某处理厂CASS池改造工艺选择及运行效果

随着污水处理厂排到受纳水体标准的不断提高及区域污染物排放限值的要求,已建的污水处理厂需要提标改造提高排放标准。本文所提工程对现有的CASS池进行改造,通过投加悬浮填料形成CASS+MBBR工艺,其中TN污染物的去除率可提高到8%~15%间,其它污染物也能达到预期的设计标准。     

Controls on Nutrients Across a Prairie Stream Watershed: Land Use and Riparian Cover Effects

Nutrient inputs generally are increased by human-induced land use changes and can lead to eutrophication and impairment of surface waters. Understanding the scale at which land use influences nutrient loading is necessary for the development of management practices and policies that improve water quality. The authors assessed the relationships between land use and stream nutrients in a prairie watershed dominated by intermittent stream flow in the first-order higher elevation reaches. Total nitrogen, nitrate, and phosphorus concentrations were greater in tributaries occupying the lower portions of the watershed, closely mirroring the increased density of row crop agriculture from headwaters to lower-elevation alluvial areas. Land cover classified at three spatial scales in each sub-basin above sampling sites (riparian in the entire catchment, catchment land cover, and riparian across the 2 km upstream) was highly correlated with variation in both total nitrogen (r² = 53%, 52%, and 49%, respectively) and nitrate (r² = 69%, 65%, and 56%, respectively) concentrations among sites. However, phosphorus concentrations were not significantly associated with riparian or catchment land cover classes at any spatial scale. Separating land use from riparian cover in the entire watershed was difficult, but riparian cover was most closely correlated with in-stream nutrient concentrations. By controlling for land cover, a significant correlation of riparian cover for the 2 km above the sampling site with in-stream nutrient concentrations could be established. Surprisingly, land use in the entire watershed, including small intermittent streams, had a large influence on average downstream water quality although the headwater streams were not flowing for a substantial portion of the year. This suggests that nutrient criteria may not be met only by managing permanently flowing streams.     

面向区域二次污染风险控制的臭氧及其前体物卫星遥感监测

日益突出的臭氧(O_3)污染已成为继PM2. 5之后我国大气污染防治的又一艰巨任务。由于氮氧化物(NO_x)、挥发性有机物(VOCs)这2种前体物的减排难度较大,且与O_3浓度存在复杂的非线性关系,准确获取O_3及NO_x、VOCs的时空分布对制定有效的防控措施至关重要。基于卫星遥感可定量反演O_3及2种前体物的代表性物种——二氧化氮(NO_2)、甲醛(HCHO)及乙二醛(C_2H_2O_2)的时空分布信息。面向区域O_3污染分析和防控应用,综述了卫星遥感对O_3及NO_2、HCHO、C_2H_2O_2的探测能力,以及利用遥感手段分析区域O_3及其前体物的传输。进而从O_3与NO_x、VOCs关系的角度,分析了利用卫星反演的前体物表征O_3生成风险的可行性。最后对卫星在区域O_3及其前体物监测方面的前景趋势提出了思考。     

水力停留时间对膜生物反应器复合工艺污水处理特性的影响

开发了厌氧-多级好氧/缺氧-膜生物反应器复合工艺,在不同水力停留时间(HRT)下,考察了系统对污染物去除效果及其膜污染的特性.结果表明,在试验选定的HRT范围内,系统对TN和TP的去除率随着HRT的降低而升高,当HRT为8.70、6.96、4.97 h时,系统对TN和TP的平均去除率分别为73.15%、79.76%、81.98%和67.79%、80.99%、92.16%.但是,较低HRT条件下膜通量较高,会加剧膜污染进程.解决这一问题的措施是增加膜组件个数,从而在不提高膜通量的情况下使系统保持较低的HRT,保证系统高效稳定的污染物去除效果.     

超重力技术治理火炸药行业氮氧化物的初步研究

火炸药行业排放氮氧化物(NOX)具有浓度高、排放点不集中和间歇排放的特点,采用超重力技术对尾气中高浓度的NOX进行湿法吸收.以清水为吸收剂,研究了进气量、液气比和超重力因子等因素对NOX吸收率的影响.结果表明,单级NOX吸收率可达64.69%(β＝90).超重力旋转填料床具有占地面积小、投资低和操作方便等优点,适宜于火炸药行业吸收NOX.     

射流曝气周期活性污泥法脱氮除磷研究

针对零星居民点的污水处理,开发了射流曝气周期活性污泥法工艺.它是一种连续进水、周期性间歇曝气的改良型SBR工艺,也是一种时间程序和空间程序相结合的污水处理工艺,具有良好的脱氮除磷效果.试验表明,在水力负荷4 m3/d,曝气周期为每2 h曝气15 min、静置105 min的条件下,出水COD为48.8～53.5 mg/L,去除率达79.4%～80.5%;出水TN为2.81～3.98 mg/L,去除率达82.4%～89.4%;出水NH3-N为0.36～0.78 mg/L,去除率高达96.4%～98.4%;出水TP为0.63～1.18 mg/L,去除率为67.2%～78.9%,均可达到《城镇污水处理厂污染物排放标准》(GB 18918-2002)中的一级B排放标准.     

沸石用于去除废水中的氨氮

天然沸石及改性沸石对氨氮有很强的选择性吸附能力。介绍了沸石去除废水中氨氮的应用研究,包括在O/A生物处理系统、二级氧化塘处理系统、土地处理系统、湿地系统和堆肥系统等中的应用。分析了氨氮在沸石上发生吸附和离子交换的主要影响因素和规律。为开拓沸石在废水处理中的应用提供科学与技术基础。     

The food-print of Paris: long-term reconstruction of the nitrogen flows imported into the city from its rural hinterland

Between the tenth and twentieth century the population of Paris city increased from a few thousand to near 10 million inhabitants. In response to the growing urban demand during this period, the agrarian systems of the surrounding rural areas tremendously increased their potential for commercial export of agricultural products, made possible by a surplus of agricultural production over local consumption by humans and livestock in these areas. Expressed in terms of nitrogen, the potential for export increased from about 60 kg N/km2/year of rural territory in the Middle Ages, to more than 5,000 kg N/km2/year from modern agriculture. As a result of the balance between urban population growth and rural productivity, the rural area required to supply Paris (i.e. its food-print) did not change substantially for several centuries, remaining at the size of the Seine watershed surrounding the city (around 60,000 km2). The theoretical estimate of the size of the supplying hinterland at the end of the eighteenth century is confirmed by the figures deduced from the analysis of the historical city toll data (octroi). During the second half of the twentieth century, the ‘food-print’ of Paris reduced in size, owing to an unprecedented increase in the potential for commercial export associated with modern agricultural systems based on chemical N fertilization. We argue that analysing the capacity of territories to satisfy the demand for nitrogen-containing food products of local or distant urban population and markets might provide new and useful insights when assessing world food resource allocation in the context of increasing population and urbanization.     

Modelling the long-term soil response to atmospheric deposition at intensively monitored forest plots in Europe

The dynamic soil chemistry model SMART was applied to 121 intensive forest monitoring plots (mainly located in western and northern Europe) for which both element input (deposition) and element concentrations in the soil solution were available. After calibration of poorly known parameters, the model accurately simulated soil solution concentrations for most plots as indicated by goodness-of-fit measures, although some of the intra-annual variation especially in nitrate and aluminium concentrations could not be reproduced. Model evaluations of two emission-deposition scenarios (current legislation and maximum feasible reductions) for the period 1970-2030 show a strong reduction in sulphate concentrations between 1980 and 2000 in the soil due to the high reductions in sulphur emissions. However, current legislation hardly reduces future nitrogen concentrations, whereas maximum feasible reductions reduces them by more than half. Maximum feasible reductions are also more effective in increasing pH and reducing aluminium concentrations, mostly below ‘critical’ values.     

The importance of ammonium mobility in nitrogen-impacted unfertilized grasslands: A critical reassessment

The physico-chemical absorption characteristics of ammonium-N for 10 soils from 5 profiles in York, UK, show its high potential mobility in N deposition-impacted, unfertilized, permanent grassland soils. Substantial proportions of ammonium-N inputs were retained in the solution phase, indicating that ammonium translocation plays an important role in the N cycling in, and losses from, such soils. This conclusion was further supported by measuring the ammonium-N leaching from intact plant/soil microcosms. The ammonium-N absorption characteristics apparently varied with soil pH, depth and soil texture. It was concluded for the most acid soils especially that ammonium-N leached from litter horizons could be seriously limiting the capacity of underlying soils to retain ammonium. Contrary to common opinion, more attention therefore needs to be paid to ammonium leaching and its potential role in biogeochemical N cycling in semi-natural soil systems subject to atmospheric pollution.