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761.
This study investigated a combined low-thermal and CaO2 pretreatment to enhance the volatile fatty acid (VFA) production from waste activated sludge (WAS). The fermentative product was added to a sequencing batch reactor (SBR) as an external carbon source to enhance nitrogen removal. The results showed that the combined pretreatment improved WAS solubilization, releasing more biodegradable substrates, such as proteins and polysaccharides, from TB-EPS to LB-EPS and S-EPS. The maximum VFA production of 3529 ± 188 mg COD/L was obtained in the combined pretreatment (0.2 g CaO2/g VS + 70 °C for 60 min), which was 2.1 and 1.4-fold of that obtained from the sole low-thermal pretreatment and the control test, respectively. Consequently, when the fermentative liquid was added as an external denitrification carbon source, the effluent total nitrogen decreased to Class A of the discharge standard for pollutants in rural wastewater treatment plants in most areas of China. 相似文献
762.
More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and pH all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks. 相似文献
763.
为评价炼化装置中各控制回路的性能,基于控制回路关键品质指标要求,采用控制回路的设定值、输出值、测量值、控制模式等过程参数设计了准确性指标、稳定性指标及快速性指标等性能评估指标。辅助技术人员在线进行控制回路性能评估,识别性能较差的控制回路,诊断异常原因并进行优化,提高装置的自动化水平。 相似文献
764.
Effects of the type of sintering atmosphere on the chromium leachability of thermal-treated municipal solid waste incinerator fly ash 总被引:4,自引:0,他引:4
The sintering process offers an opportunity to combine detoxification and resource recovery for the treatment of municipal solid waste (MSW) incinerator fly ash. However, the chromium (Cr) in the sintered fly ash becomes more readily leachable with increasing sintering time and temperature, thus posing severe threats to the environment and human health when the sintered ash is recycled or reused. This study investigated the enhanced leachability of fly ash containing Cr, by heating the chromium (III) oxide (Cr2O3)-spiked fly ash to 800 degrees C in atmospheres containing air, nitrogen gas (N2), and 5% H2 + 95% N2, respectively. The results indicated that trivalent chromium was converted to its soluble hexavalent form during sintering in the air atmosphere; whereas sintering in a nitrogen atmosphere significantly reduced the leachability of Cr due to lack of oxygen (O2) to oxidize. The effects of the sintering temperature on the total chromium content and the leaching concentration in the toxicity characteristic leaching procedure (TCLP) extract are also discussed. 相似文献
765.
Cement solidification of simulated off-gas condensates from vitrification of low-level nuclear waste solutions 总被引:1,自引:0,他引:1
Katz A Brough AR Kirkpatrick RJ Struble LJ Sun GK Young JF 《Waste management (New York, N.Y.)》2001,21(6):543-553
Solidification in a cementitious matrix is a viable alternative for low-level nuclear waste management; it is therefore important to understand the behavior and properties of such wasteforms. We have examined the cementitious solidification of simulated off-gas waste streams resulting from the vitrification of low-level nuclear waste. Different possible methods for scrubbing the off-gasses from a vitrifier give rise to three possible types of waste compositions: acidic (from aqueous dissolution of volatile NOx and POx carried over from the vitrifier), basic (from neutralizing the former with sodium hydroxide), and fully carbonated (arising from a direct-combustion vitrifier). Six binder compositions were tested in which ordinary Portland cement was replaced at different proportions by fly ash and/or ground granulated blast furnace slag. A high solution to binder ratio of 1l/1 kg was used to minimize the volume of the wasteform and 10% attapulgite clay was added to all mixes to ensure that the fresh mix did not segregate prior to setting. The 28-day compressive strengths decreased when a high proportion of cement was replaced with fly ash, but were increased significantly when the cement was replaced with slag. The heats of hydration at early age for the various solids compositions decreased when cement was replaced with either fly ash or slag; however, for the fly ash mix the low heat was also associated with a significant decrease in compressive strength. High curing temperature (60 degrees C) or the use of extra-fine slag did not significantly affect the compressive strength. Recommendations for choice of binder formulations and treatment of off-gas condensates are discussed. 相似文献
766.
无剩余污泥A/O生物接触氧化法 总被引:1,自引:1,他引:1
孙国华 《石油化工环境保护》1994,(2):27-30
A/O系统在70年代开发以来,广泛应用于城市污水处理,它具有同时去除废水中碳、氨、磷的特点。1985年上海石化.总厂涤纶厂首先将A/O法用于石化行业废水处理中,并经过实践总结出一套完整的无剩余污泥A/O生物接触氧化法处理流程。本流程操作管理方便,耐冲击,氮、磷、COD的去除率高、能耗低,并达到了无剩余污泥。 相似文献
767.
以北京油松(Pinus tabuliformis)人工林为研究对象,采用独立样本T检验、冗余分析等方法,分析重度火烧1年后林下植被(灌木层和草本层)的物种多样性、叶功能性状及其与土壤因子的关系.结果显示:(1)与对照样地相比,重度火烧后灌木层物种丰富度指数极显著降低(P <0.01),但Shannon指数、Simpson指数以及Pielou指数虽呈下降趋势但未达显著水平(P> 0.05);草本层除Pielou指数外,各物种多样性指数均显著增加(P <0.05).(2)重度火烧样地灌木层和草本层的叶厚度(LT)、叶干物质含量(LDMC)、叶碳含量(LCC)、叶磷含量(LPC)均高于对照样地,而比叶面积(SLA)、叶氮含量(LNC)、叶片氮磷比(N:P)、叶绿素含量(CHL)低于对照样地,除灌木层LPC和N:P及草本层SLA、LCC和LPC外,其他各叶功能性状在火烧与对照间差异均达显著水平.对于不同生活型而言,对照样地的LDMC、LNC、LCC、CHL存在显著差异,而在重度火烧后差异不显著;LT、SLA在重度火烧和对照样地上均呈现显著差异;而LPC、N:P在重度火烧与对照样地上均无显著差异.(3)重度火烧后1年,灌木层和草本层的叶功能性状均仅与土壤含水率、容重和非毛管孔隙度密切相关.本研究表明在油松人工林重度火烧后1年,灌木层物种多样性降低,而草本层物种多样性增加,灌草层的各叶功能性状主要受土壤物理性质的影响呈现不同的变化规律.(图4参45) 相似文献
768.
2020年12月在深圳市城市区域典型生境特征溪流——城市山区源头溪流金龟河、国家地质公园保护区入海溪流杨梅坑河与黑臭水体治理后溪流石溪河,开展底栖动物多样性与生境质量状况取样,通过多元统计分析探明各溪流底栖动物群落结构差异及其主要环境影响因子.结果表明:(1)金龟河底质异质性(SI)最高;杨梅坑河水质最好且流态异质性(Fr)最优,石溪河水质最差且底质异质性(Fr)最低.(2)共采集鉴定大型底栖动物118个分类单元,隶属于3门6纲14目87科.水生昆虫均占绝对优势,其中金龟河67属(81.7%),杨梅坑河62属(95.4%),石溪河12属(52.2%).金龟河中底栖动物Shannon-Wiener多样性指数、改进的Shannon-Wiener多样性指数、Pielou均匀度均高于杨梅坑河与石溪河.(3)金龟河的主要功能摄食类群是滤食者(45.5%),杨梅坑河(38.3%)与石溪河(58.7%)的主要功能摄食类群均为收集者.(4)冗余分析(RDA)结果显示,氨氮、海拔、湿宽、水温、溶氧、底质异质性(SI)、电导率和流态异质性(Fr)为影响深圳市溪流的大型底栖动物群落结构的主要环境因子.研究表明:(1)深圳市的山区溪流可作为深圳市生物多样性保护的重点区域.(2)在城市溪流生态系统中,水环境化学因子并非为主要影响因子,生境多样性发挥了重要作用.(图6表3参43) 相似文献
769.
Yuwei Guo Xian Xiao Yuan Zhao Jianguo Liu Jizhong Zhou Bo Sun Yuting Liang 《Frontiers of Environmental Science & Engineering》2022,16(7):91
770.
Jibin Li Jinxing Ma Li Sun Xin Liu Huaiyu Liao Di He 《Frontiers of Environmental Science & Engineering》2022,16(7):86