混凝-微气泡气浮法处理含藻废水的研究

采用日本菊池环保株式会社生产的新型TCRI-17微气泡气浮装置混凝气浮处理北京某富营养化景观水体的含藻废水，其结果表明，当混凝剂用量分别为PAC 40 mg/L和PAM 2 mg/L，混凝2 min, 气浮2 min时，SS和COD去除率分别达到98.4%和85.7%。与混凝沉降相比，可减少PAC用量1/3，且节省处理时间。由于微小气泡停留时间长，气浮效率高，且有增加水中溶解氧的作用，可促进水体的净化，具有较强的技术优势。     

Dietary contribution of the microphytobenthos to infaunal deposit feeders in an estuarine mudflat in Japan

The food sources of benthic deposit feeders were investigated at three stations in an estuarine mudflat (Idoura Lagoon, Sendai Bay, Japan) during July and August 2005, using δ¹³C and δ¹⁵N ratios. Sediment at the stations was characterized by low chlorophyll (chl) a content (0–1 cm depth, <4 μg cm⁻²) and the dominance of riverine–terrestrial materials (RTM) in the sediment organic matter (SOM) pool. Surface-deposit feeders (Macoma contabulata, Macrophthalmus japonicus, and Cyathura muromiensis) exhibited much higher δ¹³C values (−18.4 to −12.4‰) than did the SOM pool (<−25‰). A δ¹³C-based isotopic mixing model estimated that benthic diatoms comprised 45–100% (on average) of their assimilated diet, whereas RTM comprised a lesser fraction (29% maximum). The major diet of the deep-deposit feeding polychaetes Notomastus sp. and Heteromastus sp. was benthic diatoms and/or marine particulate organic matter (POM), with little RTM assimilated (39% maximum). The consumers appeared to lack specific digestive enzymes and to use detritus-derived carbon only after its transfer to the microbial biomass. The isotopic mixing model also showed that the dietary contribution of RTM increased slightly (15% maximum) in the vicinity of freshwater input, suggesting that spatial changes in RTM supply affect the dietary composition of deposit feeders. These results clearly demonstrate that deposit feeders selectively ingest and/or assimilate the more nutritious microalgal fractions in the SOM pool. Such adaptations may allow enhanced energy gain in estuarine mudflats that are rich in vascular plant detritus with low nutritive value.     

Relationship between egg productivity and RNA/DNA ratio in Paracalanus sp. in the frontal waters of the Kurshio

The relationship between RNA/DNA ratio and egg productivity of adult Paracalanus sp. females was investigated in the frontal area of the Kuroshio current off Kinkazan Island and Boso Peninsula, Pacific coast of Japan in 1989 and 1990, respectively. In the Kuroshio front off Kinkazan Island, the RNA/DNA ratio of females in the surface layer ranged from 3.87 to 6.92 along a transect 8 miles across the front. In the Kuroshio front off Boso Peninsula, the RNA/DNA ratio varied between 5.15 and 7.27 for 32 h in the course of tracking a drifter launched in the front. The RNA/DNA ratio of the females in both frontal areas tended to increase together with ambient chlorophyll-a concentration, and the relationship fitted to Ivlev's formula (P<0.05). The number of eggs laid in filtered sea-water during 24 h (egg productivity) was also positively correlated with the ambient chlorophyll a concentration (P<0.05). There was a positive correlation (P<0.001) between RNA/DNA ratio and egg productivity, and RNA/DNA ratios accounted for about 70% of variation of the egg productivity. Judging from RNA/DNA ratios and female egg productivity in both frontal areas, relatively large physiological or reproductive changes could possibly occur in small temporal and spatial scales in association with change in phytoplankton abundance.     

Thymic involution produced by diesel exhaust particles and their constituents in mice

Epidemiological studies suggest that diesel exhaust particles (DEP) contribute to an increase in allergic diseases. To assess the effects of DEP on the central immune system, mice were exposed to DEP by intraperitoneal (IP) administration. Exposure to DEP resulted in severe thymic involution accompanied by a reduction in the number of thymocytes, especially in cortical CD4⁺CD8⁺ double positive and double negative subsets. Core carbon particles associated with a mixture of chemical compounds in DEP did not appear to be responsible for the DEP-induced thymic involution because carbon graphite does not affect neither the number nor the CD4/CD8 profile of thymocytes. Extraction of DEP by ether, acidic and basic solvents showed that several independent fractions including the neutral ether fraction, which contains polycyclic aromatic hydrocarbons (PAH), induced thymic involution. Among major PAH components of DEP, benzo[b]fluoranthene (BbF), benzo[a]pyrene (BaP), and benzo[k]fluoranthene (BkF) were very potent inducers of thymic involution at an ED50 of less than 100?ng per mouse body. Nonetheless, DEP treatment of mice with targeted disruption of genes encoding the aryl hydrocarbon receptor (AHR), AHR nuclear translocator (ARNT), or microsomal epoxide hydolase (mEH) indicated that DEP produced thymic involution even in the absence of PAH-induced AHR/ARNT signal transduction or mEH-mediated PAH catabolism. On the other hand, BaP-mediated thymic involution was completely dependent on AHR, partially dependent on ARNT in T cells, and independent of mEH. These results indicate that DEP-induced thymic involution is mediated both by PAH-AHR/ARNT-dependent and -independent mechanisms.     

Indirect identification of an unstable intermediate in γ-HCH degradation by Pseudomonas paucimobilis UT26

While a postulated intermediate, 1,3,4,5-tetrachlorocyclohexa-1,4-diene(1,4-TCDN), is one of the key-compounds in γ-hexachlorocyclohexane(γ-HCH) degradation by Pseudomonas paucimobilis UT26(UT26), it has neither been isolated nor identified yet. Thus, an indirect identification was attempted to demonstrate its existence by a chemical oxidation of the microbial degradation products in situ.

1,2,4,5-Tetrachlorobenzene(1,2,4,5-TeCB) was newly produced by the chemical oxidation with hydrogen peroxide under iron(II) of W medium containing degradation products in situ of γ-1,3,4,5,6-pentachlorocyclohexene(γ-PCCH) by Escherichia coli MV1184(E. coli) which possesses the dehydrochlorinating activity of UT26. The chemical oxidation required the preceding enzymatic reactions to γ-PCCH by E. coli for the production of 1,2,4,5-TeCB. In facts, 1,2,4,5-TeCB was not produced from γ-PCCH by either of the chemical or enzymatic reaction alone.

Considering these results and the fact that hydrogen peroxide is known to dehydrogenate chemical compounds, it was concluded that 1,2,4,5-TeCB was produced directly from the unstable intermediate, 1,4-TCDN, on yielded from γ-PCCH by an enzymatic dehydrochlorination.     

Eco-hydrodynamic Modelling of Chini Lake: Model Description

In this study, we coupled a three-dimensional hydrodynamic model with an ecosystem model and applied it to the shallow complex floodplain wetland of Chini Lake in Malaysia. Our objective was to provide a better understanding of the lake’s ecosystem dynamics under different forcing mechanisms. Simulations and validation were performed over a dry month period. Wind speed ranged between 0 and 7.7 m s^?1, whilst air temperature ranged between 22.0 and 35.6 °C. Advective transport driven by wind stress was the dominant physical force that shaped the water quality variations during the dry season. Convective circulation intermittently influenced the circulation during calm conditions. Nutrient concentration and stratification of dissolved oxygen (DO) varied between the lakes. Wind events saw patterns of the surface DO concentrations move spatially in the direction of the wind. The ecosystem model simulation suggested that the water quality in Chini Lake was influenced by macrophyte production, although the dissolved and particulate organic carbon accounted for the major fraction of organic matter content in the lake.     

Photodecomposition of humic acid and natural organic matter in swamp water using a TiO2-coated ceramic foam filter: Potential for the formation of disinfection byproducts

This paper reports on the photodecomposition of aqueous humic acid (HA) by a TiO₂-coated ceramic foam filter (TCF) reactor and on the potential for the formation of disinfection byproducts (DBPs) upon chlorination of the photocatalytically treated solutions. This photocatalytic reactor can also be applied to the removal of natural organic matter (NOM) in swamp waters. The proposed photocatalytic reaction system was operated as per standardized methodologies. First, the ability of the TCF to decompose HA (a representative compound of NOM) was evaluated from the changes in the total organic carbon (TOC) and UV₂₅₄ with the reaction time. Remarkably, TOC removal and UV₂₅₄ values ranging from 44% to 61% and from 60% to 83%, respectively, were achieved. The potential for the formation of DBPs (total trihalomethane and total haloacetic acid) by chlorination of the phototreated solution was strongly dependent on the TOC removal and UV₂₅₄ values in the solution. The degree of photodecomposition of NOMs in the swamp water samples and the DBP formation potential showed similar trends as in the case of the standard solutions containing HA. The method used in this study could be effectively used to evaluate the efficiency of TCF for reducing HA and NOM, while suppressing the formation of DBP products.     

Vitrification Process for Treatment of Sewage Sludge and Incineration Ash

ABSTRACT

Vitrification processes, in which the operating temperature is higher than the melting point of the silica compounds contained in sewage sludge that turns into slag, are studied in this paper. The dried sludge and the incineration ash are injected into a furnace with auxiliary fuel and flux. The flux is the material used to control basicity of the ash content. Crushed limestone is used as the flux in this test. Almost all ashes in the sludge are vitrificated into slag. The flow of molten slag from the tap is smooth. After the slag is treated, it can be used as wall tile, interlocking tile, insulating material, and slag wool. This technology conforms to resource recycling.     

Steel slag quality control for road construction aggregates and its environmental impact: case study of Vietnamese steel industry—leaching of heavy metals from steel-making slag

Environmental Science and Pollution Research - Steel slag is an industrial by product of steel manufacturing processes and has been widely utilized within civil and construction materials for road...