DO对低C/N比污水生物亚硝化的影响分析

采用活性污泥法SBR工艺,考察DO对亚硝化的影响。首先进行195 d的连续培养试验,得出亚硝化系统DO保持在0.2 mg/L~0.6 mg/L的范围之内,可使得到有效降解且出水亚硝化率达50%~90%;然后研究系统周期内DO的变化规律,可以考虑以12 h为一个亚硝化反应周期,若延长反应时间至16 h,将使反应有向硝酸型硝化转移的趋势;最后通过烧杯试验,得出随着系统DO浓度的升高,氨氮降解率上升、亚硝化率下降,遵循DO与氨氮降解率和亚硝化率关系的数学模式。     

Nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica for the diazotization of aniline derivatives and subsequent synthesis of azo dyes

Imidazolium based nitrite ionic liquid containing trimethoxysilyl group was prepared from the reaction of N-methylimidazole and (3-chloropropyl) trimethoxysilane. This ionic liquid was immobilized on silica covalently to give nanoparticles with the imidazolium nitrite moiety remaining intact. The diazotization reaction was performed as a model reaction to examine the activity of these nanoparticles as a nitrosonium source. Excellent performance was exhibited in the diazotization reaction of various aniline derivatives in the presence of HCl under mild heterogeneous conditions (room temperature and short reaction time). In-situ coupling of diazonium salts to a range of tertiary anilines, phenols and naphthols afforded the requisite azo dyes in good yield, using standard experimental procedures.     

Assessment of estimated daily intake of nitrite by average consumption of processed foods in Korea

This study has been performed to estimate the average daily intake of nitrite used in Korea as a color fixative. The crude estimation of daily intake was calculated based on maximum permitted levels (MPL) and national food disappearance data in 1998. In order to refine estimated daily intake (EDI), daily food consumption nationwide National Health and Nutrition Survey in 1998 and the concentration of nitrite in their permitted foods were applied. The crude EDI of nitrite was 17.85 μg/kg bw/day, representing 25.5% of acceptable daily intake (ADI) assigned by JECFA. The refined average EDI for nitrite was 0.87 μg/kg bw/day, representing 1.25% of ADI. For average consumers of age–sex groups ranged from 0.2 to 4.8 μg/kg bw/day, representing 0.3%–6.9% of the ADI.     

流动化学分析法测定海水中硝酸盐亚硝酸盐

采用萘乙二胺分光光度法测定亚硝酸盐、锌-镉还原法测定硝酸盐与连续流动化学分析法进行同时测定对比,结果采用t检验法的"成对数据的比较"来判定,两种方法针对单个盐度点样品无显著性差异。采用流动化学分析法,进行浓度及盐度适用范围实验;本次方法实验显示硝酸盐氮和亚硝酸盐氮含量的适用范围分别为0.005～1.0 mg N/L和0.004～0.1 mg N/L;盐度适用范围实验显示盐度0～40的水样测定结果一致性良好。     

Beyond celery and starter culture: advances in natural/organic curing processes in the United States

Over the past 10years there has been ongoing development of curing processes with natural ingredients designed to meet consumer demand and regulatory requirements for natural and organic processed meats. Initially, these processes utilized celery concentrates with a high nitrate content combined with a nitrate-reducing starter culture. Subsequent advances included celery concentrates with the nitrate converted to nitrite by suppliers. Further, as questions developed concerning reduced concentration of preservatives and the microbiological safety of these processed meats, additional advances have resulted in a wide variety of ingredients and processes designed to provide supplementary antimicrobial effects for improved product safety.     

Effect of rosemary extract dose on lipid oxidation, colour stability and antioxidant concentrations, in reduced nitrite liver pâtés

The oxidative stability of liver pâté was investigated in relation to different doses of rosemary extract (RE) and sodium nitrite. Colour stability, lipid oxidation (TBARS) and concentrations of ascorbic acid, α-tocopherol, carnosic acid and nitrite were measured on the batters before cooking and on the cooked liver pâté before and after exposure to light and air for 48 h at 4 °C. Results showed that the use of RE significantly reduced lipid oxidation, whereas it had no effect on colour stability. Ascorbic acid and nitrite concentrations were significantly higher and lower respectively when RE was added. RE dose-dependently increased the concentration of carnosic acid. Lower sodium nitrite doses resulted in significantly lower nitrite concentrations and slightly lower TBARS values. It was concluded that in liver pâté sodium nitrite levels may be lowered to 80 mg/kg without negatively affecting colour and lipid stability and that the use of RE may help in maintaining lipid stability.     

Influence of the electron acceptor on nitrite reductase gene (nir) diversity in an activated sludge community

Analyses of the nitrite reductase gene diversities (nirK and nirS) in an activated sludge community fed with both nitrite and glucose were conducted. Results suggest that the topology of nirK and nirS gene fragment-based phylogenetic trees is influenced more by the available electron acceptor than by the carbon source. A denitrification reactor was operated for 53 days and a clone library constructed when the denitrifying communities in the SBR were supplied with both nitrite and glucose. Half of the nirK and nearly all the nirS gene fragments formed a cluster that was separate from a cluster containing nirK and nirS sequences derived from other communities in nitrate-fed reactors. On the other hand, nirK and nirS fragments obtained with glucose as the carbon source were similar to those detected in communities fed with other carbon sources.     

常温下生物陶粒反应器中亚硝酸型硝化的试验研究

采用生物陶粒反应器,研究了常温下亚硝酸型硝化的实现过程。试验结果表明,在水力负荷0．6m／h,气水比(3-5):1,水温20-25℃,进水CODCr负荷1．91-5．59kg／(m3·d),氨氮负荷0．77-1．33kg／(m3·d)的条件下,生物陶粒反应器对氨氮的平均去除率可达到80．91％,出水中亚硝酸氮占到亚硝酸氮和硝酸氮总和的90％以上。对生物陶粒反应器中各种不同无机氮化合物沿程变化的研究进一步表明,在反应器中实现了稳定的亚硝酸盐积累。对影响亚硝酸型硝化的各因素进行了分析,认为溶解氧控制是常温下反应器实现亚硝酸型硝化的最关键因素。     

ANAMMOX工艺在生活污水深度处理中的应用研究

随着水环境质量的恶化,高能低耗的污水深度处理技术成为当前研究热点,尤其是对于低C/N比的城市生活污水脱氮技术的研究。试验以城市生活污水的二级出水为研究对象,采用ANAMMOX下向流生物滤池,当二级出水NH3-N=15-35mg/L,CODCr=25-45mg/L,TOC=9-12mg/L,水温=25-28℃时,ANAMMOX下向流生物滤池脱氨率达80%-100%,不仅适用于处理高氨废水,也可用于城市生活污水深度处理中。试验发现pH可以用来指示ANAMMOX反应的进行,同时也可以用来指示ANAMMOX反应进程的快慢。试验中还发现,厌氧氨氧化反应速率与NO2--N含量有关,原水中NO2--N含量的增多有利于ANAMMOX工艺处理效果。