低温等离子体法去除苯和甲苯废气性能研究

对低温等离子体法去除苯和甲苯废气的性能进行了探讨,在理论分析的基础上进行实验研究。低温等离子体法去除苯和甲苯的机理是放电反应产生的高能电子与苯和甲苯分子发生非弹性碰撞并将能量全部或部分传递给目标分子,使其裂解、激化。被裂解、激化的分子与臭氧、活性基团发生一系列物理、化学反应后生成二氧化碳、一氧化碳和水。实验结果表明,苯和甲苯的去除率随着电场强度的增强而增大,随着气体流速的增大而减小。在较高电场强度下,有钛酸钡填料的反应器比无填料的反应器对苯和甲苯的去除率高得多,苯最高去除率可达92 6%,甲苯可达到96 8%。相同条件下甲苯比苯更容易去除。     

絮凝DAF中试工艺处理密云水库低温低浊水的影响因素

系统研究以硫酸铝和聚铝为絮凝剂时絮凝-DAF工艺中的水力学参数对除浊率的影响 .结果表明聚铝表现出了更优越的参数值 .在凝聚段 ,聚铝需要的高速混合时间为 15s,而硫酸铝则为 30s以上 ,2者对混合强度的要求为G=300～1000s^-1.聚铝的絮凝反应时间为 5.0min以上 ,硫酸铝为 7.5min以上 ,而且搅拌强度范围平均G值 =40～140s^-1;确定合适的总平均GT值≥2×10⁴.当应用聚铝为絮凝剂时 ,可以采用两级或三级等速搅拌 .对于仿MJ型的释放器 ,在实验的范围内释气压力为 2.5～3.3kg/cm² 时 ,5.0 %～8.3%的回流比较合适 .气浮接触区的水力条件和停留时间对絮凝气浮的除浊效果有较大的影响 .     

Magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering (MPEOD) of activated sludge: Role and behavior of moisture and organics

In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering (MPEOD) process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression (MMPC–DG–MC–EC) stages was established to study the distribution and migration of water, extracellular polymeric substances (EPS), and other organic matter in the activated sludge (AS) matrix at each stage. Results showed that the MPEOD process could attain 53.52% water content (WC) in dewatered AS with bound water (BW) and free water (FW) reduction rates of 82.97% and 99.67%, respectively. The coagulation and time-delayed magnetic field effects of magnetic micro-particles (MMPs) along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB- and TB-EPS, which contributed to improvement of AS dewaterability.     

Analysis of a broad range of perfluoroalkyl acids in accipiter feathers: method optimization and their occurrence in Nam Co Basin,Tibetan Plateau

Perfluoroalkyl acids (PFAAs) are ubiquitous in the environment. They are prone to accumulate in organisms and have raised public attention in recent decades. Feather samples have been successfully applied as nondestructive indicators for several contaminants. However, a sophisticated analytical method for determining PFAAs in feathers is still lacking. In the present study, a series of conditions, such as the use of the solid-phase extraction cartridge type and extraction/digestion methods, were optimized for the analysis of 13 PFAAs in feathers. According to the spiked recoveries, a weak-anion exchange cartridge was chosen and the methanol was selected as the extraction solvent. In the present study, an optimized pretreatment procedure combined with high-performance liquid chromatography–electrospray ionization–tandem mass spectrometric (HPLC–ESI–MS/MS) method was established for the determination of PFAAs in feathers. The recoveries and method detection limits of the PFAAs ranged from 71 to 120% and 0.16 to 0.54 ng/g, respectively. Finally, 13 PFAAs in four accipiter feather samples from Nam Co Basin, Tibetan Plateau, were analyzed, indicating that PFOS was the predominant PFAA in accipiter feathers, with an average of 4.67 ng/g, followed by the short-chain PFAAs, PFBS and PFBA, with averages of 1.91 and 1.39 ng/g, respectively. These results partly indicated the current situation of PFAA pollution in the Nam Co Basin, especially the existence of short-chain PFAAs in this region.     

Fractal analysis of polyferric chloride-humic acid （PFC-HA） flocs in different topological spaces

The fractal dimensions in different topological spaces of polyferric chloride-humic acid (PFC-HA) flocs, formed in flocculating different kinds of humic acids (HA) water with different initial pH (9.00, 7.00, 5.00) and PFC dosages, were calculated by effective density-maximum diameter, image analysis, and N2 absorption-desorption methods, respectively. The mass fractal dimensions (Df) of PFC-HA flocs, being more than 2.0, calculated by bi-logarithm relation of effective density-maximum diameter and Logan empirical formula at initial pH of 7.00 had 11-13 percentage greater than those at pH 9.00 and 5.00, indicating the most compact flocs formed in flocculated HA water at initial pH of 7.00. The image analysis for those flocs indicates that after flocculating the HA water at initial pH greater than 7.00 with PFC flocculant, the fractal dimensions of D2 (logA vs. logdL) and D3 (logVsphere vs. logdL) of PFC-HA flocs decreased with the increase of PFC dosages, and PFC-HA flocs showed a gradually looser structure. At the optimum dosage of PFC, the D2 (logA vs. logdL) values of the flocs show 14%--43% difference with their corresponding Df, and they even had different tendency as the change of initial pH values. However, the D2 values of the flocs formed at three different initial pH in HA solution, calculated from the horizontal projected images with magnification about 9, had a same tendency with the corresponding Df. Based on fractal Frenkel-Halsey-Hill (FHH) adsorption and desorption equations, the pore surface fractal dimensions (Ds) for dried powders of PFC-HA flocs formed in HA water with initial pH 9.00 and 7.00 were all close to 2.9421, and the Ds values of flocs formed at initial pH 5.00 were less than 2.3746. It indicated that the pore surface fractal dimensions of PFC-HA flocs dried powder mainly show the irregularity from the mesopore-size distribution and some marcopore-size distribution.     

给水厂浓缩污泥的稳态流变特征研究

针对给水厂浓缩污泥,采用旋转流变仪研究了其稳态流变特性,分别探讨了污泥的典型流变图、污泥浓度和温度对浓缩污泥极限粘度的影响.结果表明,污泥具有触变及剪切变稀的性质,其极限粘度(η∞)与污泥浓度(TSS)的关系符合指数关系,可用方程η∞=24.43-494.62e-0.14TSS描述.极限粘度与温度的关系服从于阿伦尼乌斯公式,相应的反应活化能为14.91J·mol-1.此外,宾汉模型可以描述污泥的流变性质,屈服应力随污泥浓度的升高而增加.     

Physical characteristics of conditioned anaerobic digested sludge – A fractal, transient and dynamic rheological viewpoint

The changes in the physical characteristics of unconditioned and conditioned anaerobic digested sludge (ADS) biosolids, such as capillary suction time (CST), yield stress, average size and fractal dimensions, were investigated through a CST test, transient and dynamic rheological test and image analysis. The results showed that the optimum polymer dose range was observed when CST or its reciprocal value was employed as an indicator. There were good correlations between the yield stresses determined from both a controlled shear stress test and a strain amplitude sweep test. The yield stress and storage modulus (G′) increased as the polymer dose increased in most cases. A frequency sweep test revealed that polymer conditioning could extend the frequency sweep ranges for their elastic behaviors over viscous behaviors as well as the gel-like structure in the linear viscoelastic range. These results implied that more deformation energy was stored in this rigid structure, and that elastic behavior became increasingly dominant with the addition of the polymer in most cases. In addition, both the average sizes and two-dimensional fractal dimensions for conditioned ADS biosolids presented a similar up-climax-down variation trend as the polymer doses increased, whereas the critical polymer doses at the highest average sizes or two-dimensional fractal dimensions, were different. Correlation analysis revealed that the conditioned ADS dewaterability was not correlated with the yield stresses, while the average sizes or the two-dimensional fractal dimensions for conditioned ADS biosolids could be taken as the indication parameters for ADS dewaterability.     

聚合氯化铁-腐殖酸(PFC-HA)冷冻干燥絮体的表面微观形貌及其孔表面分形特征

采用低温急速冷冻-真空干燥技术制备了不同pH(9.0、7.0、5.0)原水在45.89mg·L-1(以Fe3 计,原水pH=9.0)或28.41mg·L-1(以Fe3 计,原水pH=7.0、5.0)投药量下混凝后形成的PFC-HA絮体的粉末样品,研究了它们的表面微观形貌和孔表面分形特征.SEM图像表明,PFC-HA絮体具有不规则的块、片状形貌,而且在原水pH=9.0或pH=7.0时形成絮体也存在簇状结构.3种样品对N2的吸附-脱附等温线上均存在滞后圈,但样品3的形状不同.它们的吸附量、BJH累积吸附孔体积与脱附平均孔径的大小顺序均为:样品3＞样品2＞样品1,即随原水pH的降低而升高,而且孔尺度分布曲线显示样品3的表面存在大孔.BET比表面积的变化趋势与它们不一致,且样品2的比样品3稍大,样品1的最小.基于分形FHH方程,采用吸附等温线和脱附等温线数据计算出样品1和样品2的孔表面分形维Ds数均在2.94左右,而样品3的均小于2.38.这些Ds值似乎不能完全表示出因孔表面粗糙性而导致的空间填充能力的大小,主要表达了3种样品的中孔甚至大孔的尺度分布引起的不规则性.本试验中采用热力学模型计算出的3个样品Ds值大都超过3,它们已经失去了维数的实际意义;但样品3因其吸附-脱附等温线上的滞后圈接近圆桶式的A类,如果缩小分形标度区间,可以得到与分形FHH方程计算出的Ds接近的值.     

聚合氯化铁-腐殖酸(PFC-HA)絮体的粒度和分形维数的动态变化

通过采集PFC-HA絮体的单个样品和拍摄它们的二维图像,研究了在不同混凝条件下絮体的粒度和分形维数的变化.结果表明,原水pH的下降滞后了PFC-HA絮体的出现.原水pH≥7.0时,随着投药量的增加,PFC-HA絮体的分形维数D2(lgA-lgdL)和D3(lgV1-lgdL)随之降低,表明絮体的结构越来越疏松;而原水pH=5.0时,PFC-HA絮体的分形维数存在波动.在PFC的最佳投药量时,水力条件的优化可以提高HA的去除效果,但随着原水pH的下降,HA去除效果的提高程度也随之减小.在最佳水力条件下,PFC-HA絮体的粒度为数百微米,其分形维数值较大,表明絮体的结构较为密实.此外,PFC-HA絮体的粒度分布具有(类)分形特征,最佳水力条件下正的D.值表明絮体的粒度分布趋向平稳.在整个混凝搅拌过程中,PFC-HA絮体的分形维数的变化是与混凝的溶液化学条件、搅拌时间和分形维数类型有关,其D2具有先上升后下降的趋势,这一过程中絮体结构先趋向密实,然后趋向疏松.而且慢速搅拌过程中絮体的尺度也是先增加后下降.