Matching Items (23)
Description
Mining-influenced water (MIW) is an acidic stream containing a typically acidic pH (e.g., 2.5), sulfate, and dissolved metal(loid)s. MIW has the potential to affect freshwater ecosystems and thus MIW requires strategies put in place for containment and treatment. Lignocellulosic sulfate-reducing biochemical reactors (SRBRs) are considered a cost-effective passive treatment for MIW and have been documented to continuously treat MIW at the field-scale. However, long-term operation (> 1 year) and reliable MIW treatment by SRBRs at mining sites is challenged by the decline in sulfate-reduction, the key treatment mechanism for metal(loid) immobilization. This dissertation addresses operational designs and materials suited to promote sulfate reduction in lignocellulosic SRBRs treating MIW. In this dissertation I demonstrated that lignocellulosic SRBRs containing spent brewing grains and/or sugarcane bagasse can be acclimated in continuous mode at hydraulic retention times (HRTs) of 7-12 d while simultaneously removing 80 ± 20% – 91 ± 3% sulfate and > 98% metal(loid)s. Additionally, I showed that decreasing the HRT to 3 d further yields high metal(loid) removal (97.5 ± 1.3% – 98.8 ± 0.9%). Next, I verified the utility of basic oxygen furnace slag to increase MIW pH in a two-stage treatment involving a slag stage and an SRBR stage containing spent brewing grains or sugarcane bagasse. The slag reactor from the two-stage treatment increased MIW pH from 2.6 ± 0.2 to 12 ± 0.3 requiring its re-combination with fresh MIW to reduce pH to 5.0 ± 1.0 prior to entering the lignocellulosic SRBRs. The lignocellulosic SRBRs from the two-stage treatment successfully continued to remove metal(loid)s, most notably cadmium, copper, and zinc at ≥ 96%. In additions to these outcomes, I performed a metadata analysis of 27 SRBRs employing brewers spent grains, sugarcane bagasse, rice husks and rice bran, or a mixture of walnut shells, woodchips, and alfalfa. I found that sugarcane bagasse SRBRs can remove between 94 and 168 mg metal(loid) kg–1 lignocellulose d–1. In addition, Bacteroidia relative abundances showed a positive correlation with increasing sulfate removal across all 27 SRBRs and are likely essential for the degradation of lignocellulose providing electron donors for sulfate reduction. Clostridia and Gammaproteobacteria were negatively correlated with sulfate reduction in the 27 SRBRs, however SRBRs that received alkalinized MIW had lower relative abundances of Clostridia, Gammaproteobacteria, and methanogenic archaea (known competitors for sulfate-reducing bacteria). Overall, my dissertation provides insight into lignocellulosic materials and operational designs to promote long-term sulfate-reduction in lignocellulosic SRBRs treating MIW.
ContributorsMiranda, Evelyn Monica (Author) / Delgado, Anca G (Thesis advisor) / Santisteban, Leonard (Committee member) / Hamdan, Nasser (Committee member) / Rittmann, Bruce (Committee member) / Arizona State University (Publisher)
Created2023
Description
Enzyme induced carbonate precipitation (EICP) treatment is a stabilization method of dust mitigation that applies a spray-on treatment to form a soil crust and increase the wind erosion resistance of a disturbed soil surface. The purpose of this work was to evaluate the EICP treatment with multiple field and laboratory test methods for measuring the wind erosion resistance of EICP treated soil. The threshold friction velocity (TFV) is defined as the minimum wind speed required to initiate continuous particle movement and represents the wind erosion resistance of a soil surface. Tested soil type and textures included a clean fine sand to a loamy sandy soil that contained a significant amount of fines. Dry untreated soil and disturbed field soil surfaces were compared to a chloride salt solution treatment and an EICP treatment solution in both laboratory and field testing to evaluate the wind erosion resistance of the treatments.
ContributorsWoolley, Miriam Arna (Author) / Kavazajian, Edward (Thesis advisor) / van Paassen, Leon (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Hamdan, Nasser (Committee member) / Arizona State University (Publisher)
Created2023
Description
Microbially- and enzyme-induced carbonate precipitation (EICP and MICP) offer potentially sustainable and cost-effective mitigation methods for fugitive dust by forming an erosion-resistant crust on the soil through precipitation of a natural calcium carbonate (CaCO3) cement. While there have been isolated studies on the efficacy of the carbonate precipitation process, there are few systematic studies of the influence of the properties of the soil being treated (e.g., gradation, salt content) on the precipitation and the resulting wind erosion resistance. Moreover, the influence of environmental conditions on the durability of the crust formed by the induced carbonate precipitation has not been systematically investigated. In this research program, the efficacy and durability of EICP and MICP for dust mitigation were investigated for a variety of soil types and in different environmental conditions. Soil samples from seven sites with fugitive dust problems were treated with MICP or EICP and subjected to lab or field testing. The results of these tests showed that the effectiveness of biocementation treatment varies depending on the grain size distribution of soil and mineralogical composition. Testing on iron ore tailings materials demonstrated that treating by application of EICP solutions at lower concentrations (i.e., 0.5M and 0.75M of urea and calcium chloride) yielded effective results for poorly graded fine sand-sized tailings but the same solutions were ineffective for the well graded sand-sized tailings that contained large gravel-sized particles. Additionally, the application of MICP and EICP on sediments adjacent to a shrinking lake (the Salton Sea) with different salt contents exhibited enhanced performance in soils with lower salt content. The effect of temperature during deployment and precipitation cycles are shown to be significant environmental factors by simulating wetting-drying and freeze-thaw cycles in the laboratory. A dust-resistance crust formed through biocementation remained mostly intact after undergoing multiple cycles of wetting-drying. However, the durability of a dust-resistance crust formed through biocementation to multiple cycles of freeze-thaw depended on treatment solution concentration and soil grain size. Additionally, high temperature during field deployment of MICP adversely effected crust formation due to rapid evaporation that inhibited the complete hydrolysis of urea and the precipitation of carbonate.
ContributorsEhsasi, Farideh (Author) / Kavazanjian, Edward (Thesis advisor) / van Paassen, Leon (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Arizona State University (Publisher)
Created2023