Fe extraction from high-silicon and aluminum cyanide tailings by pretreatment of water leaching before magnetic separation

Pretreatment of high content of Si- and Al-containing cyanide tailings by water leaching to remove some impurities, such as the major impurities minerals of Si and A1, as well as its effect on Fe extraction in the water leaching process was investigated. The effects of different parameters on iron recovery were studied, and the reaction parameters were proposed as follows： sodium carbonate content of 30%, water leaching at 60 ~C for 5 min, liquid/solid ratio of 15：1, and exciting current of 2 A. Under these optimal conditions, magnetic concentrate containing 59.11% total iron and a total iron recovery rate of 76.12% was obtained. In addition, the microstructure and phase transformation of the process of water leaching were studied by X-ray powder diffraction technique （XRD）, Electronic image of backscattering （BEI）, X-ray fluorescence （XRF）, and energy dispersive spectrometry （EDS）. The results indicate that the soluble compound impurities generated in the roasting process are washed out, and the dissoluble substances enter into nonmagnetic materials by water leaching, realizing the effective separation of impurities and Fe.

Coupled effect of cement hydration and temperature on hydraulic behavior of cemented tailings backfill

Cemented tailings backfill(CTB) is made by mixing cement, tailings and water together, thus cement hydration and water seepage flow are the two crucial factors affecting the quality of CTB. Cement hydration process can release significant amount of heat to raise the temperature of CTB and in turn increase the rate of cement hydration. Meanwhile, the progress of cement hydration consumes water and produces hydration products to change the pore structures within CTB, which further influences the hydraulic behavior of CTB. In order to understand the hydraulic behavior of CTB, a numerical model was developed by coupling the hydraulic,thermal and hydration equations. This model was then implemented into COMSOL Multiphysics to simulate the evolutions of temperature and water seepage flow within CTB versus curing time. The predicted outcomes were compared with correspondent experimental results, proving the validity and availability of this model. By taking advantage of the validated model, effects of various initial CTB and curing temperatures, cement content, and CTB's geometric shapes on the hydraulic behavior of CTB were demonstrated numerically. The presented conclusions can contribute to preparing more environmentally friendly CTB structures.

Spatial Variation and Risk Assessment of Arsenic and Heavy Metals in Surface Water and Suspended Particulate Matter in Tail Reaches of the Yellow River, China

To determine the pollution levels and potential toxic risks of arsenic(As) and heavy metals(Cr, Ni, Cu, Zn, Pb and Cd) in water and suspended particulate matter(SPM) in tail reaches(including freshwater reach and low-salinity reach) of the Yellow River as the Flow-Sediment Regulation Project(FSRP) has been carried out for approximately 15 yr, the surface water and SPM were sampled at pre-flood(April) and post-flood seasons(October). Results showed that similar changes of As and metal levels in water and SPM were observed along the tail reaches at pre-flood or post-flood season. Compared to pre-flood season, the levels of As, Cu, Cr and Ni in freshwater reach and the concentrations of Cr and Ni in low-salinity reach rose greatly at post-flood season. The levels of As and metals in SPM of freshwater reach or low-salinity reach at pre-flood season were significantly higher than those at post-flood season(P < 0.01).The pollutions of As and metals in surface water of tail reaches at pre-flood or post-flood season were not serious. The SPM in freshwater reach at pre-flood season were polluted by Cd, As, Cr, Cu and Ni while those in low-salinity reach were polluted by Cd and Cr. The SPM in freshwater reach at post-flood season were polluted by Cd and Pb while those in low-salinity reach were polluted by Cd and Cr.Cd was identified as heavy metal of primary concern at both pre-flood and post-flood seasons. Combined with the existed data reported in present research, this study found that the toxic risk of As and metals in SPM of tail reaches at pre-flood season was higher than that at post-flood season, implying that the implementation of FSRP during flooding season, to a great extent, reduced the toxic risk of these elements. With the long-term implementation of FSRP, the pollution levels of As and metals(particularly for Cd) in SPM of tail reaches might be elevated and the potential toxic risk primarily produced by Cr, Ni and As might be increased if effective measures were not taken in future.

Review on Pond Aquaculture Tail Water Treatment Technologies

Carrying out the treatment of aquaculture tail water and realizing the discharge and recycling of the aquaculture tail water are the inevitable trend in the development of the fishery industry at present and in the future.For this reason,this paper reviewed the characteristics of pond aquaculture tail water,the sources of pollutants in intensive aquaculture tail water,the important parameters in the water body that affect the growth of cultured organisms,and the water treatment methods in the process of aquaculture,and prospected from the technical level and industrial policy level,hoping to accumulate data for promoting the green development of aquaculture and cleaner production.

Comparison on Purification Effect of Two Macroalgae Species on Prawn Tailwater

[Objectives]This study was conducted to investigate the purification effects of two common large seaweeds on the tail water of prawn farming in greenhouses,and to determine the best culture density of seaweeds.[Methods]Two large seaweed species,Gracilaria lichevoides and Ulva lactuca,were selected to set four culture densities of 0.5,2,4 g/L and a blank control group,respectively.The seaweeds were cultured in 100 L white polyethylene buckets,each of which contained 50 L of tail water from prawn culture.[Results]After 5 d,the nutrient removal rates of the two seaweeds were directly proportional to the density.There was no significant difference in NH_(4)-N removal rate between G.lichevoides and U.lactuca(P>0.05)by two-way analysis of variance,and the NH_(4)-N removal rate of the latter was higher.The removal rates of NO_(3)-N,TN and TP by G.lichevoides were significantly higher than those by U.lactuca(P<0.05).The specific growth rates of seaweeds were negatively correlated with their culture densities.The specific growth rates of G.lichevoides were 5.73%,1.654%and 0.48%,respectively,and those of U.lactuca were 2.01%,1.187%and 0.138%,respectively,when the culture densities were 0.5,2.0 and 4.0 g/L.Two-factor analysis of variance showed that the former was significantly higher than the latter,when the culture density of the two species of seaweeds was 0.5 g/L(P<0.05).The two-way analysis of variance showed that when the culture density of the two kinds of seaweeds was 0.5 g/L,the specific growth rate of G.lichevoides was significantly higher than that of U.lactuca(P<0.05).Based on the above research,the two macroalgae could reduce the nutrients in the wastewater to a large extent,but the culture density determined the scale and economic benefits of seaweed cultivation and further affected the normal growth,metabolism and quality of the seaweeds.[Conclusions]This study provides some theoretical basis for large-scale seaweed farming and biological selection of in-situ ecological restoration of eutrophic seawater.

盾尾刷更换时液氮冻结温度场及冻结参数影响的数值模拟分析

为合理确定高水压下液氮冻结止水更换盾尾刷的冻结设计参数及掌握温度场变化规律,结合某过江通道长距离盾构掘进过程中盾尾刷更换时的液氮冻结止水工程,利用ADINA大型有限元分析软件建立液氮冻结止水及盾尾刷更换数值模型,模拟温度-时间变化曲线与现场实测数据对比,验证模型的合理性,并对土层、去路液氮温度、冻结管长度、冻结管间距、冻结方式进行敏感性因素分析。结果表明:1)冻结效果随土层的不同而发生改变,在卵石层、砾砂层、粉细砂层3种土层中,粉细砂层的冻结效果最差,卵石层最好;2)在有限的冻结时间内,去路液氮温度的不同,只影响土体从开始冻结至越过0℃完成相变这期间的降温速度,不影响完成冻结以后的土体降温速率;3)冻结管长度对土层冻结的影响较小,可以采用较短的冻结管,以降低施工成本和液氮消耗量,但不能过短,应保证其纵向有足够的支撑范围,经计算分析,当冻结管长度为1.52 m时,能在轴面处满足2.0 m的冻结壁厚度要求;4)冻结管间距对冻结效果影响大,冻结管越密,冻结速度越快,效果越好;5)在相同条件下,双环预埋冻结管液氮冻结效果优于管片上直接打孔液氮冻结。

排渗失效下尾矿库溃坝三维模型试验研究

针对尾矿库渗透破坏模式,为克服二维试验槽边壁效应对模型渗流走向及溃决位置的影响,本文以某尾矿库为原型,基于自主设计的三维尾矿库溃坝模型试验平台,进行了排渗设施失效诱发的尾矿库溃坝模型试验研究,揭示了该尾矿库的溃决模式及溃决机理。结果表明:(1)排渗失效导致的溃坝呈现局部流土破坏-坝体累计变形-深层滑动面发展贯通-整体突发失稳的渐进伴突发型溃决演化模式;(2)坝体孔隙水压力骤变是坝体发生滑动破坏的关键响应指标,预示着坝体将在短时间内由滑动体前后缘局部散浸软化、流土、塌陷转变为大范围溃决,可作为坝体溃决事故的前兆信息;(3)排渗失效导致的尾矿库溃坝过程具有渐进性和突发性的特点,发生散浸与流土破坏的过程时间较长,发生深层滑动和溃决的时间短暂,该特征可为尾矿库渗透破坏隐患治理及坝体溃决应急响应提供参考。研究结果对尾矿库溃坝的灾害预防具有重要的现实意义。

尾闾河道形态演变特征的模拟试验研究

尾闾河道是河流与海洋交互的关键地带,对其形态演变研究具有生态环境意义。采用物理试验方法对常见的喇叭状和蜿蜒状(河口左偏与右偏)尾闾河道演变过程进行模拟,研究不同水沙条件下河道演变规律,并以河相系数和相对粗糙度为基准对不同河型稳定性进行评估。试验发现:河道平面形态会经历一个“稳定—微变—强变”阶段;河床平均高程和比降随时间的增加而增大,模型河道上游和河口段变化最大,中游段变化最小;加沙时上游河岸侵蚀、河床淤积,加沙停止后下游与河口段河岸侵蚀大于河床侵蚀,河口分汊、摆动。平面形态不稳定区域:蜿蜒状为下游段,最大与最小河相系数相差6.51倍以上;喇叭状为河口段,最大与最小河相系数相差3.32倍以上。断面形态不稳定区域:左偏蜿蜒状为下游段,最大与最小相对粗糙度相差3倍以上;右偏蜿蜒状为上游段,最大与最小相对粗糙度相差2.03倍以上;喇叭状为下游段,最大与最小相对粗糙度相差4.09倍以上。

铁尾矿废石免烧透水砖制备及性能研究

以铁尾矿废石、水泥和铁尾矿粉为原材料,静压成型制备铁尾矿废石免烧透水砖,研究了成型压力、保压时间、养护时间、水胶比、孔隙率对透水砖抗压强度、透水系数的影响,通过SEM分析样品的微观形貌。结果表明:配合比设计参数为设计孔隙率20%,水泥10%,铁尾矿粉10%,铁尾矿废石80%,水胶比0.4,减水剂掺量为1.5%;透水砖的最佳工艺条件为成型压力8 MPa,保压时间50 s,标准养护28 d,在此条件下制得的透水砖抗压强度为10.4 MPa,透水系数为2.24×10^(-2) cm/s。

冷水鱼养殖尾水治理技术试验

为保护水域生态环境,实施环保养殖,加强养殖业自身环保建设,采用固液分离、沉淀吸收、氧化降解、微生物降解过滤净化和植物吸收等生态处理技术,开展冷流水养殖尾水综合处理技术研究,在处理系统为养殖面积40%的情况下,能有效降低尾水中的COD和氮磷,处理效果分别达到了100%、87.13%、75.56%。

焦化废水生化尾水特征及其深度处理技术进展

焦化废水污染负荷高、有机污染物组成复杂、生物毒性强,是一类非常难处理的煤化工废水。经传统的“物化+生化”工艺处理后,其生化尾水中仍残留部分难降解有机物与一定的生物毒性,COD难以达到《炼焦化学工业污染物排放标准》(GB 16171—2012)的限值要求,需进一步处理。分析了焦化废水生化尾水中的残余有机物和生物毒性特征,归纳总结了混凝、吸附、膜过滤等分离技术,Fenton、催化臭氧氧化、电磁强化氧化、过硫酸盐氧化与电化学氧化等转化技术及分离转化协同工艺对生化尾水中难降解有机物的去除效能和不同有机组分及生物毒性的变化规律,指出在认识水质特征与生物毒性转化规律的基础上,兼顾有机物高效去除和处理出水的生物安全性,开发协同组合工艺与短流程技术是焦化废水生化尾水深度处理技术的发展方向。

硫自养反硝化系统处理化工园区尾水特征分析

采用硫自养反硝化装置对某农药化工园区水处理系统末端排水进行脱氮处理,系统成功启动且运行平稳后,在室温约16℃,HRT为22 h情况下,分别运行硝酸盐模拟废水和实际废水。试验结果表明,以NO3--N模拟废水运行25 d,NO_(3)^(-)-N平均去除率为87%,出水平均浓度为21 mg/L;以实际尾水运行20 d,TN平均去除率为88%,出水平均浓度为17mg/L,反硝化系统脱氮效果良好且运行稳定。对反应器内不同阶段的微生物进行高通量测序分析,在门水平上的结果表明Proteobacteria为占比最大的菌门,Campilobacterota由模拟废水过渡到实际废水运行阶段,丰富度显著增加。在属水平上Sulfurimonas和Thiobacillus为系统内存在的典型菌属,二者具有硫自养反硝化功能,反应后丰度均有较大提升。其中Thiobacillus表现在硫自养反硝化功能上表现出优势,在无机硫的氧化和硝酸盐的还原中发挥了重要作用。

长江大保护试点城市某污水处理厂尾水湿地净化效果研究

为探寻污水处理厂配套尾水湿地净化效果,以长江大保护试点城市某污水处理厂尾水湿地为例,通过现场调查与采样,分析湿地出水水质特征,探讨影响湿地污染物去除效率因素。结果表明:尾水湿地出水COD、NH_(3)-N及TP浓度满足设计目标,潜流湿地对COD去除率较高,表流湿地对氨氮及磷的去除率较高,优于涵养塘;湿地实际运行水力负荷、水力停留时间和污染物负荷与设计值不符,影响污染物去除效果;据此提出湿地运行优化建议,促进湿地深度脱氮除磷,提升尾水湿地效能;运行优化可提高潜流湿地污染物去除率,同时污水处理厂减少碳排放94.74 gCO_(2)m^(3)。研究结果可为该尾水湿地运行管理及长江大保护试点城市系列污水处理厂配套尾水湿地设计与运维提供参考。

接种两株有益菌的生物絮团净水性能及饲料化潜力

为强化新的絮团形成菌伪杜擀氏菌YN12(Pseudoduganella eburnea YN12,YN)利用养殖尾水生成生物絮团效果,并将絮团制成饲料,探讨在胡子鲶(Claris fuscus)饲养上的可行性。在生物絮团系统中,接种活性污泥(Activated sludge,AS)、伪杜擀氏菌YN12和枯草芽孢杆菌(Bacillus subtilis,BS)并配制成7组(AS、YN、BS、AS+YN、AS+BS、YN+BS和AS+YN+BS),分析絮团形态结构差异,评估出对模拟养殖尾水氮去除效果及微生物群落结构优势的最佳组合,最终收集最佳组合絮团烘干研磨成粉末添加到商业饲料制粒,分成对照组和絮团组两组,探讨对胡子鲶的生长性能、饲料利用率、肌肉营养成分及肝脏的消化酶和免疫酶活性的影响。结果表明:YN+BS组水质净化效果稳定,总氮去除效果(89.6%)良好,氨氮、亚硝酸盐和硝酸盐积累低,具有良好的絮团生成量(9.0 ml/L)及占据优势(47.5%)的反硝化菌群(包括Hydrogenophaga、Flavobacterium、Pseudoxanthomonas、Burkholderiaceae、Comamonas、Acinetobacter等)。该组絮团粉以5%比例与商业饲料混合、研磨加工制粒后用于胡子鲶养殖,发现胡子鲶生长性能[包括存活率:(100±0.00)%>(95±0.00)%;增重:(2.81±0.35)g>(2.52±0.52)g;体长增加(1.68±0.36)cm>(1.51±0.34)cm]和饲料系数55±0.03>46±0.12均优于纯商业饲料的对照组,然而在淀粉酶等消化酶、免疫酶包括过氧化氢酶、总超氧化物歧化物、谷胱氨酸过氧化物酶等及肌肉营养成分包括谷氨酸、天冬氨酸、丙氨酸和甘氨酸等鲜味氨基酸上均低于对照组。YN+BS组絮团饲料在生长性能占据优势,然而在消化能力、免疫活性及肌肉营养成分上并未表现出明显优势,需要进一步调整水平絮团添加水平以优化胡子鲶饲养效果。

PHBV-硫铁矿基人工湿地处理实际污水处理厂尾水混合营养反硝化研究

以河南省新乡市某大型污水处理厂尾水为研究对象,开展模拟人工湿地尾水深度脱氮除磷研究。选用聚羟基丁酸戊酸酯(PHBV)和硫铁矿作为湿地系统的主要功能填料,构建异养反硝化与自养反硝化相结合的混合营养反硝化系统。通过水质指标监测和高通量测序等手段,探究工艺运行效果与微生物群落结构机制。构建PHBV+硫铁矿组(实验组)和PHBV+陶粒组(对照组),反应器连续运行77天,结果表明,当水力停留时间(HRT)为2小时,进水水质为NO_(3)^(−)-N=8.39±1.72 mg/L,TN=10.41±1.58 mg/L,TP=0.37 mg/L,COD=15.7 mg/L时,平均出水TN浓度达到2.22 mg/L,TP浓度达到0.28 mg/L,COD浓度为32.7 mg/L,PHBV+硫铁矿组人工湿地脱氮效率(78.55%)明显优于PHBV+陶粒组(51.25%),基本上达到地表水环境质量标准(GB 3838—2002)V类。微生物群落结构分析表明,PHBV+硫铁矿组人工湿地中的优势菌属为自养菌Desulfobacter和异养菌unclassified_k__norank_d__Bacteria,丰度分别为23.98%和12.30%,通过自养与异养菌的协同,实现混合营养反硝化,其中与硫代谢相关Desulfobacter主导的自养反硝化在系统脱氮中可能起主要作用。研究结果可为PHBV+硫铁矿基人工湿地尾水生物脱氮除磷的工程实践提供参考。

稻田-沟渠协同净化池塘养殖尾水效果

为了实现养殖尾水达标排放和循环利用,本研究构建了稻田-农沟-强化沟协同净化系统,考察了各净化单元对池塘养殖尾水中TN、TP、COD_(Mn)和TSS的处理效果,并采用水质标识指数法评价其去除特征和效果,通过浓度沿程衰减的模型拟合分析了相关水质指标沿流程变化规律。结果显示:净化系统出水中TN、TP、COD_(Mn)和TSS浓度平均值分别为1.33、0.19、6.61和12.00 mg/L,去除率分别为86.73%、89.26%、85.77%和93.68%。池塘养殖尾水经净化系统处理后综合水质得到明显改善,其中主要污染物TN得到了显著改善,相关水质达到《淡水池塘养殖水排放要求》(SC/T 9101—2007)一级排放要求;TN、TP和COD_(Mn)沿流程变化规律符合线性削减模型。结果表明稻田-沟渠系统可用于池塘养殖尾水的达标排放。

一株嗜碱兼性好氧反硝化菌Marinobacter sp.B3的分离鉴定及脱氮性能研究

为获得反硝化脱氮效率较好的菌株,实验从海水螺旋藻培养体系中分离获得一株嗜碱兼性好氧反硝化菌,通过观察细菌形态以及16S rRNA基因序列的同源性分析,鉴定该菌株为海杆菌属,命名为Marinobacter sp.B3。为明确该海杆菌的反硝化性能及氮转化途径,研究开展了溶解氧(DO),碳氮摩尔比(C/N),pH和温度等不同单因素对反硝化性能影响实验和氮平衡实验。单因素影响实验结果表明,当硝酸钾(KN0_(3))作为唯一氮源,NO_(3)^(-)-N的初始浓度为100 mg/L,盐度32,振荡速度为150 r/min(初始DO质量浓度是5.6 mg/L),C/N=10,pH=8.0±0.2,温度为35℃时,可获得最大脱氮效果。氮平衡实验结果得出,在好氧环境下,有20.11%的NO_(3)^(-)-N转化为胞内氮,5.58 mg/L的NO_(3)^(-)-N转化为其他形态(NO_(2)^(-)-N、NH_(4)^(+)-N和有机氮),74.72%转化为N2释放;厌氧环境下,有26.65%的NO_(3)^(-)-N转化为胞内氮,72.86%的NO_(3)^(-)-N转化为气态产物释放。最终实验结果表明,Marinobacter sp.B3在好氧和厌氧条件下,48 h对NO_(3)^(-)-N的去除率分别为99.89%和93.80%,具有较好的反硝化脱氮能力,且在好氧条件下NO_(3)^(-)-N去除效率更高,在海水工厂化循环水养殖尾水处理方面具有良好的应用前景。

MBR技术与工艺在水产养殖尾水处理中的研究进展

膜生物反应器技术(MBR)被认为是水产养殖中先进水处理的潜在技术,在水产养殖尾水处理领域的应用还有很大进步空间。以已有的理论知识为基础,结合国内外文献,分别对养殖尾水的高效处理技术、膜污染控制技术、尾水回收技术以及MBR技术改进工艺的研究现状展开描述。然后对不同MBR脱氮除磷组合工艺进行优劣对比,最后提出MBR技术与工艺在水产养殖尾水处理研究中存在处理成本高、处理技术与养殖技术未很好融合的问题,并认为未来该技术可在集成模块化、膜材料和稳定工艺等方面深入研究。为后续MBR技术在水产养殖尾水处理中的高效化、经济化研究提供参考和方向。