Nitrogen evolution during the co-combustion of hydrothermally treated municipal solid waste and coal in a bubbling fluidized bed

Nitrogen evolution was studied during the co-combustion of hydrothermally treated municipal solid wastes (HT MSW) and coal in a bubbling fluidized bed (BFB). HT MSW blending ratios as 10%, 20% and 30% (wt.%) were selected and tested at 700, 800, 900 °C. Emissions of NO and N₂O from blends were measured and compared with the results of mono-combustion trials. Moreover, concentrations of precursors like NH₃ and HCN were also quantified. The results are summarized as follows: NO emissions were predominant in all the cases, which rose with increasing temperature. The blending of HT MSW contributed to the NO reduction. N₂O emissions decreased with temperature rising and the blending of HT MSW also presented positive effects. At 30% HT MSW addition, both NO and N₂O emissions showed the lowest values (391.85 ppm and 55.33 ppm, respectively at 900 °C). For the precursors, more HCN was detected than NH₃ and both played important roles on the gas side nitrogen evolution.     

Co-treatment of fruit and vegetable waste in sludge digesters. An analysis of the relationship among bio-methane generation,process stability and digestate phytotoxicity

The co-digestion of a variable amount of fruit and vegetable waste in a waste mixed sludge digester was investigated using a pilot scale apparatus. The organic loading rate (OLR) was increased from 1.46 kg VS/m³ day to 2.8 kg VS/m³ day. The hydraulic retention time was reduced from 14 days to about 10 days. Specific bio-methane production increased from about 90 NL/kg VS to the maximum value of about 430 NL/kg VS when OLR was increased from 1.46 kg VS/m³ day to 2.1 kg VS/m³ day. A higher OLR caused an excessive reduction in the hydraulic retention time, enhancing microorganism wash out. Process stability evaluated by the total volatile fatty acids concentration (mg/l) to the alkalinity buffer capacity (eq. mg/l CaCO₃) ratio (i.e. FOS/TAC) criterion was <0.1 indicating high stability for OLR <2.46 kg VS/m³ day. For higher OLR, FOS/TAC increased rapidly. Residual phytotoxicty of the digestate evaluated by the germination index (GI) (%) was quite constant for OLR < 2.46 kg VS/m³ day, which is lower than the 60% limit, indicating an acceptable toxicity level for crops. For OLR > 2.46 kg VS/m³ day, GI decreased rapidly. This corresponding trend between FOS/TAC and GI was further investigated by the definition of the GI ratio (GIR) parameter. Comparison between GIR and FOS/TAC suggests that GI could be a suitable criterion for evaluating process stability.     

Defining the Impact of Non‐Native Species

Non‐native species cause changes in the ecosystems to which they are introduced. These changes, or some of them, are usually termed impacts; they can be manifold and potentially damaging to ecosystems and biodiversity. However, the impacts of most non‐native species are poorly understood, and a synthesis of available information is being hindered because authors often do not clearly define impact. We argue that explicitly defining the impact of non‐native species will promote progress toward a better understanding of the implications of changes to biodiversity and ecosystems caused by non‐native species; help disentangle which aspects of scientific debates about non‐native species are due to disparate definitions and which represent true scientific discord; and improve communication between scientists from different research disciplines and between scientists, managers, and policy makers. For these reasons and based on examples from the literature, we devised seven key questions that fall into 4 categories: directionality, classification and measurement, ecological or socio‐economic changes, and scale. These questions should help in formulating clear and practical definitions of impact to suit specific scientific, stakeholder, or legislative contexts. Definiendo el Impacto de las Especies No‐Nativas     

308 nm光作用下α-Fe2O3表面HNO3的光解

采用紫外可见光谱(UV-Vis)、傅立叶变换红外光谱(FTIR)及离子色谱(IC)技术对HNO3在α-Fe2O3表面暗反应和308nm下光解反应进行了研究.考察了时间、HNO3浓度、相对湿度(RH)等条件对反应的影响.结果表明,随着HNO3浓度、光照时间的增加,HNO3在气相与α-Fe2O3表面光解产物浓度均呈指数增加;HNO3在α-Fe2O3表面光解产生的NO2、NO分别为气相产生的3.27及3.87倍,而无论气相还是表面光解的NO2浓度均约为NO的2倍.随着RH的增加,HNO3光解产生的HONO的浓度随之呈指数增大,其产率从RH 20%时的0.023增加到90%时的0.087.α-Fe2O3的表面效应在HNO3的表面光解反应中起主导作用.     

流态对生物添加强化硝化效果的影响

在15℃、相同氮负荷和添加强度条件下运行SBR和CSTR以对比分析两种典型流态(推流式和完全混合式)对硝化菌添加强化硝化效果的影响.结果表明,添加期间,SBR中氨氧化速率(AUR)和亚硝酸盐氧化速率(NUR)分别为添加前的2.34和2.39倍,停止添加后又分别降为添加前的2.01和1.78倍;添加期间CSTR中AUR和NUR分别为添加前的2.63和2.44倍,停止添加后又分别降为添加前的1.48和1.31倍.荧光原位杂交结果显示,添加期间,SBR中氨氧化菌(AOB)和亚硝酸盐氧化菌(NOB)的个数百分比分别为添加前的2.67和2.71倍,添加停止后,又分别降至原来的2.14和1.95倍;CSTR中AOB和NOB分别为添加前的2.91和1.77倍,但在添加停止后CSTR中AOB和NOB分别降至添加前的1.25和1.50倍.因此,硝化菌添加期间,两种流态的添加效果接近,但是在添加停止后,由于流态对硝化菌中K-决策者(Nitrosospira、Nitrospira)和r-决策者(Nitrosomonas europaea、Nitrobacter)的选择作用,添加的硝化菌在完全混合式条件下比推流式条件下更容易被系统淘汰.     

不同运行模式下改良型CAST工艺处理生活污水的除磷性能

实验采用改良型CAST工艺,以生活污水为研究对象,考察了C/P、回流比及温度等不同运行模式对系统除磷性能的影响.结果表明,常温条件下进水C/P由50升至100,系统除磷率均值从15%迅速升至95.6%,除磷性能显著提高;继而降低C/P至75,除磷性能因进水碳源不足再度下降,除磷率均值为51.4%,且长期投加易降解碳源引发系统污泥膨胀并导致污泥大量流失.C/P较低情况下,回流比由25%降低至12.5%,除磷性能提高2.3倍,继续降低回流比至0,除磷性能反而下降;温度实验研究则表明,低温系统(14℃±1℃),除磷率稳定维持在90%以上,而高温短程硝化系统(27℃±1℃)除磷率仅为14.1%,可见低温更有利于系统磷的去除.吸磷小试发现,常温系统污泥以O_2、NO_3~-和NO_2~-为电子受体均能进行吸磷,而低温系统污泥能以O_2、NO_3~-为电子受体进行吸磷,高温系统污泥则仅能以O_2为电子受体进行少量吸磷.此外,实验还发现,系统短期闲置导致的污泥"饥饿"有利于系统除磷率的提高.     

常规施肥条件下农田不同途径氮素损失的原位研究:以长江中下游地区夏玉米季为例

为了解农田常规施肥条件下的不同途径氮素损失特征,本文通过田间原位试验同步研究了长江中下游地区夏玉米生长季氮肥施用后的农田N2O排放、NH3挥发、氮渗漏和地表径流的变化.结果表明,在复合肥为基肥,尿素为追肥,基追肥氮素水平均为150 kg·hm-2的条件下,整个玉米生长季N2O排放系数为3.3%,NH3挥发损失率为10.2%,氮渗漏和地表径流损失率分别为11.2%和5.1%.此外,基肥施用以氮素渗漏损失为主,而追肥氮素损失以氨挥发和渗漏为主,表明不同途径化肥氮素损失主要受氮肥品种影响,玉米季追肥可改用低氨挥发氮肥品种以减少氮素损失.     

微气泡臭氧催化氧化-生化耦合工艺深度处理煤化工废水

采用微气泡臭氧催化氧化-生化耦合工艺对煤化工废水生化出水进行深度处理,考察耦合系统处理性能及不同臭氧投加量和进水COD量比值的影响.结果表明,微气泡臭氧催化氧化处理能够有效降解废水中难降解含氮芳香族污染物,去除部分COD并释放氨氮,显著提高废水可生化性,臭氧利用率接近100%,无需进行臭氧尾气处理;同时为生化处理提供充足溶解氧(DO),实现生化处理对COD和氨氮的进一步有效去除,生化处理无需曝气.在系统出水回流比为30%、臭氧投加量和进水COD量之比为0.44 mg·mg~(-1)的运行条件下,耦合系统处理性能较好.微气泡臭氧催化氧化处理对COD去除率为42.5%,臭氧消耗量与COD去除量比值为1.38 mg·mg~(-1),臭氧利用率为98.0%;生化处理对COD去除率为42.3%;耦合系统整体COD去除率为66.7%,最终平均出水COD浓度为91.5 mg·L~(-1),估算整体臭氧消耗量与COD去除量比值为0.68 mg·mg~(-1),具有较优的技术经济性能.     

微生物燃料电池改性阳极处理PTA废水

探讨了不同改性阳极对微生物燃料电池(microbial fuel cell,MFC)产电性能及其对MFC处理难降解废水能力的影响.以单室空气阴极为基础,利用0.1 g电气石、质量分数75%二氧化锰/埃洛石纳米管(manganese bioxide/halloysite nanotube,MnO_2/HNT)和多壁碳纳米管-羧基(multi-walled carbon nanotube-carboxyl,MWCNT-COOH)对MFC阳极进行修饰.结果表明,不同改性阳极的MFC对含精对苯二甲酸(purified terephthalic acid,PTA)废水的去除率均高于70%,且化学需氧量(chemical oxygen demand,COD)去除率在79%以上.相较于其他几种改性阳极,以MWCNT-COOH改性材料作阳极的MFC产生的最大输出电压最高,获得的最大功率密度最高,分别为529 mV和252.73 mW·m~(-2).     

Re-evaluation of thyroid hormone signaling antagonism of tetrabromobisphenol A for validating the T3-induced Xenopus metamorphosis assay

We developed the T3-induced Xenopus metamorphosis assay, which is supposed to be able to sensitively detect thyroid hormone(TH) signaling disruption of chemicals. The present study aimed to validate the T3-induced Xenopus metamorphosis assay by re-evaluating the TH signaling antagonism of tetrabromobisphenol A(TBBPA), a known TH signaling disruptor. According to the assay we developed, Xenopus tadpoles at stage 52 were exposed to 10–500 nmol/L TBBPA in the presence of 1 nmol/L T3. After 96 hr of exposure, TBBPA in the range of 10–500 nmol/L was found to significantly inhibit T3-induced morphological changes of Xenopus tadpoles in a concentration-dependent manner in term of body weight and four morphological endpoints including head area(HA), mouth width(MW), unilateral brain width/brain length(ULBW/BL), and hind-limb length/snout-vent length(HLL/SVL).The results show that these endpoints we developed are sensitive for characterizing the antagonistic effects of TBBPA on T3-induced metamorphosis. Following a 24-hr exposure,we found that TBBPA antagonized expression of T3-induced TH-response genes in the tail,which is consistent with previous findings in the intestine. We propose that the tail can be used as an alternative tissue to the intestine for examining molecular endpoints for evaluating TH signaling disruption. In conclusion, our results demonstrate that the T3-induced Xenopus metamorphosis assay we developed is an ideal in vivo assay for detecting TH signaling disruption.