For over two decades the 40 CFR Part 503 has been the regulatory framework guiding land application of biosolids in the US. During this period public perception about the practice has worsened as evidenced by increases in partial and full biosolids land application bans across the US. In this work, the Multimedia, Multipathway and Multi-receptor Risk Assessment (3MRA) model was applied to four biosolids land application sites across the US (two sites in WA, one site each in VA and GA) to evaluate human health risk concerns from regulated (As and Cd) and non-regulated (B(a)P and DEHP) chemical constituents present in biosolids. The excess cancer risk from ingesting soil contaminated with As and Cd was higher than 1x10-6 when accounting for the background concentration. However, after separating the risk to reflect just the land application practice, the excess cancer risk estimates for the soil ingestion pathway were well below the acceptable risk criteria (several orders of magnitude lower). The non-cancer risk, for both As and Cd, was below 1. As and Cd remained mostly in the zone of biosolids incorporation. The combined As and Cd mass lost to all pathways for a 20-year consecutive application scenario was less than 15%. The classes of organic environmental toxins evaluated also did not cause concern. Both B(a)P and DEHP aerobically degraded and less than 3% remained in the zone of biosolids incorporation after a 100-year consecutive biosolids application based on model predictions. Scenarios considering biosolids application at typical agricultural rates did not result in groundwater impairment for the sites evaluated; however, scenarios with biosolids applications that are similar to a surface disposal practice resulted in groundwater impairment. In addition to this work, sites across the US (in WA, VA and GA) were evaluated for groundwater impairment scenarios. The results from this effort clearly point towards no additional excess cancer (>1x10-6) or non-cancer (HQ>1) health risks associated specifically with the practice of land application of biosolids for agricultural production for the sites and chemical contaminants evaluated.

Land filling provides a major, safe, and economical disposal route for biosolids and sludges. With an expanding world, the demand for larger and higher capacity landfills is rapidly increasing. Proper analysis and design on such fills have pushed the boundaries of geotechnical engineering practice, in terms of proper identification and assessment of strength and deformation characteristics of waste materials. The engineering properties of Municipal Solid Waste (MSW) with co-disposal of biosolids and sludges with regards to moisture characteristics and geotechnical stability are of utmost importance. Significant changes in the composition and characteristics of landfill may take place with the addition of sludges and biosolids. In particular, the stability of waste slopes needs to be investigated, which involves the evaluation of the strength properties of the mixture of the waste and biosolids. This thesis deals with impact of the addition of biosolids on the geotechnical properties of class I landfill as determined from field investigations. The geotechnical properties are evaluated using an in-situ deep exploration test, called the Cone Penetration Test (CPT). CPT provides a continuous log of subsurface material properties using two measuring mechanisms, namely, tip resistance and side friction. The areas receiving biosolids are compared with areas without, to evaluate the effect of landfilling of biosolids. The required geotechnical shear strength parameters (angle of internal friction and cohesion) of MSW and biosolids mixture are determined by correlation with CPT results similar to the procedure followed in evaluating soil properties. The shear strength parameters obtained from the CPT data are then used to study the stability of different slope configurations of the landfill. The slope stability analysis is conducted on the various landfill models using the computer software SLOPE/W. This software was designed for soils but was found to be suitable for modeling landfills, as the waste is assumed to act similar to a cohesionless soil. Based on the field investigations, the angle of internal friction was found to be about 29° and the determination of any cohesion was not possible. It was concluded that the most suitable practical solution to adding biosolids into the landfill was in the form of trenches. From the slope stability study, it was found that the factor of safety reduces significantly with the introduction of biosolids due to a reduction in shear strength and increase in the overall moisture content. From a parametric study, the stability of a 1:2 side slope with an angle of friction lower than about 20° was found to be less than the safe limit of 1.5. In addition, the factors of safety for landfills with trenches extending close to the edges of the slopes were also found to be unsafe and this situation needs to be avoided in practice.

As populations increase and cities become denser, the production of waste, both sewage sludge and food biomass, increases exponentially while disposal options for these wastes are limited. Landfills have minimal space for biosolids; countries are now banning ocean disposal methods for fear of the negative environmental impacts. Agricultural application of biosolids cannot keep up with the production rates because of the accumulation of heavy metals in the soils. Gasification can convert biosolids into a renewable energy source that can reduce the amount of waste heading to the landfills and reduce our dependence on fossil fuels. A recently published chemical kinetic computer model for a fluidized-bed sewage sludge gasifier (Champion, Cooper, Mackie, & Cairney, 2014) was improved in this work based on limited experimental results obtained from a bubbling fluidized-bed sewage sludge gasifier at the MaxWest facility in Sanford, Florida and published information from the technical literature. The gasifier processed sewage sludge from the communities surrounding Sanford and was operated at various air equivalence ratios and biosolid feed rates. The temperature profile inside of the gasifier was recorded over the span of four months, and an average profile was used in the base case scenario. The improved model gave reasonable predictions of the axial bed temperature profile, syngas composition, heating value of the syngas, gas flow rate, and carbon conversion. The model was validated by comparing the simulation temperature profile data with the measured temperature profile data. An overall heat loss coefficient was calculated for the gasification unit to provide a more accurate energy balance. Once the model was equipped with a heat loss coefficient, the output syngas temperature closely matched the operational data from the MaxWest facility. The model was exercised at a constant equivalence ratio at varying temperatures, and again using a constant temperature with varying equivalence ratios. The resulting syngas compositions from these exercises were compared to various literature sources. It was decided that some of the reactions kinetics needed to be adjusted so that the change in syngas concentration versus change in bed temperature would more closely match the literature. The reaction kinetics for the Water-Gas Shift and Boudouard reactions were modified back to their original values previously obtained from the literature.

Anaerobic co-digestion of municipal sludge and food wastes high in chemical oxygen demand (COD) has been an area of interest for waste water treatment facilities looking to increase methane production, and at the same time, dispose of the wastes and increase the revenue. However, addition of food wastes containing fats, oils and grease (FOG) to the conventional anaerobic digestion process can be difficult and pose challenges to utilities. Incorporating these wastes into the treatment plants can potentially inhibit the digestion process. In this study four lab-scale, anaerobic digesters were operated under mesophilic conditions and fed municipal sludge. One of them served as the control, while the other three digesters were fed with different volumetric loadings of juice processing waste, cheese processing waste (whey), dissolved air flotation waste (DAF) from a food processor, and grease trap waste (GTW), in addition to the municipal sludge. The impact of these high strength wastes (HSWs) on digester performance was analyzed for a total period of 150 days. Among the parameters analyzed were pH, total and soluble COD (tCOD and sCOD), Total and Total Volatile Solids (TS and TVS), Total Ammonia Nitrogen (TAN), Total Kjeldahl Nitrogen (TKN), Volatile Fatty Acids (VFA), Long Chain Fatty Acids (LCFA), and alkalinity. Biogas was collected and analyzed for methane content. The dewatering characteristics of digested sludge were also studied. Volatile organic sulfur compounds were analyzed on the dewatered sludge in order to monitor odors. This study showed that different high strength wastes have different impacts on digester performance. HSWs have the ability to degrade along with municipal sludge and to increase biogas production. However, anaerobic digestion can be inhibited by the presence of FOG, and addition of these wastes might not always be cost effective. Careful selection of these wastes is necessary to ensure stable digester operation, while bringing about increases in gas production. Utilities need to be cautious before adding any high strength wastes to their digesters. / Master of Science

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.