Toward better understanding and feasibility of controlling greenhouse gas emissions from treatment of industrial wastewater with activated sludge

Wastewater treatment plants (WWTPs) have been recognized as important sources for anthropogenic greenhouse gas (GHG) emission. The objective of the study was to thoroughly investigate a typical industrial WWTP in southern Taiwan in winter and summer which possesses the emission factors close to those reported values, with the analyses of emission factors, mass fluxes, fugacity, lab-scale in situ experiments, and impact assessment. The activated sludge was the important source in winter and summer, and nitrous oxide (N₂O) was the main contributor (e.g., 57 to 91 % of total GHG emission in a unit of kg carbon dioxide-equivalent/kg chemical oxygen demand). Albeit important for the GHGs in the atmosphere, the fractional contribution of the GHG emission to the carbon or nitrogen removal in wastewater treatment was negligible (e.g., less than 1.5 %). In comparison with the sludge concentration or retention time, adjusting the aeration rate was more effective to diminish the GHG emission in the activated sludge without significantly affecting the treated water quality. When the aeration rate in the activated sludge simulation was reduced by 75 %, the mass flux of N₂O could be diminished by up to 53 % (from 9.6 to 4.5 mg/m²-day). The total emission in the WWTP (including carbon dioxide, methane, and N₂O) would decrease by 46 % (from 0.67 to 0.36 kg CO₂-equiv/kg COD). However, the more important benefit of changing the aeration rate was lowering the energy consumption in operation of the WWTP, as the fractional contribution of pumping to the total emission from the WWTP ranged from 46 to 93 % within the range of the aeration rate tested. Under the circumstance in which reducing the burden of climate change is a global campaign, the findings provide insight regarding the GHG emission from treatment of industrial wastewater and the associated impact on the treatment performance and possible mitigation strategies by operational modifications.

     

Hydroponic root mats for wastewater treatment—a review

Hydroponic root mats (HRMs) are ecotechnological wastewater treatment systems where aquatic vegetation forms buoyant filters by their dense interwoven roots and rhizomes, sometimes supported by rafts or other floating materials. A preferential hydraulic flow is created in the water zone between the plant root mat and the bottom of the treatment system. When the mat touches the bottom of the water body, such systems can also function as HRM filter; i.e. the hydraulic flow passes directly through the root zone. HRMs have been used for the treatment of various types of polluted water, including domestic wastewater; agricultural effluents; and polluted river, lake, stormwater and groundwater and even acid mine drainage. This article provides an overview on the concept of applying floating HRM and non-floating HRM filters for wastewater treatment. Exemplary performance data are presented, and the advantages and disadvantages of this technology are discussed in comparison to those of ponds, free-floating plant and soil-based constructed wetlands. Finally, suggestions are provided on the preferred scope of application of HRMs.     

Exposure,epidemiology, and mechanism of the environmental toxicant manganese

It has become increasingly apparent that global manganese (Mn) pollution to air and water is a significant threat to human health. Despite this recognition, research is only beginning to comprehend the detrimental effects of exposure. Mn, while essential, is particularly harmful to the central nervous system, and overexposure is symptomatic of several neurological disorders. At-risk populations have been identified, but it is still unclear whether typical exposure levels have any long-term consequences. Those at an elevated risk have diminished intellectual function, learning and memory, and mental development. While the overall mechanism of toxicity is undetermined, Mn has been found to induce oxidative stress, exacerbate mitochondrial dysfunction, dysregulate autophagy, and promote apoptosis, ultimately enhancing neurodegeneration. Extrapolation of this in vitro and in vivo data to humans is difficult. There is a definite need to correlate epidemiological studies with causative effects. It is imperative that research efforts endure, so threats are appropriately identified and exposure properly regulated.     

Pollination ecology of <Emphasis Type="Italic">Eomecon chionantha</Emphasis> Hance (Papaveraceae), an endemic species in China

Eomecon chionantha Hance, the only species in the genus Eomecon, is an angiosperm species endemic to China. Here we investigated the pollination syndrome, pollinator generalization of E. chionantha. Our results showed that the individual flower longevity of E. chionantha was 3–5 days. The flowering phenology of E. chionantha can be divided into five phases. We found significant differences in the pollination efficiency of the different insects visiting E. chionantha with bees and flies being the most efficient pollinators. This, in addition to floral morphology and phenology, suggests that E. chionantha is generalized on bees and flies and possesses an outcrossing, partially self-compatible and pollinator-dependent breeding system.     

Toxicity of sediment cores from Yangtze River estuary to zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>) embryos

Toxicity evaluation is an important segment in sediment quality monitoring in order to protect aquatic organisms and human health. The purpose of this study is to assess the toxicity of sediments from three sediment cores in Yangtze River Estuary, China, using the zebrafish (Danio rerio) embryo tests. Fertilized zebrafish eggs were exposed to both whole sediments and sediment organic extracts prepared from collected sediments, in order to provide a comprehensive and realistic insight into the bioavailable toxicity potential of the sediments. As end points, development parameters (mortality, hatching rate, and abnormality) in the developing embryos were recorded during the 96-h exposure. The results showed that some samples increased mortality, inhibited the hatching of embryos, and induced morphological abnormalities. The embryonic toxicities presented serrated changes and irregular distribution with depth, which may be related to hydrodynamic effect and unstable environmental input. However, lethal and sub-lethal effects were more significant at the sub-surface sediments (10～40 cm), which indicated that the pollution is more serious in recent decades.     

电化学氧化法处理垃圾渗滤液纳滤浓缩液

实验利用电化学氧化法处理垃圾渗滤液纳滤浓缩液,以提高废水的可生化性。研究考察了水力停留时间、进水流量、循环流量、电流强度和原水氯离子浓度对有机物去除的影响。研究结果表明,电化学氧化法的最佳运行条件如下:水力停留时间为3 h,进水流量为1 m3/h,循环流量为15 m3/h,电流强度为420 A。在上述条件下,原水COD浓度从3 100mg/L降到1 311.3 mg/L,去除率达到57.7%,BOD/COD值由0.03提升至0.31。氯离子对电解有促进作用,但原水氯离子浓度超过5 000 mg/L,不需要外加工业盐。     

铜绿微囊藻胁迫对宽叶香蒲叶片光呼吸特性的影响

采用共生培养的实验方法,通过追踪测定宽叶香蒲(Typha latifolia)叶片中叶绿素含量、净光合速率、光呼吸速率及乙醇酸氧化酶(GO)、谷氨酰胺合成酶(GS)及过氧化氢酶(CAT)的活性,研究不同初始密度铜绿微囊藻(Microcystis aeruginosa)对宽叶香蒲叶片光呼吸特性的影响。结果表明,铜绿微囊藻初始密度为1.0×104ind/m L时,宽叶香蒲叶片叶绿素含量、净光合速率、光呼吸速率及GO、GS及CAT的活性增加,说明低密度铜绿微囊藻对宽叶香蒲叶片的光合作用及光呼吸具有促进作用;铜绿微囊藻初始密度为1.0×107ind/m L时,宽叶香蒲叶片净光合速率、光呼吸速率及GO、GS及CAT的活性呈现先增加后降低的趋势,表明经过一段时间培养后,高密度铜绿微囊藻对宽叶香蒲叶片的光合作用和光呼吸呈现出抑制作用。但是在净光合速率急剧降低的时候,光呼吸速率在短时间内仍然维持在一个较高水平,说明宽叶香蒲可能通过维持或增强光呼吸在一定程度上抵抗逆境胁迫。     

石油降解菌Pseudomonas stutzeri TH-31的分离与降解条件优化

使用稀释富集法,从大港油田采油废水处理站生化池中定向快速的分离出多株高效石油降解菌株。对分离获得的1株优势菌株进行生理生化和分子生物学鉴定,显示属于Pseudomonas stutzeri的1个新菌株,命名为Pseudomonas stutzeri TH-31。通过批次实验,对菌株TH-31的生长条件和石油降解条件进行了优化,经过条件优化,P.stutzeri TH-31在初始p H 7,原油投加量为300 mg/L,35℃培养5 d后,获得最高石油烃降解率92.7%。     

300MW燃煤锅炉机组超细颗粒聚并器的实验研究

为了解决燃煤锅炉烟气中超细颗粒难以脱除的问题,基于流体动力学原理设计了一种超细颗粒聚并器,并在300 MW燃煤锅炉机组电除尘器的前置烟道中进行了实验研究。结果表明,聚并器内部存在超细颗粒之间以及超细颗粒与大颗粒之间的相互聚集行为,从而使超细颗粒数量显著减少。例如,对于粒径在2.65和10.48μm以下的颗粒,其体积比例在聚并器出口分别减少了56.7%和62.3%,在电除尘器出口的粉尘浓度减少了26.34 mg/Nm3,这表明,基于流体动力学原理的聚并器对超细颗粒的聚并作用明显,具有良好的应用前景。