R-PFR与CSTR厌氧消化餐厨垃圾运行效率及微生物群落结构对比

以中温餐厨垃圾(FW)厌氧消化反应器为研究对象,结合稳定运行过程中的微生物群落结构特征,考察了两种常见的厌氧消化反应器—完全混合式反应器(CSTR)和有回流的推流式反应器(R-PFR)的运行效率和稳定性.结果表明,两种构型的反应器均能在3.0 kg·m-3·d-1(以VS计)负荷下稳定高效地运行.R-PFR具有更稳定的稳定性指数,如总碱度(TA)和挥发性脂肪酸比TA值(VFA/TA),以及更低的氨氮(TAN)和游离氨(FAN)浓度,但产气效率(如比甲烷产率(SMP))不及CSTR.R-PFR中以Chloroflexi门(37.35%)和Firmicutes门(31.22%)为优势细菌,而CSTR中以Bacteroidetes门(31.14%)与Firmicutes门(44.41%)为优势细菌.CSTR和R-PFR均以Methanosaeta属为优势产甲烷菌(98.72%和84.90%),乙酸型产甲烷途径为主要的产甲烷途径.但CSTR中除Methanosaeta属以外还有一定丰度的混合营养型的Methanosarcina,以及氢营养型Methanospirillum和Methanolinea.CSTR中具有对VFA和TAN更具耐受性的产甲烷菌群,更有利于餐厨垃圾产甲烷过程的稳定进行.由于R-PFR的敏感性较低,有利于处理剧烈变化的底物,但R-PFR容易出现严重的局部酸化现象,不利于长期处理过高负荷的易降解底物(如餐厨垃圾).这些结果可为优化餐厨垃圾厌氧消化工艺设计提供基础依据.     

ASBR处理热水解污泥的启动试验研究

进行了中温、高温厌氧序批式反应器(ASBR)处理热水解污泥的启动试验,同时与中温连续流搅拌反应器(CSTR)进行对比,ASBR 启动期包括种泥驯化期、过渡期和稳态期 3 个阶段.启动过程中污泥固体物质在 ASBR 中不断积累而保持较高的固体停留时间(SRT),有助于提高处理效率.污泥中蛋白质生化降解产生的氨氮提高了体系的缓冲能力,pH值保持在 6.60~7.72之间.当水力停留时间(HRT)为 20d、容积负荷为 2.71kg COD/(m3d) 时,中温 ASBR、高温 ASBR 和中温 CSTR 的总 COD(TCOD)去除率分别为 67.71%、64.55%、60.25%.相应地, ·中温、高温 ASBR 的平均日产气量比中温 CSTR 分别提高 15%、10%.     

测定废水重金属样品的高压蒸汽消解方法

本文采用正交实验方法,用自己研制的“自控式高压蒸汽消解器”,详细研究了测定废水重金属,样品的最佳消解条件,并用于实际废水样的消解和重金属的测定,准确度和精密度均优于传统的敞口消解法,并具有试剂用量少、时间短、不受污染、操作简单,批处理样品量大等优点,可作为测定废水中重金属,样品的常规消解方法。     

高压蒸汽消解法测定土壤、底质中的有机质

用“自控式高压蒸汽消解器”作加热器,将测定土壤、底质中有机质由敞口油浴法转变为密封高压蒸汽消解法,用实际土样全面优化了温度、硫酸浓度、时间等消解条件,建立了高压蒸汽消解法测定土壤、底质中有机质的方法,并用于不同地方、不同类型土壤和底质中有机质测定,同时用油浴法作对照,相对误差在－３７～５３％之间。该方法精密度好,无实验室二次污染,批处理样品数量多,可作为测定土壤、底质中有机质的常规方法。     

直接加热消解法测定土壤底质中的有机质

选用ＸＪⅠ型ＣＯＤ消解装置作加热器,测定土壤、底质的有机质。通过不同消解时间的实验设计,选取８ｍｉｎ作为该法的消解时间;通过４种不同类型土壤、底质有机质的测定,并将其测定值与甘油浴法〔１〕作比较,得出该法精密度好,准确度高,相对标准偏差在１４％～２７％之间,相对误差在－３４％～１５％之间     

闭管消解-萘乙二胺分光光度法测定水中总氮

通过实验研究了一种采用闭管消解-萘乙二胺分光光度法测定水样中总氮的新方法,分析了不同测试条件对测定结果的影响。结果表明:方法最佳消解时间为25min,宜选用535nm为实验波长,在10～25℃下显色5～20min完成测定。与标准方法比较,该方法具有灵敏度高、测定时间短的优点,可用于环境监测中水和废水的总氮分析。     

Environmental impacts of different food waste resource technologies and the effects of energy mix

The environmental impacts of food waste management strategies and the effects of energy mix were evaluated using a life cycle assessment model, EASEWASTE. Three different strategies involving landfill, composting and combined digestion and composting as core technologies were investigated. The results indicate that the landfilling of food waste has an obvious impact on global warming, although the power recovery from landfill gas counteracts some of this. Food waste composting causes serious acidification (68.0 PE) and nutrient enrichment (76.9 PE) because of NH₃ and SO₂ emissions during decomposition. Using compost on farmland, which can marginally reduce global warming (−1.7 PE), acidification (−0.8 PE), and ecotoxicity and human toxicity through fertilizer substitution, also leads to nutrient enrichment as neutralization of emissions from N loss (27.6 PE) and substitution (−12.8 PE). A combined digestion and composting technology lessens the effects of acidification (−12.2 PE), nutrient enrichment (−5.7 PE), and global warming (−7.9 PE) mainly because energy is recovered efficiently, which decreases emissions including SO₂, Hg, NO_x, and fossil CO₂ during normal energy production. The change of energy mix by introducing more clean energy, which has marginal effects on the performance of composting strategy, results in apparently more loading to acidification and nutrient enrichment in the other two strategies. These are mainly because the recovered energy can avoid fewer emissions than before due to the lower background values in power generation. These results provide quantitative evidence for technical selection and pollution control in food waste management.     

A comparison of on-site nutrient and energy recycling technologies in algal oil production

Research on biofuel production pathways from algae continues because among other potential advantages they avoid key consequential effects of terrestrial oil crops, such as competition for cropland. However, the economics, energetic balance, and climate change emissions from algal biofuels pathways do not always show great potential, due in part to high fertilizer demand. Nutrient recycling from algal biomass residue is likely to be essential for reducing the environmental impacts and cost associated with algae-derived fuels. After a review of available technologies, anaerobic digestion (AD) and hydrothermal liquefaction (HTL) were selected and compared on their nutrient recycling and energy recovery potential for lipid-extracted algal biomass using the microalgae strain Scenedesmus dimorphus. For 1 kg (dry weight) of algae cultivated in an open raceway pond, 40.7 g N and 3.8 g P can be recycled through AD, while 26.0 g N and 6.8 g P can be recycled through HTL. In terms of energy production, 2.49 MJ heat and 2.61 MJ electricity are generated from AD biogas combustion to meet production system demands, while 3.30 MJ heat and 0.95 MJ electricity from HTL products are generated and used within the production system.Assuming recycled nutrient products from AD or HTL technologies displace demand for synthetic fertilizers, and energy products displace natural gas and electricity, the life cycle greenhouse gas reduction achieved by adding AD to the simulated algal oil production system is between 622 and 808 g carbon dioxide equivalent (CO₂e)/kg biomass depending on substitution assumptions, while the life cycle GHG reduction achieved by HTL is between 513 and 535 g CO₂e/kg biomass depending on substitution assumptions. Based on the effectiveness of nutrient recycling and energy recovery, as well as technology maturity, AD appears to perform better than HTL as a nutrient and energy recycling technology in algae oil production systems.