Effect of wastewater COD/N ratio on aerobic nitrifying sludge granulation and microbial population shift

The effect of COD/N ratio on the granulation process and microbial population succession was investigated. Four identical sequencing batch reactors, R1, R2, R3 and R4, were operated with various initial COD/N ratios ranging from 0/200 to 800/200 (m/m). Ethanol was fed as the source of COD. Aerobic granules were successfully cultivated in R2 and R3, operating with the COD/N ratio of 200/200 and 400/200, respectively. Scanning electron microscope observations indicated that short rod-shaped and spherical bacteria were dominant in R2, while granules produced in R3 were surrounded with a large amount of filamentous bacteria. The average specific nitritation rate in R2 and R3 were 0.019 and 0.008 mg N/(mg MLVSS.hr), respectively. Fluorescence in situ hybridization results demonstrated that nitrifying bacteria population was enriched remarkably in R2. It indicated that nitrification ability and nitrifying bacteria population were enriched remarkably at low COD/N ratio. However, no granules were formed in R1 and R4 which might attribute to either limited or excessive extracellular polymeric substances production. This study contributed to a better understanding of the role of COD/N ratio in nitrifying sludge granulation.     

生物甲烷抑制剂缓释扩散模型推导与优化

以石蜡和松香为缓释基质,以碳化钙为生物甲烷抑制材料,对有效抑制组分——乙炔的扩散规律进行了研究.以T.Higuchi方程为基础,针对复杂基质的气体缓释进行了修正,得到缓释抑制剂的扩散机制模型,该模型可以有效预测乙炔的扩散系数De.同时考察了基质优化对扩散系数的影响,如果缓释基质的硬度不够,碳化钙与水反应产生的热量可导致缓释抑制剂内部膨胀从而影响缓释效果.当基质中松香的质量分数为20%,基质与碳化钙的质量比为1/1时,缓释基质的硬度和致密度提高,乙炔的扩散系数达到2.2849×10-8cm2/min(R2=0.9901),该缓释抑制剂可以有效地解决生活垃圾填埋场等人为源生物甲烷的减排问题.     

三相流化床中人苍白杆菌与硝化菌对苯胺废水的共基质降解

将人苍白杆菌(Ochrobactrum anthropi)降解苯胺的过程与硝化反应相结合,在三重环流三相流化床中实现共基质降解,充分降低废水中的苯胺和苯胺降解过程中产生的NH4 -N.以自行研制的聚氨酯填料为载体,研究了流化床内苯胺、DO以及NaHCO3等对该共基质降解过程的影响.挂膜过程中苯胺质量浓度下降和NH4 质量浓度上升,证明了此过程中人苍白杆菌生物膜优先形成,而且NH4 质量浓度先增后降反映了人苍白杆菌生物膜的形成为硝化菌生物膜的形成创造了条件.通过苯胺对硝化菌的抑制性实验发现,苯胺质量浓度从100 mg/L下降到4 mg/L的过程中,其对硝化菌的抑制作用由强变弱.当苯胺质量浓度小于4 mg/L时,对硝化菌无抑制作用.其中亚硝化细菌比硝化细菌活性恢复更快,表明硝化菌比亚硝化菌对苯胺的毒性抑制更为敏感.流化床高效的传氧能力可以改善硝化细菌摄O2的条件.DO 2～3 mg/L,pH=7.5～8.5及适当的NaHCO3添加量是苯胺与NH4 -N共基质降解的适合条件.此条件下进水COD和苯胺质量浓度分别为540 mg/L及210 mg/L左右时,出水能够达到国家一级排放标准.     

Evaluation of the inhibitory effect of abamectin on mammalian butyrylcholinesterase: Enzyme kinetic and molecular docking studies

ABSTRACT

Abamectin, a blend of the natural avermectins B_1a and B_1b, is a widely-used insecticide/miticide with relatively low toxicity to mammals. Exposure to high doses of it, however, leads to cholinergic-like neurotoxic effects. Butyrylcholinesterase, which is best known for its abundant presence in plasma, is a serine hydrolase loosely coupled with the cholinergic system. It protects and supports the neurotransmitter function of its sister enzyme acetylcholinesterase. Here, using experimental and computational studies, we provide evidence demonstrating that abamectin is a potent (IC₅₀ = 10.6 μM; K_i = 2.26 ± 0.35 μM) inhibitor of horse serum butyrylcholinesterase and that it interacts with the enzyme in a reversible, competitive manner predictively to block the mouth of the active-site gorge of the enzyme and to bind to several critical residues that normally bind/hydrolyze choline esters.     

Effect of selected herbicides on activities of microorganisms in soils

Abstract

With the exception of EPTC, herbicide treatments showed inhibitory effects on bacterial colony counts in a sandy loam soil for the first week. Monolinuron and simazine were stimulatory to the growth of fungi in the organic soil after 2 wk. None of the herbicide treatments affected nitrification during the first week of incubation. Except the treatment of EPTC in organic soil, all herbicides inhibited nitrification after 2 wk in both soils. All herbicide treatments stimulated SO₄ formation during the 8‐wk period in the sandy loam soil. Simazine and tridiphane also stimulated sulfur oxidation after 4 wk in an organic soil. With the exception of EPTC and nitrapyrin, no significant inhibitory effect on the amount of biomass‐C was observed in the organic soil. A stimulatory effect on denitrification was observed with EPTC for 2 wk and monolinuron for 1 wk in the sandy loam soil and with simazine and tridiphane after 2 wk in the organic soil. It is apparent that the indigenous soil microorganisms can tolerate the effects of the chemicals for control of soil weeds.     

农田中氮肥的损失与对策

评述了我国有关农田中氮肥的损失及其对策的研究结果。主要涉及农田中氮肥的损失程度、途径和机理;氮肥损失对环境的影响;减少氮肥损失、提高氮肥利用率的技术原则和主要措施。这些措施包括确定适宜的施氮量,以及采用深施、水肥综合管理、平衡施肥、脲酶抑制剂、硝化抑制剂、液态分子膜等。     

二级SBR法处理高浓度氨氮化工废水研究

用直接活性污泥法完成了各反应器的污泥驯化启动。二级ＳＢＲ工艺主要由硝化ＳＢＲ和反硝化ＳＢＲ反应器构成,其中硝化ＳＢＲ反应器采用悬浮生长法和固定生物膜法两种工艺作对比试验。结果表明,后者较前者具有更大的ＮＨ３－Ｎ容积负荷,最大可达７６６．５４ｍｇＬ＾－１ｄ＾－１;而且能节省碱的消耗量１１．０％～３８．７％和反硝化所需碳源量为３０％～４０％。在ｔＨＲ为２４ｈ的条件下,二级ＳＢＲ法能处理ρＩｎ（ＮＨ３－     

重金属对活性污泥微生物毒性的比较研究

采用发光细菌毒性、活性污泥脱氢酶毒性、硝化抑制毒性3种方法测定Hg、Cd、Zn、Pb 4种重金属对活性污泥微生物的毒性,并对测定结果进行了比较.结果表明,发光细菌毒性测定方法的灵敏度最高,测得的重金属半数有效浓度(ECSO)最低,4种重金属对发光细菌发光强度的抑制程度由大到小顺序依次为Hg>Cd>Zn>Pb;活性污泥脱氢酶毒性和硝化抑制毒性的测定结果与发光细菌毒性测定结果相比,灵敏度相对较低,测得的重金属ECSO相对较高,测得的活性污泥脱氢酶活性的抑制程度由大到小顺序依次为Cd>Hg>Zn>Pb,与测得的活性污泥硝化速率抑制程度大小顺序一致.但2者测得的EC50有所差别.为了更准确的判定重金属对活性污泥微生物的毒性影响.至少应取不同的重金属毒性终点指示指标做一组毒性实验,而不能以发光细菌毒性测定结果作为唯一的判定依据,这可能会过分夸大重金属对污水处理工艺的冲击能力,导致污水处理成本无谓增加.     

A/O_1/H/O_2工艺处理焦化废水硝化过程的实现及其抑制

针对焦化废水中的有毒污染物会对敏感易受干扰的硝化细菌产生不利影响从而破坏硝化过程稳定性的现象,采用A/O1/H/O2工艺处理焦化废水的实际工程为研究对象,根据工程运行的水质监测数据分析,发现几种主要污染物的浓度变化会对二级好氧段的硝化过程产生抑制影响。序批式毒性抑制实验结果表明,苯酚、硫氰化物和喹啉对硝化过程具有毒性抑制作用,半抑制浓度EC50分别为34.26、278.5和73.24 mg/L。当二级好氧工艺段运行正常时(C/N约4.3/1,pH8～8.5,DO 4～4.5 mg/L),出水氨氮浓度可低于5 mg/L,是由于焦化废水经厌氧/好氧/水解工艺后毒物浓度大幅下降,毒性得到削减,表明焦化废水生物处理A/O1/H/O2组合流化床工艺具有较强抵抗毒物抑制并实现高效的硝化作用。