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.

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.

Nutrient rich agricultural runoff is a major source of phosphorus (P) and nitrogen (N) loading to surface waters, resulting in eutrophication and harmful algal blooms. The most effective nutrient removal technologies often have cost, land, or operational requirements that limits use in the decentralized areas that need it most. This dissertation investigated combined physical-chemical and microbiological technologies for combined P and N removal from nonpoint sources. Chapter 2 investigated the combination of basic oxygen furnace (BOF) steel slag and woody mulch for P removal by mineral precipitation and N removal by microbial denitrification. When combined with mulch in column experiments, slag with high fines content achieved complete P removal under unsaturated conditions. Batch experiments showed that microbial denitrification occurred under the highly alkaline conditions created by steel slag, but the timescale differential between P and N removal was a critical barrier to combining these treatment technologies. Chapter 3 evaluated a field-scale slag filter to treat agricultural tile drainage and lab-scale column experiments to provide insight on field conditions that impacted P removal. Increases in alkalinity had negative influences on P removal through inhibition of P mineral precipitation by BOF slag, while blast furnace (BF) steel slag was less impacted by alkalinity due to primarily adsorptive P removal. Regeneration strategies were identified based on water quality and slag type.Chapters 4 and 5 explored biological ion exchange (BIEX) as an option for addressing the timescale offset identified in Chapter 1. In Chapter 4 columns fed with dissolved organic matter (DOM) were not regenerated and over 50% DOM removal was observed, with the primary mechanism of removal identified as secondary ion exchange (SIEX) between sulfate and DOM fractions with high affinities for ion exchange. Chapter 5 aimed to expand BIEX to N treatment through batch denitrification and adsorption experiments, which revealed a positive relationship between molecular weight of organic molecules and their ability to displace nitrate. This work shows that by having an improved understanding of impacted water characteristics, the information presented in this work can be used to select and implement effective treatment technologies for decentralized areas.

Oxic beds containing basic oxygen furnace slag were evaluated as potential post-treatment method for sulfate reducing bioreactor (SRB) treatment of acid rock drainage. SRB effluent was pumped into BOF slag/sand leach beds, also known as oxic slag beds (OSBs), at various flow rates. OSB influent versus effluent concentrations of dissolved metals (specifically magnesium and manganese) and water quality parameters (pH, dissolved oxygen concentration, and conductivity) were compared. The OSBs increased the pH of the SRB effluents from 6.2–6.7 to 7.5–8.3. Dissolved oxygen concentration increased from 2-4 mg L^(-1) to approximately 8 mg L^(-1). Conductivity remained similar, with some effluent values being less than influent. Manganese concentration was observed to be reduced through OSB post-treatment by an average of 8.2% reduction and a maximum of 23 % reduction. Magnesium was not reduced during OSB post-treatment. Other metal concentrations changes were analyzed. Recommendations the design of OSBs for future studies were made, and a proposed design was configured.

The public has expressed a growing desire for more sustainable and green technologies to be implemented in society. Bio-cementation is a method of soil improvement that satisfies this demand for sustainable and green technology. Bio-cementation can be performed by using microbes or free enzymes which precipitate carbonate within the treated soil. These methods are referred to as microbial induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP). The precipitation of carbonate is the formation of crystalline minerals that fill the void spaces within a body of soil.

This thesis investigates the application of EICP in a soil collected from the Arizona State University Polytechnic campus. The surficial soil in the region is known to be a clayey sand. Both EICP and MICP have their limitations in soils consisting of a significant percentage of fines. Fine-grained soils have a greater surface area which requires the precipitation of a greater amount of carbonate to increase the soil’s strength. EICP was chosen due to not requiring any living organisms during the application, having a faster reaction rate and size constraints.

To determine the effectiveness of EICP as a method of improving a soil with a significant amount of fines, multiple comparisons were made: 1) The soil’s strength was analyzed on its own, untreated; 2) The soil was treated with EICP to determine if bio-cementation can strengthen the soil; 3) The soil had sand added to reduce the fines content and was treated with EICP to determine how the fines percentage effects the strength of a soil when treated with EICP.

While the EICP treatment increased the strength of the soil by over 3-fold, the strength was still relatively low when compared to results of other case studies treating sandy soils. More research could be done with triaxial testing due to the samples of the Polytechnic soil’s strength coming from capillarity.

Microbially induced calcium carbonate precipitation (MICP) is attracting increasing attention as a sustainable means of soil improvement. While there are several possible MICP mechanisms, microbial denitrification has the potential to become one of the preferred methods for MICP because complete denitrification does not produce toxic byproducts, readily occurs under anoxic conditions, and potentially has a greater carbonate yield per mole of organic electron donor than other MICP processes. Denitrification may be preferable to ureolytic hydrolysis, the MICP process explored most extensively to date, as the byproduct of denitrification is benign nitrogen gas, while the chemical pathways involved in hydrolytic ureolysis processes produce undesirable and potentially toxic byproducts such as ammonium (NH4+). This thesis focuses on bacterial denitrification and presents preliminary results of bench-scale laboratory experiments on denitrification as a candidate calcium carbonate precipitation mechanism. The bench-scale bioreactor and column tests, conducted using the facultative anaerobic bacterium Pseudomonas denitrificans, show that calcite can be precipitated from calcium-rich pore water using denitrification. Experiments also explore the potential for reducing environmental impacts and lowering costs associated with denitrification by reducing the total dissolved solids in the reactors and columns, optimizing the chemical matrix, and addressing the loss of free calcium in the form of calcium phosphate precipitate from the pore fluid. The potential for using MICP to sequester radionuclides and metal contaminants that are migrating in groundwater is also investigated. In the sequestration process, divalent cations and radionuclides are incorporated into the calcite structure via substitution, forming low-strontium calcium carbonate minerals that resist dissolution at a level similar to that of calcite. Work by others using the bacterium Sporosarcina pasteurii has suggested that in-situ sequestration of radionuclides and metal contaminants can be achieved through MICP via hydrolytic ureolysis. MICP through bacterial denitrification seems particularly promising as a means for sequestering radionuclides and metal contaminants in anoxic environments due to the anaerobic nature of the process and the ubiquity of denitrifying bacteria in the subsurface.