Anaerobic digestion is perhaps the simplest and most widely accepted method for solids and residuals management in the field of wastewater treatment. An emerging trend with regard to anaerobic digestion is the addition of additional organic or industrial wastes rich in degradable material (COD) that can lead to increased methane production and reduce the energy demand of the facility. The objective of this research was to evaluate the effect of adding significant quantities (>20% of feed volume) of High Strength Food Wastes (HSW) to digesters treating conventional municipal sludge by monitoring key parameters such as pH, influent and effluent solids, ammonia, Volatile Fatty Acids (VFAs) and alkalinity. Daily gas production was also closely monitored. Four digesters were set up and exposed to different food waste loading rates. A comparison was drawn between the performance of these reactors, one of which was fed only with sewage sludge and served as the control. If the bacteria in the system are able to metabolize this additional COD, it should show up as an increase in gas production with little or no increase in effluent COD. Ammonia is another crucial parameter that needs to be closely watched as it can have an inhibitory effect on methane production. As part of this study, the impact of addition of free ammonium (simulating high ammonium concentration in the feed sludge or food waste) on digester performance was assessed. The digesters were closely monitored for signs of poor performance or failure. / Master of Science

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