天津城区雨水利用的前景分析

水资源紧缺已成为全球性问题。城市雨水作为一种宝贵的资源,已经成为一些国家和地区的重要水源。通过对天津市降水特征的监测分析,得出天津市降雨量较为充足且集中在6、7、8三个月份,初期径流雨水污染较为严重(路面SS和COD浓度分别为235 mg/L和131 mg/L,屋面SS和COD浓度分别为72 mg/L和53 mg/L),但经弃流初期雨水后的雨水水质较好(路面SS和COD浓度分别为93 mg/L和57 mg/L,屋面SS和COD浓度分别为30 mg/L和21 mg/L),适合作为回用水水源。讨论了在天津市中心城区内具有代表性区域的雨水利用方案,老城区内宜采用小规模雨水利用装置;新建小区宜将雨水集蓄利用、渗透与园艺水景观等相结合;文化保护区内宜将雨水有组织的快速排除,在该区域外实施雨水利用工程;公园、广场可作为大型雨水储蓄池,在少雨季节时,作为回用水水源。     

顶板水力挠动强制卸压煤层瓦斯抽采工程实践*

对塑性松软煤体进行水力挠动较难取得理想的瓦斯增浓提效效果,为克服该措施的局限性,使松软煤层有效卸压增透,可将挠动对象转移至煤层顶板砂岩。基于对顶板砂岩水力挠动裂隙发育、延展及煤层卸压增透机理分析,在试验矿井的松软煤层及顶板砂岩中分别施工钻孔进行水力挠动试验,同时采用多级指标对措施后的瓦斯抽采效果进行考察。结果表明:水力挠动作用下砂岩体内部形成有利于下部煤层瓦斯流动的裂隙网络,抽采流量、浓度及累计抽采纯量大幅提高;但由于高压水作用下松软煤体内部发生塑性变形、裂隙堵塞、瓦斯流动性弱化,导致抽采流量、浓度及累计抽采纯量不升反降。研究结果可为松软煤层实施水力挠动提供参考,以期实现较理想的瓦斯治理效果。     

屋面雨水回收用于冷却补水设计实例

以广州某商业中心为例,介绍了屋面雨水回收用于空调冷却塔补水的设计。根据广州地区雨水资源丰富、水质良好及工程项目的特点,确定了雨水回收范围、回收用途,并进行了月均水量平衡计算。经济效益分析表明,该系统每年可节约市政供水34000m3,经济效益和环境效益显著。     

华丰矿采场顶板破裂位置实时微地震监测技术研究

简单介绍了微地震监测的原理,结合华丰煤矿的具体应用情况,介绍了微地震监测技术的应用方法、特点及其效果.应用矿山压力理论建立了华丰矿采场顶板运动规律模型,并计算得出了直接顶和老顶的范围.与微地震监测结果比较,发现两者结果基本一致,证明微地震监测可以用于预测顶板运动规律.微地震监测技术对确定采场覆岩"两带"高度、预报采场顶板破坏、预测煤与瓦斯突出,从而预防灾害发生、保证煤矿安全生产并提高资源回采率等具有重要意义.     

城市典型不透水下垫面径流中邻苯二甲酸酯的污染特征

在我国属于优先控制污染物的邻苯二甲酸酯(PAEs)应用依然广泛,径流中的PAEs对受纳水体的污染值得高度关注.对上海典型的城市不透水下垫面路面及屋面降雨径流中6种优先控制PAEs的质量浓度进行监测,评价城市不透水下垫面径流中PAEs的污染特征.结果表明,上海市路面及屋面径流中Σ_6PAEs的EMC平均值分别为170. 64μg·L~(-1)和40. 92μg·L~(-1),与国外城市相比污染严重,DEHP为主要PAEs污染物.对不同类型水样中PAEs含量差异的显著性分析发现,不同下垫面径流中低分子量(LMW) PAEs浓度不存在显著性差异,路面径流中高分子量(HMW) PAEs浓度显著高于屋面径流及雨水(P 0. 01),道路交通是造成下垫面径流PAEs污染的重要因素.路面径流中PAEs、TSS及COD浓度随降雨历时的变化特征表明,PAEs的变化趋势与TSS及COD相同,初期径流浓度较高,存在初期冲刷效应.不透水下垫面径流中PAEs浓度及其影响因素的相关分析表明,屋面径流中Σ_6PAEs浓度与降雨强度呈负相关,与TSS呈正相关.路面径流中Σ_6PAEs浓度与降雨量、降雨强度呈负相关,与前期晴天数、TSS、COD呈正相关.下垫面径流中Σ_6PAEs浓度与表面累积的颗粒物含量有关. DEHP、DBP为我国《地表水环境质量标准》控制污染物,路面及屋面径流中DEHP的浓度超过8μg·L~(-1)的标准值分别达到32、7倍,路面径流中DBP浓度在多数降雨事件中超过标准值3μg·L~(-1),屋面径流中DBP浓度在多数降雨事件中低于标准值,下垫面径流直接排放对受纳水体,特别是饮用水水源地存在威胁.     

不同降雨条件下植被对绿色屋顶径流调控效益影响

植被是绿色屋顶的重要组成部分,可通过截留雨水和蒸散耗水等过程影响绿色屋顶的径流调控效益.本文基于太阳花(Portulaca grandiflora)、佛甲草(Sedum lineare)、高羊茅(Festuca elata)和无植被等4种植被覆盖类型绿色屋顶2017年雨季26场降雨径流过程的监测数据,从径流和洪峰削减、产流和峰现时间延迟四方面定量分析植被在不同降雨条件下对绿色屋顶径流调控效益的影响.结果表明,绿色屋顶径流削减率与降雨量呈显著负相关(P 0. 01),降雨量10 mm时,绿色屋顶径流削减率等于或接近100%;降雨量超过30 mm,所有绿色屋顶的径流削减率降低到70%以下;当降雨量达到监测期内最大的81. 4 mm时,各绿色屋顶径流削减率都低于55%.植被覆盖类型对绿色屋顶径流调控效益的影响随降雨条件而改变,大雨条件下不同植被覆盖类型绿色屋顶的径流削减率差异最大,中雨和暴雨条件下次之,小雨条件下因各绿色屋顶几乎都不产流而无明显差异.在中雨、大雨和暴雨条件下,有植被覆盖绿色屋顶的径流削减率、洪峰削减率、产流和峰现时间延迟等4个指标都明显优于无植被覆盖的绿色屋顶.株高和单位面积地上生物量最高的太阳花绿色屋顶的径流调控效益优于佛甲草绿色屋顶.     

天津中心城区典型区域雨水径流污染特性

不同生活水平区域因生产结构、生活方式等因素的不同,导致雨水径流指标呈现出区域差异性特征。针对天津雨水径流污染问题,以天津中心城区降雨特征为研究对象,选取天津中心城区5个区域,研究不同生活水平区域与径流污染之间的关系。通过对试验区域内9个监测点5次降雨径流过程分析发现,天津中心城区道路径流中固体悬浮物（SS）、化学需氧量（COD）、总氮（TN）、氨氮（NH₃-N）和总磷（TP）的次降雨径流平均浓度（EMC）值分别为159.5~386.1 mg/L,74.6~157.6 mg/L,6.5~10.2 mg/L,1.9~5.4 mg/L和0.38~1.07 mg/L,屋面径流中SS、COD、TN、NH₃-N和TP的EMC值分别为107.7~135.1 mg/L,70.5~102.3 mg/L,8.3~9.1 mg/L,3.1~4.1 mg/L,0.24~0.69 mg/L;对于道路径流,SS、COD和TP浓度与生活水平拟合线的斜率分别为-104.7,-44.8和-0.28,SS、COD显著受区域生活水平影响,呈负相关关系;径流中SS与COD的相关系数为0.86,具有很强的相关性;区域生活水平越低,降雨量对径流污染的影响越大;对于屋面径流,污染浓度与区域生活水平拟合程度较差,无显著关系;降雨量对屋面径流的影响较小,主要影响因素为初期效应的强弱;区域污染源为生活源且具有高生活水平时,可采用Sartor-Boyd冲刷模型进行模拟。     

HEALTH RISKS ASSOCIATED WITH CONSUMPTION OF UNTREATED WATER FROM HOUSEHOLD ROOF CATCHMENT SYSTEMS1

ABSTRACT: Rainwater harvesting is receiving increased attention worldwide as an alternative source of drinking water. Although collected rainwater is typically consumed without any type of disinfection, the microbial quality of this type of water source can be poor. Around the world, consumers of collected and stored rainwater may be at considerable risk to a variety of infectious diseases. This review presents studies attributing specific risks of diseases to the consumption of contaminated rainwater. Diseases attributed to the consumption of untreated rainwater include bacterial diarrheas due to Salmonella and Campylobacter, bacterial pneumonia due to Legionella, botulism due to Clostridium, tissue helminths, and protozoal diarrheas from Giardia and Cryptosporidium. Simple indicator systems such as fecal coliform measurements may prove to be inadequate for determining microbial risks associated with consumption of water from rainwater catchment systems.     

Stability and Mixing of a Vertical Axisymmetric Buoyant Jet in Shallow Water

The stability, mixing and effect of downstream control on axisymmetric turbulent buoyant jets discharging vertically into shallow stagnant water is studied using 3D Reynolds-averaged Navier–Stokes equations (RANS) combined with a buoyancy-extended k –ε model. The steady axisymmetric turbulent flow, temperature (or tracer concentration) and turbulence fields are computed using the finite volume method on a high resolution grid. The numerical predictions demonstrate two generic flow patterns for different turbulent heated jet discharges and environmental parameters (i) a stable buoyant discharge with the mixed fluid leaving the vertical jet region in a surface warm water layer; and (ii) an unstable buoyant discharge with flow recirculation and re-entrainment of heated water. A stratified counterflow region always appears in the far-field for both stable and unstable buoyant discharges. Provided that the domain radius L exceeds about 6H, the near field interaction and hence discharge stability is governed chiefly by the jet momentum length scale to depth ratio l_M/H, regardless of downstream control. The near field jet stability criterion is determined to be l_M/H = 3.5. A radial internal hydraulic jump always exists beyond the surface impingement region, with a 3- to 6-fold increase in dilution across the jump compared with vertical buoyant jet mixing. The predicted stability category, velocity and temperature/concentration fields are well-supported by experiments of all previous investigators.     

Calculation of Entrainment in Density Jumps

The density jump in a two-layer channel flow of miscible fluids, in which one of the layers is infinitely deep and at rest, is analyzed using the momentum flux and mass flux conservation equations. The analysis yields simple equations relating the heights upstream and downstream of the jump with the upstream Froude number and the rate of entrainment into the moving layer, as well as a relation between the maximum possible entrainment and the upstream Froude number. The analysis also shows that when the flow down-stream of the jump is controlled by an obstruction or a contraction, the entrainment rate into the jump depends solely on the dimensionless obstruction height contraction ratio and the upstream Froude number.