混凝沉淀法处理含砷选矿废水

某钨矿含砷选矿废水砷含量高且砷以As(V)为主要存在形态,采用混凝沉淀法处理,详细考察了生石灰、硫酸亚铁和六水三氯化铁3种混凝剂对废水中砷的去除效果。实验结果表明,在PAM投加量40 mg/L,静沉时间60 min条件下,比较分析3种混凝剂对砷的去除效果,三氯化铁为最佳除砷混凝剂。三氯化铁最佳除砷工艺条件为:pH 7.5,三氯化铁投加量986.67 mg/L,混凝反应时间25 min,PAM投加量为40 mg/L,静沉60 min,含砷选矿废水经该工艺处理后,砷去除率可达99.14%,出水砷浓度降至0.361 mg/L,达到国家污水综合排放标准(GB8978-1996)。     

混凝沉淀-Fenton-NaClO氧化深度处理垃圾渗滤液

用混凝沉淀-Fenton-NaClO氧化联合深度处理垃圾渗滤液,利用单因素变量法得出:混凝实验在PFS投加量为1.2g/L、pH=6、搅拌时间为30min的条件下进行,COD、氨氮和色度的去除率分别达到56.60%、15.62%和56.52%;混凝出水在初始pH为4、H2O2投加量为80mmol/L、n(H2O2)∶n(F2+)比为1∶1、反应时间为60min的条件下进行Fenton氧化,COD、氨氮和色度的去除率分别达到71.38%、21.43%和95.24%;Fenton氧化出水在pH为6、NaClO投加量为60mmol/L、反应时间为60min的条件下进行NaClO氧化,COD和氨氮去除率分别为83.42%和99.57%;联合工艺COD、氨氮和色度去除率分别为96.68%、99.69%和98.04%,出水浓度分别为63mg/L、0.47mg/L和18倍,均可满足《生活垃圾填埋污染控制标准(GB16889-2008)》中规定的排放标准。     

次氯酸钠处理终冷水中氰化物硫化物的研究

以次氯酸钠为氧化剂,用正交实验研究了次氯酸钠处理终冷水中氰化物和硫化物,得出正交实验中各因素的主次关系及对除氰除硫的影响。研究结果表明,反应体系的pH是影响脱氰脱硫的重要因素。在最佳处理条件,即pH为10．0,反应温度为25℃,投氯量系数为1．4,反应时间为45min．能使氰化物的质量浓度降至0．267mg／L,脱氰率高达99．8％,硫化物的质量浓度降到0．387mg／L,脱硫率达92．0％,达到≤0．5mg／L的国家排放标准。文章还对工业化提出了一些设想。     

混凝-化学沉淀法处理含氰废水的实验研究

采用“分步混凝 化学沉淀”法处理苯乙腈生产过程中排放的高浓度含氰废水 ,对混凝剂种类、用量、pH、搅拌速率等因素对总氰去除效果的影响进行了探讨 ,找到了此方法处理含亚铁氰化物废水的最佳工艺条件。在最佳工艺条件下处理废水 ,出水无色透明 ,总氰降到 1mg/L以下。该方法工艺简单 ,运行费用低 ,处理效果好 ,是一种具有推广价值的新方法     

钢渣微粉与混凝剂复合对城市污水处理厂尾水深度除磷的试验研究

针对北方严寒地区低温时生物单元处理效能低下,污水处理厂二级出水TP浓度较高且不稳定的问题,将钢渣微粉与混凝剂复合处理城市污水处理厂尾水,以提高TP的处理效能。研究结果表明,钢渣微粉投加量为4g/L时,其对50mg/L含磷溶液处理效果最佳,处理2h后TP去除率可达75.16%;溶液初始pH对除磷效果有一定影响,最佳初始pH为7～8;小试试验表明,与单独聚合硫酸铁(PFS)混凝沉淀除磷相比,投加4g/L钢渣微粉使PFS最佳投加量由10mg/L降至6mg/L,且TP去除率显著提高,絮体沉降时间缩短,钢渣微粉-PFS絮体沉降2min时絮体体积分数降至10%,远低于PFS絮体。在连续30d的中试运行中,进水TP为1.40～1.98mg/L时,出水TP质量浓度可稳定维持在0.35～0.46mg/L,运行后期pH可降至9以下,满足《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A排放标准,运行期间药剂成本仅为0.06元/m3,具有一定经济性。     

沉淀回流对石灰软化法去除地下水硬度的影响

针对地下水硬度去除问题,在传统石灰软化法基础上,通过静态实验对比研究了沉淀回流过程对石灰软化法处理效果的影响。结果表明:在进水硬度385 mg/L,Ca O投加量200 mg/L条件下,经"沉淀回流-石灰软化"处理后,出水滤后总硬度为140 mg/L,比传统石灰软化法低40 mg/L;出水滤前浊度在20 NTU以下,比传统石灰软化法低100 NTU;石灰有效利用率为88%,比传统石灰软化法高25%。这表明通过沉淀回流有效提高了石灰有效利用率,降低了出水浊度。在Ca O投加量200 mg/L,Fe Cl_3投加量3.6 mg/L条件下,通过"沉淀回流-石灰软化/Fe Cl3混凝"处理12 min,静沉30 min后,出水滤后总硬度可维持在140 mg/L左右,浊度低于1 NTU,达到《生活饮用水卫生标准》(GB 5749-2006),加热煮沸后无沉淀和漂浮物产生。     

异相Fenton试剂催化氧化-混凝沉淀深度处理焦化废水

针对焦化废水二级生化处理出水COD、色度和浊度无法达标的问题,实验研究了异相Fenton试剂催化氧化法和混凝沉淀法以及二者联合深度处理焦化废水的效果,分别探讨了H2O2、FeOOH投加量、初始pH,混凝剂投加量及种类对COD去除的影响,确定了最佳运行条件,采用GC-MS分析了联合工艺对废水中有机物的去除规律。异相Fenton试剂催化氧化静态实验研究表明,当H2O2(10%)投加量为2 mL/300 mL,FeOOH投加量为3 g/L,初始pH为4~6之间,处理效果最佳;混凝沉淀实验中最佳的混凝剂为聚丙烯酰胺阳离子,最佳投加量为8 mg/L。异相Fenton试剂催化氧化-混凝沉淀联合工艺深度处理焦化废水,出水COD基本在90 mg/L左右,浊度为0.8NTU左右,色度为40度以下,满足国家污水综合排放二级标准(GB8978-1996)。GC-MS分析显示,联合工艺能有效减少废水中有机物的种类和浓度,并将废水中长链大分子化合物和杂环化合物分解为短链的小分子化合物,构成联合工艺出水COD的主要是小分子有机物,尤其是卤代烷烃含量较高。     

铁碳微电解-混凝对印染废水二级生化出水的深度处理

针对印染废水二级生化出水水质难降解且难以达标的现状,研究在不调节p H的前提下,采用铁碳微电解混凝工艺进行处理研究。通过单因素实验确定最优条件范围,建立响应面(response surface methods,RSM)分析实验,确定铁碳微电解的最佳工艺条件为:Fe的投量为72.1 g/L、m(C)∶m(Fe)为2.98∶1、水力停留时间(HRT)为2.6 h。最佳混凝条件为:Al2(SO4)3投量为100 mg/L、混凝沉淀时间为30 min。实验结果表明,在上述最优工艺条件下对该废水进行深度处理,对COD的去除率能达到50%以上,出水COD低至46.1 mg/L,达到提标后的《纺织染整工业水污染物排放标准》新标准(COD≤60 mg/L),其药剂处理成本为每吨印染废水0.355元左右,该法技术可行、经济合理。     

制浆造纸废水生化出水的混凝处理研究

研究了硫酸铝和三氯化铁对制浆造纸废水生化出水的处理效果.研究发现,不调节原水pH值,硫酸铝投加量为600 mg/L或三氯化铁投加量为300mg/L时,混凝后废水的COD＜150 mg/L,色度＜50倍,出水均符合现阶段排放标准.混凝剂比较发现,在最佳反应条件下,2种混凝剂的处理效果相当,但硫酸铝混凝的成本低于三氯化铁....     

絮凝沉淀+臭氧氧化工艺深度处理印染废水二级出水

以实际印染厂二级生化出水为处理对象,以COD、色度、UV254为评价指标,采用先絮凝沉淀后臭氧氧化及先臭氧氧化后絮凝沉淀2种工艺分别进行印染废水深度处理实验。结果表明,当进水水质为:COD 80~120 mg/L、UV2540.30~0.70、色度72~84倍,在絮凝剂投加量为13.5 mg/L、臭氧投加量为16 mg/L、氧化反应30 min时,先絮凝沉淀后臭氧氧化工艺出水的COD、UV254、色度平均值分别为45.1 mg/L和0.11、4倍;在臭氧投加量为16 mg/L、氧化反应30 min、絮凝剂投加量为10.1 mg/L时,先臭氧氧化后絮凝沉淀工艺出水的COD、UV254、色度分别为45 mg/L和0.10、4倍,说明2种工艺均是可行的,且先臭氧氧化后絮凝沉淀为较优工艺。     

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.     

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.     

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.     

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 and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

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.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Knowledge transfer initiative between molecular biologists and environmental researchers and regulators

A Natural Environment Research Council (NERC) funded Knowledge Transfer (KT) workshop was held in the United Kingdom (UK) to identify the needs and opportunities in the application of molecular biology and ‘omics’ techniques to environmental monitoring and risk assessment. Attendees highlighted a lack of effective communication between end-users and researchers as well as difficulties with data interpretation as reasons behind the slow uptake of molecular biology and omics techniques. A number of promising areas in which new techniques could be implemented at a practical level in the very near future were identified, thereby raising the profile of these recent technologies and providing vital proof of concept work. Molecular taxonomy, bacterial source tracking and pre-screening of chemicals for potential toxicities were all viewed as areas in which omics and molecular techniques could have immediate value, with the aim of reducing cost, increasing efficiency and providing more comprehensive data of improved quality.     

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.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine～ amitrole～ simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K_ow) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.