acase@tulane.edu / Worldwide, more than two billion people rely on onsite sanitation technologies for excreta treatment and/or disposal. The proper management of domestic septage remains a challenge in most cities in developing countries. A field experiment was conducted in Kinshasa/DR Congo from June 2013 to September 2015 to explore the effectiveness of lagoon treatment for the disinfection and the stabilization of domestic septage. Four lagoons were designed by combining two design factors: Total Solids content (< 5% versus 8% - 12%) and the protection from rainfall (Yes versus No). Each lagoon was a truncated pyramid with a usable volume of 28 m3 and 3m depth. The monitoring of pathogens inactivation was conducted from September 2014 over 12,4 months using coliforms bacteria and Ascaris lumbricoides eggs in sentinel chambers as indicator organisms, respectively with the multiple tubes technique and the Tulane Method. Local climate conditions and abiotic characteristics of the stored septage were monitored monthly. Four-log reduction of fecal coliforms organisms were observed within 10 months of septage storage in the two types of lagoons. At the end of this study, 3-log and less than 2-log reductions of Ascaris eggs were observed, respectively in the lagoons with high and low solids content. The inactivation curve of Ascaris eggs was characterized by a lag phase with a slight inactivation followed by an active inactivation phase. The inactivation rate constants for the active phase were 0.071 and 0.034 day-1, respectively in the lagoons with high and low solids content. Multiple linear regression model showed that the storage time, pH, and TS were significantly associated with percent Ascaris eggs inactivation. Trace elements concentrations in the final product were below threshold ceiling values for their reuse in agriculture. Total volatile solids concentration reduction in the lagoons with high solids content was below the stabilization limit set at 38% by USEPA. In conclusion, lagoon storage of domestic septage with at least 8% TS for 12 to 15 months is an effective option for the disinfection of domestic septage under the conditions of this study. The resulting biosolids constitute a value-added product which can be safely reused in agriculture. / 1 / Konde, Nkiama N.

The nitrification process, the biologically mediated process of ammonia treatment in water resources recovery facilities (WRRF), remains the most common treatment process to mitigate the adverse effects of effluent ammonia discharges in surface water. However, it is well established that the temperature-sensitive process of nitrification remains hindered at low temperatures in conventional suspended growth technologies; specifically, passive treatment systems such as the lagoons, representing over 50% of Canadian treatment facilities in operation. As such, nitrification in lagoon facilities remains unreliable during the cold seasons with no nitrification occurring at 1°C. In contrast to suspended growth systems, attached growth technologies such as the moving bed biofilm reactors (MBBR) have recently been proven capable of achieving significant nitrification rates at temperatures as low as 1°C and are proposed as suitable upgrade systems to the common lagoon facility to reach year-long ammonia treatment targets. As such, the main objective of this research is to investigate and expand the current knowledge by investigating the key research questions lacking in the current literature on post-carbon, low temperature nitrifying MBBR systems. With this aim, a temperature-controlled study of attached growth nitrification kinetics was conducted to isolate the effects of low temperatures on nitrifying MBBR system performance down to 1°C. A removal rate of 98.44 ± 4.69 gN/m³d is identified as the 1°C intrinsic removal rate and the design removal rate for nitrifying MBBR systems at low temperatures. Considering this intrinsic rate at 1°C, an assessment of reactor efficiency at elevated TAN concentrations typical of non-combined sewer systems indicates that a two reactor in-series MBBR system configuration is recommended for retrofitting lagoon facilities connected to sanitary sewers. The study of the reactor performance to temperatures as low as 1°C demonstrates a non-linear decline in removal efficiency between 10°C and 1°C, with the existence of a kinetic threshold temperature delineated between 4°C and 2°C. As such, this delineated temperature range accounts for a significant decline in the performance of low carbon nitrifying MBBR systems during the onset of the cold seasons. This research identifies new recommended Arrhenius correction coefficient values taking into account this kinetic threshold temperature, with a coefficient of 1.049 being recommended above the kinetic threshold (≥4°C) and 1.149 below the threshold temperature at 1°C. Moreover, since the elapsed time to low temperature was identified as a key factor of attached growth nitrification kinetics, a modified theta model accounting for temperature and time is proposed in this research to accurately model the rate of nitrifying MBBR systems between 4°C and 1°C. Finally, with the severe adverse effects of sudden decreases in temperature, or cold shocks, on nitrification kinetics being previously demonstrated but not well understood, this research compares acclimatized and cold shocked MBBR reactors down to 1°C. The findings indicate 21% lower kinetics in the cold shocked reactor with reactor efficiencies never reaching those of the acclimatized reactor despite extended operation at 1°C. Thus, the research delineates the potentially lasting effects of extreme weather events such as cold air outbreaks and snowmelt periods on nitrifying MBBR system performance. On the other hand, these same findings demonstrate the resiliency of nitrifying MBBR reactors as nitrification was maintained within these systems despite being cold-shocked down from 10°C and 1°C. This study of attached growth kinetics was coupled with an investigation of the nitrifying biofilms, biomass, and microbiome responses to low temperatures and cold shock down to 1°C to provide an understanding of the changes occurring in these systems down to the cellular level. Comparisons of acclimatized and cold shocked nitrifying biofilms responses down to 1°C were characterized by increases in biofilm thickness, increases in biomass viability; and, greater shifts in microbiome communities occurring above 4°C in the acclimatized biofilm. Considering these observations, results also indicated a significant increase in nitrifiers per carrier above 4°C. As such, these findings suggested that the bulk of nitrifying biofilm adaptation to cold temperatures occurs above 4°C, a crucial adaptation phase in acclimatized systems. This adaptation phase is shown to be lacking in cold-shocked systems, with the cold shocked biofilm and microbiome demonstrating significant differences with the acclimatized systems’ biofilm and microbiome. This research was performed to answer the critical research questions relating to the design and operation of the post-carbon, low temperature nitrifying MBBR systems, with the first low temperature MBBR systems being scheduled to begin operation in the fall of 2020. This research expands the current knowledge on low temperature attached growth nitrification kinetics as well as cold shocked attached growth nitrification kinetics in MBBR systems down to 1°C. In addition, this research delineates the effects of low temperatures and cold shocks on the nitrifying MBBR system’s biofilms and their embedded cells.