污水生物脱氮过程中N_2O的释放途径和影响因素

为了更好地理解和掌握污水处理过程中N 2O的释放规律,结合近年来已经发表的研究结果,就传统的污水生物脱氮过程(全程硝化反硝化过程)和新型污水生物脱氮过程(同步硝化反硝化、短程硝化反硝化和厌氧氨氧化)中N2O的释放途径以及影响因素进行了综述。通过综述发现,硝化和反硝化过程均有可能导致N2O的释放,且硝化过程更易产生N2O;与传统的脱氮过程相比,同步硝化反硝化等新型脱氮过程产生N2O的概率更大;影响N2O释放的因素主要有DO浓度、NO-2浓度、进水氨氮负荷、SRT和COD/N等运行工况和细菌种类及其活性。最后,展望了该领域的研究方向。     

煤气化废水处理技术现状及发展趋势

介绍了国内煤气化企业在废水处理上的困境和煤气化废水的水质特点,从预处理、生化处理、深度处理三个方面总结了国内煤气化废水的研究和应用现状,分析了各处理技术对污染物的去除效果和潜在的应用问题,指出目前煤气化废水处理技术的研究大多局限于小型试验并且缺乏对耦合工艺的总体分析,认为物化技术与生化技术的优化组合是未来研究的主题。     

高效接触氧化-分段进水A/O工艺处理咖啡因生产废水的中试研究

采用"高效接触氧化-分段进水A/O"工艺处理咖啡因生产废水。结果显示:在中试实验条件下,该技术对咖啡因生产废水具有良好的处理效果,出水ρ(COD)<300 mg/L,去除率达85%以上;出水ρ(NH_3-N)<30 mg/L,去除率达90%以上。整套工艺对进水具有较强的耐冲击负荷能力,可适应高盐度、高有机氮废水,具有较好的经济效益。     

生化-混凝-吸附-离子交换工艺处理电镀废水

采用生物接触氧化-混凝沉淀-磁性树脂吸附-离子交换组合工艺对某公司排出的电镀综合废水进行处理,系统地阐述了各处理单元对废水的处理效果,经该工艺处理后的废水能稳定达到GB 21900—2008《电镀污染物排放标准》表3水污染物特别排放标准。     

Destruction of 4-phenolsulfonic acid in water by anodic contact glow discharge electrolysis

Destruction of 4-phenolsulfonic acid (4-PSA) in water was carried out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon (TOC) in water correspondingly decreased, while the sulfonate group of 4- PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH.     

环境内分泌干扰物的评价方法及其生物检测技术

由于化学分析设备与技术的不断提高,大量的有机化学物质不断地从环境介质和食品中被检出。尽管这些物质的浓度很低,但是毒理学的研究表明,一些环境内分泌干扰物质(Environmental Endocrine Disruptors,EDCs)在很低浓度就能导致生物健康负效应。如何在种类众多的环境化学物质,以及在成分复杂的环境提取物中识别具有低剂量效应的有害物质并加以管理十分重要。本文以EDCs为对象,结合近几年来的文献,综述了其可能造成的危害,重点分析了EDCs的作用机制、筛选评估方法及生物检测技术,旨在为今后环境有害物质的筛选与风险识别研究提供借鉴。     

Living with floating vegetation invasions

Invasions of water bodies by floating vegetation, including water hyacinth (Eichhornia crassipes), are a huge global problem for fisheries, hydropower generation, and transportation. We analyzed floating plant coverage on 20 reservoirs across the world’s tropics and subtropics, using > 30 year time-series of LANDSAT remote-sensing imagery. Despite decades of costly weed control, floating invasion severity is increasing. Floating plant coverage correlates with expanding urban land cover in catchments, implicating urban nutrient sources as plausible drivers. Floating vegetation invasions have undeniable societal costs, but also provide benefits. Water hyacinths efficiently absorb nutrients from eutrophic waters, mitigating nutrient pollution problems. When washed up on shores, plants may become compost, increasing soil fertility. The biomass is increasingly used as a renewable biofuel. We propose a more nuanced perspective on these invasions moving away from futile eradication attempts towards an ecosystem management strategy that minimizes negative impacts while integrating potential social and environmental benefits.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01360-6) contains supplementary material, which is available to authorized users.     

Enhancing the efficiency of nitrogen removing bacterial population to a wide range of C:N ratio (1.5:1 to 14:1) for simultaneous C & N removal

• Simultaneous C & N removal in Methammox occurs at wide C:N ratio. • Biological Nitrogen Removal at wide C:N ratio of 1.5:1 to 14:1 is not reported. • Ammonia removal shifted from mixotrophy to heterotrophy at high C:N ratio. • Acetogenic population compensated for ammonia oxidizers at high C:N ratio. • Methanogens increase the plasticity of nitrogen removers at high C:N ratio. High C:N ratio in the wastewater limits biological nitrogen removal (BNR), especially in anammox based technologies. The present study attempts to improve the COD tolerance of the BNR process by associating methanogens with nitrogen removing bacterial (NRB) populations. The new microbial system coined as ‘Methammox’, was investigated for simultaneous removal of COD (C) and ammonia (N) at C:N ratio 1.5:1 to 14:1. The ammonia removal rate (11.5 mg N/g VSS/d) and the COD removal rates (70.6 mg O/g VSS/d) of Methammox was close to that of the NRB (11.1 mg N/g VSS/d) and the methanogenic populations (77.9 mg O/g VSS/d), respectively. The activities established that these two populations existed simultaneously and independently in ‘Methammox’. Further studies in biofilm reactor fetched a balanced COD and ammonia removal (55%–60%) at a low C:N ratio (≤2:1) and high C:N ratio (≥9:1). The population abundance of methanogens was reasonably constant, but the nitrogen removal shifted from mixotrophy to heterotrophy as the C:N ratio shifted from low (C:N≤2:1) to high (C:N≥9:1). The reduced autotrophic NRB (ammonia- and nitrite-oxidizing bacteria and Anammox) population at a high C:N ratio was compensated by the fermentative group that could carry out denitrification heterotrophically. The functional plasticity of the Methammox system to adjust to a broad C:N ratio opens new frontiers in biological nitrogen removal of high COD containing wastewaters.     

A balancing act: Optimizing free chlorine contact time to minimize iodo-DBPs, NDMA, and regulated DBPs in chloraminated drinking water

Many drinking water treatment plants in the U.S. have switched from chlorination to chloramination to lower levels of regulated trihalomethane (THM) and haloacetic acid (HAA) disinfection byproducts (DBPs) in drinking water and meet the current regulations. However, chloramination can also produce other highly toxic/carcinogenic, unregulated DBPs: iodo-acids, iodo-THMs, and N-nitrosodimethylamine (NDMA). In practice, chloramines are generated by the addition of chlorine with ammonia, and plants use varying amounts of free chlorine contact time prior to ammonia addition to effectively kill pathogens and meet DBP regulations. However, iodo-DBPs and nitrosamines are generally not considered in this balancing of free chlorine contact time. The goal of our work was to determine whether an optimal free chlorine contact time could be established in which iodo-DBPs and NDMA could be minimized, while keeping regulated THMs and HAAs below their regulatory limits. The effect of free chlorine contact time was evaluated for the formation of six iodo-trihalomethanes (iodo-THMs), six iodo-acids, and NDMA during the chloramination of drinking water. Ten different free chlorine contact times were examined for two source waters with different dissolved organic carbon (DOC) and bromide/iodide. For the low DOC water at pH 7 and 8, an optimized free chlorine contact time of up to 1 h could control regulated THMs and HAAs, as well as iodo-DBPs and NDMA. For the high DOC water, a free chlorine contact time of 5 min could control iodo-DBPs and NDMA at both pHs, but the regulated DBPs could exceed the regulations at pH 7.     

Classification of coastal waters according to the new Italian water legislation and comparison with the European Water Directive

New legislation for the protection of inland surface waters, transitional waters, coastal waters and ground waters has recently been established in Italy. This law presents a new integrated approach, where all water bodies are considered as complex ecosystems to be studied in each of their components. The new concept of environmental quality of the water body, based on the ecological and chemical status, is also introduced. At the same time (i.e. the end of 2000), the European Community approved the European Water Framework Directive based on the same basic environmental concepts and criteria of the new Italian law. This paper analyses the important points and innovations required by the new Italian legislation for monitoring and classification of marine coastal waters. Details of definitions, parameters, analysis and monitoring programs are discussed. A comparison with the European Water Framework Directive is eventually given, underlining the specific characteristics of the Mediterranean sea, which have to be taken into consideration when applying the European Directive to this particular ecoregion.