城市污水中部分亚硝化-厌氧氨氧化工艺NOB抑制策略的研究进展

城市污水具有低温低氨氮(NH₄⁺-N)的特点,不利于亚硝酸盐氧化菌(NOB) 的长期稳定抑制,而NOB的过度增殖会导致出水硝氮 (NO₃⁻-N) 指标升高,对其他功能微生物产生竞争性抑制作用,进而降低部分亚硝化-厌氧氨氧化 (PN/A) 系统的脱氮性能和稳定性。以氨氧化菌 (AOB) 、NOB、厌氧氨氧化菌 (AnAOB) 等功能微生物动力学参数、生长特性为基础,探讨了主流条件下的城市污水处理系统中优势功能微生物的变迁。综述了当前普遍采用的低溶氧 (DO) 限制、好氧-缺氧交替、生物强化、投加抑制剂、泥龄 (SRT) 筛选、低亚氮等NOB抑制策略,并总结了单一抑制策略无法长期、稳定抑制NOB活性,需进一步考察多重策略的联合作用。继而,从性能和工艺复杂程度,对目前普遍采用的实现多重策略联合调控的反应系统进行了探讨。提出采用活性污泥模型 (ASM) 与实验相结合的方法,为助力主流PN/A工艺运行调控提供了新思路,并指出深化基础理论的研究,开发新型的组合工艺强化NOB的抑制及脱氮性能稳定也是可行的发展方向。     

激冷水合改性镁渣脱硫剂性能实验

为了达到以废治废的目的,对镁冶炼产生的废弃物-镁还原渣通过激冷水合方式制备脱硫剂进行研究。采用XRD获得不同激冷条件下样品的物质组成,通过SEM研究炽热镁渣激冷样品的表观形貌。通过实验室激冷水合实验研究不同水合参数对水合反应以及脱硫性能的影响。对比现场炽热镁渣激冷水合与实验室激冷水合活化方式下水合样品的脱硫性能。结果表明：镁渣激冷后的主要成分为β-C2S,且表面变得粗糙多孔;脱硫钙转化率与水合反应程度间存在抛物线关系;当激冷温度为950℃,水合温度为50℃,实验室炽热镁渣激冷水合反应所制备的脱硫剂在水合时间为6 h时,钙转化率最高,为14.1%,而水合时间为8 h时,水合反应程度最大,为0.16 g·g-1;与实验室炽热镁渣激冷水合样品和自然冷却水合样品相比,现场炽热镁渣激冷水合样品的钙转化率最高,达30.33%。     

Validation of the UK Met. Office’s name model against the ETEX dataset

The ETEX 1 data set has been used to assess the performance of the UK Met Office’s long-range dispersion model NAME. In terms of emergency response modelling the model performed well, successfully predicting the overall spread and timing of the plume across Europe. However, in common with most other models, NAME overpredicted the observed concentrations. This is in contrast with other NAME validation studies which indicate either no significant bias or a tendency to underpredict concentrations. This suggests the reasons for overpredicting are specific to the ETEX situation. Explanations include inadequate vertical diffusion or transport, possible venting by convective activity, and experimental errors. An assessment of a range of advection schemes of varying complexity indicated no clear advantage, at present, in using more sophisticated random walk techniques at long range, a simple diffusion coefficient based scheme providing some of the best results. A brief look is also taken at a simulation of the more problematical ETEX 2 release.     

微波催化燃烧技术处理印刷包装行业VOCs

微波催化燃烧技术将微波辐照与吸波型催化剂相结合,可用于对挥发性有机化合物(VOCs)进行催化燃烧处置。研制了Pt/CuMnCeO_x/堇青石和Pt/CuMnCeO_x/纳米陶瓷整体式蜂窝状催化剂,并开发了微波催化燃烧VOCs的装置,将其应用于印刷包装行业的VOCs治理。通过操作条件的优化,考察了微波催化燃烧技术对VOCs的实际处理效果。同时,对催化剂表面形貌、比表面积和晶体结构等进行了测试分析。结果表明：Mn₃O₄/Mn₂O₃、CeO₂/Ce₂O₃、CuMn₂O₄和PtO等尖晶石的存在降低了反应温度、提高了储氧释氧能力和催化剂活性;催化剂的介孔结构和较大的比表面积有利于VOCs在孔隙内部的扩散,并可延长VOCs在催化剂上的停留时间。在催化剂床层体积330 L、微波功率13.6 kW、进气质量浓度1 520 mg·m^-3和进气量440 m³·h⁻¹的条件下,床层温度可达到420 ℃,此时催化剂床层温度及VOCs去除率保持稳定。当进气质量浓度分别为约4 500 mg·m⁻³和2 800 mg·m⁻³时,VOCs的去除率分别为90%和96%。考察燃烧热量发现,大气量的VOCs在催化剂表面的停留时间短且带走热量多,从而导致VOCs去除率下降;高浓度VOCs在燃烧时会因释放出更多热量,从而提高床层温度和VOCs去除率。在确保催化剂表面活性位点充足的条件下,微波催化燃烧工艺适合处理中高浓度的印刷包装行业VOCs。同时,利用VOCs燃烧释放的热量来保持床层高温,还可达到节能降耗的目的。本研究可为印刷包装行业的VOCs治理提供参考。     

Effects of pore volume-transmissivity correlation on transport phenomena

The relevant velocity that describes transport phenomena in a porous medium is the pore velocity. For this reason, one needs not only to describe the variability of transmissivity, which fully determines the Darcy velocity field for given source terms and boundary conditions, but also any variability of the pore volume. We demonstrate that hydraulically equivalent media with exactly the same transmissivity field can produce dramatic differences in the displacement of a solute if they have different pore volume distributions. In particular, we demonstrate that correlation between pore volume and transmissivity leads to a much smoother and more homogeneous solute distribution. This was observed in a laboratory experiment performed in artificial fractures made of two plexiglass plates into which a space-dependent aperture distribution was milled. Using visualization by a light transmission technique, we observe that the solute behaviour is much smoother and more regular after the fractures are filled with glass powder, which plays the role of a homogeneous fault gouge material. This is due to a perfect correlation between pore volume and transmissivity that causes pore velocity to be not directly dependent on the transmissivity, but only indirectly through the hydraulic gradient, which is a much smoother function due to the diffusive behaviour of the flow equation acting as a filter. This smoothing property of the pore volume-transmissivity correlation is also supported by numerical simulations of tracer tests in a dipole flow field. Three different conceptual models are used: an empty fracture, a rough-walled fracture filled with a homogeneous material and a parallel-plate fracture with a heterogeneous fault gouge. All three models are hydraulically equivalent, yet they have a different pore volume distribution. Even if piezometric heads and specific flow rates are exactly the same at any point of the domain, the transport process differs dramatically. These differences make it important to discriminate in situ among different conceptual models in order to simulate correctly the transport phenomena. For this reason, we study the solute breakthrough and recovery curves at the extraction wells. Our numerical case studies show that discrimination on the basis of such data might be impossible except under very favourable conditions, i.e. the integral scale of the transmissivity field has to be known and small compared to the dipole size. If the latter conditions are satisfied, discrimination between the rough-walled fracture filled with a homogeneous material and the other two models becomes possible, whereas the parallel-plate fracture with a heterogeneous fault gouge and the empty fracture still show identifiability problems. The latter may be solved by inspection of aperture and pressure testing.     

Perfluorocarbon background concentrations in Europe

Five studies of the background level of several perfluorocarbon compounds in Europe are here presented together with measurements from the European Tracer Experiment (ETEX). The tracers used during the two ETEX tracer releases were the perfluorocarbons (PFCs); perfluoromethylcyclohexane (C₇F₁₄, PMCH) and perfluoromethylcyclopentane (C₆F₁₂, PMCP). Their background concentrations were detected by using both passive and active sampling techniques, to define the spatial and temporal variation of the PFCs over Europe. Also the background variations of four isomers of the PFC compound perfluorodimethylcyclohexane (C₈F₁₆, PDCH) were studied. The results were compared to other PFC tracer studies in the U.S.A. and Europe. The mean and median values of the measured PFCs were found to vary slightly and randomly in space and time. They were found to be higher and to have a larger standard deviation than the measurements from the American studies. The background concentrations were still found to be low and stable enough for PFCs to be highly suitable for use in tracer studies. The following concentrations were found: PMCP; 4.6±0.3 fl ℓ^-1, PMCH: 4.6±0.8 fl ℓ^-1, ocPDCH: 0.96±0.33 fl ℓ^-1, mtPDCH: 9.3±0.8 fl ℓ^-1, mcPDCH: 8.8±0.8 fl ℓ^-1, ptPDCH: 6.1±0.8 fl ℓ^-1. A study of the correlation between the measured PFC compounds showed a significant correlation between most of the compounds, which indicate that there are no major PFC sources in Europe.     

A multi-directional tracer test in the fractured Chalk aquifer of E. Yorkshire, UK

A multi-borehole radial tracer test has been conducted in the confined Chalk aquifer of E. Yorkshire, UK. Three different tracer dyes were injected into three injection boreholes and a central borehole, 25 m from the injection boreholes, was pumped at 330 m(3)/d for 8 days. The breakthrough curves show that initial breakthrough and peak times were fairly similar for all dyes but that recoveries varied markedly from 9 to 57%. The breakthrough curves show a steep rise to a peak and long tail, typical of dual porosity aquifers. The breakthrough curves were simulated using a 1D dual porosity model. Model input parameters were constrained to acceptable ranges determined from estimations of matrix porosity and diffusion coefficient, fracture spacing, initial breakthrough times and bulk transmissivity of the aquifer. The model gave equivalent hydraulic apertures for fractures in the range 363-384 microm, dispersivities of 1 to 5 m and matrix block sizes of 6 to 9 cm. Modelling suggests that matrix block size is the primary controlling parameter for solute transport in the aquifer, particularly for recovery. The observed breakthrough curves suggest results from single injection-borehole tracer tests in the Chalk may give initial breakthrough and peak times reasonably representative of the aquifer but that recovery is highly variable and sensitive to injection and abstraction borehole location. Consideration of aquifer heterogeneity suggests that high recoveries may be indicative of a high flow pathway adjacent, but not necessarily connected, to the injection and abstraction boreholes whereas low recoveries may indicate more distributed flow through many fractures of similar aperture.     

油基岩屑热脱附处理工艺参数优化

为了探究热脱附装置降低能耗的方法,对新疆油田某井油基岩屑热脱附处理工艺参数进行了研究。结果表明：在残渣的含油率≤2%的标准下,当加热温度、停留时间、油基岩屑固相含量这3个关键因素变量分别为350~550 ℃、35~55 min、60%~90%时,油基岩屑热脱附处理后残渣的含油率能达到标准要求;在以上条件下,以能耗为考核指标,通过响应曲面法研究发现,单因素变量的交互项均对能耗影响显著;将加热温度由550 ℃降低至430 ℃时,停留时间由45 min降至40 min,能耗可节约17.47%,残渣的含油率<0.3%;通过调整热脱附工艺参数,可在油基岩屑热脱附处理后残渣的含油率达标的基础上,实现节能降耗。上述研究结果可为合理设置油基岩屑热脱附装置的运行工艺参数提供参考。     

Evaluation of the effect of meteorological data resolution on Lagrangian particle dispersion simulations using the ETEX experiment

This paper presents results from a series of numerical experiments designed to evaluate operational long-range dispersion model simulations, and to investigate the effect of different temporal and spatial resolution of meteorological data from numerical weather prediction models on these simulations. Results of Lagrangian particle dispersion simulations of the first tracer release of the European Tracer Experiment (ETEX) are presented and compared with measured tracer concentrations. The use of analyzed data of higher resolution from the European Center for Medium-Range Weather Forecasts (ECMWF) model produced significantly better agreement between the concentrations predicted with the dispersion model and the ETEX measurements than the use of lower resolution Navy Operational Global Atmospheric Prediction System (NOGAPS) forecast data. Numerical experiments were performed in which the ECMWF model data with lower vertical resolution (4 instead of 7 levels below 500 mb), lower temporal resolution (12 h instead of 6 h intervals), and lower horizontal resolution (2.5° instead of 0.5°) were used. Degrading the horizontal or temporal resolution of the ECMWF data resulted in decreased accuracy of the dispersion simulations. These results indicate that flow features resolved by the numerical weather prediction model data at approximately 45 km horizontal grid spacing and 6 h time intervals, but not resolved at 225 km spacing and 12 h intervals, made an important contribution to the long-range dispersion.     

合肥地区不同类型源头溪流暂态存储能力及氮磷滞留特征

为揭示合肥地区不同类型源头溪流暂态存储能力及氮磷吸收滞留的基本特征,在城区和城郊筛选4条典型源头溪流,并以NH4Cl、KH2PO4为添加营养盐,以NaCl为保守型示踪剂,开展现场示踪实验.在此基础上,利用OTIS模型水文参数(D、A、As和α),计算暂态存储指标(Ts、Tc、Ls、Rh和 Fmed200),进而开展暂态存储能力分析,并以NH4+-N 和 SRP一阶吸收系数(λ、λs)解析氮磷滞留特征.结果表明:4条溪流水体的α值均处于10-4~10-3数量级;各溪流Tc基本都显著超过Ts,意味着这些溪流水体溶质滞留效应主要来自主渠道流动水体,而不是暂态存储区;根据Tc、Ts、Ls和Rh等指标,得到各源头溪流暂态存储能力排序为:二十埠河二级支流>二十埠河一级支流>十五里河源头段>关镇河支渠;4条源头溪流主渠道流动水体与暂态存储区的NH4+-N、SRP滞留特征存在很大的差异,并且二十埠河一、二级支流和十五里河均不同程度出现λ-NH4+、λs-NH4+为负值的现象,意味着这些水体对于NH4+-N既具有短期存储作用,也起着\"源\"的作用.