曝气生物活性炭滤池深度处理高浓度氨氮原水

实验研究曝气生物活性炭滤池对于高浓度氨氮原水的处理效果以及工艺运行稳定情况。以某自来水厂常规工艺沉淀池出水预加硫酸铵作为研究对象,原水氨氮平均浓度3.67 mg/L,实验条件:温度31.2℃,pH 7.13,滤速8~12 m/h,气水比0.5和1。采用3种不同工况条件进行实验,确定滤速10 m/h和气水比0.5的为最佳运行工况。在此工况下曝气生物活性炭滤池对于氨氮和COD Mn的平均去除率分别达到87.5%和19.2%,亚硝酸盐积累率为0.9%;出水氨氮浓度达到生活饮用水卫生标准GB5749-2006。同时炭滤池的出水浊度相比进水略微上升。     

叠式曝气生物滤池在给水预处理中的挂膜启动

针对低污染原水进行叠式曝气生物滤池的自然挂膜启动实验。在HRT为20～30 min,温度为28～33℃,气水比为0.5,滤速为12.5 m/h的条件下,研究分析叠式曝气生物滤池在自然挂膜启动过程中各项水质指标的变化情况与生物膜生长之间的相互关系,判断挂膜启动的进程。结果表明,在南方夏季,叠式曝气生物滤池能够进行快速启动,经过7 d左右自然挂膜启动完成,对CODMn的平均去除率为33%,对氨氮的平均去除率达到85.5%,对亚硝酸盐氮的去除率为82.9%。     

炭砂滤池对农村饮用水中浊度及细菌的去除效果

粗滤-炭砂过滤是简单实用的农村水处理工艺。通过中试装置,检测了滤池对浊度、细菌总数和大肠杆菌的去除效果,研究了炭砂滤池出水安全性。结果表明：炭砂滤池能进一步降低粗滤池出水浊度,并将其控制在0.7~2.2 NTU;砂层作为保证出水浊度的屏障,其浊度去除率在炭层基础上可再增加11.1%;炭砂滤池对大肠杆菌的平均去除率随着滤速的降低而增大,且该差异主要是由炭层贡献的;当滤速为5 m·h⁻¹时,炭砂滤池对大肠杆菌平均对数去除率为0.79;但滤池运行过程中会产生微生物泄露的现象,对细菌总数基本无去除作用。因此,为保障出水的微生物安全性,炭砂滤工艺后须增加行之有效的消毒工艺。     

碳源对反硝化生物滤池运行及微生物种群的影响

以某城市污水厂二级出水为原水,以甲醇、乙酸钠为碳源,研究了不同碳源对反硝化生物滤池运行的影响,并借助16S rDNA测序技术对滤池生物膜的微生物群落组成和结构进行了解析。结果表明,采用逐渐增加滤速的方式进行挂膜,乙酸钠滤池在启动7 d后出水水质稳定,NO_3~--N去除率在96%以上,NO_2~--N积累消失;甲醇滤池则需要9 d。稳定运行期,甲醇和乙酸钠滤池达到最大反硝化效率所需碳氮比均为4.5~5.5,出水TN1.0 mg·L~(-1)。乙酸钠滤池沿过滤方向硝酸盐氮降解较快。与甲醇相比,乙酸钠微生物产量高、运行周期短、反冲洗时间长,且药剂投加量高。从滤池脱氮效率、运行稳定性和成本等方面综合考虑,甲醇可作为最佳碳源。微生物在属水平进行聚类分析结果表明,以甲醇、乙酸钠为碳源的反硝化生物滤池中的微生物种群存在差异。甲醇滤池中与反硝化有关的属占36.68%,其中优势菌属Methylophilus,属于嗜甲基型菌属。乙酸钠滤池中与反硝化有关的菌属占58.38%。其优势菌属为Arobacter,可利用有机酸还原硝酸盐。     

扩展流好气滤池反冲洗机理与试验分析

采用对照研究的方法对扩展流好气滤池反冲洗方式进行选择。结果表明 ,脉冲反冲洗方式以其高效、低耗的特点明显优于气水连续反冲洗方式 ,并遵循好气滤池反冲洗的要求。扩展流好气滤池脉冲反冲洗的最佳运行参数确定为 :气冲强度 8～ 10 L/( s·m2 ) ;水冲强度 2～ 4L/( s·m2 ) ;反冲时间 5 min。     

硝化型曝气生物滤池的挂膜与启动

近年来,曝气生物滤池广泛应用于污水硝化过程中,硝化型曝气生物滤池应运而生。采用快速排泥挂膜法和自然挂膜法相结合的复合挂膜法,考察了进水是否含有机物对硝化型曝气生物滤池挂膜的影响。在19℃、HRT=55 min、出水DO=8 mg/L、进水NH4+-N约为50 mg/L的条件下,两滤池挂膜启动时间差异较大,进水不含有机物的1#滤池挂膜成功仅需18 d,当其运行稳定时NH4+-N的去除率达到100%;而进水含有机物的2#滤池挂膜成功需24 d,当其运行稳定时,COD和NH4+-N去除率分别为84.6%和91.2%。此结果表明,与含有机物的实际生活污水相比,采用不含有机物的模拟生活污水启动硝化型曝气生物滤池挂膜启动时间可缩短6 d,这主要是由于异氧菌产率系数比硝化菌大。     

活性炭柱中砂垫层在微污染水源水处理工艺中的应用

以嘉兴市某水厂沉后水为进水进行实验,研究炭砂滤池对污染物的去除性能,以及炭砂滤池取代活性炭＋砂滤池的可能性,探讨了短流程工艺的适用性。结果表明,炭砂滤池能有效去除水中的浊度、氨氮、CODMn和铁、锰等污染物,与活性炭柱相比,炭砂滤池在降低出水浊度和水中颗粒数方面具有一定优势,即砂垫层对控制出水浊度和保障微生物安全能够起到积极作用。在实验条件下,增加活性炭层厚度或者降低滤速,在一定程度上有利于提高对CODMn的去除率。在设计滤速为9～10 m/h,CODMn〈4.5 mg/L时,可直接以炭砂滤池取代活性炭池＋砂滤池,仍然能保证出水CODMn〈3 mg/L。     

纤维过滤器用于污水回用的研究

采用新型的纤维束过滤器对污水厂的二级出水进行了直接过滤和絮凝、过滤回用的研究。结果表明,过滤器在10~30 m/h的滤速下均能有效去除水中的SS和浊度,出水SS低于10 mg/L;对COD、BOD、TP和细菌总数的去除率分别为10%~80%、21%~50%、11%~81%和87%。采用硫酸铝作为絮凝剂与纤维过滤器联合处理技术能进一步提高出水的水质。通过单一水反冲洗和气水联合反冲洗的对比研究,发现气水联合反冲洗是适合恢复纤维束过滤器过滤效能的冲洗方式。在反冲洗水流量10~12 L/m2.s、水压0.1 MPa、空气流量60 L/m2.s、气压0.1 MPa的条件下,冲洗30 m in能够有效地恢复纤维过滤器的过滤性能。     

2种曝气生物滤池的启动比较分析

分别采用陶粒和沸石作为曝气生物滤池的填料,在相同运行参数下进行曝气生物滤池启动对比研究,分析挂膜过程中COD、NH4+-N和浊度的去除效果。试验结果表明,在平均气温为30℃的条件下,2种曝气生物滤池都能很快完成启动挂膜,陶粒曝气生物滤池所需时间为12d,沸石曝气生物滤池所需时间为15d;陶粒曝气生物滤池具有更好的COD去除效果,沸石曝气生物滤池具有更好的NH4+-N去除效果;2个滤池对浊度都能够达到95%左右的去除率。     

生物活性炭滤池对水源水中邻苯二甲酸酯的降解性能

研究活性炭滤池在挂膜期间对水源水中4种微量PAEs的降解情况,以及挂膜成功后的生物活性炭滤池及改变运行条件如空床停留时间、4种PAEs的进水浓度、反冲洗膨胀度对降解4种PAEs的影响。结果表明:未挂膜时,活性炭滤池对DMP、DEP、DBP和DEHP的去除率为77.41%、82.40%、88.87%和96.17%,挂膜成功后,生物活性炭滤池对DMP、DEP和DBP的去除率分别增至99.3%、100%和95.27%,而对DEHP的去除率降为61.9%。当生物活性炭滤池成功启动并稳定运行后,15 min的空床停留时间下能够去除进水中94%以上的DMP、DEP、DBP以及74%以上的DEHP;如果持续提高进水中4种PAEs的浓度,滤池对其去除率会相应降低;当反冲洗时滤池膨胀度大小为20%,生物活性炭滤池对4种PAEs的去除率不仅能快速恢复正常水平,且能维持更长时间。     

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)