The soaking method's capability in detecting biofilm formation was confirmed when percentage coverage obtained through fluorescence microscopy and intensity values exhibited a linear correlation (R(2) = 0.96). Continuous cross-flow experiments confirmed the ability and reliability of the soaking method in giving biofouling potential on RO membranes when a good correlation (R(2) = 0.87) between intensity values of biofilms formed on the membrane during soaking and filtration conditions was obtained. Applicability of the test developed was shown when three commercially available polyamide (PA) RO membranes were assessed for biofouling potential. This new method can also be applied for the determination of biofouling potential in water with more than 3.6 mg L(-1) easily degradable organic carbon.

Evaluation of steelmaking slag as basal media for coastal primary producers.

The use of granular steelmaking slag as a substitute for natural sand in the construction of tidal flats was investigated. Using an intertidal flat simulator, we evaluated dephosphorization slag mixed with 8% by dry weight of dredged sediment (DPS+DS) as a basal medium for the growth of benthic macro- and microalgae in comparison with silica sand mixed with 8% dredged sediment (SS+DS). Species compositions of macro- and microalgae were distinctly different between DPS+DS and SS+DS. The mean dry weight of macroalgae on DPS+DS was three orders of magnitude higher than that on SS+DS. Sediment shear strength and pH were higher in DPS+DS than in SS+DS or in the sediment of natural tidal flats. These results suggest that DPS contributes to changing the sediment environment, thereby changing the algal composition compared to the composition on natural tidal flats.

Solvent-free synthesis and application of nano-Fe/Ca/CaO/[PO4] composite for dual separation and immobilization of stable and radioactive cesium in contaminated soils.

This study assessed the synthesis and application of nano-Fe/Ca/CaO-based composite material for use as a separation and immobilizing treatment of dry soil contaminated by stable ((133)Cs) and radioactive cesium species ((134)Cs and (137)Cs). After grinding with nano-Fe/CaO, nano-Fe/Ca/CaO, and nano-Fe/Ca/CaO/[PO4], approximately 31, 25, and 22 wt% of magnetic fraction soil was separated. Their resultant (133)Cs immobilization values were about 78, 81, and 100%, respectively. When real radioactive cesium contaminated soil obtained from Fukushima was treated with nano-Fe/Ca/CaO/[PO4], approximately 27.3 wt% of magnetic and 72.75% of non-magnetic soil fractions were separated. The highest amount of entrapped (134)Cs and (137)Cs was found in the lowest weight of the magnetically separated soil fraction (i.e., 80% in 27.3% of treated soil). Results show that (134)Cs and (137)Cs either in the magnetic or non-magnetic soil fractions was 100% immobilized. The morphology and mineral phases of the nano-Fe/Ca/CaO/[PO4] treated soil were characterized using SEM-EDS, EPMA, and XRD analysis. The EPMA and XRD patterns indicate that the main fraction of enclosed/bound materials on treated soil included Ca/PO4 associated crystalline complexes. These results suggest that simple grinding treatment with nano-Fe/Ca/CaO/[PO4] under dry conditions might be an extremely efficient separation and immobilization method for radioactive cesium contaminated soil.

Production of mono- and di-carboxylated polyethylene glycols as a factor obstacle to the successful ozonation-assisted biodegradation of ethoxylated compounds.

Ozonation is believed to improve the biodegradability of organic compounds. In the present study, degradation of nonylphenol ethoxylates (NPEOs) was monitored in hybrid treatment systems consisting of ozonation and microbial degradation processes. We found that ozonation of NPEOs decreased, rather than increased, the biodegradability under certain conditions. The timing of ozonation was a definitive factor in determining whether ozonation increased or decreased the biodegradation rates of NPEOs. Initial ozonation of NPEOs prior to biodegradation reduced the rate of dissolved organic carbon (DOC) removal during the subsequent 14 d of biodegradation, whereas intermediate ozonation at the 9th day of biodegradation improved subsequent DOC removal during 14 d of NPEO biodegradation. Furthermore, reduction of DOC removal was also observed, when initial ozonation prior to biodegradation was subjected to cetyl alcohol ethoxylates. The production of less biodegradable intermediates, such as mono- and dicarboxylated polyethylene glycols (MCPEGs and DCPEGs), was responsible for the negative effect of ozonation on biodegradability of NPEOs. DCPEGs and MCPEGs were produced by biodegradation of polyethylene glycols (PEGs) that were ozonolysis products of the NPEOs, and the biodegradability of DCPEGs and MCPEGs was less than that of the precursor PEGs. The results indicate that, if the target chemicals contain ethoxy chains, production of PEGs may be one of the important factors when ozonation is considered.

Variations in macrobenthic community structures in relation to environmental variables in the Seto Inland Sea, Japan.

A data set of 425 sites investigated by the Ministry of the Environment in 2001-2005 was used to evaluate the current sediment situation and its effect on macrobenthic community structure in the Seto Inland Sea, Japan. Cluster analysis and principle component analysis of sediments using physico-chemical parameters revealed that total organic carbon, mud, sulfide contents, and oxidation-reduction potential were important parameters influencing macrobenthic population size and biodiversity. A total organic carbon of 1 mg g(-1) interval was highly negatively correlated with two biodiversity indices in the range of 1-20 mg g(-1). Overall, 42% of total sites were organically enriched with much lower macrobenthic population sizes and biodiversity, while 26% were characterized by sandy sediment with a high population size and high proportion of Arthropoda. Nemertea sp., Glycera sp., Notomastus sp. and Ophiophragmus japonicus were common macrobenthos, while Theora fragilis and Ptychoderidae were typical macrobenthos in organically enriched sediments.

Dynamic immobilization of simulated radionuclide 133Cs in soil by thermal treatment/vitrification with nanometallic Ca/CaO composites.

Although direct radiation induced health impacts were considered benign, soil contamination with (137)Cs, due to its long-term radiological impact (30 years half-life) and its high biological availability is of a major concern in Japan in the aftermath of the Fukushima nuclear power plant disaster. Therefore (137)Cs reduction and immobilization in contaminated soil are recognized as important problems to be solved using suitable and effective technologies. One such thermal treatment/vitrification with nanometallic Ca/CaO amendments is a promising treatment for the ultimate immobilization of simulated radionuclide (133)Cs in soil, showing low leachability and zero evaporation. Immobilization efficiencies were 88%, 95% and 96% when the (133)Cs soil was treated at 1200 °C with activated carbon, fly ash and nanometallic Ca/CaO additives. In addition, the combination of nanometallic Ca/CaO and fly ash (1:1) enhanced the immobilization efficiency to 99%, while no evaporation of (133)Cs was observed. At lower temperatures (800 °C) the leachable fraction of Cs was only 6% (94% immobilization). Through the SEM-EDS analysis, decrease in the amount of Cs mass percent detectable on soil particle surface was observed after soil vitrified with nCa/CaO + FA. The (133)Cs soil was subjected to vitrified with nCa/CaO + FA peaks related to Ca, crystalline phases (CaCO3/Ca(OH)2), wollastonite, pollucite and hematite appeared in addition to quartz, kaolinite and bentonite, which probably indicates that the main fraction of enclosed/bound materials includes Ca-associated complexes. Thus, the thermal treatment with the addition of nanometallic Ca/CaO and fly ash may be considered potentially applicable for the remediation of radioactive Cs contaminated soil at zero evaporation, relatively at low temperature.

Preferential removal and immobilization of stable and radioactive cesium in contaminated fly ash with nanometallic Ca/CaO methanol suspension.

In this work, the capability of nanometallic Ca/CaO methanol suspension in removing and/or immobilizing stable ((133)Cs) and radioactive cesium species ((134)Cs and (137)Cs) in contaminated fly ash was investigated. After a first methanol and second water washing yielded only 45% of (133)Cs removal. While, after a first methanol washing, the second solvent with nanometallic Ca/CaO methanol suspension yielded simultaneous enhanced removal and immobilization about 99% of (133)Cs. SEM-EDS analysis revealed that the mass percent of detectable (133)Cs on the fly ash surface recorded a 100% decrease. When real radioactive cesium contaminated fly ash (containing an initial 14,040Bqkg(-1)(134)Cs and (137)Cs cumulated concentration) obtained from burning wastes from Fukushima were reduced to 3583Bqkg(-1) after treatment with nanometallic Ca/CaO methanol suspension. Elution test conducted on the treated fly ash gave 100BqL(-1) total (134)Cs and (137)Cs concentrations in eluted solution. Furthermore, both ash content and eluted solution concentrations of (134)Cs and (137)Cs were much lower than the Japanese Ministry of the Environment regulatory limit of 8000Bqkg(-1) and 150BqL(-1) respectively. The results of this study suggest that the nanometallic Ca/CaO methanol suspension is a highly potential amendment for the remediation of radioactive cesium-contaminated fly ash.

Chemical behavior of sand alternatives in the marine environment.

Steel slag and granulated agglomerates from the steelmaking process, clinker ash and granulated agglomerates from thermal power stations, and molten slag from municipal solid waste incineration plants are some of the promising alternatives to marine sand for restoration of coastal marine habitats. In this study, the characteristics of elution of Ca from the six sand alternatives during aging in the marine environment was determined. The maximum calcium elution potentials of decarburized slag, dephosphorized slag, granulated slag, clinker ash, granulated ash, and molten slag were 204, 75, 26, 6, 19, and 5mgg(-1), respectively. However, the elution of Ca from decarburized and dephosphorized slags was limited to depths of about 140 and 300µm from the surface of the slag, whereas there was no limitation in calcium elution in 3mm from granulated agglomerates and ash. The maximum amount of calcium eluted into seawater during 500d was estimated to be almost the same for the four alternatives if the particle diameters were about 4.75mm because of the shallow maximum calcium elution depth of the decarburized and dephosphorized slag, even though their maximum elution potentials were 3-10 times those of granulated slag and granulated ash.

Removal of coagulant aluminum from water treatment residuals by acid.

Sediment sludge during coagulation and sedimentation in drinking water treatment is called "water treatment residuals (WTR)". Polyaluminum chloride (PAC) is mainly used as a coagulant in Japan. The recycling of WTR has been desired; one method for its reuse is as plowed soil. However, WTR reuse in this way is inhibited by the aluminum from the added PAC, because of its high adsorption capacity for phosphate and other fertilizer components. The removal of such aluminum from WTR would therefore be advantageous for its reuse as plowed soil; this research clarified the effect of acid washing on aluminum removal from WTR and on plant growth in the treated soil. The percentage of aluminum removal from raw WTR by sulphuric acid solution was around 90% at pH 3, the percentage decreasing to 40% in the case of a sun-dried sample. The maximum phosphate adsorption capacity was decreased and the available phosphorus was increased by acid washing, with 90% of aluminum removal. The enhancement of Japanese mustard spinach growth and the increased in plant uptake of phosphates following acid washing were observed.

Simultaneous decontamination of cross-polluted soils with heavy metals and PCBs using a nano-metallic Ca/CaO dispersion mixture.

In the present work, we investigated the use of nano-metallic calcium (Ca) and calcium oxide (CaO) dispersion mixture for the simultaneous remediation of contaminated soils with both heavy metals (As, Cd, Cr, and Pb) and polychlorinated biphenyls (PCBs). Regardless of soil moisture content, nano-metallic Ca/CaO dispersion mixture achieved about 95-99% of heavy metal immobilization by a simple grinding process. During the same treatment, reasonable PCB hydrodechlorination efficiencies were obtained (up to 97%), though higher hydrodechlorination efficiency by preliminary drying of soil was observed.