Antimicrobial susceptibility of Escherichia coli isolated from shrimp (Litopenaeus vannamei) and pond environment in northeastern Brazil

This study aimed to test the susceptibility of Escherichia coli strains isolated from the water, bottom sediments and individuals cultivated in shrimp farm ponds, to antibiotics belonging to different families, namely B-Lactams: Imipenem (IPM; 10 μ g), Ampicillin (AMP; 10 μ g), Cephalothin (CEP; 30 μ g), Cefoxitin (FOX; 30 μ g), Ceftriaxone (CRO; 30 μ g); Tetracycline: Tetracycline (TCY; 30 μ g); Aminoglycosides: Gentamicin (GEN; 10 μ g), Amikacin (AMK; 30 μ g); Chloramphenicol: Chloramphenicol (CHO; 30 μ g); Fluoroquinolones: Ciprofloxacin (CIP; 5 μ g); Nitrofurans: Nitrofurantoin (NIT; 300 μ g); Sulfonamides: Trimethoprim-Sulfamethoxazole (SXT; 30 μ g); Quilononas: Nalidixic Acid (NAL; 30 μ g). In the laboratory, the method of dissemination (Test Kirby-Bauer) was performed in order to fulfill the antibiogram tests. The results showed high indices of resistance to Imipenem, Cephalothin and Ampicillin. Chloramphenicol, Nitrofurantoin, Cefoxitin, Ceftiaxone and Ciprofloxacin have displayed the highest index of sensitive strains. The antibiotic resistance index (ARI) and the multiple resistance index (MAR) varied within the ranges of 0.068–0.077 and 0.15–0.39, respectively. More than 90.5% of strains of Escherichia coli showed a variety of resistance profiles to the tested antibiotics. The high indices of resistance may be a consequence of indiscriminate use of antibiotics, but also the transfer of resistance through mobile genetic elements found in shrimp farms.     

Biohydrogen production through fermentation using liquid swine manure as substrate

In this paper, continuous production of hydrogen through fermentation with liquid swine manure as substrate was researched using a semi-continuously fed fermenter (8 L in total volume and 4 L in working volume). The pH and temperature for the fermenter were controlled at 5.3 ± 0.1 and 35 ± 1°C, respectively, throughout the experiment. Three hydraulic retention times (16, 20, and 24 h) were investigated for their impact on the efficiency and performance of the fermenter in terms of hydrogen yields. The results indicate that hydraulic retention time (HRT) has a strong influence on the fermenter performance. An increasing HRT would increase the variation in hydrogen concentration in the offgas. To produce hydrogen with a fairly consistent concentration, the HRT of the fermenter should not exceed 16 h, which, however, did not appear to be short enough to control methanogenesis because the offgas still contained about 5% methane. When methane content in the offgas exceeded 2%, an inverse linear relationship between hydrogen and methane was observed with a correlation coefficient of 0.9699. To increase hydrogen content in the offgas, methane production has to be limited to below 2%. Also, keeping oxygen content in the fermenter below 1.5% would increase the hydrogen concentration to over 15%. The product to substrate ratio was found to be around 50% for the fermenter system studied, evidenced by the observation that for every 6 liters of manure fermented, 3 liters of pure hydrogen were produced, which was significant and encouraging.     

Organophosphorus insecticide residues in farm ditches of the Lower Fraser Valley of British Columbia

Abstract

Farm ditches flowing into three important rivers in the Lower Fraser Valley of British Columbia, Canada, were sampled periodically at seven locations from July to December in 1991, to determine the occurrence and levels of seven organophosphorus (OP) insecticides. Based oh sales records for the year, the uses of OP insecticides in this area were as follows: malathion > diazinon > parathion > dimethoate > azinphos‐methyl > fensulfothion, but no sales of chlorfenvinphos. Residues of parathion, diazinon, fensulfothion, dimethoate and chlorfenvinphos were detected at levels ranging from 1 ‐ 7,785 >μg/kg in cropped soils collected from areas adjacent to the sites for sampling ditch water and sediments. Malathion and azinphos‐methyl were not detected in any of the substrates studied, demonstrating their rapid degradation in the environment. Diazinon and dimethoate were consistently found in ditch water at seven locations, with an average concentration of 0.07 μg/L and 0.27 μg/L, respectively. Fensulfothion and parathion, with an average concentration of 0.08 μg/L and 0.17 μg/L, respectively, were sporadically found in ditch water at two locations. In ditch sediments, diazinon was detected at three locations and fensulfothion at two. The average concentrations of these two insecticides were 16 μg/kg and 9 jug/kg, respectively. The potential impact on aquatic organisms of these OP insecticides in ditches is discussed.     

耐寒抗逆藻种筛选及其处理寒区沼液效果

针对寒区低温条件下采用沼液养藻进行资源化存在能耗高、效率低的问题,筛选了可快速适应15 ℃低温环境的6株微藻。考察了其对沼液氨氮（ammonia nitrogen,NH₄⁺-N）耐受力与污染物去除效果,并探索了微藻对低温抑制的解除机制。结果表明,6株微藻在15 ℃下可耐受400 mg∙L⁻¹ NH₄⁺-N,生物量最高可达204.67~223.79 mg∙L⁻¹。叶绿素a、叶绿素b、类胡萝卜素浓度为4.77~5.84、1.73~2.23、1.46~2.09 mg∙L⁻¹。NH₄⁺-N、总磷（total phosphorus,TP）去除率分别为44.09%~47.02%与6.63%~15.60%。培养10 d后,衣藻（W-4）生物量最高（223.79 mg∙L⁻¹）;NH₄⁺-N（47.02%）、TP（15.60%）去除效果最好;总叶绿素、叶绿素a、叶绿素 b、类胡萝卜素浓度分别达8.07、5.84、2.23与2.09 mg∙L⁻¹,比极地裂丝藻和普通衣藻分别高17.09%~55.81%、7.66%~9.49%、264.49%~437.93%、35.89%~42.88%、46.97%~47.87%、13.48%~31.27%、31.21%~42.73%。较高的类胡萝卜素含量表明,沼液中高营养盐浓度可能削弱了微藻在低温条件下细胞内生成的氧化应激（ROS）的伤害,提高了藻体生物量。所筛藻种具有耐低温、耐高氨氮的双重功能,且生长周期较短,为寒区微藻养殖及沼液资源化提供了宝贵的种质资源。     

A/O系统处理低C/N奶牛场废水中的抗生素

为处理奶牛场废水中常检出抗生素,考察了小试规模缺氧/好氧(A/O)系统对低C/N奶牛场废水中常规污染物和抗生素的处理效果。当进水COD、总氮、氨氮和总磷分别在1 242~4 350、830~1 367、818~1 291和6~12 mg·L⁻¹,A池和O池水力停留时间(HRT)分别为3~4 d和2.05~5.4 d时,系统出水COD<400 mg·L⁻¹、氨氮<10 mg·L⁻¹、总氮去除率为40%~60%(无外加碳源)、总磷基本没有去除;通过调节硝化液回流比(1.0∶1~1.3∶1)可在进水COD/总氮≥3.1时实现碱度的自给自足;对11种磺胺类和8种β-内酰胺类抗生素研究发现,共检出9种磺胺类和1种β-内酰胺类抗生素(总浓度为5.89~17.31 μg·L⁻¹),系统对抗生素的总去除率大于93%;先后2次向进水中人为添加8种磺胺类抗生素(每种浓度先后为50 μg·L⁻¹和200 μg·L⁻¹)不会影响系统运行的稳定性,且抗生素的总去除率大于90%,A池和O池的抗生素去除率分别为15.0%~34.2%和69.1%~91.4%;在O池中的HRT降低50%时,系统对抗生素的总去除率基本不变。除甲氧苄啶外,其余7种磺胺类抗生素主要在O池中均得到去除,这与其分子结构中的S—N键有关。以上结果对奶牛场废水处理后还田具有重要的参考价值。     

Atrazine leaching through surface and subsurface of a tropical Oxisol

The fate of ¹⁴C atrazine was investigated using microcosms and an undisturbed Red-Yellow Latossol (Oxisol) under simulated rainfall conditions of 200 mm water month^?1. Experiments were carried out using microcosm cores, the first with an uncovered surface soil; the second set with uncovered subsurface soil; the third with subsurface soil covered with 3 cm of cow manure and the last with subsurface soil covered with 5 cm of grass straw. Average values for the amount of atrazine leached after 60 days were as follows: surface soil 1.6%; subsurface 47.3%; subsurface plus manure 17.3% and subsurface plus straw 24.8%. In the surface soil, 53% of the ¹⁴C atrazine remained within the upper 1 cm, while in the subsurface microcosms the atrazine was more evenly distributed. The authors report that surface soil was retained atrazine and its metabolites for 60 days. The addition of a straw or manure covering to exposed subsoil helped to retard atrazine leaching.     

响应面法优化厌氧消化过程中抗生素去除效果

为了深入探究厌氧消化过程中厌氧消化时间、猪粪含固率、抗生素初始质量分数对磺胺二甲嘧啶和磺胺甲噁唑去除效果的相互影响,本研究采用响应面优化法,以厌氧消化时间、猪粪含固率、抗生素质量分数为3因素,以抗生素残留质量分数和厌氧消化产气量为响应值,探索使用厌氧消化法降低抗生素残留质量分数的最佳工艺参数。结果表明,根据响应面分析可知,当猪粪含固率为3%,初始质量分数为40 mg·kg⁻¹TS,厌氧消化时间为30 d,预测的磺胺二甲嘧啶残留质量分数最低为0.428 mg·kg⁻¹TS;当猪粪含固率为7%,磺胺二甲嘧啶初始质量分数为40 mg·kg⁻¹TS,厌氧消化时间为20 d,预测的磺胺甲噁唑残留质量分数最低为0.1063 mg·kg⁻¹TS。综合产气量考虑,当猪粪含固率为5.58%,磺胺二甲嘧啶初始质量分数为80 mg·kg⁻¹TS,厌氧消化时间为27.8 d,预测的产气量最高为389.3 mL·kg⁻¹TS。当猪粪含固率为5.89%,磺胺甲噁唑初始质量分数为80 mg·kg⁻¹TS,厌氧消化时间为30 d,预测的产气量最高为389.6 mL·kg⁻¹TS。该研究可为猪粪厌氧消化过程中的降低抗生素残留、提高产气量的工艺优化提供参考。     

改进型升流式固体反应器处理猪粪污新工艺研究

对传统升流式固体反应器（USR）进行改进,反应器内设置专用搅拌器,搅拌器间歇开启,在保留USR各项优势的前提下,使料液与厌氧微生物接触更充分,反应温度更均匀,提高产气率,同时还解决了传统USR的“结壳”问题,提高了反应器的传质效率、甲烷产气率和COD去除效果。进料含固量在12.1%时,水利停留时间为17 d,反应器最高容积负荷达到4.9 kg COD/(m³·d),产气速率为2.55 m³/(m³·d),产气率达到0.359 m³/kg干猪粪。     

化学沥浸与硫化钠钝化联合处理猪粪中重金属

利用柠檬酸浸提猪粪中重金属,减少总量,再利用硫化钠钝化经柠檬酸浸提后的猪粪残渣,降低猪粪中剩余重金属的生物可利用性。柠檬酸浸提实验表明：0.2 moL·L-1柠檬酸与猪粪按固液比1:5混合,反应24 h,对猪粪中Cu、Zn、Mn的浸出率为18.10%、66.16%、43.85%;硫化钠投加量5%,钝化7 d,猪粪中离子交换态Cu、Zn、Mn的浓度由酸浸后的14.08、116、81.75 mg·kg-1降为8.77、12.04、21.02 mg·kg-1,硫化钠对酸浸后猪粪中Cu、Zn的钝化率为52.00%、63.72%,猪粪残渣中离子交换态Mn所占全量的比例由对照组的30.22%降到7.77%;柠檬酸酸浸和硫化钠钝化对猪粪中Cu、Zn、Mn总处理效率为73.00%、61.44%、29.90%。重金属分离技术和钝化技术联合处理猪粪中重金属,可以有效减少猪粪中Cu、Zn、Mn的总量并降低其生物可利用性。