Treese D.P.,Environmental Engineering Program |
Clark S.E.,Environmental Engineering Program |
Baker K.H.,Life Science Program
Advances in Civil Engineering | Year: 2012
Subsurface infiltration and surface bioretention systems composed of engineered and/or native soils are preferred tools for stormwater management. However, the disturbance of native soils, especially during the process of adding amendments to improve infiltration rates and pollutant removal, may result in releases of nutrients in the early life of these systems. This project investigated the nutrient release from two soils, one disturbed and one undisturbed. The disturbed soil was collected intact, but had to be air-dried, and the columns repacked when soil shrinkage caused bypassing of water along the walls of the column. The undisturbed soil was collected and used intact, with no repacking. The disturbed soil showed elevated releases of nitrogen and phosphorus compared to the undisturbed soil for approximately 0.4 and 0.8m of runoff loading, respectively. For the undisturbed soil, the nitrogen release was delayed, indicating that the soil disturbance accelerated the release of nitrogen into a very short time period. Leaving the soil undisturbed resulted in lower but still elevated effluent nitrogen concentrations over a longer period of time. For phosphorus, these results confirm prior research which demonstrated that the soil, if shown to be phosphorus-deficient during fertility testing, can remove phosphorus from runoff even when disturbed. Copyright © 2011 Daniel P. Treese et al.
Crampton M.,University of Delaware |
Crampton M.,Delaware State University |
Ryan A.,Life Science Program |
Eckert C.,Life Science Program |
And 2 more authors.
Applied and Environmental Microbiology | Year: 2014
The use of green roofs is a growing practice worldwide, particularly in densely populated areas. In an attempt to find new methods for recycling crumb rubber, incorporation of crumb rubber into artificial medium for plant growth in green roofs and similar engineered environments has become an attractive option for the recycling of waste tires. Though this approach decreases waste in landfills, there are concerns about the leaching of zinc and other heavy metals, as well as nutrient and organic compounds, into the environment. The present study analyzed the impact of leachate from crumb rubber and zinc on the growth and viability of Salmonella enterica subsp. enterica serovar Typhimurium. Zinc was chosen for further studies since it has been previously implicated with other biological functions, including biofilm formation, motility, and possible cross-resistance to antimicrobial agents. The study showed that Salmonella can colonize crumb rubber and that crumb rubber extract may provide nutrients that are usable by this bacterium. Salmonella strains with reduced susceptibility (SRS) to zinc were obtained after subculturing in increasing concentrations of zinc. The SRS exhibited differences in gene expression of flux pump genes zntA and znuA compared to that of the parent when exposed to 20mMadded zinc. In biofilm formation studies, the SRS formed less biofilm but was more motile than the parental strain. © 2014, American Society for Microbiology.
Baker K.H.,Life Science Program |
Harrow D.I.,Life Science Program |
Ritchey B.A.,Life Science Program
Low Impact Development 2010: Redefining Water in the City - Proceedings of the 2010 International Low Impact Development Conference | Year: 2010
Greywater is household wastewater containing all used water except sewage. In order to conserve water, it has been proposed to use greywater for irrigational purposes. If this was the case, greywater would travel straight from the house to outside for use, minimizing the need for installing pipelines and such to carry the water elsewhere. However the widespread use of a variety of antibacterial and there subsequent presence in greywater raises concerns regarding impact on environment and health. Our research looked at the possible modification of microbial communities within the soil due to the presence of a commonly used antibacterial agent, triclosan. Along with the community structure, we also looked at any antibiotic resistance due to the constant exposure to triclosan. This experiment involved of three groups: control, greywater only and greywater with triclosan. Each group consisted of four soil filled columns treated with their designated solutions on a weekly basis. The effluent was collected from each column and cultured onto plates. Isolates were then taken from the plates for further testing. Our findings show that under constant exposure, the community structure did, in fact, change showing two very distinct heterotrophic populations between those that were treated with triclosan and those that were not. It was also seen that due to the exposure to triclosan, resistance to the four tested antibiotics (ampicillin, chloramphenicol, streptomycin and tetracycline) increases. Our results indicate that triclosan in greywater can have significant impacts on soil microbes. The changing of the microbial community structure could lead to a change in available nutrients and the form those nutrients are found. While the antibacterial products may be present in very minute concentrations, their constant presence may be selecting for bacteria that are resistant to all types of antibiotics, thus making it harder to treat. It is possible that all this is avoidable by treating the greywater before using it or by removing antibacterial products. In congruence with our data, there is a need for further investigation. © 2010 ASCE.