The Effect of Cations on Volatile Solids Destruction, Odors, and Dewatering in anaerobic digestion

The primary purpose of this study is to understand the effects of wastewater sludge feed cations on volatile solids destruction, odor control, and dewaterability. The role of influent feed cations and addition of chemical coagulants to sludge were evaluated for those characteristics following anaerobic digestion. Wastewater sludge samples were obtained from seven municipal wastewater treatment plants. Subsequently, batch digestion of the sludges was performed anaerobically in the laboratory with 30 days of SRT. Conditioning with cationic polymer and dewatering simulating a high solids centrifuge were performed after digestion. It was found that volatile solids destruction and volatile organic sulfur compounds generation increased proportionally as iron content in influent increased. However, they decreased as aluminum content in influent increased. It was also found that as iron content in influent increased, higher optimum polymer dose was required for dewatering. On the contrary, increase in aluminum content in influent resulted in decrease in the amount of optimum polymer dose. Direct addition of iron to the digesting sludge can be the most efficient point of addition with respect to volatile solids destruction, odor control, and conditioning of digested sludge.