Sustainability practices are leading to the development and use of alternative products in the floriculture and wastewater industries, such as the use of biodegradable containers instead of plastic containers. The objective of this research was to evaluate the efficacy of using digested biosolids from a regional wastewater treatment plant as an ingredient in creating a biodegradable transplant biocontainer. The biosolids were tested for metals limits as specified by the U.S. EPA Part 503 Rule, and met the requirements for Class B. Multiple mixes of biosolids, fibers, starch, polymer, and natural glue were developed to provide overall pot stability and structural strength. Engineering tests, such as tensile strength, pH, and saturated paste tests, were conducted on the different mixes to determine the optimum strength that could be produced. The top-performing biosolids mixes were used to make 10.2 cm (four-inch) pots that were compared in various ways to the market leaders, Peat Pots and standard plastic pots. A two-part mold was created on a 3D printer, which would allow for positive pressure to be used in forming the BioPots. Mixes were transferred to the lower half of the mold, the upper part was then plunged and fastened into the lower half, and then the mold with its mix was placed in an oven to dry. Laboratory germination bioassays were performed to test for the presence of phytotoxic compounds. Construction of BioPots for the lab-scale studies was tedious. Different methods (e.g., negative pressure systems) need to be investigated for use in producing the BioPots commercially. Most of the BioPots survived the resiliency study. Leachate quality from the biocontainers was no worse than from the plastic containers. Some discoloration was observed on the biocontainers, but it was not due to algal/fungal growth. Growth of soybeans, marigolds, and romaine in the biocontainers was significantly better (e.g., increased height, leaf sizes, and weight) than in the plastic containers. / Master of Science / The Western Virginia Water Authority serves the City of Roanoke, and Counties of Roanoke, Franklin and Botetourt. Approximately 141 million liters per day (37 million gallons per day) of wastewater from the service area is treated at the Roanoke Regional Water Pollution Control Plant (RRWPCP). Solids are anaerobically digested and lagooned prior to agricultural land application; biogas is stored and used to generate electricity. After about nine months in the lagoon, 9.07 million dry kilograms (10,000 dry tons) of biosolids are land applied locally each year. Solids management costs are a significant part of the RRWPCP’s operating budget. In an effort to decrease costs and increase sustainability, there has been growing interest in resource recovery by producing a high-quality nutrient product that can be beneficially used. In January 2014, research to develop a high-quality biosolids product for beneficial use was initiated by Virginia Tech, in collaboration with the RRWPCP. The drivers, research goals, methodology, and results from that research will be presented. The general public is familiar with several commercially available biocontainer products, such as Peat Pots and CowPots^TM. They are used in nurseries, greenhouses, and households, and minimize plastic waste while also contributing organic material for healthy plant growth. The WPCP was intrigued with developing a biosolids product that could be marketed and used like the Peat Pots. The objective of this research was to evaluate the efficacy of using digested biosolids from Roanoke WPCP as an ingredient in creating a biodegradable transplant pot. The biosolids were tested for and met the metals and contaminants limits as required by the U.S. EPA Part 503 Biosolids Rule. In addition to the biosolids, other fibrous materials, such as used cardboard or cellulose, were used to stabilize and add structural strength. Multiple blends, or mixes, were developed, each varying in biosolids and fiber content on a dry weight basis, as well as different additives such as starch, polymer, or a natural glue. Tensile and puncture tests were conducted on the different mixes to determine the optimum strength that could be produced. The top performing mixes were used to create four-inch pots, for comparison to market leader, Peat Pots, and standard plastic pots. Greenhouse studies were conducted in two phases: • Phase 1 – analysis of leachate and assessment of pot stability through watering cycles. • Phase 2 - growth studies for soybeans, marigolds, and romaine. These plants were selected based on growth ability and/or sensitivity. The RRWPCP does not currently produce Class A biosolids, but by producing biodegradable transplant pots, they hope to produce a high-value, sustainable product that meets Class A requirements and diversifies their current biosolids management program.

Large quantities of biosolids are produced from treatment of municipal wastewater and can be processed into a nutrient and organic-rich soil amendment that has great value for agriculture. The drying process involves converting solids at approximately 25-30% solids content to a dry, stable biosolids pellet. The majority of the input material is recycled to the mixing step upstream of the dryer to achieve a more uniform particle size distribution. The objective of this work was to investigate use of polyelectrolyte amendments to promote uniformity in dried biosolids pellet size. Biosolids samples were collected at the New England Fertilizer Company (NEFCO) facility located in Quincy, MA, U.S. The biosolids samples were characterized by scanning electron microscopy (SEM), inductively coupled plasma/mass spectrometry (ICP-MS), dynamic light scattering (DLS) and zeta potential measurements. Five polyelectrolytes, polyethyleneimine (PEI), polydiallyldimethyl-ammonium chloride (PDADMAC), polyallyamine (PAM), polyacrylic acid (PAA) and polyethylene oxide (PEO) were selected as candidate amendments for surface properties modification trials. The results indicated that three cationic polyelectrolytes, PDADMAC, PEI and PAM, reduced the (absolute value) zeta potentials of the biosolids surfaces to near zero. The optimal doses for reducing the zeta potentials were found to be 0.008 mg PEI/mg solids; 0.005 mg PAM/mg solids and 0.03 mg PDADMAC/mg solids, respectively. The anionic polyelectrolyte PAA and nonionic polymer PEO were found to be ineffective for modifying the zeta potential of the biosolids. The changes in particle size distributions of the biosolids using the three cationic polyelectrolytes were determined by dynamic light scattering (DLS) measurements. Of the three cationic polyelectrolytes, only PDADMAC was found to increase the biosolids particle size from average size of 340 nm to 3600 nm with 240 min contact time. This indicates the potential for PDADMAC as an amendment for improving the biosolids drying process as it was able to decrease the number of fines and increase the “green” biosolids pellet size.

Sanitation is fundamental to reducing disease and sustaining a high standard of living. The evolution of sewer systems and the modern engineering of wastewater treatment plants work to decrease health risk and manage environmental concerns associated with the reuse and disposal of treated effluent and solid wastes generated as byproducts. The recycling of treated solid wastes (biosolids) continues to be an environmental challenge due to the shear volume produced, and its potentially hazardous composition. Solar drying of biosolids was studied in semi-arid regions as a sustainable method for reducing pathogens. The initial studies were performed with no intervening treatments. Average fecal coliform inactivation rates for digested biosolids during summer experiments were determined to be 0.17 ± 0.03/day⁻¹ and 0.17 ± 0.04/day⁻¹, respectively. Salmonella inactivation rates in aerobically digested biosolids were 0.11 ± 0.08 day⁻¹ and 2.0 ± 2.0 day⁻¹ for aerobically and anaerobically digested biosolids, respectively for the summer seasons. Solar drying during warm dry seasons was effective in reducing pathogens. Microbial testing to verify the quality of biosolids can be expensive. Utilizing a mathematical model to predict pathogen density levels during the solar drying process can minimize such testing. The first order mathematical model, N(t) = N(o) * 10⁻ᵏᵈᵗ where the inactivation constant, k(d), is further defined as a function of moisture (Θ) and temperature (T), i.e. k(d) = f(Θ,T): k(d) = (k₁/( k₁ + Θ) * (T/(k₂-T)) * k₃, k₁ = 0.112, k₂ = -41.88, and k₃ = -0.5357; for all T greater than or equal to 38ºC, T=38°C provided a good estimate of the inactivation rate of fecal coliforms in biosolids. During subsequent field studies, treatments were employed to manage the drying cycle of biosolids - tilling increased the rate of drying, a covered solar drying bed increased the inactivation rate of fecal coliforms by 300%, and an automated rain shield was engineered to limit enteric bacterial regrowth due to rainfall. Finally, since biosolids are to be considered a source of nitrogen when land-applied, temporal samples of biosolids from various solar drying experiments were analyzed to ascertain the levels of NH⁺₄-N and NO⁻₃-N throughout the drying process. Chemical analyses revealed that as much as 34-92% of nitrogen was lost via volatilization during the drying process.

This study evaluated the influence of annual land applications of Class B biosolids on the soil microbial and chemical properties monitored over 20 year period. The study was initiated in 1986 at the University of Arizona Marana Agricultural Center, Tucson, Arizona. The final application of biosolids was in March 2005, followed by growth of cotton from April through November 2005. Surface soil samples (0-30 cm) were collected monthly from March 2005 through December 2005, and analyzed for soil microbial properties. Soil cores (0-150 cm) were also collected in December and analyzed for various soil chemical properties. The study showed that land application of Class B biosolids had no significant effect on the number of indigenous soil microbial numbers including bacteria, actinomycetes, and fungi (no bacterial or viral pathogens were present in soil samples collected in December) but enhanced microbial activity in the biosolid amended plots. Bacterial diversity was not impacted after 20 years of land application when evaluated through cloning and sequence analysis of bacterial 16S rRNA. Both soils had a broad phylogenetic diversity comprising more than five major phyla including: Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. Chemical analyses showed that land application of biosolids significantly increased soil pH but did not affect soil salinity and CaCO3 values as compared with the control plots. However, this lack of increase in salinity was likely due to the leaching of soluble salts through the soil profile since irrigation rates. Land application significantly increased soil macro-nutrients including C, N and P and caution should be taken with respect to phosphate loadings to prevent nutrient contamination of surface waters. The biosolid amended soil concentrations of available and total metals were low (compared to the typical background soil metal concentrations). Metal concentrations attenuated rapidly with increasing soil depth, and were generally similar to values found in control soils at a depth of 150cm. Increases in available metal concentrations were modest. It is important to note that there are differences between these studies with respect to different cropping systems, biosolids type, climate and soil type, as well as irrigation rates in the arid southwest.

The long-term mobility and availability of trace metals has been cited as a potential hazard by critics of EPA 503 rule governing the land application of biosolids. The purpose of this research was to investigate the long-term effects of biosolids application on trace metals distribution and mobility. A single application of aerobically digested biosolids was applied to 1.5 x 2.3 m confined plots of a Davidson clay loam (clayey, kaolinitic, thermic, Rhodic Paleudult) in 1984 at 0, 42, 84, 126, 168, and 210 Mg/ha. The highest biosolids application supplied 4.5, 760, 43, and 620 kg ha-1 of Cd, Cu, Ni, and Zn, respectively. Radish (Raphanus sativus L.), lettuce (Lactuca sativa Var longifolia) and barley (Hordeum vulgare) were planted at the site. Soils were sampled to a depth of 0.9 m and sectioned into 5 cm increments after separating the Ap horizon. Total (EPA 3050B), available (Mehlich-I), sequential extraction, and dispersible clay analyses were performed on samples from the control, 126 Mg/ha and 210 Mg/ha treatments. Extractable (0.005 DTPA, 0.01 M CaCl2, and Mehlich-1) Cd, Cu, Ni, and Zn were measured on 15 cm-depth samples from each plot. Simple linear regression between plant metal concentration and biosolids-added trace metals were computed to determine uptake coefficients (UC) of crops for each metal as outlined by USEPA Part 503 Rule. Results indicated that more than 80% of the applied Cu and Zn are still found in the topsoil where biosolids were incorporated with slight enrichment down to 0.3 m. Biosolids application increased the concentration of trace metals in all the extracted fractions, with a large proportion of Zn and Cd present in the available forms. The major portion of Cu, Zn and Ni was associated with the metal-oxides fraction. Biosolids treatments had no significant effect on the yield of the crops. Plant uptake of trace metals differed among crops. Plant tissue metal concentrations increased with biosolids rate but were within the normal range for these crops. Trace metals concentration in plants generally correlated well with their concentrations extracted with 0.005 M DTPA, 0.01 M CaCl2 and Mehlich-1. Mehlich-1 gave the highest correlation coefficients for Cu and Zn and, therefore, was the most reliable in predicting their availability and uptake by the crops grown. Availability of trace metals as measured by Mehlich-I, DTPA, and CaCl2 extraction were higher in amended plots as compared to the control and increased linearly in response to biosolids addition. Metal concentration in the plants exhibited a plateau response in most cases. Several linear increases were observed in some cases in 2003 when the soil pH decreased below 5.5. The uptake coefficients values generated for the different crops were in agreement with the values set by the Part 503 Rule. / Ph. D.

Significant deposits of heavy mineral sands (primarily ilmenite and zircon) are located in Virginia in Dinwiddie, Sussex and Greensville counties. Most deposits are located under prime farmland, and thus require intensive reclamation when mined. The objective of this study was to determine the effect of four different mine soil reconstruction methods on soil properties and associated rowcrop productivity. Treatments compared were 1) Biosolids-No Tillage, 2) Biosolids-Conventional Tillage, 3) Lime+NPK fertilized tailings (Control), and 4) 15-cm Topsoil over lime+P treated tailings. Treated plots were cropped to corn (Zea Mays L.) in 2005 and wheat (Triticum aestivum L.) in 2006. Yields were compared to nearby unmined prime farmland yields. Over both growing seasons, the two biosolids treatments produced the highest overall crop yields. The Topsoil treatment produced the lowest corn yields due to relatively poor physical and chemical conditions, but the effect was less obvious for the following wheat crop. Reclaimed land corn and wheat yields were higher than long-term county averages, but they were consistently lower than unmined plots under identical management. Detailed morphological study of 20 mine soil pedons revealed significant root-limiting subsoil compaction and textural stratification. The mine soils classified as Typic Udorthents (11), Typic Udifluvents (4) and Typic Dystrudepts (5). Overall, mined lands can be successfully returned to intensive agricultural production with comparable yields to long-term county averages provided extensive soil amendment and remedial tillage protocols are implemented. However, a significant decrease (~25 to 35%) in initial productivity should be expected relative to unmined prime farmland. / Master of Science

Soils disturbed by strip mining practices may have increased colloid loads moving to groundwater resources, also enhancing the transport of contaminants into our water resources. We hypothesize that contaminant transport within soils following mining is enhanced by colloid mobility. Two sites were chosen for this study, a 30-year old reclaimed strip mine in southwest Virginia and a recently mined area from eastern Kentucky. Intact reclaimed soil monoliths were retrieved from sandstone derived soils in southwestern Virginia. Reclaimed monoliths from eastern Kentucky were recreated in the lab. Intact undisturbed (native) soil monoliths representing the soils before mining were also sampled for comparison. Biosolids were added to an additional reclaimed monolith at a rate of 20 T/acre. Leaching experiments with deionized water at a rate of 1.0 cm/h involved 6 cycles of 8 hours each, giving each monolith at least 2 pore volumes of leaching. Native soil monoliths from Virginia had an average colloid elution of 857 mg over all cycles, reclaimed soil monoliths had an elution of 1460 mg, reclaimed soil monoliths with spoil material had a colloid elution of 76 mg, and when biosolids were amended to reclaimed soil and spoil monoliths, 870 mg colloids were eluted. Native soil monoliths from eastern Kentucky eluted 7269 mg colloids, reclaimed monoliths from eastern Kentucky eluted 10,935 mg colloids, and reclaimed soils with spoil material eluted no colloids. Lime stabilized biosolids enhanced colloid elution due to high pH dispersing material within the monoliths, while spoil materials with high density and salt content reduced colloid elution. Metal loads in solution were mobilized by DOC, particularly in low sulfate environments, while colloid bound metals increased the total metal loads in the order of Pb > Ni > Cu > Cd > Zn > Cr.

The annual production of biosolids in the Perth region during the period of this study was approximately 13,800 t dry solids (DS), being supplied by three major wastewater treatment plants. Of this, 70% was typically used as a low-grade fertiliser in agriculture, representing an annual land use area of around 1,600 ha when spread between 5 and 7 t DS/ha. Loading rates of biosolids are typically based on the nitrogen (N) requirements of the crop to be grown, referred to as the N Limiting Biosolids Application Rate (NLBAR). A consequence of using the NLBAR to calculate loading rates is that phosphorus (P) is typically in excess of plant requirement. The resultant high loading rates of P are considered in the guidelines developed for the agricultural use of biosolids in Western Australia, but lack research data specific to local conditions and soil types. Regulatory changes throughout Australia and globally to protect the environment from wastewater pollution have created a need for more accountable and balanced nutrient data. Experiments presented in this thesis were undertaken to ascertain: the percentage relative effectiveness (RE) of biosolids as a source of plant available P compared with inorganic P fertiliser; loading rates to best supply P for optimum crop growth; P loading rates of risk to the environment; and the forms of P in local biosolids. Therefore, both the agronomic and environmental viewpoints were considered. Anaerobically digested and dewatered biosolids produced from Beenyup Wastewater Treatment Plant, Perth with a mean total P content of 2.97% dry weight basis (db) were used in a series of glasshouse, field and laboratory experiments. The biosolids were sequentially fractionated to identify the forms of P present and likewise in soil samples after applying biosolids or monocalcium phosphate (MCP). / The biosolid P was predominantly inorganic (92%), and hence the organic fraction (8%) available for mineralisation at all times would be extremely low. The most common forms of biosolid P were water-soluble P and exchangeable inorganic P (66%), followed by bicarbonate extractable P (19%) and the remaining P as inorganic forms associated with Fe, Al and Ca (14%). Following the application of biosolids to a lateritic soil, the Fe and Al soil fractions sorbed large amounts of P, not unlike the distribution of P following the addition of MCP. Further investigation would be required to trace the cycling of biosolid P in the various soil pools. The growth response of wheat (Triticum aestivum L.) to increasing rates of biosolids and comparable rates of inorganic P as MCP, to a maximum of 150 mg P/kg soil was examined in the glasshouse. The percentage relative effectiveness (RE) of biosolids was calculated using fitted curve coefficients from the Mitscherlich equation: y = a (1-b exp–cx) for dry matter (DM) production and P uptake. The initial effectiveness of biosolid P was comparable to that of MCP with the percentage RE of biosolids averaging 106% for DM production of wheat shoots and 118% for shoot P uptake at 33 days after sowing (DAS) over three consecutive crops. The percentage residual value (RV) declined at similar rates for DM production in MCP and biosolids, decreasing to about 33% relative to freshly applied MCP in the second crop and to approximately 16% in the third crop. The effectiveness of biosolid P was reduced significantly compared with inorganic P when applied to a field site 80 km east of Perth (520 mm annual rainfall). An infertile lateritic podsolic soil, consistent with the glasshouse experiment and representative of a soil type typically used for the agricultural application of biosolids in Western Australia was used. / Increasing rates of biosolids and comparable rates of triple superphosphate (TSP), to a maximum of 145 kg P/ha were applied to determine a P response curve. The percentage RE was calculated for seasonal DM production, final grain yield and P uptake in wheat followed by lupin (Lupinus angustifolius L.) rotation for the 2001 and 2002 growing seasons, respectively. In the first year of wheat, the RE for P uptake in biosolids compared with top-dressed TSP ranged from 33% to 55% over the season and by grain harvest was 67%. In the second year, and following incorporation with the disc plough at seeding, the RE for P uptake by lupins in biosolids averaged 79% over the growing season compared with top-dressed TSP, and by grain harvest the RE was 60%. The residual value (RV) of lupins at harvest in biosolids compared with freshly applied TSP was 47%. The non-uniform placement of biosolids (i.e. spatial heterogeneity) was primarily responsible for the decreased ability of plant roots to absorb P. The P was more effective where biosolids were finely dispersed throughout the soil, less so when roughly cultivated and least effective when placed on the soil surface without incorporation. The RE for grain harvest of wheat in the field decreased from 67% to 39% where biosolids were not incorporated (i.e. surface-applied). The RE could also be modified by factors such as soil moisture and N availability in the field, although it was possible to keep these variables constant in the glasshouse. Consequently, absolute values determined for the RE need to be treated judiciously. Calculations showed that typical loading rates of biosolids required to satisfy agronomic P requirements of wheat in Western Australia in the first season could vary from 0 to 8.1 t DS/ha, depending on soil factors such as the P Retention Index (PRI) and bicarbonate available P value. / Loading rates of biosolids were inadequate for optimum P uptake by wheat at 5 t DS/ha (i.e. 145 kg P/ha) based on the NLBAR on high P sorbing soils with a low fertiliser history (i.e. PRI >15, Colwell bicarbonate extractable P <15 mg P/kg). On soils of PRI <2 mL/g however, biosolids applied at identical loading rates would result in high concentrations of available P. Further work on sites not P deficient would be necessary to validate these findings on farmed soils with a regular history of P fertiliser. The sieving of soil samples used in the field experiment to remove stones and coarse organic matter prior to chemical analysis inadvertently discarded biosolids particles >2 mm, and thus their was little relationship between soil bicarbonate extractable P and P uptake by plants in the field. The risk of P leaching in biosolids-amended soil was examined over a number of different soil types at comparable rates of P at 140 mg P/kg (as either biosolids or MCP) in a laboratory experiment. Given that biosolids are restricted on sites prone to water erosion, the study focussed on the movement of water-soluble P by leaching rather than by runoff of water-soluble P and particulate P. In general the percentage soluble reactive P recovered was lower in soils treated with biosolids than with MCP, as measured in leachate collected using a reverse soil leachate unit. This was particularly evident in acid washed sand with SRP measuring 14% for biosolids and 71% for MCP, respectively, although the differences were not as large in typical agricultural soils. Specific soil properties, such as the PRI, pH, organic carbon and reactive Fe content were negatively correlated to soluble reactive P in leachate and thus reduced the risk of P leaching in biosolids-amended soil. / Conversely, the total P and bicarbonate extractable P status of the soils investigated were unreliable indicators as to the amount of P leached. On the basis of the experiments conducted, soils in Western Australia were categorised according to their ability to minimise P enrichment and provide P necessary for crop growth at loading rates determined by the NLBAR. Biosolids applied at the NLBAR to soils of PRI >2mL/g with reactive Fe >200 mg/kg were unlikely to necessitate P loading restrictions. Although specific to anaerobically digested biosolids cake applied to Western Australian soils, the results will be of relevance to any industry involved in the land application of biosolids, to prevent P contamination in water bodies and to make better use of P in crop production.

The term biosolids refers to the nutrient-rich organic materials resulting from the treatment of domestic sewage at a wastewater treatment facility. It is a widely acceptable term for sewage sludge that has been treated at a wastewater treatment plant and is beneficially recycled. Biosolids inherently come from sewage sludge, so they have the same origin and biological nature, but a different applicability. The quantity of municipal biosolids produced increases annually in the United States. The production of biosolids has increased because of both the advance of sanitation and wastewater treatment and the growth of population. Sludge or biosolids are contaminated by varying amounts of heavy metals or hazardous organic compounds from industrial and commercial wastewater. Therefore, society has to face the potential for increased negative impacts on the environment from the increasing volume of biosolids being produced. Public concerns about applied biosolids treatment or reuse methods are potential health, environmental, or aesthetic impacts (such things as disease, odors), because of the pollutants in the biosolids. The most commonly used methods for biosolids treatment and recycling are briefly reviewed in the first two chapters of this thesis. However, the current biosolids treatment or recycling options have their own defects. A new and innovative technology, deep biosolids injection, is proposed for the treatment of biosolids and is to be implemented by Los Angeles where the City has been granted underground solids injection control permits under Class V wells by the US Environmental Protection Agency. Deep biosolids injection is a process referred to as one type of several deep underground injection techniques. It shares many similarities with slurried solids injection above the fracture pressure, which has been successfully used for the treatment of slurried non-hazardous solid materials produced in the oil industry such as drill cuttings, viscous emulsions with clay, oily sand, NORMs (naturally occurring radioactive materials), pipe scale, tank bottoms, soil from spill clean-up, and so on. The distinctive biosolids properties result in injection mechanisms different from other slurry injection processes. Filtration and consolidation processes occur simultaneously along with injection of biosolids, and these must be understood in order to properly design and manage a biosolids injection operation. Hydraulic fracture mechanisms, filtration theory and consolidation principles provide the basis for the interpretation of biosolids injection process. A semi-analytical hydraulic fracture model for injection of a compressible substance (biosolids) is developed as a modification of the Perkins-Kern-Nordgren (PKN) hydraulic fracture model. The PKN model is modified with a pseudo-dynamic leak-off function that describes the deposition of biosolids (filtration) and plugging effect of biosolids on the fracture wall in a porous medium. The pseudo-dynamic leak-off function is given in terms of the net pressure and the resistance of the filter cake to flow. The hydraulic fracture model is employed to compute the volume of biosolids slurry remaining in an open induced fracture. The consolidation process in the closure phase of deep biosolids injection is described using the biosolids properties under different stress conditions. A Terzaghi-type relationship is used to compute the volume change in the closure phase using compressibility data available from published literature. In contrast to the conventional PKN leak-off model, simulation results using the new model show that the induced fracture volume is much larger because of the impaired leak-off and because of the volumetric effects and consolidation of the biosolids in the fracture. Solids contents and biosolids compaction behavior have significant impacts on the geometry of fracture (width, length, volume) over time. The model was developed to help guide large-scale injection of municipal and animal biosolids as an environmentally more secure method of treatment than surface approaches.

The term biosolids refers to the nutrient-rich organic materials resulting from the treatment of domestic sewage at a wastewater treatment facility. It is a widely acceptable term for sewage sludge that has been treated at a wastewater treatment plant and is beneficially recycled. Biosolids inherently come from sewage sludge, so they have the same origin and biological nature, but a different applicability. The quantity of municipal biosolids produced increases annually in the United States. The production of biosolids has increased because of both the advance of sanitation and wastewater treatment and the growth of population. Sludge or biosolids are contaminated by varying amounts of heavy metals or hazardous organic compounds from industrial and commercial wastewater. Therefore, society has to face the potential for increased negative impacts on the environment from the increasing volume of biosolids being produced. Public concerns about applied biosolids treatment or reuse methods are potential health, environmental, or aesthetic impacts (such things as disease, odors), because of the pollutants in the biosolids. The most commonly used methods for biosolids treatment and recycling are briefly reviewed in the first two chapters of this thesis. However, the current biosolids treatment or recycling options have their own defects. A new and innovative technology, deep biosolids injection, is proposed for the treatment of biosolids and is to be implemented by Los Angeles where the City has been granted underground solids injection control permits under Class V wells by the US Environmental Protection Agency. Deep biosolids injection is a process referred to as one type of several deep underground injection techniques. It shares many similarities with slurried solids injection above the fracture pressure, which has been successfully used for the treatment of slurried non-hazardous solid materials produced in the oil industry such as drill cuttings, viscous emulsions with clay, oily sand, NORMs (naturally occurring radioactive materials), pipe scale, tank bottoms, soil from spill clean-up, and so on. The distinctive biosolids properties result in injection mechanisms different from other slurry injection processes. Filtration and consolidation processes occur simultaneously along with injection of biosolids, and these must be understood in order to properly design and manage a biosolids injection operation. Hydraulic fracture mechanisms, filtration theory and consolidation principles provide the basis for the interpretation of biosolids injection process. A semi-analytical hydraulic fracture model for injection of a compressible substance (biosolids) is developed as a modification of the Perkins-Kern-Nordgren (PKN) hydraulic fracture model. The PKN model is modified with a pseudo-dynamic leak-off function that describes the deposition of biosolids (filtration) and plugging effect of biosolids on the fracture wall in a porous medium. The pseudo-dynamic leak-off function is given in terms of the net pressure and the resistance of the filter cake to flow. The hydraulic fracture model is employed to compute the volume of biosolids slurry remaining in an open induced fracture. The consolidation process in the closure phase of deep biosolids injection is described using the biosolids properties under different stress conditions. A Terzaghi-type relationship is used to compute the volume change in the closure phase using compressibility data available from published literature. In contrast to the conventional PKN leak-off model, simulation results using the new model show that the induced fracture volume is much larger because of the impaired leak-off and because of the volumetric effects and consolidation of the biosolids in the fracture. Solids contents and biosolids compaction behavior have significant impacts on the geometry of fracture (width, length, volume) over time. The model was developed to help guide large-scale injection of municipal and animal biosolids as an environmentally more secure method of treatment than surface approaches.