Monitoring bacterial community structure and variability in time scale in full-scale anaerobic digesters

Using a high-throughput pyrosequencing technology, this study assessed bacterial community structure and time-scale variability in great detail in seven full-scale anaerobic digesters operated variously in terms of influent substrate, digestion temperature, and reactor configuration. Pyrosequencing generated a total of 83,774 sequence reads from 40 digester sludge samples collected monthly for six months. The highest number of sequence reads were detected within Proteobacteria (20.5%), followed by those within Bacteroidetes (19.7%), Firmicutes (17.8%), and Chloroflexi (4.8%). The relative composition of bacterial populations was varied within the digesters as well as between the digesters, and the bacterial community structures were mainly influenced by digestion temperature. Detailed bacterial community structures were assessed by analyzing the operational taxonomic units (OTUs) based on 97% sequence similarity, which resulted in a total of 9051 OTUs. Among these, a total of 31 core OTUs were analyzed and inferred phylogenetically, which enabled us to classify the sequences within an unclassified phylum. Unclassified sequences were mostly affiliated with the sequences within Spirochaetes and Firmicutes. Interestingly, numerically dominant novel phylotypes (18% of the total sequence reads) presumably involved in anaerobic digestion within Spirochaetes were identified. Temporal variability was further explored using a non-metric multidimensional scaling ordination which demonstrated that the variability of the bacterial community within the digesters was smaller than between digesters. Correlation analysis demonstrated that digester performance and operational conditions affected the pattern of bacterial community in the ordination. Additionally, a multi-response permutation procedure revealed that the bacterial communities within the digesters were more similar than those belonging to other digesters statistically, demonstrating a patchiness of the digesters in the distribution of bacterial populations. Overall, this study revealed the correlation of bacterial community structure and time-scale variability with digester performance and operating conditions.     

Concentrations of As, Be, Cr, Hg, Mn, and Ni in ambient air at four urban locations in Japan

The metal concentrations of As, Be, Cr, Hg, Mn, and Ni in ambient air were measured at four sites in Japan from October 1997 to March 2006. The mean metal concentration data measured from the four sites (K1, K2, M, and Y) are found on the order of Mn > Cr–Ni > As > Hg > Be. The concentrations of Mn with the highest mean value were fairly variable across four sites such as 45.9 ± 42.8 (K1), 25.6 ± 19.4 (K2), 22.5 ± 19.7 (M), and 25.4 ± 19.8 ng m^???3 (Y). In contrast, the concentrations of Be with the lowest mean value were less variable across four sites with means of 0.03 to 0.04 ng m^???3. Inspection of the seasonal patterns indicates the peak occurrence of most metals during spring, although relative dominance during winter is seen at the most polluted area (K1). Evaluation of long-term patterns indicates that the noticeably high values of metals in the early stage of study reduced gradually across the years, although the metal concentration levels in most areas were affected significantly by anthropogenic activities. However, efforts to control pollution levels seemed to gradually contribute to a decrease in metal concentration levels of all study sites through the years.     

Photochemical degradation of atrazine in UV and UV/H2O2 process: pathways and toxic effects of products

The degradation of atrazine in aqueous solution by UV or UV/H₂O₂ processes, and the toxic effects of the degradation products were explored. The mineralization of atrazine was not observed in the UV irradiation process, resulting in the production of hydroxyatrazine (OIET) as the final product. In the UV/H₂O₂ process, the final product was ammeline (OAAT), which was obtained by two different pathways of reaction: dechlorination followed by hydroxylation, and the de-alkylation of atrazine. The by-products of the reaction of dechlorination followed by hydroxylation were OIET and hydroxydeethyl atrazine (OIAT), and those of de-alkylation were deisopropyl atrazine (CEAT), deethyl atrazine (CIAT), and deethyldeisopropyl atrazine (CAAT). OIAT and OAAT appeared to be quite stable in the degradation of atrazine by the UV/H₂O₂ process. In a toxicity test using Daphnia magna, the acute toxic unit (TUa) was less than 1 of TUa (100/EC₅₀, %) in the UV/H₂O₂ process after 30 min of reaction time, while 1.2 to 1.3 of TUa was observed in the UV process. The TUa values of atrazine and the degradation products have the following decreasing order: OIET> Atrazine> CEAT≈CIAT> CAAT. OIAT and OAAT did not show any toxic effects.     

Optimal operating parameters in the composting of swine manure with wastepaper

Abstract

A series of experiments were conducted to determine the optimal conditions for composting of swine manure and wastepaper. The aeration rate and mixing ratio were the variables investigated. In the first study (Study‐1), four experiments each with the same mixing ratio but a different aeration rate were carried out. In the second study (Study‐2), different mixing ratios were investigated, each however with the same aeration rate which was found to be optimal from Study‐1. Composting efficiencies were evaluated on the temperature profile and the reduction of C/N ratio. From the aeration rates of 200, 500, 1000, and 1500 mL/min.kg_vs that were evaluated, the aeration rate of 500 mL/min.kg_vs and higher showed good results. In Study‐2, where the initial C/N ratios were 20, 25, 30, and 35 respectively, the C/N ratio of 30 was found to be optimal. In conclusion, the composting of swine manure with the amendment of wastepaper was best carried out at the aeration of >500 mL/min.kg_vs and C/N ratio of 30.     

Effect of Solids Concentration on Bacterial Leaching of Heavy Metals from Sewage Sludge

Abstract

Microbial metal leaching from sewage sludge (2-9% w/v) was carried out with the iron-oxidizing bacterium Thiobacillus ferrooxidans. Measurements of pH, oxidation-reduction potential, and concentration of Fe²⁺ indicated that T. ferrooxidans was effective in removing metals from an incubation bath containing less than 5% sludge solids concentration. Specifically, Cu leaching was completely suppressed at a high solids concentration of 9% (w/v). Results indicated that the deactivation of T. ferrooxidans at a high sludge content was mainly due to the presence of inhibiting materials such as organic matter. A mixed culture of sulfur-oxidizing bacteria was obtained by enrichment from anaerobically digested sewage sludge to enhance the efficiency of the microbial leaching process. These bacteria were much more effective in metal leaching than was iron-oxidizing T. ferrooxidans. At 9% (w/v) solids concentration, the leaching efficiencies of Zn and Cu were 78% (2.66 g/kg dry sludge) and 59% (1.36 g/kg dry sludge), respectively. Therefore, when removing heavy metals from the anaerobically digested sewage sludge, the indigenous sulfur-oxidizing bacteria isolated in the current study were more efficient than T. ferrooxidans, especially at high sludge solids concentrations.     

Investigation of hit-and-run crash occurrence and severity using real-time loop detector data and hierarchical Bayesian binary logit model with random effects

Objective: Most of the extensive research dedicated to identifying the influential factors of hit-and-run (HR) crashes has utilized typical maximum likelihood estimation binary logit models, and none have employed real-time traffic data. To fill this gap, this study focused on investigating factors contributing to HR crashes, as well as the severity levels of HR.

Methods: This study analyzed 4-year crash and real-time loop detector data by employing hierarchical Bayesian models with random effects within a sequential logit structure. In addition to evaluation of the impact of random effects on model fitness and complexity, the prediction capability of the models was examined. Stepwise incremental sensitivity and specificity were calculated and receiver operating characteristic (ROC) curves were utilized to graphically illustrate the predictive performance of the model.

Results: Among the real-time flow variables, the average occupancy and speed from the upstream detector were observed to be positively correlated with HR crash possibility. The average upstream speed and speed difference between upstream and downstream speeds were correlated with the occurrence of severe HR crashes. In addition to real-time factors, other variables found influential for HR and severe HR crashes were length of segment, adverse weather conditions, dark lighting conditions with malfunctioning street lights, driving under the influence of alcohol, width of inner shoulder, and nighttime.

Conclusions: This study suggests the potential traffic conditions of HR and severe HR occurrence, which refer to relatively congested upstream traffic conditions with high upstream speed and significant speed deviations on long segments. The above findings suggest that traffic enforcement should be directed toward mitigating risky driving under the aforementioned traffic conditions. Moreover, enforcement agencies may employ alcohol checkpoints to counter driving under the influence (DUI) at night. With regard to engineering improvements, wider inner shoulders may be constructed to potentially reduce HR cases and street lights should be installed and maintained in working condition to make roads less prone to such crashes.     

The application and development of country-specific parameters for accurate estimations of methane emissions from solid-waste disposal sites

To identify the application and development of country-specific parameters for methane emission estimations from solid-waste disposal sites, National Inventory Reports of 41 Annex I countries and National Communications of ten non-Annex I countries of the United Nations Framework Convention on Climate Change were analyzed. A first-order decay method was applied to 38 out of 41 Annex I countries and to five out of ten non-Annex I countries in national GHG inventory submissions up to 2012. Country-specific parameters were approximately 26 % of the total number of parameters used in the 38 Annex I countries and were mostly developed for degradable organic carbon and reaction constants that cover certain waste compositions. The UNFCCC encourages countries to develop more country-specific parameters reflecting the distinct characteristics of each country in which solid-waste disposal site is a key source. Depending on a country’s condition, a stepwise approach regarding the development of country-specific parameters needs to be done so as to improve the accuracy of methane emission estimates in the solid-waste disposal site category.     

Sea lamprey orient toward a source of a synthesized pheromone using odor-conditioned rheotaxis

Characterization of vertebrate chemo-orientation strategies over long distances is difficult because it is often not feasible to conduct highly controlled hypothesis-based experiments in natural environments. To overcome the challenge, we couple in-stream behavioral observations of female sea lampreys (Petromyzon marinus) orienting to plumes of a synthesized mating pheromone, 7α,12α,24-trihydroxy-5α-cholan-3-one-24-sulfate (3kPZS), and engineering algorithms to systematically test chemo-orientation hypotheses. In-stream field observations and simulated movements of female sea lampreys according to control algorithms support that odor-conditioned rheotaxis is a component of the mechanism used to track plumes of 3kPZS over hundreds of meters in flowing water. Simulated movements of female sea lampreys do not support that rheotaxis or klinotaxis alone is sufficient to enable the movement patterns displayed by females in locating 3kPZS sources in the experimental stream. Odor-conditioned rheotaxis may not only be effective at small spatial scales as previous described in crustaceans, but may also be effectively used by fishes over hundreds of meters. These results may prove useful for developing management strategies for the control of invasive species that exploit the odor-conditioned tracking behavior and for developing biologically inspired navigation strategies for robotic fish.     

A review on the usage of POP pesticides in China, with emphasis on DDT loadings in human milk

This article attempts to review the usage of nine pesticides included in the 12 Stockholm Convention persistent organic pollutants (POPs) in China and to examine the extent of DDT contamination in human milk, focusing on the Chinese populations. By comparing all the data available concerning DDTs in human milk from 19 countries, it is revealed that the Chinese populations exhibit rather high concentrations of DDTs, due to the fact that China has been a major producer and consumer of DDTs in the past, and also uses DDT for vector control, resulting in higher background levels of DDTs in different ecological compartments. The high body loading of DDT in Chinese populations is also related to the high dietary intake due to contamination of food. When comparing the data obtained recently (1998-2002), the coastal populations such as Guangzhou (DDE+DDT 2.13 microgg(-1) fat), Hong Kong (2.87 microgg(-1) fat) and Dalian (2.13 microgg(-1) fat) contain higher concentrations of DDTs which may reflect the dietary difference of consuming more meat and fish, than other Chinese populations (Beijing 1.96 microgg(-1) fat; Shenyang 0.87 microgg(-1) fat). In general, the rather low ratio of DDE/DDT (e.g., 4.07 for Guangzhou) of the Chinese milk samples reflected the more recent releases of DDT. It is recommended to impose a tighter control on the use of DDT for vector control as well as for agricultural application, conduct regular monitoring of DDT concentrations in different ecological compartments which include air, water, sediment and biota. Human milk is a preferred indicator reflecting human body loadings of POPs including DDTs, as well as the risk which may impose on our next generation. A national wide survey is needed to investigate the intake of POPs, including POP pesticides, due to dietary differences, with a strong focus on the more sensitive populations, e.g., coastal residents who consume a large amount of fish.