包气带土体反硝化作用对NO_3~-转化的试验研究

就河北平原山前地区包气带土体中的氮素循环转化及污染地下水的过程、包气带土体中反硝化细菌对硝酸盐转化的作用强度进行了试验研究。结果表明,生物反硝化作用是土壤包气带氮素转化的主要作用之一。该区包气带土体中由于有机物较少并随深度增加而减少,因此对NO-3细菌的反硝化作用强度也随深度加大而减弱,从而造成包气带土体中硝酸盐积累,进而污染地下水。如对包气带的有机碳源加以调控,可阻止地下水的污染。     

基于硝酸盐液膜微电极的动态膜反硝化特性研究

制成性能良好的硝酸盐微电极与氧化还原电位(ORP)微电极,对动态膜在不同进水COD负荷下的内部反硝化过程进行研究.结果表明,动态膜中的反硝化作用出现在膜水界面0.6～1mm以下;在反硝化发生的区域,用ORP微电极测得氧化还原电位在88.6～-128.4mV之间,是反硝化发生的适宜ORP范围.当进水COD负荷为0.45 kg/(m³·d)时,动态膜的反硝化速率(以氮计)最大,可以达到0.634 7×10^-6mol/(L·s).增加进水COD负荷能够拓展动态膜内部的     

湿地缓冲带对氮磷营养元素的去除研究

湿地缓冲带是介于水-陆之间特殊的生态交错带,具有独特的水体净化功能。基于国内较少开展自然湿地水体净化功能的研究,选取扎龙湿地湖滨湿地缓冲带剖面作为研究对象,利用电导率的剖面变化判断水流的方向,同时利用氯离子作为示踪剂验证剖面水体来自同一水源。在此基础上,发现其对水体中营养元素具有明显的去除效应,TN、TP的去除率分别达74.1%、84.6%。缓冲带内的湿地植物量较小,决定了植物吸收并非氮磷去除的主要机制。根据溶解有机碳和重碳酸酸根的变化,认为反硝化作用是湿地缓冲带去除氮的主要途径,剖面末段处的浅水位和相对茂盛的植物,使其具有相对较强的脱氮能力;土壤吸附与沉淀作用是湿地缓冲带去除磷的主要途径,剖面起始处较高的磷浓度使其具有较高的磷去除能力。因此,利用并强化湿地缓冲带的自然净化能力有助于控制湿地水体富营养化的发展。     

Development of PCR primers targeting fungal nirK to study fungal denitrification in the environment

Fungal denitrification in soils is receiving considerable attention as one of the dominant N₂O production processes. However, because of the lack of a methodology to detect fungal denitrification-related genes, the diversity and ecological behavior of denitrifying fungi in soil remains unknown. Thus, we designed a primer set to detect the fungal nitrite reductase gene (nirK) and validated its sensitivity and specificity. Through clone library analyses, we identified congruence between phylogenies of the 18S rRNA gene and nirK of denitrifying fungal isolates obtained from the surface-fertilized cropland soil and showed that fungi belonging to Eurotiales, Hypocreales, and Sordariales were primarily responsible for N₂O emissions in the soil.     

Soil pH is a good predictor of the dominating N2O production processes under aerobic conditions

It is commonly believed that nitrification is the dominant process for N₂O production under aerobic conditions. However, this has been challenged by recent studies on acidic soils, where denitrification has been found to dominate N₂O production. Analyzing the data collected from peer‐reviewed literature, we found that pH was a critical factor regulating N₂O production pathways under aerobic conditions. There is a pH threshold of approx. 4.4, below which denitrification dominated N₂O production and vice versa. A decrease in soil pH can significantly increase the contribution of denitrification to N₂O production. Overall, this mini‐review increases our understanding of N₂O sources in soils under aerobic conditions.     

A/O-MBR处理低C/N生活污水的脱氮因素研究

采用A/O-MBR工艺处理低C/N(3~5)生活污水,考查溶解氧(DO)、水力停留时间(HRT)及回流比(R)对脱氮效果的影响,并对处理过程进行全氮分析。结果表明,该工艺NH4+-N去除率在95%以上,但TN去除率最高仅为66%,TN去除在DO=2~3 mg/L、HRT=9 h及R=300%时分别出现峰值,缺氧段处理效果明显优于好氧段。对处理过程的全氮分析表明,28~32℃水温条件下,系统亚硝化率(NO2-/TN)保持在3%以下的低比率,说明短程硝化反硝化作用可以忽略,TN去除主要依赖硝化反硝化;控制DO=2~3 mg/L、HRT=9 h,系统好氧池硝化率(NO3-/TN)维持在61%~90%之间,缺氧池硝化率随R增加逐渐上升,在R=300%时达到高点76%;控制DO=2~3 mg/L、R=300%,缺氧池硝化率也在HRT=9 h时达到高点。结果表明,A/O-MBR工艺维持TN去除效果的先决条件是缺氧池达到足够的硝化率。由于反硝化细菌是典型的异养菌,TN去除不够理想主要源于进水碳源相对缺乏。除了增加碳源的传统措施外,提高TN去除率应更多地关注工艺条件的改进。     

利用反硝化技术净化养殖水体的研究进展

随着水产养殖业的大力发展,养殖水体净化技术的研究受到普遍重视,利用反硝化技术净化养殖水体的研究日益增多。本文中阐述了养殖水体中硝酸盐积累所造成的危害,详细介绍了养殖水体反硝化净化机理以及生物载体、碳源选择、脱氧方法和反硝化工艺等的研究进展,并对反硝化技术在养殖水体净化方面的应用前景进行了探讨分析。     

异养硝化在水产养殖中的应用

比较了异养硝化作用与传统自养硝化作用,结果表明:异养硝化作用不仅客观存在,而且某些特殊的异养细菌能同步进行异养硝化和好氧反硝化,在养殖水体水质改善方面具有广泛的应用前景。     

Treatment of Wastewater with High Concentration of Ammonia Nitrogen through ASBR Combining with Pulsed SBR

In order to analyze the nitrogen removal performance of anaerobic-aerobic process treating landfill leachate, a system combining ASBR with pulsed SBR was applied to treat real landfill leachate with high concentration of ammonia nitrogen. The HRT of ASBR was 2 d; middle water tank regulated the COD/NH +4-N (3～5) and NH +4-N concentration of pulsed SBRs influent; the cycle of pulsed SBR consisted of four anoxic stages and three oxic stages in which three equal feeds model was applied. In the fourth anoxic stage (An4), internal carbon source was used to implement denitrification without any extra carbon source addition. The results indicate that efficient nitrogen removal performance of this system was achieved in the series running period (157 d). Influent chemical oxygen demand (COD) concentration of ASBR was from 7 338 mg·L -1 to 1 0445 mg·L -1 of which above 83% was removed; pulsed SBRs influent NH +4-N concentration could be divided into four phases in which improving from 296.1±14.5 mg·L -1 to 912.0±41.7 mg·L -1, and the effluent total nitrogen (TN) concentration of pulsed SBR was below 40 mg·L -1 all the time, which means TN removal rate reached over 90%. To sum up, the COD and TN removal rate of the combined system were above 87% and 97%, respectively. Endogenous denitrification rate(DNR) of An4 changed from the fast one to the slow one, and the mean value of theoretical denitrification rate (TDNRm) of pulsed SBRs An4 could reach 1.531 mg N·h -1·gMLVSS -1. Advanced nitrogen removal of the system was realized without extra carbon source addition and physicochemical pre-treatment.     

好氧反硝化复合菌剂的研制及其在海水养殖废水处理中的应用

从天津某海水养殖场底泥中分离筛选好氧反硝化菌,获得3株具有高效反硝化特性的微生物,分别为MCW148、MCW151和MCW154。采用正交试验对功能菌进行优化组合,研制好氧反硝化复合菌剂。结果表明,MCW148、MCW151、MCW154的最优配比为3∶2∶1,其在12 h内对海水养殖废水中无机氮的去除率为60.39%。