高浓度氨氮污泥脱滤液的半硝化实验研究

对高浓度氨氮污泥脱滤液进行了半硝化实验研究。运行结果表明,反应器进水氨氮浓度在402 mg/L、HRT=5.5 h、温度为22～31℃、DO〈1.0 mg/L、pH值在7.4～8.2时,半硝化反应器出水的NO 2--N/NH3-N维持在1.13～1.32,且负荷达到1.76 kg N/（m3.d）,NO2--N/NOx...     

低温条件下硝化污泥的驯化

为了在低温13～14％下取得较好的硝化效果,分3个温度阶段25℃,16～17℃,13—14℃对活性污泥进行了驯化培养,研究了进水氨氮浓度和混合液COD对硝化污泥的影响。实验结果表明,硝化污泥经过驯化培养后,氨氮去除率可达80％以上,且在DO浓度为2ing／L,pH为6．7～7．5,进水氨氮为300mg／L,混合液COD为80mg／L条件下,硝化污泥能取得较快的增长,氨氮平均去除率可达89％。     

生物膜反应器中低氨氮浓度废水的亚硝化

在连续流生物膜反应器中通过控制DO、pH和HRT,对低氨氮浓度废水进行了亚硝化的实验研究。结果表明,在进水氨氮浓度为35～45 mg/L,温度为34℃的情况下,当DO=1.4～1.5 mg/L,pH=8.3,HRT=6 h时,氨氮的去除率与亚硝态氮的积累率均可达到80%左右,实现了较好的氨氮降解及稳定的亚硝态氮的积累。     

序批式反应器处理垃圾渗滤液的污泥颗粒化及污染物去除性能研究

应用序批式反应器(SBR)处理垃圾渗滤液,以絮状活性污泥为接种污泥,经过37 d的运行,反应器内出现小粒径颗粒污泥。第50 d,反应器中污泥完全颗粒化。稳定运行期间,反应器内污泥的平均粒径为0.7 mm;SVI5min一直维持在较低的水平(27~47 mL/g);MLSS基本稳定在3 700~4 500 mg/L;当COD和氨氮的平均进水浓度为2 150 mg/L和312 mg/L时,平均出水浓度分别为540 mg/L和35 mg/L,去除率分别为75%和89%。     

DO和pH值在短程硝化中的作用

在SBR反应器中对DO和pH值在短程硝化和半亚硝化过程中的作用进行试验研究,结果表明,控制低DO和适宜的pH值在短程硝化过程中起着重要的作用.本试验条件下,当DO为0.5～1.0 mg/L、pH值为7.5～8.0时,在SBR反应器中很容易实现短程硝化;当DO＞0.3 mg/L时,DO越低,出水NO2--N积累率越高;当pH值＞6.8时,不会影响系统NO2--N积累的稳定性.另外,研究结果还表明,通过控制DO和pH值可以实现半亚硝化.本试验条件下,当进水氨氮浓度为120 mg/L时,控制DO为0.3～0.4 mg/L可实现出水半亚硝化;当进水氨氮浓度为200 mg/L时,控制DO为0.5～0.6 mg/L或pH值为6.8也可以实现出水半亚硝化.     

氨氮负荷的变化对部分硝化的影响及部分亚硝化的快速启动

部分硝化的稳定运行在一体式部分硝化-厌氧氨氧化工艺(PN/A)中至关重要。探索了在内循环接触氧化型膜生物反应器(ICCOMBR)中改变进水氨氮负荷(ALR)后,反应器中部分硝化过程受到的影响及恢复过程。结果表明：在HRT为24 h,DO为2.0~2.5 mg·L⁻¹时,系统进水ALR降为0.10 kg·(m³·d)⁻¹(氨氮为100 mg·L⁻¹),部分硝化过程迅速破坏;当系统进水ALR升至0.40 kg∙(m³·d)⁻¹(氨氮为400 mg·L⁻¹),部分硝化过程在3 d内迅速恢复;部分硝化恢复稳定后,再提高ALR至0.60 kg·(m³·d)⁻¹(氨氮为400 mg·L⁻¹),并通过调整HRT和DO,最终在HRT为16 h、DO为0.5~1.0 mg·L⁻¹时成功实现部分硝化;通过改变曝气量(AR),在AR为0.9 L·min⁻¹时,控制DO为(0.76±0.11) mg·L⁻¹,系统pH为9.7~8.2,可成功启动部分亚硝化。     

碱度对膜生物反应器硝化过程和膜污染的影响

采用一体化浸没式膜生物反应器处理生活污水,研究进水碱度对硝化过程和膜污染过程的影响。结果表明,碱度对膜生物反应器工艺的硝化过程影响较大;当碱度充足(224~510 mg/L)时,氨氮去除率达到98.6%,出水的pH基本稳定,当进水碱度不足时,氨氮去除率下降,出水的pH低于6,pH变化滞后于碱度的变化;进水碱度变化对COD去除影响不大,去除率稳定在91%以上;随着进水碱度下降,膜生物反应器内的胞外聚合物EPS由10 mg/g MLSS上升至26 mg/g MLSS,碱度充足时MBR运行周期最长可达10 d,当碱度不足引起反应器中的EPS浓度上升,导致膜污染加剧,膜生物反应器的运行周期下降到2 d。     

短程硝化在垃圾渗滤液处理工程中的应用

针对垃圾填埋场渗滤液生物脱氮高耗能的问题,通过对A/O/N工艺处理垃圾渗滤液进行短程硝化反硝化调试,对溶解氧(DO)、污泥浓度(MLSS)、污泥龄(SRT)、混合液回流比、pH、碱度进行定性定量分析,研究了不同条件下垃圾渗滤液生物处理阶段COD、氨氮及总氮去除效果,探讨了影响亚硝酸盐氮积累的因素。结果表明,好氧池低溶解氧能成功启动短程硝化,垃圾渗滤液稳定实现短程硝化反硝化脱氮。运行条件为:O反应器DO浓度0.5～0.8 mg·L~(-1),N反应器DO浓度1.5～2.2 mg·L~(-1),MLSS 3 500～4 500 mg·L~(-1),污泥龄9～13 d,混合液回流比1 100%,N反应器pH 7.6～8.2,N反应器碱度1.1 g·L~(-1)。短程硝化调试后,硝化阶段亚硝化率稳定在85%以上,COD、氨氮及总氮去除率分别达95%、98.6%、94.2%以上,节省30%碳源量和20%曝气量。     

固定化包埋填料高氨氮负荷下短程硝化稳定运行特征

为了探讨固定化包埋填料高氨氮负荷下短程硝化的稳定运行研究,以固定化技术包埋一定量硝化菌填料为载体,并利用序批次反应器进行处理人工配置的氨氮废水实验,该实验研究了实现短程硝化影响因素DO、有机物的控制范围,驯化期间,分别将温度、pH值、DO控制在（31±1）℃、7.8~8.2、1.8~2.0 mg·L-1范围内,进水有机物浓度始终保持在50 mg·L-1以下,体积填充率为15%,采用高游离氨（3.03~14.18 mg·L-1）对NOB产生抑制作用,使活性填料中的AOB成为优势菌群,通过历时55 d的培养实现了该填料短程硝化的启动及稳定运行,结果表明,进水氨氮浓度保持200 mg·L-1左右,氨氮去除速率高达28.29 mg NH4+-N·（L·h）-1的同时,氨氮的去除率>97%,亚硝酸盐积累NO2--N/NOx--N>85%,实验同时还考察了活性填料的抗冲击负荷能力与单个周期内短程硝化运行特征。     

CAST工艺常规模式下脱氮性能研究

研究了有效容积为21.6 L的循环式活性污泥法反应器在常规模式下,处理模拟废水时,有机污染物和氮污染物的去除情况,并分析了反应器脱氮过程中的限制性因素。结果表明,在反应器的运行周期为4 h(进水曝气2 h,沉淀和排水各1 h)好氧区DO2 mg/L,污泥浓度MLSS稳定在4 000 mg/L时,污泥回流比为20%,COD和氨氮的去除率可达90%。对一个典型周期进行监测分析,氨氮去除彻底,出水主要是硝态氮,总氮去除率约为69%。静态试验测得氨氮氧化速率为8.0 mg NH4+-N/(g MLSS.h),硝态氮生成速率为3.3 mg NO3--N/(g MLSS.h)。从实验结果可以分析出,在上面运行条件下CAST工艺脱氮限制性因素是回流比和污泥龄。     

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.     

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.     

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.     

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.     

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.     

Biochemical interaction of six op delayed neurotoxicants with several neurotargets

Abstract

Five organophosphorous insecticides: Leptophos, EPN, Cyano‐fenphos, trichloronate and salithion proved to cause irreversible ataxia not only to chicken but also to mice and sheep. TOCP was included as a reference. Cyanofenphos blocked the catecholamine B‐receptor binding activity with ³H‐norepinephrine at a level similar to that of the specific inhibitor propranolol in the mouse heart preparation. In the lamb heart preparation, the B‐receptor was more sensitive to Leptophos, salithion and TOCP than to propranolol. The six compounds and their oxons were screened for their in‐vitro inhibition to monamine oxidase (MAO), acetyl cholinesterase (AChE) and neurotoxic esterase (NTE) in the brain of either mouse, lamb or chicken. It is believed that their AChE inhibition stands for their acute toxicity, while NTE inhibition is responsible for their paralytic ataxia.     

Phytoextraction of lead-contaminated soil using vetivergrass (<Emphasis Type="Italic">Vetiveria zizanioides</Emphasis> L.), cogongrass (<Emphasis Type="Italic">Imperata cylindrica</Emphasis> L.) and carabaograss (<Emphasis Type="Italic">Paspalum conjugatum</Emphasis> L.)

Background, Aims and Scope The global problem concerning contamination of the environment as a consequence of human activities is increasing. Most of the environmental contaminants are chemical by-products and heavy metals such as lead (Pb). Lead released into the environment makes its way into the air, soil and water. Lead contributes to a variety of health effects such as decline in mental, cognitive and physical health of the individual. An alternative way of reducing Pb concentration from the soil is through phytoremediation. Phytoremediation is an alternative method that uses plants to clean up a contaminated area. The objectives of this study were: (1) to determine the survival rate and vegetative characteristics of three grass species such as vetivergrass, cogongrass and carabaograss grown in soils with different Pb levels; and (2) to determine and compare the ability of the three grass species as potential phytoremediators in terms of Pb accumulation by plants. Methods The three test plants: vetivergrass (Vetiveria zizanioides L.); cogongrass (Imperata cylindrica L.); and carabaograss (Paspalum conjugatum L.) were grown in individual plastic bags containing soils with 75 mg kg⁻¹ (37.5 kg ha⁻¹) and 150 mg kg⁻¹ (75 kg ha⁻¹) of Pb, respectively. The Pb contents of the test plants and the soil were analyzed before and after experimental treatments using an atomic absorption spectrophotometer. This study was laid out following a 3 × 2 factorial experiment in a completely randomized design. Results On the vegetative characteristics of the test plants, vetivergrass registered the highest whole plant dry matter weight (33.85–39.39 Mg ha⁻¹). Carabaograss had the lowest herbage mass production of 4.12 Mg ha⁻¹ and 5.72 Mg ha⁻¹ from soils added with 75 and 150 mg Pb kg⁻¹, respectively. Vetivergrass also had the highest percent plant survival which meant it best tolerated the Pb contamination in soils. Vetivergrass registered the highest rate of Pb absorption (10.16 ± 2.81 mg kg⁻¹). This was followed by cogongrass (2.34 ± 0.52 mg kg⁻¹) and carabaograss with a mean Pb level of 0.49 ± 0.56 mg kg⁻¹. Levels of Pb among the three grasses (shoots + roots) did not vary significantly with the amount of Pb added (75 and 150 mg kg⁻¹) to the soil. Discussion Vetivergrass yielded the highest biomass; it also has the greatest amount of Pb absorbed (roots + shoots). This can be attributed to the highly extensive root system of vetivergrass with the presence of an enormous amount of root hairs. Extensive root system denotes more contact to nutrients in soils, therefore more likelihood of nutrient absorption and Pb uptake. The efficiency of plants as phytoremediators could be correlated with the plants’ total biomass. This implies that the higher the biomass, the greater the Pb uptake. Plants characteristically exhibit remarkable capacity to absorb what they need and exclude what they do not need. Some plants utilize exclusion mechanisms, where there is a reduced uptake by the roots or a restricted transport of the metals from root to shoots. Combination of high metal accumulation and high biomass production results in the most metal removal from the soil. Conclusions The present study indicated that vetivergrass possessed many beneficial characteristics to uptake Pb from contaminated soil. It was the most tolerant and could grow in soil contaminated with high Pb concentration. Cogongrass and carabaograss are also potential phytoremediators since they can absorb small amount of Pb in soils, although cogongrass is more tolerant to Pb-contaminated soil compared with carabaograss. The important implication of our findings is that vetivergrass can be used for phytoextraction on sites contaminated with high levels of heavy metals; particularly Pb. Recommendations and Perspectives High levels of Pb in localized areas are still a concern especially in urban areas with high levels of traffic, near Pb smelters, battery plants, or industrial facilities that burn fuel ending up in water and soils. The grasses used in the study, and particularly vetivergrass, can be used to phytoremediate urban soil with various contaminations by planting these grasses in lawns and public parks. ESS-Submission Editor: Dr. Willie Peijnenburg (wjgm.peijnenburg@rivm.nl)