Enhanced triallyl isocyanurate (TAIC) degradation through application of an O3/UV process: Performance optimization and degradation pathways

• UV/O₃ process had higher TAIC mineralization rate than O₃ process. • Four possible degradation pathways were proposed during TAIC degradation. • pH impacted oxidation processes with pH of 9 achieving maximum efficiency. • CO₃^2– negatively impacted TAIC degradation while HCO₃^– not. • Cl^– can be radicals scavenger only at high concentration (over 500 mg/L Cl^–). Triallyl isocyanurate (TAIC, C₁₂H₁₅N₃O₃) has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact. TAIC degradation was enhanced when an ozone(O₃)/ultraviolet(UV) process was applied compared with the application of an independent O₃ process. Although 99% of TAIC could be degraded in 5 min during both processes, the O₃/UV process had a 70%mineralization rate that was much higher than that of the independent O₃ process (9%) in 30 min. Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent O₃ and O₃/UV processes. pH impacted both the direct and indirect oxidation processes. Acidic and alkaline conditions preferred direct and indirect reactions respectively, with a pH of 9 achieving maximum Total Organic Carbon (TOC) removal. Both CO₃^2– and HCO₃^– decreased TOC removal, however only CO₃^2– negatively impacted TAIC degradation. Effects of Cl^– as a radical scavenger became more marked only at high concentrations (over 500 mg/L Cl^–). Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO· accordingly.     

Biological conversion pathways of sulfate reduction ammonium oxidation in anammox consortia

• The SRAO phenomena tended to occur only under certain conditions. • High amount of biomass and non-anaerobic condition is requirement for SRAO. • Anammox bacteria cannot oxidize ammonium with sulfate as electron acceptor. • AOB and AnAOB are mainly responsible for ammonium conversion. • Heterotrophic sulfate reduction mainly contributed to sulfate conversion. For over two decades, sulfate reduction with ammonium oxidation (SRAO) had been reported from laboratory experiments. SRAO was considered an autotrophic process mediated by anammox bacteria, in which ammonium as electron donor was oxidized by the electron acceptor sulfate. This process had been attributed to observed transformations of nitrogenous and sulfurous compounds in natural environments. Results obtained differed largely for the conversion mole ratios (ammonium/sulfate), and even the intermediate and final products of sulfate reduction. Thus, the hypothesis of biological conversion pathways of ammonium and sulfate in anammox consortia is implausible. In this study, continuous reactor experiments (with working volume of 3.8L) and batch tests were conducted under normal anaerobic (0.2≤DO<0.5 mg/L) / strict anaerobic (DO<0.2 mg/L) conditions with different biomass proportions to verify the SRAO phenomena and identify possible pathways behind substrate conversion. Key findings were that SRAO occurred only in cases of high amounts of inoculant biomass under normal anaerobic condition, while absent under strict anaerobic conditions for same anammox consortia. Mass balance and stoichiometry were checked based on experimental results and the thermodynamics proposed by previous studies were critically discussed. Thus anammox bacteria do not possess the ability to oxidize ammonium with sulfate as electron acceptor and the assumed SRAO could, in fact, be a combination of aerobic ammonium oxidation, anammox and heterotrophic sulfate reduction processes.     

Enhanced debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by zero-valent zinc with ascorbic acid

• Highly efficient debromination of BDE-47 was achieved in the ZVZ/AA system. • BDE-47 debromination by the ZVZ/AA can be applied to a wide range of pH. • AA inhibits the formation of (hydr)oxide and accelerates the corrosion of ZVZ. • Reduction mechanism of BDE-47 debromination by the ZVZ/AA system was proposed. A new technique of zero-valent zinc coupled with ascorbic acid (ZVZ/AA) was developed and applied to debrominate the 2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47), which achieved high conversion and rapid debromination of BDE-47 to less- or non-toxic forms. The reaction conditions were optimized by the addition of 100 mg/L ZVZ particles and 3 mmol/L AA at original solution pH= 4.00 using the solvent of methanol/H₂O (v:v= 4:6), which could convert approximately 94% of 5 mg/L BDE-47 into lower-brominated diphenyl ethers within a 90 min at the ZVZ/AA system. The high debromination of BDE-47 was mainly attributed to the effect of AA that inhibits the formation of Zn(II)(hydr)oxide passivation layers and promotes the corrosion of ZVZ, which leads to increase the reactivity of ZVZ. Additionally, ion chromatography and gas chromatography mass spectrometry analyses revealed that bromine ion and lower-debromination diphenyl ethers formed during the reduction of BDE-47. Furthermore, based on the generation of the intermediates products, and its concentration changes over time, it was proposed that the dominant pathway for conversion of BDE-47 was sequential debromination and the final products were diphenyl ethers. These results suggested that the ZVZ/AA system has the potential for highly efficient debromination of BDE-47 from wastewater.     

Metabolic uncoupler, 3,3′,4′,5-tetrachlorosalicylanilide addition for sludge reduction and fouling control in a gravity-driven membrane bioreactor

• Effects of metabolic uncoupler TCS on the performances of GDMBR were evaluated. • Sludge EPS reduced and transformed into dissolved SMP when TCS was added. • Appropriate TCS increased the permeability and reduced cake layer fouling. • High dosage aggravated fouling due to compact cake layer with low bio-activity. The gravity-driven membrane bioreactor (MBR)system is promising for decentralized sewage treatment because of its low energy consumption and maintenance requirements. However, the growing sludge not only increases membrane fouling, but also augments operational complexities (sludge discharge). We added the metabolic uncoupler 3,3′,4′,5-tetrachlorosalicylanilide (TCS) to the system to deal with the mentioned issues. Based on the results, TCS addition effectively decreased sludge ATP and sludge yield (reduced by 50%). Extracellular polymeric substances (EPS; proteins and polysaccharides) decreased with the addition of TCS and were transformed into dissolved soluble microbial products (SMPs) in the bulk solution, leading to the break of sludge flocs into small fragments. Permeability was increased by more than two times, reaching 60–70 L/m²/h bar when 10–30 mg/L TCS were added, because of the reduced suspended sludge and the formation of a thin cake layer with low EPS levels. Resistance analyses confirmed that appropriate dosages of TCS primarily decreased the cake layer and hydraulically reversible resistances. Permeability decreased at high dosage (50 mg/L) due to the release of excess sludge fragments and SMP into the supernatant, with a thin but more compact fouling layer with low bioactivity developing on the membrane surface, causing higher cake layer and pore blocking resistances. Our study provides a fundamental understanding of how a metabolic uncoupler affects the sludge and bio-fouling layers at different dosages, with practical relevance for in situ sludge reduction and membrane fouling alleviation in MBR systems.     

Degradation of polyacrylamide (PAM) and methane production by mesophilic and thermophilic anaerobic digestion: Effect of temperature and concentration

• PAM degradation in thermophilic AD in comparison with mesophilic AD. • PAM degradation and its impact on thermophilic and mesophilic AD. • Enhanced methane yield in presence of PAM during thermophilic and mesophilic AD. • PAM degradation and microbial community analysis in thermophilic and mesophilic AD. Polyacrylamide (PAM) is generally employed in wastewater treatment processes such as sludge dewatering and therefore exists in the sludge. Furthermore, it degrades slowly and can deteriorate methane yield during anaerobic digestion (AD). The impact or fate of PAM in AD under thermophilic conditions is still unclear. This study mainly focuses on PAM degradation and enhanced methane production from PAM-added sludge during 15 days of thermophilic (55°C) AD compared to mesophilic (35°C) AD. Sludge and PAM dose from 10 to 50 g/kg TSS were used. The results showed that PAM degraded by 76% to 78% with acrylamide (AM) content of 0.2 to 3.3 mg/L in thermophilic AD. However, it degraded only 27% to 30% with AM content of 0.5 to 7.2 mg/L in mesophilic AD. The methane yield was almost 230 to 238.4 mL/g VSS on the 8th day in thermophilic AD but was 115.2 to 128.6 mL/g VSS in mesophilic AD. Mechanism investigation revealed that thermophilic AD with continuous stirring not only enhanced PAM degradation but also boosted the organics release from the sludge with added PAM and gave higher methane yield than mesophilic AD.     

中国低碳城市试点的政策设计逻辑

政策试点是中国国家治理策略体系的重要组成部分,是中国政府遵循“由点到面”逻辑以试验手段制定政策的一种常规性工作方法。低碳城市试点是中国应对气候变化战略的重要组成部分,通过选择不同类型、不同发展阶段、不同资源禀赋的地区开展试点,探索经济增长与碳排放脱钩的模式。现有文献侧重低碳城市建设的内涵、建设模式与路径、温室气体的核算方法、政策手段、峰值研究与达峰路径、效果评估等,有力地支持了低碳城市建设决策,但对于低碳城市试点的政策设计鲜有涉及。本文从政策过程理论、央地关系两个视角,结合府际学习与竞争关系,建构了中国低碳城市政策“试点–扩散”机制与政府行为的分析框架。中国的低碳城市试点具有探索型开拓性、综合型专业性、授权型自主性的特点,结合三批低碳城市试点的文件要求和实践进展,从政策试点的选点、设计、执行、监督和评估五个方面对于中国低碳城市试点进行了系统的梳理分析。相较于经济领域的其他政策试点,低碳城市政策试点具有弱激励弱约束的政策环境。地方政府基于自身的学习能力和领导力,在政策创新方面表现出争先、自主、效仿和守成四种行为特征,并以杭州、深圳、镇江、成都四个表率城市做了实证。政策“试点-扩散”的过程从本质上讲是中国政策创新与扩散的过程,可能在现实中需要往复多次进行,中国已陆续开展的三批低碳城市试点工作就遵循这样的政策逻辑。试点的意义是试出问题、解决问题、积累经验。从前三批试点城市评估结果来看,试点城市在低碳发展目标设定、转型路径探索和低碳发展动力转换等方面与社会的预期仍有差距,为此本文提出了推进低碳城市建设的四点建议:一是激发城市低碳发展的内生动力;二是完善低碳城市试点的科学论证机制;三是建立激励与约束并举的长效机制;四是强化市场公平竞争的政策导向。     

整合消费与增加值视角的中国行业碳排放变动分解研究

在研究影响我国CO 2排放因素领域,基于投入产出技术的分解模型已成为主要的分析工具,现有研究多分别基于消费视角或收益视角展开分析。为全面评估各行业收益与消费对其上游、下游行业碳排放的综合影响,整合基于收益与基于消费两个视角,运用2012年与2015年我国投入产出表,构建两层嵌套式结构分解分析模型(SDA),比较分析消费规模效应、收益规模效应、行业流入、流出增加值变动效应、增加值结构变动效应等14个影响各行业碳排放变动的关键因素,并借助对消费者原则碳排放估算公式的重构,更准确地实现从增加值视角对各行业消费者原则碳排放变动的关键影响因素分析。研究发现:①研究期内,我国在总产出增长29.14%的同时碳排放量上升1.46%,各行业碳排放强度下降是主要的减排因素,其中建筑业减排贡献最大。②增排效应方面,影响从大到小依次为消费规模、收益规模、完全投入结构与完全消费结构四项效应,且前两个规模效应的影响是后两个结构效应的2倍以上,尤其建筑业消费规模效应、煤炭采选产品业收益规模效应增排较大。③消费规模扩大导致增排的原因并非行业本身生产规模扩大,而主要在于建筑业、服务业等行业规模扩张时吸收其他行业流入的增加值量增多。④收益规模扩大导致的增排效应方面,细分来说从大到小依次为劳动者报酬、生产税净额、固定资产折旧、营业盈余四项效应,且行业差异显著,如煤炭采选产品业的劳动者报酬效应,石油、炼焦产品和核燃料加工品业的生产税净额效应以及电力、热力生产和供应业的营业盈余效应增排贡献较大,而煤炭采选产品业的营业盈余效应、批发、零售业和住宿、餐饮业的生产税净额效应则减排贡献较大。     

中国服务业碳生产率的空间收敛性研究

在经济服务化与低碳化的双重背景下,研究中国服务业碳生产率的演变轨迹,区域差异及空间收敛特征,对于推动中国服务业高质量发展具有重要的意义。采用2004—2016年中国30个省(区、市)的面板数据,对服务业碳生产率进行测度,并对其演变轨迹与区域差异进行分析,在此基础上,系统考察中国服务业碳生产率的空间收敛性。研究表明:①中国服务业碳生产率在整体上呈逐年增长态势,且呈现从东到西逐次递减的格局。②中国服务业碳生产率存在正向空间自相关关系,并且空间自相关程度表现出波动上升趋势。③全国与西部服务业碳生产率均不存在σ收敛,即服务业碳生产率的地区差异并未随着时间的推移而缩小;东、中部服务业碳生产率则在整体上呈现σ收敛特征。全国以及东、中、西部服务业碳生产率均存在绝对β收敛和条件β收敛,即服务业碳生产率落后地区对发达地区存在"追赶效应",各地区服务业碳生产率最终向自身的稳态水平趋同;空间效应加快了全国与东部服务业碳生产率的β收敛速度。④人均服务业增加值增长速度、部门结构以及能源消费结构对服务业碳生产率具有显著的负向效应,人力资本则对服务业碳生产率产生了显著的正向影响。据此,本文的政策启示如下:①重视服务业碳排放问题,构建服务业低碳绩效评估体系。②探索建立定期会商制度,加强服务业低碳技术的跨区域交流合作。③完善基础设施,促进要素空间互动和优化重组。④调整服务业能源结构与部门结构,推进人力资本积累和服务业稳增长。     

海洋碳汇渔业绿色发展空间外溢效应评价研究

海洋碳汇渔业绿色发展空间关联性及其外溢效应对于海水养殖业的有效协调和区域海洋环境的有效保护具有重要意义,科学估算沿海各省(自治区)海水养殖渔业碳汇量并探讨其空间相关性特征是制定差异化渔业碳汇发展政策的重要基础。根据2006—2016年中国大陆沿海9个省(自治区)的碳汇渔业资源清查数据,在检验和比较省域空间渔业碳汇总量相关性特征的基础上,运用空间计量模型分析了渔业碳汇的外溢效应及其影响因素。结果表明:①中国海水养殖渔业碳汇量整体上呈现上升趋势,但各省渔业碳汇量也存在明显差异。②研究期内的Moran's I指数整体呈现为"V"型的波动变化特征,渔业碳汇在省域空间分布上的差异性并不是随机的,而是具备显著的空间相关性。③海水养殖渔业碳汇存在明显的空间外溢效应,通过随机效应的杜宾模型分解后得出渔业产值、劳动力投入的直接效应为正,而渔业受灾面积和科研项目经费投入的直接效应为负;从间接效应来看,渔业产值在各省域间存在竞争与依存关系,海水养殖业劳动力投入和渔业技术推广的项目经费投入在各省域间存在互补关系。因此,中国沿海各省份在发挥海洋水产养殖业生态功能时,应当考虑省域区位因素,合理制定兼具差异化和协调性的海洋碳汇渔业发展政策。     

“竞争申请制”:可持续发展政策试点与央地关系重构

可持续发展目标(SDGs)的提出,开启了人类可持续发展领域最宏大的政策实验,也为开展国际视野的比较公共政策研究提供了难得机遇。执行SDGs及国家可持续发展政策需要处理好中央政府与地方政府间关系,而政策试点是协调这一关系的重要政策工具。已有文献对经济政策试点做了较充分的研究,然而对旨在实现经济、社会与环境协调的可持续发展政策试点,现有研究尚缺乏成型理论。在复杂央地关系格局下,对于需持续投入成本且成果难以界定的可持续发展政策试点,其具有怎样的不同于经济政策试点的机制?此外,众多西方学者将美国作为政策试点研究的制度基础并视其为“民主实验室”。然而,政策试点在以中国为代表的不同体制国家中同样存在,并以多样的机制发挥作用。那么,不同国家体制内的可持续发展政策试点又有哪些异同?政策试点影响下中国既有的央地关系发生了怎样的重构?对此,本文基于最典型案例原则,选取中国与美国响应SDGs分别开展的政策试点进行比较研究。笔者识别了不同体制下试点机制的异同,指出中国基于“竞争申请制”开展的可持续发展政策试点强化了中央部委与地方政府间关系,形成了地方官员的可持续发展激励,保障了政策试点的实施。