Genotoxicity removal of reclaimed water during ozonation

Genotoxicity in wastewater and reclaimed water now is gaining increased attention because of genotoxins' potential damage to the ecosystem and human health. The effect of ozonation on genotoxicity in reclaimed water was investigated. It was found that ozonation decreased the genotoxicy dramatically in three tertiary treatment plants. In the further batch ozonation experiment in laboratory,secondary effluent sample used exhibited the genotoxicity of(41.1 ± 4.1) μg 4NQO/L. Ozonation with a dose of 10 mg O3/L completely removed the genotoxicity in secondary effluent. However,after ozonation, the dissolved organic carbonvalue of the sample didn't change much but the specific ultraviolet absorbance(SUVA) value dropped sharply. With the help of Fourier transform infrared spectroscopy, ozonation was found to change chemical aliphatic carbon and C–O of the dissolved arganic matter, which might be the reason of the significant decreases of SUVA and genotoxicity.     

Antimony smelting process generating solid wastes and dust：Characterization and leaching behaviors

A large amount of solid waste has been produced by the antimony smelting process in the＂World Capital of Antimony＂, Xikuangshan area in China. This study comprehensively investigated the physical and chemical characteristics of the various solid wastes, as well as the leaching behavior of the solid wastes, which included water-quenched slag,arsenic-alkali residue, desulfurized slag and blast furnace dust. These four types of waste were enriched in a variety of heavy metals and metalloids and more specifically with As and Sb levels up to 8.6 × 104 and 3.16 × 105mg/kg, respectively, in arsenic-alkali residue. For desulfurized slag and water-quenched slag, the leaching concentration of Sb significantly exceeded the acceptable limits during the leaching tests using the toxicity characteristic leaching procedure and the synthetic precipitation leaching procedure. In addition, As leaching in arsenic-alkali residue was extraordinarily hazardous, being three orders of magnitude higher than the regulatory level of As. According to the results of the extraction tests, all the tested wastes were classified as hazardous waste.     

Fouling distribution in forward osmosis membrane process

Fouling behavior along the length of membrane module was systematically investigated by performing simple modeling and lab-scale experiments of forward osmosis （FO） membrane process. The flux distribution model developed in this study showed a good agreement with experimental results, validating the robustness of the model. This model demonstrated, as expected, that the permeate flux decreased along the membrane channel due to decreasing osmotic pressure differential across the FO membrane. A series of fouling experiments were conducted under the draw and feed solutions at various recoveries simulated by the model. The simulated fouling experiments revealed that higher organic （alginate） fouling and thus more flux decline were observed at the last section of a membrane channel, as foulants in feed solution became more concentrated. Furthermore, the water flux in FO process declined more severely as the recovery increased due to more foulants transported to membrane surface with elevated solute concentrations at higher recovery, which created favorable solution environments for organic adsorption. The fouling reversibility also decreased at the last section of the membrane channel, suggesting that fouling distribution on FO membrane along the module should be carefully examined to improve overall cleaning efficiency. Lastly, it was found that such fouling distribution observed with co-current flow operation became less pronounced in counter- current flow operation of FO membrane process.     

Arsenic removal from groundwater by acclimated sludge under autohydrogenotrophic conditions

Arsenic in the environment is attracting increasing attention due to its chronic health effects. Although arsenite(As(III)) is generally more mobile and more toxic than arsenate(As(V)), reducing As(V) to As(III) may still be a means for decontamination, because As(III) can be removed from solution by precipitation with sulfide or by adsorption or complexation with other metal sulfides. The performance of As(V) bio-reduction under autohydrogenotrophic conditions was investigated with batch experiments. The results showed that As(V) reduction was a biochemical process while both acclimated sludge and hydrogen were essential. Most of the reduced arsenic remained in a soluble form, although 20% was removed with no addition of sulfate, while 82% was removed when sulfate was reduced to sulfide. The results demonstrated that the reduced arsenic was re-sequestered in the precipitates, probably as arsenic sulfides. Kinetic analysis showed that pseudo first-order kinetics described the bio-reduction process better than pseudo second-order. In particular, the influences of pH and temperature on As(V) reduction by acclimated sludge under autohydrogenotrophic conditions and total soluble As removal were examined. The reduction process was highly sensitive to both pH and temperature, with the optimum ranges of pH 6.5–7.0 and 30–40°C respectively. Furthermore, Arrhenius modeling results for the temperature effect indicated that the As(V) reduction trend was systematic. Total soluble As removal was consistent with the trend of As(V) reduction.     

利用淀粉/PCL共混物作为反硝化固体碳源和生物膜载体的研究

以双螺杆挤出机制备了淀粉聚己内酯(PCL,polycaprolactone)共混物(SPCL5),研究了其浸出性能及吸水性能,并在序批试验中研究了其作为反硝化固体碳源和生物膜载体的特性。结果表明,SPCL5颗粒前3 d浸出的有机物浓度较高,随后逐渐降至1.31 mgL。SPCL5颗粒吸水率在1 d左右达到饱和,约为30.97%。SPCL5可作为固体碳源用于去除低碳氮比(CN)水中的硝酸盐。以活性污泥接种时,SPCL5颗粒在1 d后就有显著的脱氮效果。驯化结束后,SPCL5颗粒的平均反硝化速率(以N计)为0.020 8 mg(g·h)。剪切力是影响反硝化速率的重要因素,转速从70 rmin提高至140 rmin时,平均反硝化速率提升近1倍,达到0.040 3 mg(g·h)。进水NO3-N浓度为15~50 mgL时对反硝化速率无显著影响,反硝化为零级反应。红外光谱结果表明利用后的共混物中淀粉和PCL均发生了降解。     

外加碳源影响水体异养反硝化脱氮的研究进展

近年来,水体硝酸盐污染受到世界范围内的广泛关注,从去除硝酸盐污染和降低脱氮成本两个方面考虑,生物反硝化法是比较经济、实用的方法。目前,反硝化过程主要是通过异养反硝化作用实现,碳源作为反硝化过程的电子供体,是影响反硝化过程的主要因素,当污水中碳氮比偏低时,需要考虑添加额外碳源提高异养反硝化作用速率,保证反硝化过程的正常进行。针对现有问题综述常用的几种主要外加碳源以及它们对反硝化作用的影响,为今后寻找到更加经济、有效的外加碳源提供参考。     

雌激素污染对水体微生物反硝化作用的影响

针对世界各国水体雌激素污染日趋严重的环境问题,文章选择典型天然环境雌激素——17β-雌二醇(E2)为污染源,构建实验室厌氧水体微生态系统,分析E2污染对水体微生物反硝化速率、反硝化终端产物比例和厌氧微生物活性的影响规律。结果表明,E2污染对水体微生物的反硝化速率和活性存在显著性显著抑制作用,但反硝化终产物中N2O的比例得到明显促进。因此,在厌氧条件下,微量E2污染会影响厌氧微生物活性和反硝化作用,对水体的氮素循环产生影响。     

基于N：P化学计量特征的高寒草甸植物养分状况研究

土壤养分条件影响不同功能群植物的养分状况与生长,这在施肥实验中已得到充分验证.然而,自然养分梯度下植物-土壤养分耦合关系的研究仍然缺乏.基于植物N∶P化学计量学特征,本研究探讨青藏高原亚高寒草甸自然养分梯度下不同功能群植物氮状况及生物量变化.2008年、2009年N∶P比值分别为9.83和11.57,其低群落N∶P比验证了该地区自然植被主要受到N素的限制.偏冗余分析(partial RDA)结果显示,随着土壤氮素可利用性的增加杂草生物量比例上升,而豆科、禾草生物量比例下降.豆科的固氮作用以及禾草的高养分利用效率分别提高其在氮限制植被中的竞争力;这些结果表明,全球氮沉降的增加将提高杂草的优势度.豆科生物量比例与群落、非豆科植物的N∶P显著正相关,表明豆科植物能够改善群落的氮状况,包括降低非豆科植物的氮限制水平.     

陶粒CANON反应器的接种启动与运行

通过CANON接种污泥,以人工配制无机高氨氮废水为对象,研究以陶粒为填料的CANON反应器启动与运行情况,结果表明:①陶粒可以作为CANON反应器合适填料,温度通过水浴控制在30℃±1℃,HRT为9 h、pH控制在7.00~8.08之间,经过60 d成功启动了CANON反应器,TN的去除负荷达到0.79 kg·(m3·d)-1;②在温度30℃时,陶粒CANON反应器中临界DO范围在1.12~1.69 mg·L-1之间,CANON反应器中短程硝化和厌氧氨氧化性能可维持稳定,高于此范围时,会出现CANON反应器中短程硝化不稳定现象;③在温度25℃,控制DO在1.01~1.54 mg·L-1之间时,尽管NO-3-N变化值与TN变化值的比值(δNO-3-N/δTN)略微偏离理论值0.127,为0.150~0.204,但CANON反应器脱氮性能趋于稳定,TN去除率最高为75.56%,TN的去除负荷最高达到0.97 kg·(m3·d)-1,这意味着CANON工艺的适宜温度范围至少可以降低至25℃.     

半短程亚硝化与厌氧氨氧化联合脱氮工艺微生物特征研究进展

半短程亚硝化-厌氧氨氧化脱氮技术具有良好的发展前景,该工艺的发展以及应用分子生物学技术对好氧氨氧化菌种群和厌氧氨氧化种群生态学的研究备受人们关注.本文综述了工艺原理和影响因子诸如温度、pH值、氧的可利用性、游离氨浓度等对氨氧化菌及厌氧氨氧化菌的影响,并介绍了应用分子生物学方法对氨氧化菌与厌氧氨氧化菌的类别及分布的研究结果,并对该工艺提出了展望.