Search

This study involved the investigation of a contaminated soil problem in Gateshead, UK. The site was previously a dumping area from industrial activities for over a hundred years and generated problems of high sulphate concentration and heavy metals in both the soil and the leachate which discharges into the River Tyne. The combination of such contaminants has not been widely investigated in the area of contaminated soil. The study was therefore divided into 2 parts, namely bioremediation of the contaminated soil and leachate treatment by reverse osmosis. The bioremediation study involved treatability tests which included slurry, microbial growth and column tests. The reverse osmosis study involved membrane fouling and leachate pre-treatment experiments. The bioremediation study stimulated the indigenous microorganisms by the addition of nutrients and carbon sources. The soil slurry and microbial growth tests determined the combination of nitrogen and phosphorus required to produce higher C02 evolution as an assessment of microbial activity. It was found in the column tests that the addition of a carbon source and appiopriate nutrient combinations resulted in a significant reduction of sulphate in both the leachate and the soil matrix. Furthermore, this was also accompanied by an increase in the microbial population in the soil matrix. It was also considered that- assimilatory sulphate reduction by microorganisms had taken place since H2S production could not be detected in the open system of the column. However, the high pH of the soil that was higher than 8 possibly caused H2S production undetected in this study. Zinc, manganesea nd copper,i n contrastw ere not reducedi n the soil matrix. Only arsenic showed significant reduction in the soil columns. Heavy metals were precipitateda nd were still presenti n high concentrationsin the leachatea nd would require further treatmenti n the liquid phase.T his was demonstratedb y the study of the use of a LPROM (Low PressureR everseO smosisM embrane)t o treat leachate from the contaminated soil. The reverse osmosis study showed that zinc and arsenic could be reduced by up to 86% and 97% respectively. Sulphate was also satisfactorily reduced up to 99%. However, the study on membrane fouling confirmed that the sulphate concentration was the main effect of fouling. Ferric chloride, aluminium sulphate, barium chloride and polyelectrolyte Zetag 92 were used for coagulation-flocculation in the pretreatment of the leachate. The study revealed that the sulphate concentration could only be reduced at the most by 43% using a FeC13, BaC12 and Zetag 92 combination. FeC13 showed better floc characteristics than alum whereas BaC12 improved sulphate removal but increased the turbidity in the supernatants. However, the use of BaC12 would significantly increase the cost of pretreatment. The study recommended a further investigation into the use of a range of readily available carbon, nitrogen and phosphorous sources in the soil column or at pilot-scale for designing a full-scale bioremediation system. Meanwhile, an investigation into other leachate pretreatment methods such as continuous microfiltration or anti-scalant addition was also suggested.

Moisture and microbial growth are common in office environments and have been associated with adverse respiratory health effects among occupants. The purpose of this study was to investigate the association between different in-situ quantitative moisture measuring methodologies and to compare the moisture results with the presence of microbial growth. The site selected for this study was a recently built, commercially owned and operated office building. The roof envelope of the office building was destructively sampled at fifteen representative locations to characterize the conditions present inside the roof envelope. The characterization consisted of measuring the surface dampness of the building materials and establishing the presence or absence of microbial growth. The presence or absence of free water was determined by cobalt chloride (CoCl2) indicator strips. Material surface dampness was quantified by two moisture meters, one measuring on a percent wood moisture equivalent (%WME) scale and another measuring on a relative scale. The presence and speciation of viable microorganisms were determined by surface swab samples. The results showed that there was a significant correlation between the moisture results measured by the two different moisture meters (r=0.94, p2 indicator strips (OR=1.07, p=0.022). Additionally, a significant relationship was observed between %WME and the presence of specific indicator microorganisms that are indicative of building dampness and active microbial growth (OR=1.056, p=0.022). The results indicate that moisture quantification using moisture meters can be used to predict microbial growth in the field.

Due to the lead spike and its related health concern in the DC area, Point-of-Use (POU) filters were installed at public schools to reduce lead concentrations in water. However, the installation of POU filter could possibly lead to the growth of bacteria inside the filters, which could lead to health concerns. Therefore, the potential effects of POU filters on microbial growth was investigated. To explore the cause of filter effects on microbial growth, a sampling campaign was carried out between July and December 2017 from 25 outlets within 5 elementary schools in the DC area. The applicability of flow cytometry results as a quantification method was validated and then used to quantify the biological growth. Our results revealed that the installation of POU filters may lead to nitrification and an increase in microbial growth. Along with the increase in microbial growth, the microorganism community "fingerprints" based on flow cytometry data showed that the installation of filter could also shift the community distribution of bacteria based on their morphology. This study serves as a preliminary study to investigate the mechanics of microbial colonization on POU filters.

A numerical model for subsurface solute transport is developed and applied to a contaminated field site. The model is capable of depicting multiple species transport in a three-dimensional, anisotropic, heterogeneous domain as influenced by advection, dispersion, adsorption, and biodegradation. Various hydrocarbon contaminants are simulated as electron donors for microbial growth, with electron acceptors utilized in the following sequence: oxygen, nitrate, Mn(IV), Fe(III), sulfate, and CO₂. In addition, the model accounts for products of biodegradation such as Mn (II), Fe(II), H₂S, and CH₄. Biodegradation of each hydrocarbon substrate follows Monod kinetics, modified to include the effects of electron acceptor and nutrient availability. Inhibition functions permit any electron acceptor to inhibit utilization of all other electron acceptors that provide less Gibbs free energy to the microbes. The model assumes that Fe(III) and Mn(IV) occur as solid phase ions, while the other electron acceptors are dissolved in the aqueous phase. Microbial biomass is simulated as independent groups of heterotrophic bacteria that exist as scattered microcolonies attached to the porous medium. Diffusional limitations to microbial growth are assumed to be negligible. In order to verify the accuracy of the computer code, the model was applied to simple, hypothetical test cases, and the results were compared to analytical solutions. In addition, a sensitivity analysis showed that variations in model inputs caused logical changes in output. Finally, the capabilities of the model were tested by comparing model output to observed concentrations of hydrocarbons, electron acceptors, and endproducts at a leaking UST site. The model was calibrated using historical site data, and predictive capabilities of the model were tested against subsequent sets of field data. The model was used to examine the effect of porous media heterogeneities on contaminant transport and biodegradation. The turning bands method was used to produce hypothetical, yet realistic heterogeneous fields describing hydraulic conductivity, initial biomass concentration, and the maximum rate of substrate utilization. When the available electron acceptor concentrations were small compared to the hydrocarbon concentration, the overall rate of hydrocarbon mass loss increased with time, even as hydrocarbon concentrations decreased. This trend is the opposite of what would be predicted by a first order decay model.

The rate of nucleic acid synthesis was used as a measure of growth and production in planktonic marine microbial assembleages. Synthesis rates were measured by a new procedure which utilizes tritiated adenine as a precursor to both ribonucleic and deoxyribonucleic acid. This methodology provides a measure of the growth and production of the entire microbial community, including both the autotrophic and heterotrophic components, and represents an important advance in the study of aquatic microbiology. The 3H-adenine technique was extensively evaluated in the laboratory. Mathematical modeling was used to examine the relationship between the direct precursor to adenine incorporation and the nucleic acid endproduct. The technique was also calibrated with a variety of representative marine microbes grown under controlled conditions. These studies demonstrated that accurate rates of nucleic acid synthesis can be derived provided a few simple precautions are observed. The procedure was applied to the study of microbial growth and production in both the euphotic and the mesopelagic zones of the oligotrophic oceans around Hawaii. In the euphotic zone, microbial growth rates ranged from 0.5 to 0.8 day^-1, and microbial production integrated over the 0 to 150 m depth interval was 400 mg C m^-2 day^-1. Microbial growth rates in the mesopelagic depth interval were greater than in the overlying waters, and production integrated over the 150 to 900 m depth interval was approximately twice as great as in the euphotic zone. It is hypothesized that organic matter is rapidly and efficiently recycled in the mesopelagic, or that an additional source of energy, beyond that derived from autotrophic production in the euphotic zone, exists in this environment. Direct comparisons were also made of microbial production, extrapolated from DNA synthesis measurements, and 14CO2 primary production on a transect of the equatorial Pacific. In contrast to other direct comparisons of these parameters, microbial production greatly exceeded primary production. It is hypothesized that the 14CO2 primary production technique may have underestimated autotrophic carbon production on this transect. Finally, diel nucleic acid synthesis rates were examined. It is concluded that, whereas some diel variation may exist, nucleic acid synthesis rates remain relatively constant in nature over 24 h periods.

Enteral tube feeding (ETF) is used to provide nutrition via the gastrointestinal tract to individuals who are unable to meet their nutritional needs safely or adequately with oral intake. The ETF solution may support microbial growth when this growth is introduced into the ETF delivery system. Adverse patient conditions have been associated with large amounts and/or unacceptable types of microbial growth in ETF. This study investigated the prevalence of microbial growth in aspects of the ETF delivery system on single given days in 2 midsize north central hospitals. Methods of care of some aspects of the ETF delivery system were explored as well as potential adverse patient conditions in respect to microbial growth in ETF. Microbial growth that exceeded the established standards was found. Methods of care of equipment studied was associated with varying microbial growth, but was not found to be of statistical significance. Adverse patient conditions associated with microbial growth in ETF are difficult to definitively identify.