Comparison of physical technologies for biomass control in biofilters treating gaseous toluene

Excessive accumulation of biomass within gas-phase biofilters often results in the deterioration of removal performance. Compared with chemical and biological technologies, physical technologies are more effective in removing biomass and inducing less inhibition of the biofilter performance. This study applied different physical technologies, namely, air sparging, mechanical mixing, and washing with water at various temperatures, to remove excess biomass in biofilters treating toluene. Filter pressure drop, removed dry biomass, biofilter performance, and microbial metabolic characteristics were analyzed to evaluate the effectiveness of the methods. Results showed that air sparging was inefficient for biomass removal (1 kg dry biomass/m³ filter), whereas mechanical mixing significantly inhibited removal efficiencies (<30%). Washing of the packing with fluids was feasible, and hot fluids can remove a large amount of biomass. However, hot fluids reduce microbial activity and inhibit removal performance. Washing of the packing with either 20°C or 50°C water showed efficiency as >3 kg dry biomass/m³ filter can be removed at both temperatures with removal efficiencies at approximately 40% after treatment. Finally, different technologies were compared and summarized to propose an optimized strategy of biomass control for industrial biofilters.

Implications: This study is to apply different physical technologies, namely, air sparging, mechanical mixing, and washing with water of different temperatures, to remove the excess biomass in biofilters treating toluene. The filter pressure drop, removed dry biomass, biofilter performance, and microbial metabolic characteristics were all analyzed to evaluate the effectiveness of the methods. The results of this study provide useful information regarding biomass control of industrial biofilters.     

Biomonitoring of trace metals in a mine-polluted estuarine system (Spain)

In this paper, we examine metal concentrations in the water and in the crustacean Balanus balanoides from the Huelva estuary, one of the most polluted estuaries in Europe. Metal levels in waters are very high, especially those of Zn, Fe and Cu. Zn presents the highest concentrations, with a mean value of 690 microg l-1 in 2001 and 301 microg l-1 in 2002. As the water flows down through the estuary toward the sea, the metal concentrations drop sharply and the pH rises. The metal concentrations in balanoides tissues are, in general, very high, undoubtedly due to the high metal pollution of the water where it lives. Metal concentrations in Balanus balanoides tissues behave similarly to those in the water, reaching maximums in the upper part of the estuary and diminishing as we approach the sea. The element that reaches the highest levels in Balanus balanoides is Zn, with a mean value of 54.6 g kg-1 in 2001 and 29.9 g kg-1 in 2002, followed by Cu and Fe. There is a significant correlation (p<0.01) for concentrations of Cd, Cu, Fe, Mn, Ni and Zn in Balanus balanoides relative to their concentration in waters. Barnacles showed a great capacity to accumulate metals, especially Zn, Cu and Fe. Based on the results obtained, we can conclude that Balanus balanoides is a good tool for monitoring trace metals in the Huelva estuary.     

Biological removal of gaseous ammonia in biofilters: space travel and earth-based applications

Gaseous NH3 removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH3 concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH3 for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH3 removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH3 could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO3- early in the operation, but later both NO2- and NO3- accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to approximately 95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N2O, which were detected in the biofilter exhaust.     

Aerosol trace metals,particle morphology and total gaseous mercury in the atmosphere of Oxford,UK

An investigation of atmospheric trace metals was conducted in Oxford, UK, a small city ～60 miles northwest of London, in 2007 and 2008. Concentrations of Sr, Mo, Cd, Pb, V, Cr, Mn, Fe, Co, Ni, Cu and Zn in aerosol were measured in bulk and size segregated samples. In addition, total gaseous mercury (TGM) concentrations were monitored semi-continuously by cold vapour-atomic fluorescence spectroscopy. Metal concentrations in Oxford were intermediate between previously reported levels of UK rural and urban areas for most metals studied and levels of Cd, Ni and Pb were within European guidelines. Metal concentrations appeared to be influenced by higher traffic volume on a timescale of hours. The influence of traffic on the aerosols was also suggested by the observation of carbonaceous particles via scanning electron microscopy (SEM). Air mass back trajectories suggest air masses arriving in Oxford from London and mainland Europe contained the highest metal concentrations. Aerosol samples collected over Bonfire Weekend, a period of intense firework use and lighting of bonfires in the UK, showed metal concentrations 6–46 times higher than at other times. Strontium, a tracer of firework release, was present at higher concentrations and showed a change in its size distribution from the coarse to fine mode over Bonfire Weekend. The presence of an abundance of spherical Sr particles was also confirmed in SEM images. The average TGM concentration in Oxford was 3.17 ng m^?3 (st. dev. 1.59) with values recorded between 1.32 and 23.2 ng m^?3. This is a higher average value than reported from nearby rural locations, although during periods when air was arriving from the west, similar concentrations to these rural areas were seen in Oxford. Comparison to meteorological data suggests that TGM in Oxford's air is highest when wind is arriving from the east/southeast. This may be due to emissions from London/mainland Europe with a possible contribution from emissions from a local crematorium situated 4 miles east of the sampling site. A diurnal pattern was also observed in the TGM data with a minimum concentration during the day when mercury may have been diluted by thermal mixing of the atmospheric boundary layer. Additionally, this diurnal pattern may reflect variations in a local source of TGM.     

In situ stabilization of trace metals in a copper-contaminated soil using P-spiked Linz-Donawitz slag

Purpose  

A former wood exploitation revealing high Cu and As concentration of the soils served as a case study for assisted phytoextraction.     

基于新型有机多孔复合基质的生物系统去除污染水体中的氮磷

针对太湖入湖河道污染水体中的氮磷超标问题,以海绵铁、沸石、砾石和土壤为基质,采用动态吸附+生物法,对氮磷开展基于新型有机多孔复合填料的去除效果研究,结果表明,生物系统中的新型有机多孔复合基质在空间上形成了好氧-缺氧微环境,获得了较好的同步硝化-反硝化效果;通过正交实验确定流量0.00075 L/s,曝气时间24 h,pH值7,曝气量20 L/min为去除氮磷的最优条件;相对一级动力学方程、双常数方程而言,Elovich方程对3种填料的吸附动力学特征拟合最好,决定系数R2在0.81～0.92之间。通过平均去除效果较优分析,好氧条件下,NH3-N平均去除70.6%,TP平均去除81.2%;厌氧条件下,TN平均去除62.4%,COD平均去除42.6%;NH3-N、TP、TN和COD的最低浓度分别为0.75、0.095、1.1和18.3 mg/L,综合考虑主要污染物的去除效果和经济效益,本项新型有机多孔复合填料结合生物系统适宜去除河原平网地区污染水体中的氮磷。     

Removal of ammonia by biofilters: a study with flow-modified system and kinetics

The characteristics of ammonia removal by two types of biofilter (a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow) were investigated. A mixture of organic materials such as compost, bark, and peat was used as the biofilter media based on the small-scale column test for media selection. Complete removal capacity, defined as the maximum inlet load of ammonia that was completely removed, was obtained. The modified biofilter showed complete removal up to 1.0 g N/kg dry material/day. However, the removal capacity of the standard biofilter started to deviate from complete removal around 0.4 g N/kg dry material/day, indicating that the modified biofilter system has higher removal efficiency than the standard upflow one. In kinetic analysis of the biological removal of ammonia in each biofilter system, the maximum removal rate, Vm, was 0.93 g N/kg dry material/day and the saturation constant, Ks, was 32.55 ppm in the standard biofilter. On the other hand, the values of Vm and Ks were 1.66 g N/kg dry material/day and 74.25 ppm, respectively, in the modified biofilter system.     

非热平衡等离子体协同催化脱除挥发性有机化合物的研究进展

单纯运用非热平衡等离子体(NTP)技术脱除挥发性有机化合物(VOCs)的效率和能量利用率并不高,而且在降解过程中可能会产生某些有害副产物。为了克服NTP技术在VOCs治理方面的缺陷,可将NTP和化学催化方法组合运用,结合两者的优势使系统的VOCs脱除率、能量利用率和CO2选择率显著提高。从催化反应器结构、NTP与催化剂协同作用的原理等方面总结了近年来NTP协同催化技术在VOCs脱除方面的应用状况。最后指出,NTP协同催化技术在VOCs脱除方面有良好的应用前景,但要真正实现其工程应用,仍有很多问题亟待研究和解决。     

Performance evaluation of a biotrickling filter treating a mixture of oxygenated VOCs during intermittent loading

Laboratory scale-studies on the biodegradation of a 1:1:1 weight mixture of three oxygenated volatile organic compounds (VOCs), ethanol, ethyl acetate, and methyl-ethyl ketone (MEK) in a biotrickling filter (BTF) were carried out using two identically sized columns, filled with different polypropylene rings. The performance of the BTFs was examined for a period of 10 months applying several operational strategies. Similar performance was obtained for both supports. Intermittent flow rate of trickling liquid was shown beneficial to improve the removal efficiency (RE). Continuous feeding of VOC resulted in an excessive accumulation of biomass so high pressure drop was developed in less than 20-30 d of operation. Intermittent VOC loading with night and weekend feed cut-off periods passing dry air, but without addition of water, was shown as a successful operational mode to control the thickness of the biofilm. In this case, operation at high inlet loads (ILs) was extended for more than 75 d maintaining high REs and low pressure drops. Outlet emission concentrations lower than 100 mg Cm(-3) were obtained for ILs up to 100 g Cm(-3)h(-1) working at 15s of empty bed residence time. The most easily biodegradable compounds ethanol and ethyl acetate were used primarily than MEK. After a 3-wk-starvation period, the system performance was almost restored since the first d of operation, being the removal of the less biodegradable compound, MEK, partially deteriorated.     

Urine concentrations of selected trace metals in a cohort of Irish adults

Environmental Science and Pollution Research - Human biomonitoring studies are of increasing importance in regulatory toxicology; however, there is a paucity of human biomonitoring data for the...     

雨水收集系统结合自循环系统下的景观湖体氮磷特征

为评估采用雨水作为城市景观湖体补充水源的富营养化发生风险,以天津文化中心景观湖为研究案例,分析了其典型的2套运营系统：雨水收集系统（雨水经沉淀井、蓄水模块和垂直潜流湿地进入景观湖）和中心湖水体的循环及净化系统（湖水抽排至垂直潜流湿地再进入景观湖）中景观湖的氮磷浓度变化规律。采用2015年3-10月的长期监测,研究湖中氮磷营养盐的时间变化趋势以及形态变化规律,提取影响湖中氮磷浓度的因素。结果表明：2015年3-10月景观湖中总氮和总磷平均浓度分别为（1.551±0.491）mg·L-1和（0.058±0.029）mg·L-1,溶解态氮和磷分别占71.7%和50%,系统运行稳定时总氮和总磷浓度主要分布在1.0~1.3 mg·L-1和0.029~0.05 mg·L-1之间;总体上,溶解态氮为湖水中氮存在的主要形式,而磷则主要以颗粒态形式存在,在降雨条件下,部分污染物随着降雨冲刷进入湖体,因此景观湖中溶解态磷的浓度增高;湿地是否稳定运行是影响景观湖中总氮、溶解态氮以及总磷浓度的因素,而降雨条件是影响景观湖体的总磷浓度以及溶解态磷浓度的因素;景观湖的富营养化风险较低,降雨期间进入湖体的溶解态磷是最大的风险因子。     

Comparative bioavailability of trace metals using three filter-feeder organisms in a subtropical coastal environment (Southeast Gulf of California)

To evaluate the relative bioavailability of Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the coastal waters of one selected site in Mazatlán Harbor, different filter feeder organisms, an oyster (Crassostrea corteziensis), a mussel (Mytella strigata) and a barnacle (Fistulobalanus dentivarians), were sampled during 1 year. Seasonal and interspecific variations in some metal concentrations were evident, especially for Cd, Ni, Pb and Zn. In contrast with Fe, Pb and Zn, the concentrations of Cd varied accordingly in both bivalves. Even though the organisms live in the same site and have a common feeding mechanism, accumulated body Cd concentrations were different. Mussels concentrated significantly higher levels of Ni than the other organisms, while barnacles were better concentrators of Cd, Pb and Zn. A relationship existed between the concentrations of Cd, Fe and Zn in the soft tissues of the two bivalves, which is useful in monitoring studies when only one species occurs.     

Oily wastewater treatment using a novel hybrid PBR-UASB system

In this study, anaerobic treatability of oily wastewater was investigated in a hybrid reactor system consisting of a packed bed reactor (PBR) followed by an upflow anaerobic sludge blanket (UASB) reactor at 35 degrees C. The system was operated using real pet food wastewater at different hydraulic retention times and loading rates for 165 d. The PBR was packed with sol-gel/alginate beads containing immobilized enzyme which hydrolyzed the oil and grease (O&G) into free long chain fatty acids, that were biodegraded by the UASB. The hybrid system was operated up to an oil loading rate of 4.9 kg O&Gm(-3)d(-1) (to the PBR) without any operational problems for a period of 100 d, with COD and O&G removal efficiencies above 90% and no sludge flotation was observed in the UASB. Beads supplement to the PBR was less than 2 g d(-1) and the relative activity was about 70%. Further increment in O&G loading to 18.7 kg O&Gm(-3)d(-1) caused destabilization of the system with 0.35% (v float/v feed) sludge float removed from the UASB.     

Sandhopper solar orientation as a behavioural biomarker of trace metals contamination

Although many studies have focused on trace metals accumulation, investigations of talitrid amphipods as biomarkers are rare. This study explores the possibility of using the solar orientation capacity of Talitrus saltator as a behavioural marker of exposure to two essential (Cu and Zn) and two non-essential (Cd and Hg) metals. LC₅₀ analyses performed before the solar orientation tests showed that the 72 h LC₅₀ for Hg was 0.02 ppm while the 96 h LC₅₀ values for Cu, Cd and Zn were 13.28 ppm, 27.66 ppm, and 62.74 ppm, respectively. The presence of metals in seawater affects the solar orientation capacity of T. saltator in a concentration-dependent manner and according to the toxicity ranking of the metals (Hg > Cu > Cd > Zn). Therefore, the solar orientation capacity of T. saltator seems to be a promising behavioural marker for exposure to trace metals.     

耦合回流污泥预浓缩系统的新型氧化沟工艺强化除磷

针对传统的"厌氧+氧化沟"运行模式对低碳源污水除磷能力不佳的问题,采用耦合回流污泥预浓缩系统的新型氧化沟工艺对其强化除磷进行了中试实验研究。通过采用回流污泥预浓缩系统,调试回流污泥浓缩比,提高系统的除磷能力。研究结果表明,在控制最佳回流污泥浓缩比为55%的情况下,出水TP浓度和去除率分别为0.92 mg/L和67.5%,相比于浓缩比为100%、70%、50%和30%的工况,其去除率分别增加了24.3%、27.3%、8.2%和28.6%,强化了系统的除磷效果。另外,ORP可以预示预缺氧池内无效释磷和反硝化程度,以此作为自动调整最佳回流污泥浓缩比的控制参数。     

电化学反应提高生物滤池的城市污水脱氮效果

为了探明电化学反应对废水生物处理效果的影响,研制了电极一生物滤池以及相对照的普通生物滤池各一套。通过两套系统的对比试验,了解电化学反应对生物处理过程的影响。试验结果表明,电极一生物滤池与对照反应器相比较,CODCr和氨氮去除率提高不明显,而总氮的去除率提高了14．9％。     

生物滴滤塔处理苯乙烯气流的工效和生物膜微群落的分析

采用培养驯化污泥菌种、类球形陶粒和循环液等构建生物滴滤塔.研究评价气体苯乙烯浓度、气体流量、循环液喷淋量对生物滴滤塔工效的影响,并对生物膜微群落中的微种群作了定性定量检测.当进口气体苯乙烯小于1 000 mg/m3、气体流量为200 L/h、循环液流量为10 L/h时,苯乙烯净化效率达90%以上,生化去除量为30 mg/(L·h);单位体积生物膜填料对苯乙烯的最大生化去除量为35 mg/(L·h).湿润生物膜微群落的优势菌种群包括恶臭假单胞菌、梭形芽孢杆菌、罗非氏不动杆菌等5种,恶臭假单胞菌等非芽孢杆菌的最大活菌数为5.5×107 CFU/g,并随生物滴滤塔运行时间延长有减少趋势.     

Water transformation in the media of biofilters controlled by Rhodococcus fascians in treating an ethyl acetate-contaminated airstream

Biofilters do not provide much water for bacteria to grow. To use them efficiently and properly, it is essential to understand the kinetics of water transformation and to control moisture levels. This study aims to clarify whether the metabolism of microorganisms will improve the water-holding capacity of media or will intensify drying. This experiment was conducted in duplicate, that is, both with and without bacterial inoculation. Both the constant water content mode and the declining water content mode show that microbial growth in a log phase will enhance drying. In contrast, the bacteria growing in a logarithmic decline phase will improve water-holding capacity. Basically, water evaporation can result from the latent heat obtained from microbial respiration or from the physical temperature difference between the unsaturated air and the wet media. Two ways that biofilters can gain water are from water incorporated into bacteria cells and from water obtained from the oxidation of volatile organic compounds (VOCs).     

The behaviour of phosphorus and heavy metals in sewage sludge ashes

The effect of the combustion atmosphere and the additives (CaO and HCl) on the behaviour of phosphorus and heavy metals during sewage sludge combustion was investigated. The results demonstrated that the reduction combustion promoted the vapourisation of phosphorus and heavy metals during sewage sludge combustion. Moreover, the concentrations of phosphorus and heavy metals in the bottom ash decreased with increasing HCl ratio, and the addition of CaO can stabilise heavy metals and phosphorus. It was also observed that phosphorus and heavy metals increased with increasing CaO ratio. Lastly, the difference of the TG-DTA curves with and without additives is discussed.