预处理对园林垃圾混合物料联合厌氧发酵的影响

采用超声、微波及碱热预处理技术强化园林垃圾、厨余垃圾与果蔬垃圾联合厌氧发酵产气性能,并以未进行预处理的实验组作为对照。结果表明:4组实验pH值在2 d内迅速降低至7.24~7.45,反应后期可稳定在7.7~8.0,表明厌氧消化系统有较强的稳定性。挥发性脂肪酸（volatile fatty acids,VFA）浓度在第2~4天内达到最大值。乙酸和丙酸是4组实验中VFA的主要成分,两者比例之和在70%以上。VFA浓度在第13天后降低到500 mg/L以下,且以乙酸为主。氨氮（TAN）浓度在前4 d内出现一定波动,随后逐渐升高至2190~2410 mg/L。游离氨氮（FAN）浓度呈先降低后增加趋势,并在第13天后逐渐趋于稳定,为144~209 mg/L。沼气中甲烷比例在第2天后均超过50%,并在第11~12天时达到最大值61.4%~63.8%。修正的Gomperts模型模拟结果表明:预处理技术可缩短反应体系厌氧产沼的适应时间,提高前期产气速率。除此之外,超声预处理与碱热预处理可显著提高基质甲烷产率,由未处理时的396 mL/g分别提高到601,536 mL/g,而微波预处理使得反应体系甲烷产量略有降低。     

Effects of SO2 and H2O on low-temperature NO conversion over F-V2O5-WO3/TiO2 catalysts

F-V_2 O_5-WO3/Ti02 catalysts were prepared by the impregnation method.As the content of F ions increased from 0.00 to 0.35 wt.%,the NO conversion of F-V_2 O_5-WO_3/TiO_2 catalysts initially increased and then decreased.The 0.2 F-V_2 O_5-WO_3/TiO_2 catalyst(0.2 wt.% F ion)exhibited the best denitration(De-NOx) performance,with more than 95% NO conversion in the temperature range 160-360℃,and 99.0% N2 selectivity between 110 and 280℃.The addition of an appropriate amount of F ions eroded the surface morphology of the catalyst and reduced its grain size,thus enhancing the NO conversion at low temperature as well as the sulfur and water resistance of the V_2 O_5-WO3/Ti02 catalyst.After selective catalytic reduction(SCR) reaction in a gas flow containing SO_2 and H_2 O,the number of NH3 adsorption sites,active component content,specific surface area and pore volume decreased to different degrees.Ammonium sulfate species deposited on the catalyst surface,which blocked part of the active sites and reduced the NO conversion performance of the catalyst.On-line thermal regeneration could not completely recover the catalyst activity,although it prolonged the cumulative life of the catalyst.In addition,a mechanism for the effects of S02 and H_2 O on catalyst NO conversion was proposed.     

Dynamic nano-Ag colloids cytotoxicity to and accumulation by Escherichia coli: Effects of Fe3+, ionic strength and humic acid

Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials, and thus, the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag⁺ ratios. Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays, and shifts to both Ag particles and released Ag⁺ in 48 hr bioassays. Herein, as a continued study, the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically. The cytotoxicity and mechanisms of nano-Ag colloids are dynamic throughout exposure and are derived from both Ag ions and particles. Ag accumulation by E. coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure, and thereafter mainly from intracellular Ag ions. Fe³⁺ accelerates the oxidative dissolution of nano-Ag colloids, which results in decreasing amounts of Ag particles and particle-related toxicity. Na⁺ stabilizes nano-Ag colloids, thereby decreasing the bioavailability of Ag particles and particle-related toxicity. Humic acid (HA) binds Ag⁺ to form Ag⁺-HA, decreasing ion-related toxicity and binding to the E. coli surface, decreasing particle-related toxicity. HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na⁺ or Fe³⁺. The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors, and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.     

Revealing the changes of bacterial community from water source to consumers tap: A full-scale investigation in eastern city of China

This study profiled the bacterial community variations of water from four water treatment systems, including coagulation, sedimentation, sand filtration, ozonation-biological activated carbon filtration (O₃-BAC), disinfection, and the tap water after the distribution process in eastern China. The results showed that different water treatment processes affected the bacterial community structure in different ways. The traditional treatment processes, including coagulation, sedimentation and sand filtration, reduced the total bacterial count, while they had little effect on the bacterial community structure in the treated water (before disinfection). Compared to the traditional treatment process, O₃-BAC reduced the relative abundance of Sphingomonas in the finished water. In addition, ozonation may play a role in reducing the relative abundance of Mycobacterium. NaClO and ClO₂ had different effects on the bacterial community in the finished water. The relative abundance of some bacteria (e.g. Flavobacterium, Phreatobacter and Porphyrobacter) increased in the finished water after ClO₂ disinfection. The relative abundance of Mycobacterium and Legionella, which have been widely reported as waterborne opportunistic pathogens, increased after NaClO disinfection. In addition, some microorganisms proliferated and grew in the distribution system, which could lead to turbidity increases in the tap water. Compared to those in the finished water, the relative abundance of Sphingomonas, Hyphomicrobium, Phreatobacter, Rheinheimera, Pseudomonas and Acinetobacter increased in the tap water disinfected with NaClO, while the relative abundance of Mycobacterium increased in the tap water disinfected with ClO₂. Overall, this study provided the detailed variation in the bacterial community in the drinking water system.     

Metabolomic modulations in a freshwater microbial community exposed to the fungicide azoxystrobin

An effective broad-spectrum fungicide, azoxystrobin (AZ), has been widely detected in aquatic ecosystems, potentially affecting the growth of aquatic microorganisms. In the present study, the eukaryotic alga Monoraphidium sp. and the cyanobacterium Pseudanabaena sp. were exposed to AZ for 7 days. Our results showed that 0.2–0.5 mg/L concentrations of AZ slightly inhibited the growth of Monoraphidium sp. but stimulated Pseudanabaena sp. growth. Meanwhile, AZ treatment effectively increased the secretion of total organic carbon (TOC) in the culture media of the two species, and this phenomenon was also found in a freshwater microcosm experiment (containing the natural microbial community). We attempted to assess the effect of AZ on the function of aquatic microbial communities through metabolomic analysis and further explore the potential risks of this compound. The metabonomic profiles of the microcosm indicated that the most varied metabolites after AZ treatment were related to the citrate cycle (TCA), fatty acid biosynthesis and purine metabolism. We thereby inferred that the microbial community increased extracellular secretions by adjusting metabolic pathways, which might be a stress response to reduce AZ toxicity. Our results provide an important theoretical basis for further study of fungicide stress responses in aquatic microcosm microbial communities, as well as a good start for further explorations of AZ detoxification mechanisms, which will be valuable for the evaluation of AZ environmental risk.     

基于野外原位抽注试验和同位素技术的含水层反硝化速率研究

反硝化作用是地下水硝酸盐污染去除最重要的过程.由于水文地质条件和水文地球化学环境的复杂性和不确定性,精准测定含水层反硝化速率是反硝化过程的研究难点.选取潮白河冲洪积扇中部中国环境科学研究院地下水创新野外基地作为研究区,基于野外原位试验和15N同位素示踪法提出一种含水层反硝化速率的测定方法.该方法综合体现了研究区实际水文地质条件和水文地球化学环境对反硝化作用的影响,并充分考虑了硝酸盐在含水层中稀释弥散作用对计算结果的影响.结果表明:①潮白河冲洪积扇中部某地地下26~28 m处于还原环境,含水介质以粉细砂为主,ρ（NO₃-N）平均值为2.77 mg/L.②地下26~28 m反硝化速率在349.52~562.99 μg/（kg·d）（以N计,下同）之间,平均值为450.31 μg/（kg·d）.通过与研究区含水介质、采样深度和硝酸盐背景值相似的国内外案例对比研究,初步评估结果处于合理区间.③测试结果具有一定不确定性,主要来自忽略中间产物NO₂-和NO的计算方法、扰动采样方法、N₂O的操作规范程度及采样频率等方面.研究方法为测定含水层硝酸盐速率研究提供了新的思路,研究结果可为地下水中硝酸盐转化过程机理研究、地下水硝酸盐污染修复及风险管控提供关键的理论支撑数据.      

厦门市冬季PM2.5污染情境识别及其与气象条件的关系

为研究厦门市冬季不同PM_2.5污染情境与气象条件和气团轨迹路径特征的关系,结合PM_2.5观测数据,使用AGAGE（Advanced Global Atmospheric Gases Experiment）统计方法识别2014—2018年冬季厦门市PM_2.5观测值、基线值和污染值情境,通过气象数据统计和气团后向轨迹聚类对不同PM_2.5污染情境下气象条件和气团轨迹路径特征进行探究.结果表明:①厦门市冬季不同PM_2.5污染情境下,ρ（PM_2.5）及PM_2.5污染值情境时长占比均呈波动中下降的趋势,具体表现为冬季PM_2.5观测值、污染值和基线值情境下,ρ（PM_2.5）平均值分别从2014年的42.2、90.7、16.4 μg/m3降至2018年的26.3、56.9、8.8 μg/m3,冬季PM_2.5污染值情境时长占比从2014年的10.2%降至2018年的3.0%.②冬季PM_2.5污染值情境下气象要素呈低风速、低气压、高温度、高相对湿度的特征.③冬季到达厦门市的气团轨迹路径中,局地路径由于大气条件稳定易累积形成PM_2.5污染;偏北路径和西北路径易从临近省份携带污染物输入导致PM_2.5污染,属于重要的外源污染输入路径;沿海路径和偏西路径均属于清洁路径,但沿海路径易在福建省北部与偏北路径重合形成污染输入,加强了偏北路径的污染物输送能力.研究显示,近年来厦门市冬季PM_2.5污染有明显减弱趋势,但不利的气象条件和外来污染输入仍会造成PM_2.5污染的发生.      

嘉兴地区农村生活污水时空分布及处理设施现状分析

研究选取嘉兴市下辖农村的160座生活污水处理设施进出水为研究对象,分析了区域农村生活污水污染物时空分布特征及其处理设施现状,以期提高处理设施效率。结果表明:嘉兴市农村生活污水中氮、磷污染较有机污染更严重,ρ（COD）、ρ（TP）、ρ（TN）、ρ（NH₄+-N）年均值分别为142.23,4.02,44.19,27.74 mg/L,各污水处理设施处理效果有很大优化空间,COD、TP、TN、NH₄+-N年均去除率分别为50.5%、29.7%、36.8%、51.7%。农村生活污水空间上呈自西向东、由北至南逐渐减小的分布特征,时间上表现为冬季 > 春季 > 秋季 > 夏季。相关性分析表明,COD、TP、TN、NH₄+-N之间呈极显著正相关（P<0.01）,相关系数为0.688±0.946。设施进水C/N、NH₄+-N/TN年均值分别为3.21、68.9%,传统的单一A2/O处理工艺对低碳源污水处理效果不理想,可通过组合工艺设计、规范运营管理、加强后期监测等有效措施来进一步加强污水处理设施处理效果。     

日本城市有机废弃物甲烷发酵资源化系统案例分析及最新研究进展

为建设可持续发展社会,日本近年来大力推动甲烷发酵以实现城市有机废弃物的减量化和资源化。首先介绍了日本城市有机废弃物资源化的2个实用案例,长冈市厨余垃圾沼气发电中心和丰桥市生物质资源利用中心的设计和运营状况。两者的长期稳定运行及产能效果验证了甲烷发酵技术在城市有机废弃物减量化和资源化上的可行性。其次,为了应对社会发展趋势和城市有机废弃物处理的技术需求,介绍了日本有关厨余垃圾、污泥以及废纸（城市有机废弃物的3大组分）的单独发酵及共发酵的部分研究成果。此外,简要介绍了应用厌氧膜生物反应器（AnMBR）进行相关高效甲烷发酵的最新研究成果。并根据实用案例调查和实验研究结果,以100万人口城市为例,对城市有机废弃物的各种甲烷发酵系统的产能效果进行了模拟概算。     

含油污泥处理技术进展

石油工业生产的特征固体废物——含油污泥,是一种由石油烃、水、固体颗粒物和其他物质（如重金属）组成的固态/半固态复合物,因毒性和易燃性被归入危险废物管理。我国含油污泥年产量高达500万t,其中含有15%~50%的石油烃。含油污泥的处理要兼顾无害化和资源化。基于其组成、性质和危害,介绍了含油污泥的油品资源化分离法（离心、溶剂萃取、热解）和无害化剩余含油残渣处理法（焚烧、固化、生物处理）等国内外常用的处理方法。大体上,含油污泥的处理思路为,首先预处理降低含水率、提高含油率,再经油品分离法回收含油污泥中的石油烃,最后无害化处理剩余含油残渣。讨论了各方法的特点以及国内外研究进展,提出了含油污泥处理技术的发展建议。