Model-based evaluation on the conversion ratio of ammonium to nitrite in a nitritation process for ammonium-rich wastewater treatment

Modeling for nitritation process was discussed and analyzed quantitatively for the factors that influence nitrite accumulation. The results indicated that pH, inorganic carbon source and Hydraulic Retention Time(HRT) as well as biomass concentration are the main factors that influenced the conversion ratio of ammonium to nitrite. A constant high pH can lead to a high nitritation rate and results in high conversion ratio on condition that free ammonia inhibition do not happen. In a CSTR system, without pH control, this conversion ratio can be monitored by pH variation in the reactor. The pH goes down far from the inlet level means a strongly nitrite accumulation. High concentration of alkalinity can promoted the conversion ratio by means of accelerating the nitritation rate through providing sufficient inorganic carbon source(carbon dioxide). When inorganic carbon source was depleted, the nitritation process stopped. HRT adjustment could be an efficient way to make the nitritation system run more flexible, which to some extent can meet the requirements of the fluctuant of inlet parameters such as ammonium concentration, pH, and temperature and so on. Biomass concentration is the key point, especially for a CSTR system in steady state, which was normally circumscribed by the characteristics of bacteria and may also affected by aeration mode and can be increased by prolonging the HRT on the condition of no nitrate accumulation when no recirculation available. The higher the biomass concentration is, the better the nitrite accumulation can be obtained. accumulation     

Recyling manganese-rich electrolytic residues: a review

Environmental Chemistry Letters - Huge amounts of manganese-rich solid residues are yearly produced worldwide by industrial electrolysis, calling for advanced methods of recycling in the context of...     

Win-Win: Anthropogenic circularity for metal criticality and carbon neutrality

● Anthropogenic circularity science is an emerging interdisciplinary field. ● Anthropogenic circularity was one effective strategy against metal criticality. ● Carbon neutrality is becoming the new industry paradigm around the world. ● Growing circularity could potentially minimize the CO₂ emission. Resource depletion and environmental degradation have fueled a burgeoning discipline of anthropogenic circularity since the 2010s. It generally consists of waste reuse, remanufacturing, recycling, and recovery. Circular economy and “zero-waste” cities are sweeping the globe in their current practices to address the world’s grand concerns linked to resources, the environment, and industry. Meanwhile, metal criticality and carbon neutrality, which have become increasingly popular in recent years, denote the material's feature and state, respectively. The goal of this article is to determine how circularity, criticality, and neutrality are related. Upscale anthropogenic circularity has the potential to expand the metal supply and, as a result, reduce metal criticality. China barely accomplished 15 % of its potential emission reduction by recycling iron, copper, and aluminum. Anthropogenic circularity has a lot of room to achieve a win-win objective, which is to reduce metal criticality while also achieving carbon neutrality in a near closed-loop cycle. Major barriers or challenges for conducting anthropogenic circularity are deriving from the inadequacy of life-cycle insight governance and the emergence of anthropogenic circularity discipline. Material flow analysis and life cycle assessment are the central methodologies to identify the hidden problems. Mineral processing and smelting, as well as end-of-life management, are indicated as critical priority areas for enhancing anthropogenic circularity.     

新型柴油机消烟消声器的研制

通过在原柴油机消声器的底部注入对柴油机尾气有明显吸收和转化作用的吸烟液,使柴油机尾气通过此消烟消声器时同时得到净化和降噪。在１３５型柴油机上与原柴油机消声器进行同等条件下的对比试验表明,烟度下降８０％,噪声由９９ｄＢ降至８５ｄＢ效果令人满意。     

拱形双排隔离桩对既有隧道的保护效果研究

采用隔离桩来保护邻近基坑的既有隧道是工程中常用方法,目前隔离桩平面排列形式多采用传统的矩形行列式。以杭州市某房建地下室基坑工程为例,提出由直线形排桩和弧形排桩组成的拱形双排隔离桩及相应的优化方案,采用ABAQUS有限元软件建立三维模型,研究了隔离桩中心距、桩半径、平面位置以及弧形排桩曲率半径等因素对隔离效果的影响,并与实测结果进行对比。结果表明:隧道衬砌总位移存在最大值和最小值,隧道衬砌总位移最大值点位于拱底,最小值点位于拱顶,隧道衬砌整体呈现出沉降的趋势。减小隔离桩中心距或增大隔离桩半径均可减小隧道衬砌的位移,拱形双排隔离桩的保护效果优于传统形式;将拱形双排隔离桩设在距基坑10 m处,并将弧形排桩设在隧道一侧更合理;弧形排桩曲率半径对隧道保护效果存在合理值;采用优化方案时隧道位移比原方案减小45.7%,隧道更趋于安全。     

麋鹿还乡记

中国是产鹿科动物种类最多的国家,约占全世界的一半左右,其中有些还是中国特产的稀有种类,麋鹿即为其中之一。麋鹿,角似鹿,而无眉角;颈似鸵,而比鸵短;尾似牛,而比牛宽阔,故称“四不象”。驯鹿、驼鹿,我国也俗称:“四不象”,因同名异物,常把它们混淆。     

深圳市大气降水化学组成演化特征分析:1980-2004年

为了定量分析大气降水化学组成的长期变化特征, 采用深圳市1980-2004年的大气降水化学资料进行研究, 所有样品都分析了pH、Cl-、F-、SO42-、NO3-、NH4 、Na 、K 、Ca2 和Mg2 等指标.结果表明: (1) 研究时段内, 降水pH随着时间呈逐渐下降趋势,且pH值在大部分年份均低于5.6, 最低值仅为4.49, 从而对环境酸化产生明显的影响;降水pH还具有较大的时空变异性, 南山和宝安区的pH值低于其它四个区;在月度变化上, 夏秋季节的pH值低于春冬季节.(2) SO42-是降水中最主要的阴离子, 占降水中总离子质量的31.34%～38.95%, 且SO42-对降水酸度的贡献随着时间呈下降趋势;NO3-是除SO42-外最重要的酸根离子, 其浓度随着时间呈上升趋势, 从而对降水酸度的贡献逐渐增强.(3) Ca2 是降水中最主要的阳离子, 占降水中总离子质量的14.34%～20.24%.Na 是除Ca2 外最重要的阳离子, 其浓度随着时间呈增加的趋势, NH4 的浓度则随着时间呈现先上升后下降的趋势.(4) 降水化学组成受到人为源的强烈影响, 在研究时段内, 人为源呈现上升的趋势, 地表源呈现先上升后下降的趋势, 海洋源呈现先下降后上升的趋势.(5) 研究区的降水化学组成有明显的季节和区域差异, 春季和冬季离子含量较高, 在夏季较低;南山区、龙岗区降水中离子浓度高于福田区、盐田区、宝安区和罗湖区.     

低磷胁迫下云南稻形态性状的氮肥反应

采用盆栽试验每份材料栽2桶,每盆装4 kg低磷酸性红壤(速效磷2.53 mg·kg-1、速效氮156.7 mg·kg-1和pH=6.03),设置不施氮肥(速效氮156.7 mg·kg-1)和施氮肥(速效氮490.0 mg·kg-1)两种处理对539份云南稻核心种质17个形态性状及其相对指标,研究低磷胁迫下云南稻形态性状的氮肥效应结果表明:总体上低磷胁迫下云南稻核心种质籼稻氮效反应明显比粳稻敏感;按氮反应相对指标将云南稻种17形态性状划分为氮反应的强敏感、中敏感、弱敏感和不敏感型四种类型;揭示了低磷胁迫下云南稻种氮高效鉴定指标以相对穗干质量和相对总干质量为主,相对穗长、秆干质量、地上干质量、根干质量和茎蘖数可作为参考指标,其中穗干质量为氮反应的强敏感型,总干质量、地上干质量、秆干质量和茎蘖数属中敏感型,根干质量属弱敏感型和穗长属不敏感型.另外,低磷胁迫下云南稻种8个对氮反应敏感相对性状无论是在539份云南稻核心种质及其籼粳亚种间,还是在五个稻作区间总趋势是一致的;既证实了该文提出的低磷胁迫下8个氮反应敏感指标性状是十分可靠的,又揭示了低磷胁迫下5大稻作区氮反应的生态差异和土攘类型多样性是云南成为亚洲栽培稻籼粳分化中心之一的驱动力.     

痕量壬基酚及相关化合物的样品预处理和测定

对近年来环境样品中痕量内分泌干扰物壬基酚及相关化合物的分离富集方法和测定技术的研究进展进行了综合评述。重点讨论了索氏提取、液液萃取、液膜分离、回流萃取、固相萃取、固相微萃取、超临界流体萃取、超声提取八种样品预处理方法和气相色谱质谱联用、高效液相色谱两种测定方法,而且针对以上方面提出了尚需进一步研究的问题。     

软锰矿电化学协同作用对活性嫩黄模拟废水脱色率的研究

以活性嫩黄K 4G模拟废水为处理对象 ,采用软锰矿与电化学协同法 ,分别在不同软锰矿加入量、电流密度、pH值、电解时间、染料初始浓度条件下进行电解实验 ,考察了各种因素对脱色率的影响。结果表明 ,增加软锰矿的用量、增大电流密度、降低pH值、延长电解时间都能提高脱色率 ,染料初始浓度对脱色率影响不显著。溶液中溶解态锰的浓度的变化表明 ,Mn(II)在处理过程中表现出催化作用 ,外加电压可强化软锰矿的氧化作用