Competition between polyphosphate- and glycogen-accumulating organisms in enhanced-biological-phosphorus-removal systems: effect of temperature and sludge age.

Temperature and sludge age were found to be important factors in determining the outcome of competition between polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating non-polyphosphate organisms (GAOs) and the resultant stability of enhanced-biological-phosphorus removal (EBPR). At 20 degrees C and a 10-day sludge age, PAOs were dominant in an anaerobic/aerobic (A/O) sequencing-batch reactor (SBR), as a result of their higher anaerobic-acetate-uptake rate and aerobic-biomass yield than GAOs. However, at 30 degrees C and a 10-day sludge age, GAOs were able to outcompete PAOs in the A/O SBR because of their higher anaerobic-acetate-uptake rate than PAOs. At 30 degrees C and a 5-day sludge age, GAOs coexisted with PAOs in the A/O SBR, resulting in unstable EBPR performance. At 30 degrees C, reducing the sludge age from 5 to 3 days improved the EBPR efficiency drastically, and the EBPR performance was stable. The maximum specific-anaerobic-acetate-uptake rates of GAO-enriched sludge were affected by temperature with the Arrhenius temperature coefficient theta of 0.042 (degrees C(-1) between 10 and 30 degrees C. The effect of sludge age (5 and 10 days) on the maximum specific-anaerobic-acetate-uptake rates of GAO-enriched activated sludge, however, was not significant. For the PAO-enriched activated sludge, the maximum specific-anaerobic-acetate-uptake rate did not change significantly between 20 and 30 degrees C, but significantly increased from 0.38 to 0.52 mmol-C/ mmol-C/h as the sludge age decreased from 10 to 3 days at 30 degrees C.     

Pretreatment of sludge with microwaves for pathogen destruction and improved anaerobic digestion performance.

A new way of generating Class A sludge using microwaves was evaluated through a series of laboratory-scale experiments. Microwaves provide rapid and uniform heating throughout the material. Other benefits of microwave treatment include instant and accurate control and selective and concentrated heating on materials, such as sludge, that have a high dielectric loss factor. Sludge was irradiated with 2450-MHz microwaves, and fecal coliforms were counted. Fecal coliforms were not detected at 65 degrees C for primary sludge and anaerobic digester sludge and at 85 degrees C for waste activated sludge when sludge was irradiated with 2450-MHz microwaves. During the bench-scale anaerobic digester operation, the highest average log reduction of fecal coliforms was achieved by the anaerobic digester fed with microwave-pretreated sludge (> or = 2.66 log removal). The anaerobic digester fed with microwave-irradiated sludge was more efficient in inactivation of fecal coliforms than the other two digesters fed with raw sludge and externally heated sludge, respectively. It took more than three hydraulic retention times for a bench-scale mesophilic anaerobic digester to meet Class A sludge requirements after feeding microwave-irradiated sludge. Class A sludge can be produced consistently with a continuously fed mesophilic anaerobic digester if sludge is pretreated with microwaves to reach 65 degrees C.     

Remediation of arsenic-contaminated soils and washing effluents

Laboratory experiments were conducted to determine the distribution of various arsenic species in tailings and soils. Other specific goal of the tests were to evaluate the extraction efficiency of arsenic using alkaline or acid washing, to determine optimum operational parameters of alkaline washing, and to evaluate the arsenic precipitation of washing effluents by pH adjustment or ferric chloride addition. Alkaline washing using sodium hydroxide was found to be favorable in removing arsenic from tailings or soils having a higher portion of arsenic in the operationally defined crystalline mineral fraction of crystalline oxide and amorphous aluminosilicates. This is due to the ligand displacement reaction of hydroxyl ions with arsenic species and high pH conditions that can prevent readsorption of arsenic because predominant negatively charged crystalline oxides do not attract the negatively charged oxyanions. For tailings, sodium hydroxide had 10-20 times higher extraction efficiencies than hydrochloric- or citric acid. The optimum concentration of sodium hydroxide for soil washing was determined to be 200 mM for all samples, while the optimum ratios were 10:1 and 5:1 for tailings and field/river sedimentary soils, respectively. The washing effluent of river soil was effectively treated by adjusting pH to 5-6 with hydrochloric acid, resulting in arsenic concentrations of <50 microgl(-1). In the case of field soil effluent, an addition of ferric chloride with a minimum mass ratio of 11 (Fe/As) was needed to reduce the arsenic below 50 microgl(-1).     

Growth of Brassica juncea under chromium stress: influence of siderophores and indole 3 acetic acid producing rhizosphere bacteria

Plant growth promoting rhizobacterial (PGPR) strains A3 and S32 have been shown to promote the growth of Brassica juncea under chromium stress which has been related to the microbial production of siderophores and indole 3 acetic acid (IAA). The aim of the present study is to evaluate the importance of siderophores and IAA producing PGPR on the growth of Brassica juncea under chromium stress. The production of IAA and siderophores were observed in the strains A3 and S32, respectively. Both PGPR strains promote the growth of Brassica juncea under chromium stress. The maximum growth was observed in plants inoculated with siderophores producing strain 32. Both the bacterial inoculum did not influence the uptake of chromium by plants. The present observation showed that PGPR isolates A3 and S32 are capable of protecting the plants against the inhibitory effects of chromium by producing the siderophores and IAA.     

Feasibility assessment of thermophilic anaerobic digestion process of food waste

In this study, a lab-scale thermophilic anaerobic digestion of food waste collected from G-district in Seoul was performed to assess its feasibility and applicability in field-scale biogas plants. Monitoring parameters included biogas production, methane composition, pH, alkalinity, and volatile fatty acid (VFA) concentrations. Accumulation of VFA caused successive depression in pH, which inhibited microbial activity of methane-forming microorganisms. Signals of biological instability and inhibition of methanogenesis suggest possible process failure, as indicated by reduction in methane production. Results revealed that modifications in certain conditions, such as decreased organic loading rate (OLR) or additional insertion of alkalinity, must be made for its application in industrial-scale biogas plants, and that thermophilic anaerobic digestion of food waste may not be feasible without any modification.     

Predicting the impacts of climate change on nonpoint source pollutant loads from agricultural small watershed using artificial neural network

This study described the development and validation of an artificial neural network (ANN) for the purpose of analyzing the e ects of climate change on nonpoint source (NPS) pollutant loads from agricultural small watershed. The runo discharge was estimated using ANN algorithm. The performance of ANN model was examined using observed data from study watershed. The simulation results agreed well with observed values during calibration and validation periods. NPS pollutant loads were calculated from load-discharge relationship driven by long-term monitoring data. LARS-WG (Long Ashton Research Station-Weather Generator) model was used to generate rainfall data. The calibrated ANN model and load-discharge relationship with the generated data from LARS-WG were applied to analyze the e ects of climate change on NPS pollutant loads from the agricultural small watershed. The results showed that the ANN model provided valuable approach in estimating future runo discharge, and the NPS pollutant loads.     

Towards a Simple Indicator of Biodiversity

Policy makers in Canada have suggested that the scientific community should develop an indicator of biodiversity change that can be implemented quite quickly without a major new investment in monitoring systems. We propose that such an indicator can be developed from the theory of species gradients in community ecology. The term 'species gradients' refers to the increasing diversity of species through time under stable conditions, and the increasing diversity of species with the increased use of available resources. This theory is reviewed under four different headings: evolutionary ecology, the energy theory, the resource productivity theory and the thermodynamic mechanism. The theoretical arguments provide a basis to propose detection of the 'leaky ecosystem' as an indicator of biodiversity. We propose that it is possible to detect the leaky energetics of ecosystems by means of routinely available observations of outgoing longwave radiation.     

Dynamic female preference for multiple signals in <Emphasis Type="Italic">Rhinogobius brunneus</Emphasis>

Many species base their choice of mates on multiple signals which provide them with different kinds of information. Choosers may assess the signals together to evaluate the overall quality of potential mates, but individuals often pay attention to different signals in different contexts. In Rhinogobius brunneus, a fish displaying exclusive male parental care, females generally prefer males showing larger first dorsal fins (FDF) and more active courtship displays as mates. Females choosing a mate usually initially assess the FDF and later utilize courtship for the final decision. In our experiments, females with different hunger states used different signals when selecting mates. Females in both hunger states preferred males with larger FDF in the first stage. In the second stage, well-fed females showed highly repeatable choice, whereas poorly fed females responded only to variation in the courtship activity of males. The males preferred by poorly fed females exhibited significantly higher offspring survival than nonpreferred males. Under conditions of food shortage, males allocate more energy to future reproduction at the expense of the present brood, and females may prioritize signals predictive of offspring survivorship over signals reflecting other aspects in male quality to minimize the losses in direct benefits. We conclude that R. brunneus females may employ information from both signals but dynamically adjust their prioritization of each signal to current conditions to ensure the choice that is currently most adaptive.     

A comparative study of aggressiveness in eastern North American field cricket species (genus <Emphasis Type="Italic">Gryllus</Emphasis>)

To understand the variation in aggressiveness and factors important for contest outcome, we quantified and compared agonistic interactions of four field cricket species in eastern North America: Gryllus fultoni (Orthoptera; Gryllidae), G. vernalis, G. pennsylvanicus, and G. rubens. The most aggressive behavior that we observed, the grapple, was frequently displayed in agonistic trials of G. pennsylvanicus and G. rubens. By contrast, we never observed this behavior in trials involving G. fultoni and G. vernalis. Consequently, species was the only significant variable affecting the variation in aggressiveness, whereas size difference, age difference, and contest duration had no significant effect. In species with high levels of aggressiveness, G. pennsylvanicus and G. rubens, the factors that might be indicative of resource holding potential such as size or age difference seemed to be significant for contest outcome. In species with low levels of aggressiveness, G. fultoni and G. vernalis, however, there were indications that contest outcomes were determined by aggressiveness itself rather than the size and age differences between opponents. Markov chain analyses revealed that the difference in aggressiveness between species with high and low levels of aggressiveness lay in a sequence of escalating behaviors: antennal fencing, mandible flare, and grapple. The escalated state of aggressiveness characterized by this behavioral sequence in G. pennsylvanicus and G. rubens seems to be the ancestral state in the North American Gryllus phylogeny. We argue that the loss of a tendency to use burrows in G. fultoni and G. vernalis might be related to low levels of aggressiveness in these species.     

Assessment of natural and calcined starfish for the amelioration of acidic soil

Quality improvement of acidic soil (with an initial pH of approximately 4.5) with respect to soil pH, exchangeable cations, organic matter content, and maize growth was attempted using natural (NSF) and calcined starfish (CSF). Acidic soil was amended with NSF and CSF in the range of 1 to 10 wt.% to improve soil pH, organic matter content, and exchangeable cations. Following the treatment, the soil pH was monitored for periods up to 3 months. The exchangeable cations were measured after 1 month of curing. After a curing period of 1 month, the maize growth experiment was performed with selected treated samples to evaluate the effectiveness of the treatment. The results show that 1 wt.% of NSF and CSF (700 and 900 °C) were required to increase the soil pH to a value higher than 7. In the case of CSF (900 °C), 1 wt.% was sufficient to increase the soil pH value to 9 due to the strong alkalinity in the treatment. No significant changes in soil pHs were observed after 7 days of curing and up to 3 months of curing. Upon treatment, the cation exchange capacity values significantly increased as compared to the untreated samples. The organic content of the samples increased upon NSF treatment, but it remains virtually unchanged upon CSF treatment. Maize growth was greater in the treated samples rather than the untreated samples, except for the samples treated with 1 and 3 wt.% CSF (900 °C), where maize growth was limited due to strong alkalinity. This indicates that the amelioration of acidic soil using natural and calcined starfish is beneficial for plant growth as long as the application rate does not produce alkaline conditions outside the optimal pH range for maize growth.