石膏基复合胶凝材料化学激发作用研究

研究了碱型激发剂(Ca(OH)_2)和非碱型激发剂(Ca Cl_2)对石膏基复合胶凝材料砂浆蒸养强度发展的影响,对比了碱性和非碱型激发剂的作用效果,并进行了机理分析。结果表明,碱性激发剂Ca(OH)_2作用效果不佳,掺加Ca(OH)_2的试件28d抗压和抗折强度倒缩严重;非碱性激发剂Ca Cl_2作用效果显著,砂浆早期强度增长明显,龄期28d的强度与未掺者相当或略有增长。因此,在实际应用中,相对于碱性激发剂,非碱性激发剂Ca Cl_2更适用于石膏基复合胶凝材料。     

蒸汽养护对赤泥基碱激发胶凝材料性能及微观结构的影响

以烧结法赤泥为原料、水玻璃为激发剂制备碱激发胶凝材料,并对蒸汽养护(60℃)对赤泥基碱激发胶凝材料性能及产物、微观形貌的影响进行了研究。结果表明,蒸汽养护条件下,赤泥基碱激发胶凝材料的主要反应产物为C-S-H凝胶;蒸汽养护可促进赤泥基碱激发胶凝材料的水化反应,从而使基体结构更为致密,强度显著提高;经60℃蒸汽养护48 h的赤泥基碱激发砂浆,其3、28 d抗压强度可分别达到34.8、65.7 MPa。     

赤泥基碱激发胶凝材料的制备及机理研究

系统总结了国内外对赤泥基胶凝材料的研究成果,分析了赤泥种类、掺合料和激发活化措施对赤泥基碱激发胶凝材料力学性能的影响。研究表明烧结法赤泥活性较高,受热活化和水玻璃激发效果较为显著,抗压强度普遍高于25 MPa;拜尔法赤泥较则难以被激发,而目前90%的铝业公司使用拜耳法生产Al2O3。结合已有研究,利用工业固体废弃物脱硫石油焦渣激发拜耳法赤泥,确定了赤泥基激发胶凝材料的基本配合比,经标准养护28 d抗压强度达到25.6 MPa。利用XRD进行的微观分析发现,赤泥中的铝硅酸盐矿物可以在碱性激发剂的作用下发生反应,经过溶解-聚合反应生成聚合物凝胶是赤泥受激发产生强度的主要原因。研究将赤泥用于制备胶凝材料,可以实现赤泥大规模、高附加值的资源化再生利用。     

氢氧化钙对碱矿渣材料硫酸盐结晶破坏的抑制机理

通过外观变化和质量损失的发展研究了Ca(OH)₂对碱矿渣材料硫酸盐结晶破坏的抑制效率，结合抗压强度、毛细孔隙率、X射线衍射、综合热分析和扫描电子显微镜，揭示了Ca(OH)₂对碱矿渣材料硫酸盐结晶破坏的抑制机理.结果表明：质量分数为5%的Ca(OH)₂使碱矿渣水泥石的微结构变得致密，降低其毛细孔隙率和毛细吸水系数，显著减小碱矿渣材料的硫酸盐结晶破坏；质量分数为10%的Ca(OH)₂使碱矿渣水泥石内部的微裂纹增多，毛细孔隙率和毛细吸水系数增大，对抑制硫酸盐结晶破坏不利.     

油页岩渣-矿渣碱胶凝材料的研究

研究了利用油页岩渣-矿渣制备碱胶凝材料的方法,讨论了油页岩渣-矿渣碱胶凝材料的强度、强度增进率和凝结时间及其主要影响因素,同时测试了油页岩渣的组成结构和活性指标,并对油页岩渣-矿渣碱胶凝材料的硬化产物与作用机理进行了分析.结果表明:油页岩渣-矿渣碱胶凝材料的硬化产物主要为无定形硅铝酸盐物质形成的网络结构,成分以Si,O为主,Ca,Al,Na次之;利用油页岩渣与矿渣复合可合理调整碱胶凝材料组成中Ca与(Si+Al)的比值(摩尔比),使之具有优良的抗压强度且减少碱激发剂用量.     

赤泥制备碱激发胶凝材料的性能

分别以拜耳法赤泥、烧结法赤泥为原料,进行碱激发胶凝材料的制备研究,并对其制备碱激发胶凝材料的可行性进行了评价。研究结果表明,拜耳法赤泥的胶凝活性极低,不适宜用作碱激发胶凝材料的制备原料;烧结法赤泥因含有具有一定胶凝活性的β-硅酸二钙,因此可用作碱激发胶凝材料的制备原料。以烧结法赤泥和矿渣组成二元复合体系,以模数2.40的液体水玻璃为激发剂制备碱激发胶凝材料,在矿渣掺量30%、赤泥掺量70%的条件下,激发剂的最佳掺量为5.0%。所制备碱激发砂浆试样的3d、28d抗压强度可分别达到35.0 MPa、65.0 MPa以上。     

碱赤泥矿渣胶凝材料性能的研究

本文用水玻璃激发赤泥和矿渣而得到了高强的无机胶凝材料———碱赤泥矿渣胶凝材料。研究了赤泥掺量、水玻璃品种和掺量以及磷酸钠的掺量对这种胶凝材料强度的影响。通过正交试验确定了其最佳的质量配比。使用XRD分析了碱赤泥矿渣胶凝材料水化过程中的水化产物     

有机羧酸胺阻锈剂在3.5%NaCl饱和Ca(OH)2溶液中对碳钢的阻锈作用

采用干湿循环试验,线性极化(LPR),电化学阻抗谱(EIS)以及扫描电子显微镜(SEM)方法研究有机羧酸胺(ZX)与Ca(NO₂)₂在3.5%NaCl饱和Ca(OH)₂溶液中对碳钢的阻锈效果。试验结果表明,在溶液中加入阻锈剂0.2%~1.2%时,有机羧酸胺与Ca(NO₂)₂均有抑制碳钢锈蚀的作用,但在干湿循环试验中Ca(NO₂)₂的阻锈效果与其含量不成比例关系,而ZX与其含量有良好的相关性。此外,在电化学试验中,随着ZX与Ca(NO₂)₂含量的增加,阻锈效果越明显,且在3.5%NaCl饱和Ca(OH)₂溶液中ZX的阻锈效果优于Ca(NO₂)₂。     

激发剂对赤泥-矿渣地质聚合物材料的影响及产物研究

本文利用水玻璃为激发剂,烧结法赤泥和矿渣为原材料制备碱激发胶凝材料,研究水玻璃模数和掺量对赤泥-矿渣地质聚合物的影响。采用热分析(TG)、衍射分析(XRD)和扫描电镜(SEM)分别表征和分析反应产物的物相组成与微观形貌。实验结果表明:地质聚合物随着水玻璃模数增加,胶砂早期强度增加;水玻璃掺量增加地质聚合物强度增加,水玻璃适宜掺量为5.5%;赤泥-矿渣地质聚合物为非晶态无定型物质,反应产物之间相互连接成三维网状结构。     

海上风电超低水胶比水泥基灌浆料的水化过程研究

基于水泥-硅灰-矿粉三元胶凝体系,制备了海上风电超低水胶比水泥基灌浆料,通过XRD和SEM分析了灌浆料不同龄期的水化产物与微观结构,并研究了其水化过程。结果表明：硅灰和矿粉共同促进了水泥的水化反应,且随着龄期的增加,促进作用增强;90 d时,在硅灰和矿粉的协同效应下,Ca(OH)₂晶体大幅度减少,从而减少了Ca(OH)₂自身晶体取向性对灌浆料造成的缺陷;水化反应生成大量低钙型C-S-H凝胶,形成排列紧密的层状构造,灌浆料内部结构致密,使其具有较高的抗压强度和耐久性能。     

Aquatic microbial activity and macrofaunal profiles of an Oklahoma stream

A toxicity assessment was conducted on Skeleton Creek, near Enid, Okla. This creek received effluents from an oil refinery, municipal waste treatment facility, and a fertilizer processing plant. Microbial activity assays, which focused on sediments, included: dehydrogenase, alkaline phosphatase, glucosidase, amylase and protease activity. Microbial electron transport system activity was also measured in overlying waters and sediments. Results were compared to a study conducted at the same time by the U.S. Environmental Protection Agency (EPA) which measured in-stream fish, plankton and benthic communities. In addition, EPA conducted 7-day Ceriodaphnia reproductive toxicity tests and 7-day larval fathead minnow growth tests. Effects occurred below the 3 discharges and similar response patterns were noted between surrogate microbial assays and stream communities. These results highlight the importance and feasibility of multi-tiered test schemes in aquatic toxicity assessments.     

Toxicological and chemical characterization of organic micropollutants in river po waters (Italy)

River Po waters were collected at the end of the drainage basin, extracted by means of XAD-2 resins and tested for toxicity on aquatic organisms (Daphnia magna and Selenastrum capricornutum) and for mutagenicity with a modified Ames test. The extracts were analyzed by HRGC/FID and selective detectors for the determination of the most common classes of toxic compounds. The relationships between toxicological responses and analytical results are discussed.     

The use of Bacillus thuringiensis var. israelensis to control the nuisance fly Sylvicola fenestralis (Anisopodidae) in sewage filter beds

The effectiveness of using the microbial insecticide Bacillus thuringiensis var. israelensis (Bti) to control the nuisance fly Sylvicola fenestralis at Rossendale Sewage Works, Lancashire, was investigated. Following a provisional trial in 1987, the whole Works (28 filter beds) was treated with a two-stage application of Bti in 1988; the first application in late April was separated from the second in late May by about half the length of the Sylvicola life-cycle. The Bti treatment was timed to reduce fly nuisance in June, the month when most complaints (71%) had been received. For each application, 0.161. of the Bti preparation, containing nearly 10¹⁰ spores·cm⁻³, was applied per square metre of bed surface. An 80 and 98% kill of Sylvicola larvae was recorded following the first and second applications respectively. The lower kill achieved by the first application was believed to be due to insufficient mixing of the Bti with the settled sewage prior to dosing. Nuisance caused by the flies was considerably reduced; there were no complaints from the public during June, although a few were received in late July, early August. Sewage purification efficiency was not affected by Bti treatment. The maximum concentration of Bti spores in the Works' effluent was 7 × 10⁴ spores·cm⁻³. This concentration did not appear to affect the already impoverished macro-invertebrate fauna of the receiving river.     

Use of microbial and toxicant screening tests for priority site selection of degraded areas in water bodies

In this study, a new approach has been taken to evaluate Saint John River water and sediment conditions. A battery of biochemical, microbiological and bioassay tests were used to identify degraded or degrading sediments and waters. Data were obtained from waters and sediments at 38 sites within the Saint John River Basin. The data suggested that the following four sites had the highest priority concern: Little River No. 34, Grand Bay, Saint John River near Boars Head No. 33, Madawaska River below mill No. 7 and St Francois-de-Madawaska, mill stream No. 2. The data also indicated that microbial population, biochemical or bioassay tests performed independently do not provide realistic evaluations of priority concern areas and that the “battery of tests” approach is necessary to provide additional information.     

Life history responses of Daphnia magna feeding on toxic Microcystis aeruginosa alone and mixed with a mixotrophic Poterioochromonas species

The toxic effects of a mixotrophic golden alga (Poterioochromonas sp. strain ZX1) and a cyanobacterium Microcystis aeruginosa grazed by Poterioochromonas to a cladoceran were investigated through life history experiments using Daphnia magna. Poterioochromonas cultured in two ways (fed M. aeruginosa in an inorganic medium or grown in an organic medium) both induced starvation-like effects on D. magna, indicating that Poterioochromonas is neither acutely toxic nor a good food for D. magna. Despite a microcystin-LR content of 10⁻⁸ μg cell⁻¹ in M. aeruginosa, no toxins were accumulated in Poterioochromonas fed the cyanobacterium. The toxic effect of M. aeruginosa to D. magna was significantly reduced in the presence of Poterioochromonas, which may be performed in two ways: decrease M. aeruginosa cells ingestion of D. magna by grazing on M. aeruginosa; and decrease the toxicity of the medium by degrading the toxins released by M. aeruginosa. This study provides new information on the interactions between a cyanobacterium and its grazer under laboratory conditions and may increase our understanding of the ecological significance of such interactions in the aquatic food webs.     

Effect of pathogen concentrations on removal of Cryptosporidium and Giardia by conventional drinking water treatment

The presence of waterborne enteric pathogens in municipal water supplies contributes risk to public health. To evaluate the removal of these pathogens in drinking water treatment processes, previous researchers have spiked raw waters with up to 10(6) pathogens/L in order to reliably detect the pathogens in treated water. These spike doses are 6-8 orders of magnitude higher than pathogen concentrations routinely observed in practice. In the present study, experiments were conducted with different sampling methods (i.e., grab versus continuous sampling) and initial pathogen concentrations ranging from 10(1) to 10(6) pathogens/L. Results showed that Cryptosporidium oocyst and Giardia cyst removal across conventional treatment were dependent on initial pathogen concentrations, with lower pathogen removals observed when lower initial pathogen spike doses were used. In addition, higher raw water turbidity appeared to result in higher log removal for both Cryptosporidium oocysts and Giardia cysts.     

Cryptosporidium and Giardia detection in water bodies of Galicia, Spain

The objective of this study was to determine the mean concentration (per litre) of Cryptosporidium oocysts and Giardia cysts in recreational river areas (n = 28), drinking water treatments plants (DWTPs; n = 52) and wastewater treatment plants (WWTPs; n = 50) in Galicia (NW Spain). Water samples from rivers and from the influent (50–100 l) and the treated effluent (100 l) of the water plants were filtered using Filta-Max filters (IDEXX Laboratories, Inc., Westbrook, ME, USA). A total of 232 samples were processed and the (oo)cysts were concentrated, clarified by IMS and then detected by IFAT. The viability was determined by applying fluorogenic vital dye (PI).In the recreational areas, infective forms of Cryptosporidium and Giardia were detected in 16 (57.1%; 1–60 oocysts per litre) and 17 (60.7%; 1–160 cysts per litre) samples, respectively. In the water flowing into the water treatment plants, oocysts were detected in 21 DWTPs (40.4%; 1–13 oocysts per litre) and cysts were observed in 22 DWTPs (42.3%; 1–7 cysts per litre). In the effluents from the treatment plants, Cryptosporidium oocysts and Giardia cysts were identified in 17 DWTPs (32.7%; 1–4 oocysts per litre) and in 19 DWTPs (36.5%; 1–5 cysts per litre), respectively. The highest concentrations of (oo)cysts were found in the WWTPs; specifically, oocysts were detected in 29 (58.0%; 1–80 oocysts per litre) and cysts in 49 (98.0%; 2–14.400 cysts per litre) WWTP effluents. Cryptosporidium and Giardia were detected in 32 (64.0%; 1–120 oocysts per litre) and 48 (96.0%; 2–6.000 cysts per litre) WWTP effluents, respectively. The percentage viability of the (oo)cysts ranged between 90.0% and 95.0%. In all samples analysed. Moreover, it was found that the effluents from coastal WWTPs were discharged directly into the sea, while inland WWTPs were discharged directly into rivers. The concentrations of both enteropathogens detected in effluents from WWTPs therefore represent a significant risk to human and animal health.These results demonstrate the wide distribution of Cryptosporidium and Giardia in the environment, the ineffectiveness of treatments in DWTPs and WWTPs in reducing/inactivating both protozoa and the need to monitor the presence, viability and infectivity of Cryptosporidium and Giardia in water bodies. In conclusion, the findings suggest the need for better monitoring of water quality and identification of sources of contamination.     

Influence of land use and watershed characteristics on protozoa contamination in a potential drinking water resources reservoir

Relative changes in the microbial quality of Lake Texoma, on the border of Texas and Oklahoma, were investigated by monitoring protozoan pathogens, fecal indicators, and factors influencing the intensity of the microbiological contamination of surface water reservoirs. The watershed serves rural agricultural communities active in cattle ranching, recreation, and is a potential drinking water source. A total of 193 surface water samples were tested over a 27-month period to determine levels of parasite contamination. The overall occurrence of Cryptosporidium oocysts was higher in both frequency and concentration than Giardia cysts. Cryptosporidium oocysts were found in 99% and Giardia cysts in 87% of the samples. Although Cryptosporidium and Giardia occurrence were significantly but not strongly correlated, all other correlation coefficients including turbidity and total dissolved solids were non-significant. Statistically supportable seasonal variations were found suggesting that Cryptosporidium and Giardia were higher in summer and fall than in other seasons of the year. While Cryptosporidium levels were correlated with rainfall, this was not the case with Giardia. The maximum numbers for both protozoan parasites were detected from a site impacted by cattle ranching during calving season. Restriction fragment length polymorphism analysis was used for confirmation of Cryptosporidium in surface waters influenced by agricultural discharges. As we had expected, oocysts were of the bovine type indicating that the Cryptosporidium parvum detected in surface waters perhaps came from cattle living in the watershed.     

Comparison of the action spectra and relative DNA absorbance spectra of microorganisms: Information important for the determination of germicidal fluence (UV dose) in an ultraviolet disinfection of water

The action spectra of Bacillus subtilis spores (ATCC6633) and Salmonella typhimurium LT2 were characterized using physical radiometry for irradiance measurements and a multiple target model to interpret the inactivation kinetics. The observed action spectrum of B. subtilis spores deviated significantly from the relative absorbance spectrum of the DNA purified from the spores, but matched quite well with the relative absorbance spectrum of decoated spores. The action spectrum of B. subtilis spores determined in this study was statistically different from those reported in previous studies. On the other hand, the action spectrum of S. typhimurium bacteria matched quite well with the relative absorbance spectrum of DNA extracted from vegetative cells, except in the region below 240 nm. It is concluded that the common use of the relative DNA absorbance spectrum as a surrogate for the germicidal action spectrum can result in systematic errors when evaluating the performance of a polychromatic UV light reactors using bioassays. For example, if the weighted germicidal fluence (UV dose) calculated using the relative DNA absorbance spectrum as the germicidal weighting factor is found to be 40 mJ cm⁻² for a medium pressure lamp UV reactor, that calculated using the relative action spectrum of B. subtilis spores, as determined in this study, would be 66 mJ cm⁻².