细微泥沙对污水生化处理系统的影响及其归趋特性

大量运行数据表明,取消初沉池的污水厂泥沙淤积严重、污泥MLVSS/MLSS比值低,严重影响了污水厂的正常运行和功能提升。以取消初沉池后不能被有效去除的粒径≤200μm的细微泥沙为研究对象,通过对比实验的方法研究了不同粒径细微泥沙对污水生化处理系统的影响及其归趋特性。运行结果表明,当在污水中分别投加粒径为26、73、106、165和210μm的细微泥沙300 mg/L时,运行40 d后,生化系统活性污泥的MLVSS/MLSS比值将从启动初期的0.84分别下降至0.27、0.29、0.59、0.65和0.73,且随MLVSS/MLSS比值的下降,混合液SVI值也明显降低,反应器底部淤积泥沙量分别相当于进水泥沙总量的31.0%、47.4%、75.2%、75.9%和91.6%,表明小粒径颗粒更容易被活性污泥包裹,引起污泥MLVSS/MLSS下降,大粒径颗粒更容易淤积在反应器底部;由于泥沙淤积致使颗粒粒径越大,通过排放剩余污泥除砂的量越少,按照粒径递增的顺序,通过剩余污泥外排的除砂量分别相当于进水泥沙总量的44.5%、31.3%、20.3%、20.5%和7.2%。     

活性污泥中细微沙浓度的预测模型

悬浮在污泥混合液中的细微沙会导致活性污泥混合液挥发性悬浮固体与混合液悬浮固体比值(ratio of mixed liquor volatile suspended solids to mixed liquor suspended solids,MLVSS/MLSS)降低。通过向生化池进水中连续投加体积平均粒径分别为14、33、50、66和107μm的石英砂,研究不同粒径细微沙对活性污泥MLVSS/MLSS的影响,探讨不同粒径细微沙的悬浮特性,构建活性污泥中细微沙浓度的预测模型,以为污水厂运行调控提供理论基础。研究结果表明,细微沙粒径越小,悬浮比(悬浮在污泥混合液中的细微沙占生化池进水中细微沙总量的比例)越大,悬浮比与细微沙粒径呈显著的相关关系。通过预测模型得到的细微沙浓度的预测值与实测值差异较小,说明构建的活性污泥中细微沙浓度的预测模型是合理的。污水厂可在维持活性污泥MLVSS稳定的条件下,结合活性污泥中细微沙的浓度,调控污泥MLSS,保证污水处理系统的稳定运行。     

污泥淤砂分离器对分离分流污泥性质的影响

为解决我国很多城镇污水厂活性污泥的MLVSS/MLSS普遍偏低,污泥中泥沙淤积严重的问题,根据水力旋流器的分离原理,开发了污泥淤砂分离器,实现污泥中生物基质和淤砂的分离分流,研究污泥淤砂分离器主要结构参数排口比(底流口直径/溢流管直径)对分离分流污泥性质的影响。实验结果表明,排口比为0.4时,污泥经过污泥淤砂分离器后,得到的底流污泥MLVSS/MLSS比原污泥减小了34%,溢流污泥MLVSS/MLSS增大了16.8%,污泥中的生物基质富集在溢流污泥中,淤砂富集在底流污泥中;底流污泥浓度MLSS比原污泥增加了2.6倍,底流污泥SVI和CST分别减小了68%和70%,底流污泥浓缩效果明显,沉降性能和脱水性能大幅提高,有利于底流污泥的处理处置;进一步减小排口比,底流污泥浓缩效果、沉降性能和脱水性能均进一步提高。     

污泥脱水性能的关键影响因素研究

针对目前污泥脱水性能影响因素不明的问题,研究通过对SBR在7种运行工况条件下活性污泥胞外聚合物(extracellular polymeric substances,EPS)的提取和测试,并采用SPSS软件分析,探讨MLVSS/MLSS、胞外蛋白质/胞外多糖、胞外蛋白质含量、胞外多糖含量、EPS总含量对污泥脱水性能的影响。研究结果表明,MLVSS/MLSS、胞外蛋白质/胞外多糖是影响污泥脱水性能的关键因素,并建立了脱水污泥含水率和污泥结合水含量的影响因素模型:脱水污泥含水率=0.229×(MLVSS/MLSS)+0.023×(胞外蛋白质/胞外多糖)+0.539、污泥结合水含量=2.876×(MLVSS/MLSS)+0.335×(胞外蛋白质/胞外多糖)-0.012,通过对7个城市污水厂污泥脱水性能测试比较表明,模型对脱水污泥含水率和污泥结合水含量预测值相对误差分别在±1%和±5%以内,对污泥脱水性能预测效果良好。     

降雨过程对污水处理厂无机颗粒物特性及活性污泥的影响

取消初沉池的污水处理厂,粒径小于200μm细微无机颗粒物将直接进入生化池,或悬浮或沉积,进而影响生化池的运行。以山地城市某污水处理厂为例,跟踪监测了夏季2个月的6次降雨过程中旋流沉砂池进出水无机颗粒物的粒径和浓度,并同期测定了生化池活性污泥浓度以及污泥MLVSS/MLSS比值。研究发现:旱季旋流沉砂池进出、水中的无机颗粒物平均粒径分别为65.25μm及54.14μm,浓度均值分别为146 mg·L-1及128 mg·L-1,无机颗粒去除率12.33%;降雨旋流沉砂池进出、水中的无机颗粒物峰值平均粒径分别为140.48μm及94.54μm,峰值平均浓度分别为2 167 mg·L-1及1 591 mg·L-1,无机颗粒去除率26.58%;旋流沉砂池对粒径≥200μm颗粒的去除较稳定,对细微无机颗粒物的去除效率约10%。研究进一步发现,降雨中颗粒物浓度分别与雨前晴天数及平均雨强呈线性正相关关系。通过核算生化池无机颗粒物的物料平衡关系,得知研究期间生化池累积无机颗粒物总量410.25 t,其中399.45 t沉积在底部,其余悬浮于活性污泥混合液中。活性污泥MLVSS/MLSS由0.52降至0.40,MLVSS由1 410 mg·L-1降至930 mg·L-1,污泥活性下降,系统运行效能受到影响。     

旁路微氧池污泥停留时间对污泥减量化的影响

研究了新型工艺——侧流式旁路微氧污泥减量工艺在不同微氧污泥停留时间下的污泥减量效果,监测了COD去除率、污泥产率和污泥性能的变化,并探索了微氧污泥回流后曝气池内兼性菌溶胞过程。结果表明,新工艺COD去除率高于传统工艺,但随停留时间延长而降低,微氧污泥停留3 d时高达93.59%,11 d时降至89.25%;新工艺表观污泥产率(MLSS/COD)低于传统工艺,其降幅随停留时间延长而增大,停留时间由3 d延长到11 d,降幅由50.14%升到58.59%;回流后第4小时,曝气池内COD骤然上升,MLSS和MLVSS都大幅度增加,推断此时为曝气池内兼性菌大量溶胞时间点;新工艺SVI值低于传统工艺,MLVSS/MLSS值高于传统工艺,改善了污泥沉降性能,提高了污泥活性。综合考虑COD去除率和污泥产率等方面后,确定新工艺微氧池的最佳污泥停留时间为3 d。     

常温下好氧颗粒污泥的形成过程及除污性能

接种产絮脱氮菌剂TN-14强化普通活性污泥在常温下实现快速颗粒化。研究了污泥颗粒化过程中污泥形态、浓度(MLSS)、体积指数(SVI)、粒径分布、胞外多糖(PS)和蛋白(PN)的变化规律,以及除污性能。结果表明,反应器污泥在45 d内完全实现颗粒化,成熟颗粒污泥粒径多在0.6~1.0 mm之间;颗粒化期间,系统内污泥浓度略有增加,而污泥体积指数SVI值呈下降趋势。污泥PS和PN含量均明显增加,成熟稳定期污泥PS和PN含量分别维持在84.22~90.46 mg/g MLVSS以及294.22~345.26 mg/g MLVSS。污泥颗粒化后对污水除污能力都有一定的提高,颗粒污泥稳定运行阶段出水COD、氨氮、TN和TP值都能满足一级A类排放标准(GB18918-2002)。     

活性污泥法处理高钙废水中污泥特性的变化

通过单级SBR法处理模拟高钙废水,研究了活性污泥法处理高钙废水的过程中钙离子对COD,MLVSS,MLSS,SVI,污泥增长速率,污泥形态结构及生物相的影响,揭示活性污泥法处理高钙废水的过程中污泥量巨大的原因。采用逐步增加钙离子浓度的方法,检测到在污泥培养期([Ca2+]=0 mg/L),COD去除率为98.1%,MLVSS和MLSS稳定在4 900~5 500mg/L,污泥增长速率为67 mg/(L·d),SVI为55~60 mL/g;在驯化处理期([Ca2+]=120~2 400 mg/L),COD去除率降至87.37%,MLVSS降至2 500 mg/L,MLSS增加至19 300 mg/L,污泥增长速率为212.31 mg/(L·d),SVI降至25 mL/g;在冲击期([Ca2+]=4 000 mg/L),COD去除率降至69.23%,MLVSS降至1 600 mg/L,MLSS迅速增加至24 200 mg/L,污泥增长速率为816.67 mg/(L·d),SVI降至14 mL/g。经显微镜观察发现,污泥絮体由松散变得密实,生物相由钟虫等指示性微生物变为不适应环境的胞囊结构。结果表明,随Ca2+浓度的增加,COD去除率下降,MLSS迅速增加,MLVSS和SVI急剧缩小,说明活性污泥中的活性微生物逐渐减少,而无机物组分逐渐增多;钙离子的加入促使系统碳酸平衡向右移动,使离子状态的钙大部分转化为难降解的碳酸盐,并附着于污泥絮体上,污泥绒粒被压缩,使污泥颗粒密实度及MLSS迅速增加,导致污泥排放量巨大。     

污泥淤砂分离器再分离溢流污泥

研究了污泥淤砂分离器对分离原污泥所得的溢流污泥进行再分离时,分离器的分离效果和分离分流污泥的性质。实验结果表明,污泥淤砂分离器对溢流污泥进行再分离时,分离器的除砂效率为34.5%,分离度为1.60,与分离原污泥时相比,分离器的分离性能降低;分离得到的溢流污泥MLVSS/MLSS比值为0.406,仅比进料污泥增加了2.2%,未能进一步提高溢流污泥MLVSS/MLSS比值;分离得到的底流污泥浓度MLSS为16.81 g/L,仅为原污泥浓度的1.4倍,底流污泥SVI、CST分别为45.7 mL/g和1.37 s·L/g SS,与原污泥相比仅分别减小了9.3%和2.7%,溢流污泥再分离,会降低底流污泥的浓缩效果,降低底流污泥沉降性能、脱水性能的提高幅度,不利于底流污泥的处理处置。     

水解酸化应用于剩余污泥减量的试验研究

碱减量印染废水生物处理剩余污泥接种培养成熟的水解酸化菌,通过它们的新陈代谢作用,可以实现系统内生命物质的更新和减量,同时降解了污泥吸附的有机物等,达到对剩余污泥减量的目的.在系统污泥减量初期,水解酸化作用对微生物的"液化"、内容物释放和对有机物的生物降解作用是污泥减量的主要原因;随着中间代谢产物的积累,微生物活性受到抑制,试验后期剩余污泥减量主要是微生物内源呼吸的结果.试验条件下,接种了成熟水解酸化细菌的 2 组剩余污泥 MLSS 浓度分别为 7.765 和 11.250 g/L,MLVSS 浓度分别为 4.466和 6.360 g/L,经过 513 h后 MLSS、MLVSS 浓度较开始时分别下降了 40.31%、45.73%和 54.85%、63.18%.一定污泥浓度范围,污泥减量效果与污泥浓度正相关.     

Optimization of Height of Release of Air Pollutants

A number of key projects in the Environmental Protection Agency (EPA) particulate R&;D program having applicability to industry are presented. For electrostatic precipitators (ESP) there is presented the result of work on large diameter discharge electrodes which provide a decrease in penetration of up to a factor of 4 when compared to conventional small diameter electrodes. Also discussed is the multistage ESP which provides a collection efficiency that would require a collecting plate area 4 or 5 times larger with conventional ESP technology. The E-SOX technology makes use of the multistage concept to free up space in the ESP for SO₂ removals of up to 90%. Electrostatically augmented fabric filtration provides a reduction in pressure drop of about 5 0% as compared to conventional fabric filtration. Wind tunnel modeling of windbreaks for material storage piles indicates a potential for providing engineering design data that would allow significant emission reduction caused by wind erosion     

Investigation of the characteristics of the reflectivity of clouds

This paper investigates some of the reflectivity characteristics that clouds (when modelled as solid bodies) must exhibit to be compatible with observations that the reflecting surface of a cloud (i) appears almost equally bright across its face, (ii) is brightest when the cloud is opposite to the Sun but decreases in brightness as the cloud moves to other positions and (iii) increases in brightness with increasing optical thickness of the cloud in the observer's line of sight. These observations, respectively, are shown to imply that the peak value of the bidirectional total reflectivity from a cloud surface (i) increases in inverse proportion to the cosine of the angle between the Sun and the normal to the cloud surface, as the incident angle increases, (ii) appears to be directed back in the direction of the incident radiation, and (iii) increases as optical thickness of the cloud in the observer's line of sight increases. The results could have application in many fields (e.g. modelling diffuse radiance distributions for cloudy skies).     

实验室质量管理体系内部审核的实施

在实施ISO／IEC17025：1999标准《检测和校准实验室能力的通用要求》过程中，通过实验室质量管理体系内部审核的实践与系统分析，识别出内部审核实施阶段的关键环节，提出召开首次会议、收集审核证据、确定审核发现和召开末次会议的技术方法，对提高内部审核的质量和有效性、获得可靠的审核结论具有重要意义。     

Estimation of uncertainty of sampling for analysis of pesticide residues

Abstract

A computer model was used to take random samples from primary sample populations obtained from field trials to simulate the uncertainty of sampling for residue analysis of plant commodities and soil. The results indicate about 40%, 30% and 20% relative uncertainty when random samples of size 5, 10 and 25 are taken respectively, from a single lot. Therefore the sample size should be the same for establishing and enforcing legal limits.     

扬中生态环境建设的思考与实践

结合扬中生态环境的基本情况和存在的不足，进行了具体分析，对扬中未来生态建设的发展方向提出了建议及实施措施。     

An application of the theory of kinematics of mixing to the study of tropospheric dispersion

The most common technique used for numerical simulations of tracer mixing is that of the numerical solution of the advection–diffusion equation with the unresolved fluxes parameterized using the similarity theory. Despite correct predictions of the overall directions of transport, models based on a numerical solution of the advection–diffusion equation lack sufficient accuracy to correctly reproduce the coupling of mixing with small scale processes which are sensitive to the microstructure of the tracer distribution. The objective of this paper is to revisit the basic formalism employed in numerical models used to investigate atmospheric tracers. The main mathematical method proposed here is the theory of kinematics of mixing which could be applied effectively for simulations of atmospheric transport processes. At the beginning of the paper, we introduce simple mathematical transformations in order to demonstrate how complex topological structures are created by mixing processes. These idealistic flow systems are essential to explain transport properties of much more complex three-dimensional geophysical flows. An example of the application of the kinematics of mixing to the analysis of tracer transport on a planetary scale is presented in the following sections. The complex filamentary structures simulated in the numerical experiment are evaluated using some commonly applied statistical measures in order to compare the results with the data published in the literature. The results of the experiment are also analysed with the help of simple conceptual models of fluid filaments. The microstructure of the tracer distribution introduced in the paper is essential to increase our understanding of atmospheric transport and to develop more realistic parameterizations of small-scale mixing. The presented results could also be used to improve calculations of the coupling between microphysical processes and tracer mixing.     

次氯酸钠发生器的研制

介绍了电解法生产次氯酸钠的原理 ,并在原有生产工艺的基础上进行了重新设计和对设备的重新选择、改造 ,得出了各个工艺参数的最佳值 ,生产出高品质的次氯酸钠     

Comparison of methods for evaluation of activity of photocatalytic films

Objective

This work aims to investigate the correlation between the photocatalytic activity determined by methylene blue bleaching (DIN 52980), stearic acid degradation, and degradation of acetone in gas phase.

Method

The photocatalytic TiO₂ coatings included in this investigation ranged from thin commercially available coatings (Activ^TM and BioClean^TM) and ready to use suspensions (Nano-X PK1245) to lab-produced PVD and sol?Cgel coatings. XRD analysis of the photocatalytic coatings showed that all the coatings consisted of nanocrystalline anatase, although the thickness and porosity varied considerably.

Results

The study showed that the reproducibility of the activity measurements was good. However, more importantly, the investigation showed that there is a good correlation between the activities determined by the different methods even though the characteristics of the photocatalytic coatings and the organic probe molecules varied considerably.

Conclusion

The overall findings of this work suggest that there is a good correlation between the investigated methods. These results are promising for the future work concerning standardization of methods for determination of the activity of photocatalytic films.     

Impact of overexploitation of shellfish: northeastern coast of India

India has a very extensive coastline of about 7515 km, rich in diverse living resources. These resources continue to deteriorate with rampant harvesting or are altered for other uses such as aquaculture and fisheries. The present paper deals with degrading coastal habitats in northeastern India, and projects the intensity of the stress arising from the collection of tiger prawn seeds (Penaeus monodon) for aquacultural farms and molluskan shells for poultry feed and edible lime. Indiscriminate exploitation of these resources leads to a heavy reduction of the species concerned and other associated marine communities. The magnitude of such destruction has been quantified. The impacts of biodiversity loss and their after-effects on the ecobalance of this coastal system have become a matter of great concern to ecologists to maintain security and sustainability. The authors propose a public awareness program on themes relating to the importance of biodiversity for human livelihoods.