Sludge Digestion by Anaerobic Fluidized Beds. I: Lab Performance Data

Abstract

This study was undertaken to evaluate the laboratory performance of the anaerobic fluidized bed digesting secondary biological sludge at 35 °C with four hydraulic‐retention times (HRTs): 1, 2.5, 5, and 10 days. In addition, the effects of both operating temperature (15 °C, 25 °C and 35 °C) and the initial sludge solubilization on the digester performance were also examined. It was found that at 35 °C, an adequate degree of sludge digestion was obtainable with an HRT of only 1–2 days if the influent biological sludge was presolubilized by treatment with 17.5 meq/L of sodium hydroxide. If no presolubilization was used, the necessary HRT was increased to 10 days. When the temperature was decreased to 25 °C and the sludge was presolubilized, the required HRT was 2.5–3 days. However, as the temperature was further decreased to 15 °C, the system was unable to achieve adequate digestion in as long as 10 days, even with presolubilization. It was also observed that the fluidized‐bed system was able to accept abrupt increases of loading without a corresponding buildup of excessive organic acids.