MODELING FECAL COLIFORM CONTAMINATION IN THE RIO GRANDE1

This study examines sources of fecal coliform in Segment 2302 of the Rio Grande, located south of the International Falcon Reservoir in southern Texas. The watershed is unique because the contributing drainage areas lie in Texas and Mexico. Additionally, the watershed is mostly rural, with populated communities known as “colonias.” The colonias lack sewered systems and discharge sanitary water directly to the ground surface, thus posing an increased health hazard from coliform bacteria. Monitoring data confirm that Segment 2302 is not safe for contact recreation due to elevated fecal coliform levels. The goal of the study was to simulate the observed exceedences in Segment 2302 and evaluate potential strategies for their elimination. Fecal coliform contributions from ranching and colonia discharges were modeled using the Hydrologic Simulation Program‐Fortran (HSPF). Model results indicated that the regulatory 30‐day geometric mean fecal coliform concentration of 200 colony forming units (cfu) per 100 milliliters is exceeded approximately three times per year for a total of 30 days. Ongoing initiatives to improve wastewater facilities will reduce this to approximately once per year for 14 days. Best management practices will be necessary to reduce cattle access to streams and eliminate all exceedences. The developed model was limited by the relatively sparse flow and fecal coliform data.     

一株高效降解废水有机质耐冷菌的筛选、鉴定及特性研究

利用生物法进行污水处理已被国内外广泛使用,但由于温度影响微生物的生长和繁殖,使其成为生物污水处理效率的限制因子.本研究从污水处理厂活性污泥中分离出5株在低温4℃条件下生长良好的菌株,其中菌株DW1在4℃条件下,96 h时可将初始COD为800 mg·L-1的生活污水有机物去除率高达67.7%.结合菌落形态特征、生理生化特性以及16S r DNA序列分析,将菌株DW1初步鉴定为假单胞菌(Pseudomonas sp.).菌株DW1对COD负荷较高的污水处理效果较好;接种量为3%(体积分数)、p H为7.0时,菌株对污水COD去除率和DHA活性较高.在4℃和25℃条件下,菌株DW1均在96 h对污水COD去除率和DHA活性最高,分别为71.2%、11.35μg·m L·h-1(以TF计)和78.8%、15.11μg·m L-1·h-1(以TF计).     

铁还原菌shewanella oneidensis MR-1对根表铁膜中砷运移的影响

水稻根表铁膜是控制砷在根际-植物体系转运的重要区域,但是其中铁还原微生物对砷运移的作用并不清楚.实验以吸附砷磷的水铁矿以及野外采集水稻根系为研究对象,分析铁还原菌Shewanella oneidensis MR-1还原铁膜内铁氧化物过程中,铁还原、砷释放和固定速率.研究表明铁还原菌Shewanella oneidensis MR-1可以将水稻根表铁膜中的Fe(Ⅲ)快速还原为Fe(Ⅱ)并释放到溶液中.溶液中的砷在48 h内达到最大值18μmol·L-1,之后逐渐下降,120 h之后,与最大值相比减少了约60%.利用吸附砷的水铁矿模拟铁膜砷释放过程发现,微生物的固定作用是造成溶液中砷含量下降的主要原因之一.本研究表明,促进根际微生物的大量生长,可能是降低土壤环境中砷风险的途径之一.     

甲烷氧化菌在填埋场覆盖层中的工程应用(Ⅱ):基质选择性及长效性

针对已筛选获得的甲烷氧化混合菌,选取填埋场覆盖土(LCS)、矿化垃圾(AR)和塘渣(TZ)3种填埋场周边易得的材料为供试生存基质,从基质选择性及长效性角度进行了甲烷减排应用条件的探究及使用效能评估.结果表明,在TZ、LCS、AR、TZ-AR和LCS-AR这5种生存基质中,TZ-AR最适合甲烷氧化混合菌的生长,且TZ与AR的复配比例以5∶5为最佳.甲烷氧化混合菌在TZ-AR的粒径≤4 mm和含水率为20%时具有最高甲烷氧化能力.一次性接种甲烷氧化混合菌在静态体系中的最佳使用有效期为31 d.其在接种量为0.08、0.16、0.20 m L·g-1和0.25m L·g-1时甲烷氧化速率无明显差异,从工程应用角度而言,8%的接种量为最佳.     

辽河口粪便污染指示菌的时空分布特征

2013年分别于夏季和秋季对辽河口海域的粪便污染指示菌(总大肠菌群、粪大肠菌群和肠球菌)及环境、水化学要素进行分析,研究粪便污染指示菌在海水中的数量、分布特征及其与环境、水化学指标间的相关性,在此基础上,选取河口地区合适的粪便污染指示菌.结果表明:夏季总大肠菌群数量在1.7×105~6.2×106CFU·L-1之间,粪大肠菌群数量在5.0×102~8.7×104CFU·L-1之间,肠球菌数量在1.0×101~2.5×102CFU·L-1之间;秋季总大肠菌群数量在5.0×102~1.1×105CFU·L-1之间,粪大肠菌群数量在4.0×102~1.0×103CFU·L-1之间,肠球菌数量在3~95 CFU·L-1之间.总大肠菌群、粪大肠菌群和肠球菌的数量变化与环境指标之间有着密切联系,特别是与盐度存在显著相关性;粪大肠菌群、肠球菌与水化学指标Si O4-4-Si、NH+4-N、TP和COD之间均存在显著相关性;其中粪大肠菌群与SiO4-4-Si和TP的相关性系数均大于0.742(p0.01),肠球菌与TP和COD的相关性系数均大于0.742.实验结果表明,辽河口粪便污染指示菌的数量在夏季高于秋季,近岸高于远海,其中粪大肠菌群和肠球菌的数量、分布特征与陆源污染物特别是氮磷的输入量密切相关,而且两者之间呈显著正相关关系.粪大肠菌群与肠球菌在一定程度上可以反映河口粪便污染情况,建议采用粪大肠菌群与肠球菌作为河口粪便污染的指示菌.     

Mg2+ improves biomass production from soybean wastewater using purple non-sulfur bacteria

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria (PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg²⁺ under the light-anaerobic condition. Results showed that with the optimal Mg²⁺ dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L, and biomass yield also was improved by 60%. Chemical Oxygen Demand (COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg²⁺ could promote the content of bacteriochlorophyll in photosynthesis because Mg²⁺ is the bacteriochlorophyll active center, and thus improved adenosine triphosphate (ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials (biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg²⁺, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.     

Enhanced metronidazole removal by binary-species photoelectrogenic biofilm of microaglae and anoxygenic phototrophic bacteria

High efficient removal of antibiotics during nutriments recovery for biomass production poses a major technical challenge for photosynthetic microbial biofilm-based wastewater treatment since antibiotics are always co-exist with nutriments in wastewater and resist biodegradation due to their strong biotoxicity and recalcitrance. In this study, we make a first attempt to enhance metronidazole (MNZ) removal from wastewater using electrochemistry-activated binary-species photosynthetic biofilm of Rhodopseudomonas Palustris (R. Palustris) and Chlorella vulgaris (C. vulgaris) by cultivating them under different applied potentials. The results showed that application of external potentials of -0.3, 0 and 0.2 V led to 11, 33 and 26-fold acceleration in MNZ removal, respectively, as compared to that of potential free. The extent of enhancement in MNZ removal was positively correlated to the intensities of photosynthetic current produced under different externally applied potentials. The binary-species photoelectrogenic biofilm exhibited 18 and 6-fold higher MNZ removal rate than that of single-species of C. vulgaris and R. Palustris, respectively, due to the enhanced metabolic interaction between them. Application of an external potential of 0V significantly promoted the accumulation of tryptophan and tyrosine-like compounds as well as humic acid in extracellular polymeric substance, whose concentrations were 7.4, 7.1 and 2.0-fold higher than those produced at potential free, contributing to accelerated adsorption and reductive and photosensitive degradation of MNZ.     

土地集约利用程度对华北潮土农田土壤微生物群落丰度和死生物物质积累的影响

土壤微生物决定着土壤生态系统的养分周转状况,其死生物物质在土壤有机碳(SOC)积累中发挥关键作用.然而,目前缺乏对土壤微生物群落丰度及其死生物物质如何响应农业土地集约利用程度调整的了解.为弥补这一知识缺口,基于土地集约化利用程度,设置小麦-玉米周年轮作(CC)、临时草地与小麦种植交替(TG)和多年生草地(PG)这3个处理开展长期定位试验,采用基于数字PCR和微生物标志物氨基糖的检测技术,以探究农业土地集约利用程度调整对土壤细菌和真菌数量,以及细菌、真菌和总微生物死生物物质C积累及其对土壤SOC封存贡献的影响,进一步明确驱动细菌、真菌和总微生物死生物物质C积累的关键因子.结果表明,与土壤细菌群落丰度相比,真菌群落丰度受到农业土地集约利用程度调整的强烈影响,随土地集约利用程度的降低而增加.在3种土地集约利用程度处理下,土壤总微生物死生物物质C均主导SOC积累,对SOC的贡献率分别达到52.78%、 58.36%和68.87%,呈现随土地集约利用程度降低而升高的趋势;真菌死生物物质C占总微生物死生物物质C的比例均大于80%,说明其对总微生物死生物物质C的绝对主导地位,且受土地集约利用程度降低...     

高效石油降解菌修复石油污染土壤与强化机制分析

利用定向驯化高效石油降解菌系对石油污染土壤进行为期120 d原位修复,考察生物强化修复效果、土壤理化性质和酶活性的变化,结合宏基因组测序及生物信息学分析揭示其强化机制.结果表明,与空白对照组(Ctrl)相比,生物修复组(Exp-BT)总石油烃降解率显著提升,增幅达81.23%; 高效石油降解菌生物强化修复期间土壤pH变化稳定,体系氧化能力提高,电导率处于适宜农业活动范围内; 脂肪酶和脱氢酶在修复期间保持较高活性; 另对初始污染土壤样本(B0)、驯化所得高效石油降解菌系样本(GZ)和生物修复后土壤样本(BT)的分析显示,门水平上变形菌门与放线菌门相对丰度增加17.1%,属水平上Nocardioides、Achromobacter、Gordonia和Rhodococcus等丰度明显上升,COG和KEGG物种与功能贡献度分析证明以上菌属对石油烃降解有重要贡献; 修复后土壤中发现高丰度的石油烃相关代谢酶及5个降解基因:alkM、tamA、rubB、ladA 和alkB,分析表明外源石油烃降解菌群的引入增强了微生物相关酶的代谢活性与相应功能基因的表达.     

硫酸盐还原菌对碱性和酸性农田土壤中重金属的钝化效果及其作用机制

通过土壤培养实验考察了硫酸盐还原菌（SRB）包括希瓦氏菌、梭状芽胞杆菌和两者混合菌对碱性和酸性农田土中有效态重金属（Cd、Pb、Cu和Zn）的钝化效果及其作用机制.结果表明,在相同接菌量下,希瓦氏菌处理组对碱性土中有效态重金属的钝化效果优于梭状芽胞杆菌和两者混合菌的处理组;而不同种类的SRB对酸性土中有效态重金属的钝化效果无显著差异.培养第20 d后土壤中有效态重金属的钝化率不再显著变化.SRB处理对碱性土中有效态重金属的钝化率可达80%以上,而对酸性土中有效态重金属的钝化率低于40%.在碱性土中,SRB能够有效还原SO₄^2-,并且提高土壤pH值,使S^2-可与重金属紧密结合,显著提高有效态重金属钝化率.尽管SRB使酸性土壤pH值升高,但土壤仍然呈酸性使SO₄^2-还原受到抑制,不利于有效态重金属的钝化.总体来看,SRB适用于碱性和酸性土壤的重金属污染治理,但与酸性土壤相比,SRB对碱性土壤中有效态重金属的钝化效果更好.