鸟粪石法回收制肥工业废水中氨氮的中试研究

制肥工业废水中氨氮浓度高,难以直接进行生化反应,采用鸟粪石沉淀法可有效去除并回收氨氮。利用中试反应器回收某制肥工业废水中的氨氮,采用氯化镁与氧化镁作为联用镁源,通过考察不同进料方式、搅拌速度、停留时间等因素的影响,确定了鸟粪石法回收氨氮的最佳工况:采用间歇进水、固体投加镁源的投料方式,搅拌速度300 r/min,停留时间2 h。最佳条件下,氨氮去除率达到93.5%,磷残余率小于0.3%,生成的鸟粪石纯度可达85.6%,砷和铅的质量分数分别为0.0036和0.0008,符合肥料中重金属限值(GB/T 23349-2009),其他重金属均未检出。因此,回收产品有很好的利用价值。经济分析表明磷源是此方法处理成本较高的主要原因。     

鸟粪石循环利用处理高氨氮废水的热解行为

为了循环利用鸟粪石处理高氨氮废水,探讨了鸟粪石煅烧与加碱热解的脱氮率,利用电镜扫描(SEM)和X射线衍射(XRD)对2种热解产物进行了分析。鸟粪石煅烧条件为:温度100～225℃,时间1～5 h;加碱热解条件为:温度60～95℃,时间0.5～4 h,加碱量OH-∶NH4+摩尔比值0.4～1.5。结果表明,虽然XRD分析显示2种热解产物都已失去鸟粪石的特征峰,但是鸟粪石加碱热解效果更好,最佳热解条件为:加碱量OH-∶NH4+摩尔比值1,温度90℃,时间2 h,鸟粪石脱氮率95%以上;加碱热解产物表面为多孔状,完全失去了晶体结构;煅烧热解鸟粪石脱氮率仅为80%左右,热解产物晶体结构破坏不完全。鸟粪石在最佳条件下热解循环处理高氨氮废水,可循环使用6次,氨氮去除率80%以上,出水磷浓度小于8 mg/L。     

鸟粪石结晶沉淀法处理氨氮废水的应用研究

论述了鸟粪石的形成机理、形成的影响因素。在废水处理中采用鸟粪石沉淀法脱氮，具有氨氮去除率高、反应速度快、污泥体积小的优点，同时可以回收氨氮。作为缓释肥，具有良好的经济效益。重点介绍了鸟粪石沉淀法处理氨氮废水目前的研究进展，并探讨了该技术在今后的研究趋势。     

酸性条件下剩余污泥中Ca2＋和Mg2＋溶出对磷回收的影响

为了在酸性条件下实现剩余污泥中磷的高效回收,对pH=3时剩余污泥水解酸化过程中氨氮、正磷酸盐和钙镁离子的溶出现象以及磷回收进行了研究分析。结果表明：当pH=3时,所溶出的氨氮、镁离子和钙离子与磷酸盐的摩尔比均大于1,能满足采用鸟粪石沉淀法或者羟磷灰石沉淀法回收磷的要求;但所溶出的钙镁离子的摩尔比大于1,会对鸟粪石沉淀法回收磷的顺利进行有较大影响;有无外加镁剂对磷回收率影响不大。采用改型后的镁型强酸性阳离子交换树脂进行离子交换可以得到较高纯度的鸟粪石沉淀产品,通过XRD检测其纯度为95％以上。     

酸性条件下剩余污泥中Ca2+和Mg22++溶出对磷回收的影响

为了在酸性条件下实现剩余污泥中磷的高效回收,对pH=3时剩余污泥水解酸化过程中氨氮、正磷酸盐和钙镁离子的溶出现象以及磷回收进行了研究分析。结果表明：当pH=3时,所溶出的氨氮、镁离子和钙离子与磷酸盐的摩尔比均大于1,能满足采用鸟粪石沉淀法或者羟磷灰石沉淀法回收磷的要求;但所溶出的钙镁离子的摩尔比大于1,会对鸟粪石沉淀法回收磷的顺利进行有较大影响;有无外加镁剂对磷回收率影响不大。采用改型后的镁型强酸性阳离子交换树脂进行离子交换可以得到较高纯度的鸟粪石沉淀产品,通过XRD检测其纯度为95%以上。     

电化学沉淀法从废水中回收鸟粪石

从废水中以鸟粪石方式去除氮磷通常采用投加化学试剂或吹脱CO2调节p H来实现,少有采用电化学沉淀法回收鸟粪石的应用。为探讨电化学沉淀法回收鸟粪石的可行性,实验采用电解法调节p H,进行了Ⅰ、Ⅱ2个系列的实验,以确定回收鸟粪石的最优操作条件。Ⅰ实验以不锈钢网为阴极,碳棒为阳极,Ⅱ实验采用不锈钢网为阴极,镁棒为阳极。结果表明,(1)鸟粪石沉积物大部分富集在不锈钢网上,便于收集;(2)当碳棒为阳极时,最适电解电压为3 V,镁棒为阳极时,则为3.6 V;(3)不搅拌或低速搅拌有利于鸟粪石的形成,温度对电解反应影响不大;(4)低浓度Ca2+基本不影响电解反应速度,而高浓度Ca2+不仅影响反应速度,还影响鸟粪石纯度;(5)以镁棒或碳棒处理污泥脱水滤液效果接近,都能得到高纯度鸟粪石,且能节省开支。     

以农田高盐排水为替代镁源回收养殖废水中的磷素

为解决新疆南疆地区养殖废水高浓度氮磷和农田排水中的高浓度盐分的协同污染问题,以农田高盐排水为镁源对模拟养殖废水中的磷进行了回收实验,对比了高盐排水和常规镁源的磷回收效率,探讨了影响其回收的主要因素,并通过正交试验获得了高盐排水回收磷的最优反应条件.与常规MgC12镁源的磷回收对比分析结果表明,pH=10时高盐排水回收磷的效率最高,比MgCl2镁源达最大回收率所需的反应pH略高;利用L34正交试验探究了pH(8、9、10、11)、Mg:P摩尔比(1.0、1.5、2.0、2.5)、N:P摩尔比(1.0、1.5、2.0、4.0)对高盐排水镁源回收磷的影响,并结合SPSS统计分析得到高盐排水回收磷的最优反应条件为pH=10、n(Mg):n(P)=2.5,n(N):n(P)=4;高盐排水中的HCO3-和SO42-离子对磷回收有抑制作用,而Ca2+离子对磷回收有促进作用;XRD和SEM-EDS分析表明,高盐排水回收磷的产物以鸟粪石为主,并夹杂着磷灰石和粘土矿物等杂质.整体上,以高盐排水作为替代镁源回收磷的效果较好,本研究为解决鸟粪石沉淀法的镁源问题提供了一种新思路.     

工艺条件对鸟粪石晶体的粒径和沉降速度的影响

采用激光粒度仪实验测定了小型套管式空气曝气填料层磷回收装置中不同条件下生成的鸟粪石晶体的体积平均粒径,考察了其变化规律,并结合Stokes公式计算了晶体的沉降速率,同时考虑鸟粪石晶体形状的影响,进行了相应的修正。实验结果表明,鸟粪石的粒径在10—200μm之间,主要集中于20～100μm;在磷回收装置中添加填料并通人空气有利于增大鸟粪石晶体的粒径和沉降速度,无填料无空气时和有填料有空气时的平均粒径分别在30～55μm和40～65μm之间。随着pH值的增大,鸟粪石晶体的粒径和沉降速度逐渐增大,但当pH大于9．0后,鸟粪石晶体的粒径和沉降速度又逐渐减小;氮磷比值从1：1增大到2：1,鸟粪石晶体的粒径和沉降速度小幅度增加,氮磷比进一步增大,鸟粪石晶体的粒径和沉降速度基本不变;镁磷摩尔比在1：1—1．2：1的范围内时,鸟粪石晶体的平均粒径和沉降速度随镁磷比的增大而增大;镁磷摩尔比大于1．2：1后,鸟粪石晶体的平均粒径和沉降速度随镁磷比的增大逐渐减小;初始磷浓度越高,鸟粪石晶体的平均粒径和沉降速度越大。     

工艺条件对鸟粪石晶体的粒径和沉降速度的影响简

采用激光粒度仪实验测定了小型套管式空气曝气填料层磷回收装置中不同条件下生成的鸟粪石晶体的体积平均粒径,考察了其变化规律,并结合Stokes公式计算了晶体的沉降速率,同时考虑鸟粪石晶体形状的影响,进行了相应的修正。实验结果表明,鸟粪石的粒径在10~200 μm之间,主要集中于20~100 μm;在磷回收装置中添加填料并通入空气有利于增大鸟粪石晶体的粒径和沉降速度,无填料无空气时和有填料有空气时的平均粒径分别在30~55 μm和40~65 μm之间。随着pH值的增大,鸟粪石晶体的粒径和沉降速度逐渐增大,但当pH大于9.0后,鸟粪石晶体的粒径和沉降速度又逐渐减小;氮磷比值从1：1增大到2：1,鸟粪石晶体的粒径和沉降速度小幅度增加,氮磷比进一步增大,鸟粪石晶体的粒径和沉降速度基本不变;镁磷摩尔比在1：1~1.2：1的范围内时,鸟粪石晶体的平均粒径和沉降速度随镁磷比的增大而增大;镁磷摩尔比大于1.2：1后,鸟粪石晶体的平均粒径和沉降速度随镁磷比的增大逐渐减小;初始磷浓度越高,鸟粪石晶体的平均粒径和沉降速度越大。     

鸟粪石沉淀法去除酿酒废水中磷的研究

以氧化镁和硫酸镁作为镁源采用鸟粪石(MAP)沉淀法对酿酒废水开展了除磷实验研究,考察不同因素对TP去除效果的影响。结果表明:除磷效果影响因素重要性排序为pH转速Mg~(2+)与P的摩尔比。以氧化镁为镁源时,MAP沉淀法的最佳反应条件为pH=10.0,转速150r/min,Mg~(2+)与P摩尔比为1.2;以硫酸镁为镁源时,MAP沉淀法的最佳反应条件为pH=10.0,转速50r/min,Mg~(2+)与P摩尔比为1.0。正交实验与单因素实验结果基本一致,最佳条件下TP去除率均可达90%以上。受酿酒废水矿物成分影响,MAP沉淀中的MgNH_4PO_4·6H_2O纯度较低,综合考虑,采用MAP沉淀法去除酿酒废水中的磷时宜选用氧化镁作为镁源。     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.