Biofiltration of toluene in the absence and the presence of ethyl acetate under continuous and intermittent loading

BACKGROUND: Two peat biofilters were used for the removal of toluene from air for one year. One biofilter was fed with pure toluene and the other received 1:1 (by weight) ethyl acetate:toluene mixture. RESULTS: The biofilters were operated under continuous loading: the toluene inlet load (IL) at which 80% removal occurred was 116 g m^?3 h^?1 at 57 s gas residence time. Maximum elimination capacity of 360 g m^?3 h^?1 was obtained at an IL of 745 g m^?3 h^?1. The elimination of toluene was inhibited by the presence of ethyl acetate. Intermittent loading, with pollutants supplied for 16 h/day, 5 days/week, did not significantly affect the removal efficiency (RE). Biomass was fully activated in 2 h after night closures, but 6 h were required to recover RE after weekend closures. Live cell density remained relatively constant over the operational period, while the dead cell fraction increased. Finally, a 15 day starvation period was applied and operation then re‐started. Performance was restored with similar re‐acclimatization period to that after weekend closures, and a reduction in dead cell fraction was observed. CONCLUSION: This study demonstrates the capacity of the system to handle intermittent loading conditions that are common in industrial practices, including long‐term starvation. Copyright © 2008 Society of Chemical Industry     

生物过滤处理微污染饮用水源的试验研究

通过试验探讨了生物过滤对微污染饮用水源的处理效果及其影响因素。试验结果表明，生物过滤可有效去除湘江微污染饮用水源中的有机物、NH3-N、Fe、Mn和浊度。滤料介质、空床接触时间和加氯水反冲洗等因素对生物过滤均具有明显的影响。     

利用臭氧控制VOCs生物过滤塔生物量

生物过滤塔在挥发性有机物和恶臭气体处理方面具有良好的应用前景,但生物量过度累积是影响其运行稳定性的主要问题。为了探讨利用臭氧控制生物量过度累积的可行性,该研究系统考察了连续投加臭氧对于生物过滤塔甲苯去除性能、填料层压降及空隙率、生物量增长以及碳平衡的影响。研究结果表明,臭氧浓度为0～220mg/m3时,投加臭氧不会降低生物过滤塔的甲苯去除性能;臭氧浓度为100～220mg/m3时,投加臭氧可以显著控制生物量过度累积、优化填料层结构和控制压降快速升高。进一步研究表明,提高甲苯的矿化率是臭氧控制生物量快速累积的主要途径。     

生物慢滤工艺不同深度净化景观水效果研究

生物慢滤工艺对COD、SCOD和浊度去除率分别可达到49%、46%和77%;对COD、SCOD和浊度,系统表层填料对COD、SCOD和浊度的去除贡献较大;在填料5 cm以下装置对有机物和浊度的去除曲线斜率基本一致。生物慢滤池对于TP和溶解性磷酸盐可达到70%以上;系统对总氮去除率一般只有18.0%~30.0%,对氨氮去除率可达33%~67%。沿不同深度,磷和总氮的去除率基本呈不断增大的趋势;而氨氮的去除率呈现先增大后减小的规律。     

Design‐based life cycle assessment of hazardous air pollutant control options at pulp and paper mills: a comparison of thermal oxidation to photocatalytic oxidation and biofiltration

BACKGROUND: The forest products industry produces valuable industrial chemicals, wood products, and consumer goods, but is also responsible for the emission of significant quantities of hazardous air pollutants. Although many air pollution control options are available, little is known about the overall environmental impacts of implementing each option. Therefore, a life cycle assessment (LCA) was conducted to compare energy and raw material inputs, air emissions, and environmental impacts associated with construction and operation of two air pollution control systems: regenerative thermal oxidation (RTO) with wet scrubbing and photocatalytic oxidation (PCO) with biofiltration. RESULTS: LCA results indicated that environmental impacts to resource depletion, photochemical oxidant formation, and acidification were 20% higher for the use of a RTO‐scrubber than for the PCO‐biofilter. In addition, at least 25% of the RTO impacts were due to infrastructure requirements. However, the PCO‐biofilter system was responsible for more environmental impact in categories of global warming and human toxicity, because of the packing materials required and the electricity use for the PCO reactor. CONCLUSIONS: The PCO‐biofilter system could be a promising, environmentally‐friendly alternative to traditional RTO devices, provided that this system is modified to decrease resource and energy demands. Copyright © 2008 Society of Chemical Industry     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

氮和磷对生物滴滤塔净化煤矿乏风瓦斯的影响

研究了氮源类型和浓度以及磷元素浓度对生物滴滤塔净化极低浓度CH4的影响。利用空气和高纯CH4混合气模拟煤矿乏风瓦斯,生物滴滤塔填料为陶瓷鲍尔环,以实验室分离筛选到的甲烷氧化菌进行接种挂膜。结果表明,进气流量为2 L?min?1,喷淋液流量为0.1 L?min?1,进气CH4浓度在0.1%~1.1%,以Na NO3为氮源时,生物滴滤塔净化CH4的效果最好,优于(NH4)2SO4和NH4NO3为氮源时的表现。喷淋液中Na NO3浓度为70 mmol?L?1,进气CH4浓度为0.1%~1.1%时,生物滴滤塔的CH4去除负荷为10.67~39.72 g?m?3?h?1,去除负荷随CH4浓度增加而增加;CH4净化率为97.92%~39.70%,净化率随CH4浓度增加而下降。在最佳氮源条件下,进气CH4浓度为0.9%,P元素浓度为100 mmol?L?1时,滴滤塔CH4去除负荷最大为49.69 g?m?3?h?1,CH4净化率60.90%。     

凹凸棒复合滤料生物过滤去除苯酚性能研究

利用凹凸棒复合滤料良好的吸附性和生物挂膜性能对普通滤池进行生物强化,研究生物过滤对原水中苯酚的去除效果及影响因素。实验结果表明,原水浓度在0.25mg/L时,苯酚的去除率达到93.75%;温度在23℃时,苯酚的去除率达到95.97%;原水溶解氧浓度在7.4mg/L时,苯酚的去除率达到96.46%;反冲洗对生物过滤去除苯酚的影响较小,去除率在冲洗2h后能够恢复到冲洗前的水平。     

Enhancing the biofiltration of geosmin by seeding sand filter columns with a consortium of geosmin-degrading bacteria

Geosmin is a secondary metabolite that can be produced by many species of cyanobacteria and Actinomycetes. It imparts a musty/earthy taste and odour to drinking water which can result in consumer complaints and a general perception that there is a problem with the water quality. As geosmin is recalcitrant to conventional water treatment, processes are sought to ensure effective removal of this compound from potable water. Biological filtration (biofiltration) is an attractive option for geosmin removal as this compound has been shown to be biodegradable. However, effective biofiltration of geosmin can be site specific as it is highly dependent upon the types of organism present and there is often an extended acclimation period before efficient removals are achieved. We report here, a novel approach to enhance the biofiltration of geosmin by seeding sand filter columns with a bacterial consortium previously shown to be capable of effectively degrading geosmin. Geosmin removals of up to 75% were evident through sand columns which had been inoculated with the geosmin-degrading bacteria, when compared with non-inoculated sand columns where geosmin removals were as low as 25%. These low geosmin removals through the non-inoculated sand columns are consistent with previous studies and were attributed to physical/abiotic losses. The presence of an existing biofilm was shown to influence geosmin removal, as the biofilm allowed for greater attachment of the geosmin-degrading consortium (as determined by an ATP assay), and enhanced removals of geosmin. Minimal difference in geosmin removal was observed when the geosmin-degrading bacteria were inoculated into the sand columns containing either an active or inactive biofilm.     

Mathematical modeling of gas‐phase biofilter performance

In the present paper, a new mathematical model describing the physical, chemical and biological phenomena involved in the process of contaminant removal in biofilters is developed. In addition to the contaminant, the key components of the present theoretical model are carbon dioxide and oxygen. The model predicts the concentration profile of the key components in the gas phase, the biofilm and the sorption liquid retained in the solid particles composing the filter bed at both steady and transient regimes. The model equations were solved numerically and comparison between theory and experiment showed that the model results for styrene and carbon dioxide concentration profiles were in very good agreement with experimental data for the biofiltration of styrene vapors at steady state. The analysis of oxygen concentration profile in the biofilm predicted by the theoretical model revealed that oxygen limitation does not occur under the operating styrene biodegradation rate in the biofilter. Copyright © 2003 Society of Chemical Industry