Influence of recirculation over COD and N-NH4 removals from landfill leachate by horizontal flow constructed treatment wetland

Abstract

Treatment of landfill leachate is a challenge due to its complex chemical composition and high recalcitrance and because of high costs for conventional wastewater treatment. In our study, leachate from the Quitaúna Landfill, Sao Paulo Metropolitan Region, Brazil, was treated at a laboratory scale with a horizontal subsurface flow constructed treatment wetland (HF-CTW) operating under a recirculation regime. Two units planted with Heliconia psittacorum (HP) and Cyperus papyrus (CP), and one unplanted control unit were assessed. With a recirculation regime over 21?days, the planted units removed 40% of chemical oxygen demand (COD) while the control unit removed only 29%. True color removal efficiencies were 2, 22, and 23% for the control, HP, and CP HF-CTWs, respectively. The ammonium nitrogen removal efficiencies for a 21-day hydraulic retention time (HRT) were 63–81% for planted units and 72% for the control. The increase of the HRT from 7 to 21?days led to the enhancement of ammonium nitrogen removal but did not affect the COD and total nitrogen removals. This phenomenon is a consequence of leachate’s low biodegradability. The present study shows the importance of the HRT and plant presence for landfill leachate treatment using HF-CTWs.     

Soil characteristics and Cyperus spp. occurrence along a toposequence

On acrisol (locally named terre de barre in Republic of Benin, West Africa), weed and soil (0–20 cm depth) were sampled at the beginning and the end of the cropping period in 2009 to gain knowledge about interaction between nutsedge occurrence and soil parameters. The samples were taken along a toposequence at the Africa Rice Center experimental station according to the topographic positions of summit, upper slope, middle slope and foot slope. At each topographic position, a 1 m × 1 m quadrat was set to study Cyperus abundance using 0, 3 and 5 abundance indices scale. Weed species sampled were identified, oven‐dried and weighed. Soil particle sizes and organic C, total N, available P, K, Ca, Mg and extractable Fe contents were determined. Among the three species of Cyperus that were encountered, C. rotundus was the most frequent along the entire toposequence, while C. esculentus and C. sphacelatus were limited to the summit and upper slope, respectively. Sand, Fe and Pa contents of soil were influencing positively Cyperus spp. occurrence in opposition to C and Mg contents. But only the latest nutrients did so consistently and significantly. Thus, increasing organic matter and applying Mg fertilizer might enhance Cyperus control.     

不同盐度对闽江河口沉积物硝化作用的影响

选择闽江河口鳝鱼滩湿地与道庆洲湿地为对象,采集湿地沉积物在室内进行沉积物硝化培养,分析不同盐度水平对湿地沉积物硝化作用的影响.结果表明:闽江河口湿地沉积物硝化速率普遍较低,鳝鱼滩湿地沉积物最高硝化速率只有0.193 mg·kg^-1·d^-1,而道庆洲湿地沉积物硝化速率最高不超过0.050 mg·kg^-1·d^-1.盐度的升高会抑制闽江河口湿地沉积物的硝化作用.低盐度时(5),硝化速率下降的主要原因是硝化细菌活性受到抑制;随着盐度的升高(10),硝化速率略有上升但仍低于初始值,这是由于随着盐度的升高,盐度对好氧氨化细菌活性的抑制程度有所加强,导致系统产生NH_4^+-N的速率下降,从而造成好氧氨化细菌对表观硝化速率下降的贡献减少.沉积物硝化活性对于盐度的响应存在地域差异.咸水湿地(鳝鱼滩湿地)沉积物中的微生物对盐度的变化适应性较强,从而使该湿地沉积物硝化活性在高盐度条件下仍然较高.淡水湿地(道庆洲湿地)沉积物对盐度变化的适应性较弱,导致其沉积物硝化活性在高盐度条件下低于中等盐度.闽江河口鳝鱼滩与道庆洲的短叶茳芏湿地沉积物硝化作用较低的主要原因是沉积物呈酸性及淹水状态下的缺氧条件弱化了沉积物的硝化作用.两处湿地的硝化速率与硝化活性随时间的变化趋势为先升高后下降,这是由初始NH_4^+-N浓度、氧气含量和反硝化共同作用造成的.     

Natural attenuation of weathered oil using aquatic plants in a farm in Southeast Mexico

An experiment was conducted in field for three years to assess the sustainability of aquatic plants Leersia hexandra, Cyperus articulatus, and Eleocharis palustris for use in the removal of total hydrocarbons of weathered oil in four areas contaminated with 60916–119373 mg/kg of hydrocarbons. The variables evaluated were coverage of plant, dry matter, density of plant growth-promoting rhizobacteria, and the removal of total weathered oil. The variables showed statistical differences (p = 0.05) due to the effects of time and the amount of oil in the soil. The three aquatic plants survived on the farm during the 36-month evaluation. The grass L. hexandra yielded the greatest coverage of plant but was inhibited by the toxicity of the oil, which, in contrast, stimulated the coverage of C. articulatus. The rhizosphere of L. hexandra in control soil was more densely colonized by N-fixing bacteria, while the density of phosphate and potassium solubilizing rhizobacteria was stimulated by exposure to oil. C. articulatus coverage showed positive relationship with the removal of weathered oil; positive effect between rhizosphere and L. hexandra grass coverage was also identified. These results contributed to the removal of weathered oil in Gleysols flooded and affected by chronic discharges of crude oil.     

闽江河口春季互花米草入侵过程对短叶茳芏沼泽土壤碳氮分布特征的影响

2014年4月,选择闽江口鳝鱼滩湿地中未被入侵的短叶茳芏群落(A)、互花米草入侵斑块边缘(B)以及互花米草入侵斑块中央(C)为研究对象,基于时空互代研究方法,探讨了互花米草入侵序列下湿地土壤碳氮空间分布特征的差异。结果表明,互花米草入侵显著降低了土壤的NO_3~--N含量(P0.05),但整体增加了NH_4~+-N含量,这与其入侵后导致湿地土壤颗粒组成发生显著变化(砂砾含量增加33.81%),进而促进了土壤的矿化作用和硝化作用,并有助于硝态氮的垂直淋失有关。互花米草入侵整体增加了土壤的碳氮含量和C/N比,与入侵进程和入侵前相比,互花米草入侵后湿地土壤的碳储量分别增加了8.73%和24.37%,氮储量则分别增加了10.22%和17.87%,这主要与其对闽江口湿地植物群落格局、养分生物循环以及强促淤作用引起的土壤颗粒组成等显著改变有关。研究发现,闽江口互花米草入侵对短叶茳芏湿地土壤碳氮含量的影响相对于江苏盐城、长江口以及杭州湾湿地的影响可能更为显著,其互花米草入侵较大改变了土壤中陆源和海源有机质的来源比例,使得入侵后湿地土壤养分的自源性增强。     

Detection of insect Juvenile hormone III and Its precursors from<Emphasis Type="Italic">in Vitro</Emphasis> plantlets of<Emphasis Type="Italic">Cyperus aromaticus</Emphasis>

Juvenile hormone III (JH III) is one of the five closely related sesquiterpenoid compounds important in the regulation of an insect physiological processes in both the developing and the mature insect. JH III and its biosynthetic intermediates, farnesol and methyl farnesoate were detected in thein vitro Cyperus aromaticus plantlets and the mature plants growing in the field. A higher amount of methyl farnesoate (52.7%) and farnesol (31.4%) were found to be present in thein vitro plantlets as compared to the field grown mother plants which contained lower methyl farnesoate (19.5%) and farnesol (14.8%). On the other hand, the mature mother plant (4 months old) contained a higher percentage of JH III than thein vitro plantlets. The estimated content of JHIII analyzed by gas chromatography indicated that the amount of JHIII in the 10 weeks oldin vitro plantlets and the four months old mature plants of C.aromaticus was 0.076 μg/g and 0.085 μg/g respectively. This study indicated thatin vitro culture system could be a potential tool for the production of this natural derived bio-insecticide and could provide a material source for further investigations of the biosynthesis of JH III inC. aromaticus.     

Effects of ramet clipping and nutrient availability on growth and biomass allocation of yellow nutsedge

A glasshouse experiment was conducted to examine how the interactions of nutrient availability and partial ramet clipping affect growth, reproduction and biomass allocation of Cyperus esculentus, an invasive sedge. The plants sprouting from tubers were grown at low and high nutrient levels, and were subject either to no clipping, one, two or three clippings, with each clipping cutting half of the existing ramets at soil level. Our results show that nutrient availability and clipping frequency tended to independently affect most of growth, reproduction and biomass allocation parameters of Cyperus esculentus examined in the present study. Increased supply of nutrients led to an increase in plant productivity and its associated traits. All of the traits, except for the number of ramets, displayed a decreasing pattern with increasing clipping frequency, indicating that Cyperus esculentus had undercompensatory responses to ramet clipping. It is likely that the patterns of plants response to clipping are species specific, and depend on morphological characters of species. Its susceptibility to ramet clipping can offer opportunities for controlling this invasive species through mechanical methods such as mowing. Clipping had little effects on biomass allocation; however, root weight fraction increased with increasing clipping frequency. While nutrient availability and clipping frequency had no influence on leaf carbon concentration at harvest, both of them increased leaf nitrogen concentration, and hence reduced leaf C/N ratio.     

Bio-assay study of response by a parasitoid to frass and feeding substrates of its host, the stalk borer Eldana saccharina

In Petri dish and olfactometer tests Goniozus natalensis Gordh (Hymenoptera: Bethylidae) exhibited a host-searching response upon contact with, and at a short distance from, frass of its natural host, Eldana saccharina Walker (Lepidoptera: Pyralidae), whichever the substrate on which E. saccharina had been feeding. The substrates were two host plants, sugarcane or Cyperus papyrus L.; diet media based respectively on sugarcane, papyrus, or cellulose; or a synthetic diet medium, containing no plant material. Host-searching behaviour increased in intensity with age and after mating of G. natalensis females. Parasitoids responded similarly to frass produced by male and female E. saccharina larvae. The substrates themselves elicited little response in G. natalensis. Frass of another borer, Sesamia calamistis Hamps. (Lepidoptera: Noctuidae), fed on sugarcane-based medium, also elicited little response in G. natalensis. The results suggest that frass of E. saccharina larvae contains a material, evidently volatile, to which their parasitoid G. natalensis responds, irrespective of the substrate on which the E. saccharina subsist.     

不同刈割程度对油莎豆非结构性碳水化合物代谢及生物量的影响

为探讨不同留茬高度对油莎豆(Cyperus esculentus)非结构性碳水化合物代谢的影响,进一步明确不同留茬高度与油莎豆地上生物量的关系,并寻求最佳刈割高度,该研究以油莎豆为研究对象,测定6个留茬高度(10、20、30、40、50 cm和未刈割)油莎豆叶片生长生理参数、非结构性碳水化合物含量和地上生物量。结果显示:刈割对于油莎豆光合作用有刺激作用,刈割后油莎豆在第1–14天达到再生生长高峰期。留茬30cm油莎豆叶片可溶性糖含量(第7、21和28天)均高于其他处理,分别为9.22%、10.83%、9.07%,其淀粉含量(第14和21天)均高于其他处理,分别为4.88%和4.11%。留茬40 cm (第21、28天)蔗糖含量均高于其他处理,分别为7.88%和11.38%;其果糖含量(第14和21天)均高于其他处理,分别为5.29%和6.40%。刈割促进了留茬30和40cm油莎豆叶片蔗糖磷酸合成酶和蔗糖合成酶活性的提高。留茬10cm抑制了油莎豆叶片蔗糖含量增加和相关酶活性。合计刈割时和收获时的饲草质量之和,留茬30cm油莎豆干草质量最高,为10 605.11kg·hm^-2     

Host Status of Seven Weed Species and Their Effects on Ditylenchus destructor Infestation of Peanut

The host suitability to Ditylenchus destructor of seven common weed species in peanut (Arachis hypogaea) fields in South Africa was determined. Based on the number of nematodes per root unit, white goosefoot (Chenopodium album), feathertop chloris (Chloris virgata), purple nutsedge (Cyperus rotundus), jimson weed (Datura stramonium), goose grass (Eleusine indica), khaki weed (Tagetes minuta), and cocklebur (Xanthium strumarium) were poor hosts. Ditylenchus destructor survived on all weed species; population densities increased in peanut hulls and caused severe damage to seeds of peanut grown after weeds. Roots of purple nutsedge left in the soil suppressed populations of D. destructor and root and pod development in peanut grown after the weed. However, nematode populations in peanut hulls and seeds were not suppressed. Some weed species, especially purple nutsedge which is common in peanut fields, can be used to indicate the presence of D. destructor in the absence of peanut.