The integration of methanogenesis with denitrification and anaerobic ammonium oxidation in an expaned granular sludge bed reactor

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation (ANAMMOX) was studied in an expanded granular sludge bed (EGSB) reactor in this work. Experimental results from the continuous treatment of wastewater with nitrite and ammonium, which lasted for 107 days, demonstrated that wastewater with high nitrite and ammonium could be anaerobically treated in an expanded granular sludge bed reactor. More than 91% to 97% of COD were removed at up to about 3.9 g COD/(L x d) of COD volumetric loading rate. More than 97% to 100% of nitrite was denitrified at up to about 0.8 g NO2(-) -N/(L x d), which is 16 times higher than that in a conventional activated sludge system with nitrification/denitrification (0.05 gN/(L x d)). No dissimilatory reduction of nitrite to ammonium occurred in the process. However, maximum of about 40% ammonium was found to be lost. Batch tests of 15 days with sludge from the reactor showed that 100% of nitrite was denitrified completely, and about 3% of ammonium was removed when only ammonium (34.3 mg/L) and nitrite (34.3 mg/ L) were added into the sludge suspension medium. Furthermore, about 15% of ammonium amounts were lost with organic COD addition. It suggested that the methanogenesis in the system could enhance ANAMMOX because of intermediate hydrogen produced during methanogenesis.     

Removal of odors and VOCs in municipal solid waste comprehensive treatment plants using a novel three-stage integrated biofilter: Performance and bioaerosol emissions

• TSIBF was composed of ABRS, FRS and HBRS. • THIBF can effectively remove various odors, VOCs and bioaerosols. • Different reaction segments in TSIBF can remove different types of odors and VOCs. • TSIBF can reduce the emission of bioaerosols through enhanced interception. A novel three-stage integrated biofilter (TSIBF) composed of acidophilic bacteria reaction segment (ABRS), fungal reaction segment (FRS) and heterotrophic bacteria reaction segment (HBRS) was constructed for the treatment of odors and volatile organic compounds (VOCs)from municipal solid waste (MSW) comprehensive treatment plants. The performance, counts of predominant microorganisms, and bioaerosol emissions of a full-scale TSIBF system were studied. High and stable removal efficiencies of hydrogen sulfide, ammonia and VOCs could be achieved with the TSIBF system, and the emissions of culturable heterotrophic bacteria, fungi and acidophilic sulfur bacteria were relatively low. The removal efficiencies of different odors and VOCs, emissions of culturable microorganisms, and types of predominant microorganisms were different in the ABRS, FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment. The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing. The rational segmentation, filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols, thus reducing the emissions of microorganisms from the bioreactor.     

模糊控制理论在煤矿通风安全自动化系统中的应用

由于煤矿通风系统的独特性和复杂性 ,要精确地建立具有时滞及控制对象的数学模型遇到较大的困难 ,因此 ,人们寻求了一些新的解决途径。笔者基于模糊控制理论 ,并提出将其应用于煤矿通风自动化系统中 ,同时采用单片机来实现模糊控制 ,实践证明 ,此法取得良好效果 ;与常规的控制方法相比 ,模糊控制方法具有响应快、控制简单、不需建模等特点 ,适用于矿井通风自动化系统 ;笔者还讨论了调节窗模糊控制系统设计 ,系统的单片机实现及软件编制 ,并进行了实验及实验结果分析 ;最后提出了向自组织方向的深化方案。     

Enhanced effect of HAH on citric acid-chelated Fe(II)-catalyzed percarbonate for trichloroethene degradation

This work demonstrates the impact of hydroxylamine hydrochloride (HAH) addition on enhancing the degradation of trichloroethene (TCE) by the citric acid (CA)-chelated Fe(II)-catalyzed percarbonate (SPC) system. The results of a series of batch-reactor experiments show that TCE removal with HAH addition was increased from approximately 57 to 79% for a CA concentration of 0.1 mM and from 89 to 99.6% for a 0.5 mM concentration. Free-radical probe tests elucidated the existence of hydroxyl radical (HO^•) and superoxide anion radical (O₂ ^•-) in both CA/Fe(II)/SPC and HAH/CA/Fe(II)/SPC systems. However, higher removal rates of radical probe compounds were observed in the HAH/CA/Fe(II)/SPC system, indicating that HAH addition enhanced the generation of both free radicals. In addition, increased contribution of O₂ ^•- in the HAH/CA/Fe(II)/SPC system compared to the CA/Fe(II)/SPC system was verified by free-radical scavengers tests. Complete TCE dechlorination was confirmed based on the total mass balance of the released Cl⁻ species. Lower concentrations of formic acid were produced in the later stages of the reaction for the HAH/CA/Fe(II)/SPC system, suggesting that HAH addition favors complete TCE mineralization. Studies of the impact of selected groundwater matrix constituents indicate that TCE removal in the HAH/CA/Fe(II)/SPC system is slightly affected by initial solution pH, with higher removal rates under acidic and near neutral conditions. Although HCO₃ ⁻ was observed to have an adverse impact on TCE removal for the HAH/CA/Fe(II)/SPC system, the addition of HAH reduced its inhibitory effect compared to the CA/Fe(II)/SPC system. Finally, TCE removal in actual groundwater was much significant with the addition of HAH to the CA/Fe(II)/SPC system. The study results indicate that HAH amendment has potential to enhance effective remediation of TCE-contaminated groundwater.

     

水体低氧的早期暴露对青鳉(Oryzias latipes)后期的生长、性别比和繁殖能力的影响

水体低氧已是全球性生态问题,常以季节性、偶发性和昼夜间等不同形式存在于不同的水体中。长期低氧可影响鱼类正常的生长和繁殖,但鱼类早期生活阶段暴露于不同形式的低氧后,后期的生长和繁殖是否会受到不利影响,目前研究甚少。本研究在实验室模拟了连续低氧(2.8 mg·L~(-1)DO)(H1)、昼夜低氧(H2)和发生在胚胎器官形成时期的偶发性低氧(H3)等3种情景对青鳉胚胎的发育影响,评估了这一早期暴露对青鳉后期的生长、存活和繁殖的影响。我们发现,3种低氧方式都可以显著延长青鳉胚胎的孵化周期,引起胚胎卵黄囊吸收和鱼鳔发育异常;暴露结束120 d后,H1组青鳉成鱼的畸形率显著升高、存活率和生长速度都显著下降;H1、H2和H3组中成鱼的雌雄比都发生了改变,鱼群中以雄鱼为主,且产卵量和受精率都显著下降。结果表明,鱼类早期胚胎发育阶段所受到的低氧暴露可对后期生长和繁殖产生不利影响,对子代补充和种群稳定产生重要影响;鱼类关键发育期所经历的低氧事件,以及昼夜低氧事件所产生的生态后果不容忽视。     

Health risk assessment of exposure to organic matter from the use of reclaimed water in toilets

To estimate the carcinogenic and non-carcinogenic risks of six volatile organic compounds (VOCs) found in reclaimed water used for flushing toilets, a probabilistic health risk assessment based on Monte Carlo simulations was used. Before Monte Carlo simulations, the contaminant volatilization model was applied to estimate the concentration of the pollutants in air. Moreover, a questionnaire was used to acquire daily exposure time and the Batch Fit tool of Crystal Ball software was applied to find the best-fitting distribution of a part of the input parameters. The risk analysis indicated that the health risks from six VOCs were lower than the negligible risk level (1?×?10^?8) in all cases, and the health risk for females was slightly higher than that for males. Overall, exposure to organic pollutants in reclaimed water during toilet flushing does not currently pose a significant carcinogenic risk to humans. In this study, we want to provide some information on the health risk from reclaimed water used for toilet flushing in China and hope that it will be useful to promote the application of reclaimed water in water-deficient areas.     

不同碳源对活性污泥反硝化能力的影响研究

针对城镇污水处理中碳源不足影响系统脱氮能力的问题,分别以乙酸钠、葡萄糖作为外源性碳源,考察其对活性污泥反硝化脱氮能力的影响。研究结果表明:在碳源投加量分别为50,100,200 mg/L条件下,单位(g)NO-3-N去除增量所需乙酸钠/葡萄糖的投加量分别为8.24 g/49.02g、9.62g/22.57g、—/21.07g。乙酸钠可用作城镇污水脱氮除磷过程中的高效外源性碳源,但从污水处理运行经济性来看,需根据系统实际需去除NO-3-N的量,合理确定碳源投加量。     

ICP-MS同时测定饮用水中25种元素的研究

采用电感耦合等离子体质谱(ICP-MS)对饮用水中25种元素进行同时测定,并对其方法进行了研究.结果表明用ICP-MS同时测定饮用水中25种元素,其最低检出限为Th 1.238 E-5μg/L;其RSD%均小于5%;加标回收率介于98.94～100.4%之间,具有较高的灵敏度、精密度和准确,特别是对一些浓度低达ng/L级,但对人体健康却产生重要影响的超痕量组分,如Tl、Th、U等的测定,本法具有其它传统分析难以满足的优势.应用于直接测定元素浓度范围从ng/L-mg/L级的实际样品,具有快速、简便、准确等优点.