Environmental assessment of two home composts with high and low gaseous emissions of the composting process

A Life Cycle Assessment (LCA) of two home composts with low and high gaseous emissions of the composting process is presented. The study focused on the gaseous emissions of the composting process. Gaseous emissions of methane, nitrous oxides, ammonia and volatic organic compounds of the composting process were experimentally measured in field real trials. The results showed that the differences in gaseous emissions between the two home composts were 4.5, 5.8 and 52 for methane, nitrous oxides and ammonia, respectively. Higher emissions of nitrous oxides and methane affected significantly the category of global warming potential, while higher emissions of ammonia affected mainly the categories of acidification potential, eutrophication potential and photochemical oxidation. The differences found in the compost emissions were attributable to the composting production management (quality and composition of waste stream, frequency mixing of waste, humidity and temperature monitoring, among others) as well as weather conditions (temperature and humidity).     

Hydrologic Controls on Nitrogen and Phosphorous Dynamics in Relict Oxbow Wetlands Adjacent to an Urban Restored Stream

Although wetlands are known to be sinks for nitrogen (N) and phosphorus (P), their function in urban watersheds remains unclear. We analyzed water and nitrate (NO₃^?) and phosphate (PO₄^3?) dynamics during precipitation events in two oxbow wetlands that were created during geomorphic stream restoration in Baltimore County, Maryland that varied in the nature and extent of connectivity to the adjacent stream. Oxbow 1 (Ox1) received 1.6‐4.2% and Oxbow 2 (Ox2) received 4.2‐7.4% of cumulative streamflow during storm events from subsurface seepage (Ox1) and surface flow (Ox2). The retention time of incoming stormwater ranged from 0.2 to 6.7 days in Ox1 and 1.8 to 4.3 days in Ox2. Retention rates in the wetlands ranged from 0.25 to 2.74 g N/m²/day in Ox1 and 0.29 to 1.94 g N/m²/day in Ox2. Percent retention of the NO₃^?‐N load that entered the wetlands during the storm events ranged from 64 to 87% and 23 to 26%, in Ox1 and Ox2, respectively. During all four storm events, Ox1 and Ox2 were a small net source of dissolved PO₄^3? to the adjacent stream (i.e., more P exited than entered the wetland), releasing P at a rate of 0.23‐20.83 mg P/m²/day and 3.43‐24.84 mg P/m²/day, respectively. N and P removal efficiency of the oxbows were regulated by hydrologic connectivity, hydraulic loading, and retention time. Incidental oxbow wetlands have potential to receive urban stream and storm flow and to be significant N sinks, but they may be sources of P in urban watersheds.     

几种植物对潜流型湖滨湿地中氮磷的处理效果比较

湖滨带是连接湖泊水域生态系统与陆地生态系统的一个功能过渡区,是湖泊的最后一道保护屏障。在河流的入湖口建造湖滨湿地,可有效净化入湖水中携带的部分有机污染物、营养盐等。湿地净化污染物的机理极为复杂,其中植被起着重要的作用。选择适当的植物是构建湿地系统的关键。以云南省抚仙湖北岸的湖滨湿地——马料河潜流型湿地为研究对象,探讨了美人蕉(Cannaindica),菖蒲(AcoruscalamusLinn),伞竹(Cyperusalternifolius),香蒲(Typhaelatifolia)四种不同植被系统的潜流型湖滨湿地去除污水中营养盐的效果,为抚仙湖湖滨带人工湿地的合理优化选择植物提供一定的依据。结果表明,四种植被系统的潜流湿地对总氮和总磷均有一定的去除效果。但是由于湿地长期运行而疏于管理,植物没有定期收割翻新,四种植物的氮磷去除率差别不太大,去除效果均不太佳。其中,美人蕉对总氮和总磷的去除效果较好,其去除率分别是30.4%,19.13%,其次为香蒲和伞竹,效果较差的是菖蒲。并且实验表明,暴雨对四种植物湿地氮的去除效果有很大的影响。连续几天的暴雨情况下,四种植物系统氮的去除率都很低。     

水热法制备N掺杂纳米TiO2及其光催化活性研究

以钛酸四丁酯和氨水为前驱物,采用水热法制备N掺杂TiO2纳米微粒,利用X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)等技术对不同条件下制备的产物进行了表征.探讨了不同体积比的前驱物、水热温度、水热时间及煅烧温度对水热产物的影响;考察了N掺杂催化剂在紫外线和可见光下光催化降解甲基橙和苯酚的催化性能.     

液相络合-铁屑还原-酸吸收回收法脱除烟气中的NOx

用"Fe2 螯合剂吸收-铁屑还原-酸吸收"回收法脱除烟气中的NOx,研究了铁屑脱硝过程的影响因素,确定了脱硝过程的合适工艺条件,并对络合脱硝溶液的再生和循环利用进行了研究.结果表明:最佳工艺参数为:络合脱硝溶液中Fe2 EDTA浓度20mmol·l-1,pH值6.0,温度65℃;在此条件下,用两个反应器串联,对O2含量为10.5%的模拟烟气可取得90%以上的脱硝效率.     

玉米-花生混作系统中的氮铁营养效应

采用盆栽试验的方法研究了不同施氮水平和种间相互作用对花生铁营养、根瘤固氮能力以及系统氮营养的影响。结果表明,在本试验种植密度下,施氮水平和种植方式对下针期单株花生生物量无显著影响。在不同施氮水平下,玉米-花生混作不仅均显著改善了花生铁营养,而且玉米对氮素的大量吸收显著降低了混作花生根际土壤硝态氮的质量分数,从而使得花生根瘤数增加,根瘤固氮酶活性增强。混作花生铁营养受混作玉米氮营养及作物发育状况的影响较大,并且下针期花生固氮酶活性受施氮抑制及花生铁营养改善的促进。这说明,根际土壤硝态氮的质量分数的降低和花生铁营养的改善是石灰性土壤上花生固氮能力增强的关键因素,而花生生物固氮作用的增强是该混作系统体现氮营养优势的主要原因。     

Fe2+EDTA溶液络合-铁还原脱除烟气中NO

提出了“Fe2 螯合剂络合-铁粉还原-酸吸收”回收法脱除烟气中NO的新工艺,重点研究了模拟烟气中O2体积分数对NO络合量的影响,以及铁粉用量、铁粉粒径、搅拌速度对NO脱除效率的影响,确定了最佳的铁粉脱氮工艺条件,并对铁粉和铁屑的脱氮效果进行了比较。结果表明,烟气中O2的体积分数从0%增加到4.2%,NO络合量下降90.2%;NO脱除效率随铁粉用量和反应器搅拌速度的增加而增加,随铁粉粒径的增加而降低;过程的最佳工艺参数为,铁粉用量0.8g,铁粉粒径≤0.077mm,搅拌速度900r·min-1,在此条件下,对O2体积分数为5%的模拟烟气在搅拌反应器中可取得90%以上的NO脱除效率;用铁粉在1台搅拌反应器中取得的NO脱除效率和用铁屑在2个鼓泡反应器串联时所取得的效率相当。     

消泡剂硅油I在工业废水氨氮测定中的应用

对色泽较深，含杂质量较高的废水加硅油I以抑制测定中蒸馏产生的泡沫．结果表明，在250ml水样中加硅油IO．10～1．25ml，即可收到理想效果．硅油I性质稳定，不随水蒸汽蒸出，对测定无干扰．     

Dairy washwater treatment using a horizontal flow biofilm system

In Ireland, dairy farmyard washwater commonly comprises farmyard run-off and dairy parlour washings. Land-spreading is the most widely used method for treating this wastewater. However, this method can be labour intensive and can cause, in some cases, the degradation of surface and ground waters, mainly due to nitrogen contamination. In this study, a horizontal flow biofilm reactor (HFBR) with step-feed was constructed and tested in the laboratory, to remove organic carbon and nitrogen from a agricultural strength synthetic washwater (SWW). The HFBR had an average top plan surface area (TPSA) of 0.1002 m(2) and consisted of a stack of 45 polystyrene horizontal sheets--15 sheets embedded with 25 mm deep frustums above 30 sheets with 10 mm deep frustums. The frustums acted as miniature reservoirs. The sheets were alternately offset to allow the wastewater to flow horizontally along each sheet and vertically from sheet to sheet down through the reactor. Biofilms developed on the sheets and treated the wastewater. During the 212-d study, the total hydraulic loading rate based on the TPSA of the sheets was 35 l m(-2) d(-1). SWW was pumped for 10 min each hour, in a step feed arrangement at a rate of 23.33 l m(-2) d(-1) on to the top sheet during Phases 1 and 2, and 11.67 l m(-2) d(-1) onto Sheet 16 during Phase 1 (days 1-92) and onto Sheet 30 during Phase 2 (days 93-212). The substrate loading rate during Phases 1 and 2 was 94.8 g total chemical oxygen demand (COD) m(-2) d(-1) and 10.5 g total nitrogen (TN) m(-2) d(-1), based on the TPSA. At steady state in Phase 2, the unit achieved excellent carbon removal of 99.7% 5-day biochemical oxygen demand (BOD(5)) and 96.7% total COD, equivalent to TPSA removal rates of 67.5 g BOD(5)m(-2)d(-1) and 91.7 g COD m(-2) d(-1). The nitrogen removal percentages were 98.3% total ammonium-nitrogen (NH(4)-N(t)) and 72.8% TN, which equated to TPSA removal rates of 4.8 g NH(4)-N(t) m(-2) d(-1) and 7.6g TN m(-2) d(-1). No sloughing of solids or clogging of media occurred during the study. The unit was simple to construct and operate, with little maintenance.     

水生植物修复氮、磷污染水体研究进展

氮、磷是引起水体富营养化、导致水质恶化的重要因素,因此去除氮、磷一直是污水处理的重要任务.鉴于传统物理、化学方法存在的操作难、成本高、易产生二次污染等问题,人们越来越多地将目光转向利用水生植物去除氮、磷营养物质、净化水质上.介绍了近年来国内外应用水生植物修复氮、磷污染水体的方法、效果及其影响因素,探讨了水生植物净化污染水体的机制.针对目前研究中的不足,提出今后应在不同植物种类开发、植物组合优化以及植物的净化机制等方面加强研究.