油品装卸过程静电特性研究

为了研究油品装卸过程中的静电危险性,在两个城市的油库和加油站对油品的装油、卸油过程,以及装油的油罐车从油库向加油站行驶的过程中,油罐车内油品的油面电位进行了静电检测。通过对大量油罐车内油面电位的检测数据分析可以看出,在正常装卸油过程中,油罐车内油品的油面电位远远小于标准所规定安全油面电位,有缩短稳油时间的可能性。     

城市污泥中温厌氧消化过程中厌氧耐药菌的分布与去除研究

城市污泥中含有大量的耐药菌,具有向环境传播耐药菌与抗性基因的潜在危险,但目前缺乏对城市污泥厌氧消化过程中耐药菌的研究.为此对某城市污水处理厂卵形消化池污泥进行了为期1 a的调查研究,考察了中温厌氧消化过程中四环素类与β-内酰胺类抗生素厌氧耐药菌的污染特征与去除效果,并分析了耐药菌的季节性变化规律.结果表明,厌氧进泥中四环素类耐药菌浓度与耐药率均低于β-内酰胺类.中温厌氧消化过程可以去除1.48~1.64 log单位的耐药菌(P<0.05),但经过厌氧消化后氨苄西林与头孢噻吩耐药率有显著增长(分别增加了12.0%与14.3%,P<0.05).厌氧进泥中耐药菌分布有明显的季节特征,除金霉素耐药菌外,其它耐药菌的浓度均为寒冷季显著高于温暖季(P<0.05).     

微波及其组合工艺强化污泥厌氧消化研究

为提高剩余污泥的厌氧消化效能和脱水性能,考察了微波及其组合污泥预处理工艺的强化污泥厌氧消化效果,同时考察了预处理-厌氧消化过程的污泥理化特征及其脱水性能.结果表明,微波及其组合工艺可以强化污泥厌氧消化产甲烷,其中微波-过氧化氢-碱(0.2)的强化效果最为显著,不仅30 d累计产甲烷量比对照组增加了13.34%,而且产甲烷速率也得到了提升.与单独微波处理相比,过氧化氢、碱的投加显著提高了溶解性COD的释放量,这表明微波、过氧化氢、碱之间的协同作用能有效破碎污泥,进而强化厌氧消化效果;微波-酸预处理后的污泥具有良好的脱水性能,毛细吸水时间(CST)只有9.85 s,污泥脱水性能的改善与其表面电性、粒径分布的变化密切相关;不同预处理条件下的污泥经过厌氧消化后,污泥脱水性能较为接近.     

胞外聚合物磷酸盐形态对生物除磷过程的影响研究

以不同DO条件下污泥龄(SRT)分别为10 d和30 d的两组实验室A/O-SBR反应器活性污泥为研究对象,探讨了胞外聚合物(EPS)磷酸盐形态对生物除磷过程的影响.结果表明,污泥絮体中的磷主要分布于EPS中,PO3-4-P和聚磷酸盐(Poly-P,包括低分子量聚磷酸盐LMW PolyP和高分子量聚磷酸盐HMW Poly-P)是EPS磷的主要形态;EPS对生物除磷的影响明显大于细菌细胞,EPS磷的厌氧降低量和好氧升高量为胞内磷变化量的2.8~6.4倍.EPS中的LMW Poly-P和HMW Poly-P含量均表现厌氧降低和好氧升高的变化规律;对于相同SRT的污泥,中DO(2.5~3.5 mg·L-1)条件较低DO(0.7~1.0 mg·L-1)条件下EPS的LMW Poly-P和HMW Poly-P有更大的厌氧降低量和好氧升高量,对应着更明显的生物除磷过程,说明EPS不仅是生物除磷过程的中转站,而且参与了生物聚磷过程.     

微波消解ICP-AES法测定土壤中的金属元素研究

采用硝酸-盐酸-氢氟酸-双氧水作溶剂,通过微波消解技术、电感耦合等离子发射光谱法测定土壤中的锑、砷、铍、镉、铬、铜、铅、镍、硒、银、铊、锌,优化了微波消解仪和等离子发射光谱仪的工作参数,研究了共存离子的干扰和消除方法。优化后的微波消解酸体系及用量比例为HNO3∶HCl∶HF∶H2O2=5∶2∶3∶1,方法线性良好,各元素的检出限在0.000 2 mg/L~0.010 1 mg/L之间,土壤样品测定的标准偏差在0.001~0.051之间,加标回收率在85.5%~108.5%之间。该方法检出限低、精密度高、准确度好,测定结果令人满意。     

微波消解—火焰原子吸收分光光度法测定土壤中的钴、钼

土壤样品的传统消解方法是用电热板硝酸-氢氟酸-高氯酸体系,消解时间长,试剂用量大,对操作人员身体危害大,并且测定结果也不准确。本文阐述了微波消解——原子吸收分光光度法测定土壤中的钴、钼。通过硝酸-盐酸-氢氟酸-高氯酸消解体系,选择出微波消解的最佳消解条件,通过对微波消解体系和传统消解体系进行对比试验,微波消解体系具有赶酸时间短,准确度高,对人体危害小,是一种值得推广的土壤消解方法。     

零价铁对污泥高温厌氧消化过程中四环素抗性基因及第一类整合子的消减影响

为研究污泥高温厌氧消化过程中零价铁(Fe0)对抗生素抗性基因的消减影响,采用荧光定量PCR方法定量检测了7种四环素抗性基因(TC-ARGs,包括tetA、tetC、tetG、tetM、tetO、tetW和tetX)及第一类整合子int I1基因在厌氧消化过程中的丰度变化,同时检测分析了挥发性脂肪酸(VFAs)的质量浓度变化,并探讨了目标基因与VFAs之间的相关关系.结果表明,适量Fe0(如0.10 g·g~(-1),以Fe0/VSS计)不仅可以强化污泥厌氧消化进程,显著提高总VFAs和乙酸的产生量,而且能够增强TCARGs和int I1基因的消减效果.尽管如此,过量Fe0(如1.17 g·g~(-1),以Fe0/VSS计)对污泥高温厌氧消化过程中TC-ARGs和int I1基因消减的增强效果并不显著,推测可能是由于基因水平转移的发生所导致的.通过相关性分析可知,TC-ARGs(除tetO基因外)和int I1基因与乙酸之间存在显著负相关性,表明乙酸可能对TC-ARGs和int I1基因的消减具有促进作用.     

体育馆出口疏散能力的实验研究

为研究出口单位流量与人流时间之间的关系,以某体育馆为例,进行对某一出口常态下的人流观测实验.通过理论计算和建立Cubic回归模型对采集数据进行了统计分析.发现:单位出口流量最大值为2人/(m·s),稳定值为0.8-1.2人/(m·s),最小值为0.2人/(m·s).出口单位流量是人流时间的三次函数.研究结果表明:出口单位流量是随着时间的变化而变化,不是一个定值,而且单位出口流量稳定值分布在初期.本文对性能化防火设计有一定的参考价值.     

Treatment of digestate from a co-digestion biogas plant by means of vacuum evaporation: Tests for process optimization and environmental sustainability

Vacuum evaporation consists in the boiling of a liquid substrate at negative pressure, at a temperature lower than typical boiling temperature at atmospheric conditions. Condensed vapor represents the so called condensate, while the remaining substrate represents the concentrate.This technology is derived from other sectors and is mainly dedicated to the recovery of chemicals from industrial by-products, while it has not been widely implemented yet in the field of agricultural digestate treatment. The present paper relates on experimental tests performed in pilot-scale vacuum evaporation plants (0.100 and 0.025 m³), treating filtered digestate (liquid fraction of digestate filtered by a screw-press separator). Digestate was produced by a 1 MW_e anaerobic digestion plant fed with swine manure, corn silage and other biomasses. Different system and process configurations were tested (single-stage and two-stage, with and without acidification) with the main objectives of assessing the technical feasibility and of optimizing process parameters for an eventual technology transfer to full scale systems.The inputs and outputs of the process were subject to characterization and mass and nutrients balances were determined.The vacuum evaporation process determined a relevant mass reduction of digestate.The single stage configuration determined the production of a concentrate, still in liquid phase, with a total solid (TS) mean concentration of 15.0%, representing, in terms of mass, 20.2% of the input; the remaining 79.8% was represented by condensate. The introduction of the second stage allowed to obtain a solid concentrate, characterized by a content of TS of 59.0% and representing 5.6% of initial mass.Nitrogen balance was influenced by digestate pH: in order to limit the stripping of ammonia and its transfer to condensate it was necessary to reduce the pH. At pH 5, 97.5% of total nitrogen remained in the concentrate. This product was characterized by very high concentrations of total Kjeldhal nitrogen (TKN), 55,000 mg/kg as average.Condensate, instead, represented 94.4% of input mass, containing 2.5% of TKN. This fraction could be discharged into surface water, after purification to meet the criteria imposed by Italian regulation. Most likely, condensate could be used as dilution water for digestion input, for cleaning floor and surfaces of animal housings or for crop irrigation.The research showed the great effectiveness of the vacuum evaporation process, especially in the two stage configuration with acidification. In fact, the concentration of nutrients in a small volume determines easier transportation and reduction of related management costs. In full scale plants energy consumption is estimated to be 5–8 kWh_e/m³ of digestate and 350 kWh_t/m³ of evaporated water.     

A NEW LOOK AT FLOOD RISK DETERMINATION1

ABSTRACT: The probability distributions of annual peak flows used in flood risk analysis quantify the risk that a design flood will be exceeded. But the parameters of these distributions are themselves to a degree uncertain and this uncertainty increases the risk that the flood protection provided will in fact prove to be inadequate. The increase in flood risk due to parameter uncertainty is small when a fairly long record of data is available and the annual flood peaks are serially independent, which is the standard assumption in flood frequency analysis. But standard tests for serial independence are insensitive to the type of grouping of high and low values in a time series, which is measured by the Hurst coefficient. This grouping increases the parameter uncertainty considerably. A study of 49 annual peak flow series for Canadian rivers shows that many have a high Hurst coefficient. The corresponding increase in flood risk due to parameter uncertainty is shown to be substantial even for rivers with a long record, and therefore should not be neglected. The paper presents a method of rationally combining parameter uncertainty due to serial correlation, and the stochastic variability of peak flows in a single risk assessment. In addition, a relatively simple time series model that is capable of reproducing the observed serial correlation of flood peaks is presented.