EVALUATION OF PARAMETERS TO MEASURE SLUDGE AEROBIC STABILIZATION. (VOLUMES I AND II).

摘要

There are no generally accepted, rational criteria to determine sludge stabilization. This research evaluated parameters to determine sludge stability from the viewpoint of the potential for odors and putrefaction of sludges in the environment.; Batch reactors and aerobic digestion were used to evaluate parameters to measure sludge stability. Factors such as the type of sludge, initial solids concentration, sludge age in the prior activated sludge process, temperature, pH and detention time were evaluated. The hydrogen-sulfide index was used as a direct measure of sludge odor and putrefaction potential and as a yardstick to evaluate other indirect parameters such as biodegradable volatile solids content, specific oxygen uptake rate, chemical oxygen demand (soluble), five-day biochemical oxygen demand (soluble), nitrate-nitrogen, percent nitrification, pH, alkalinity and qualitative microbial observation. First-order and retardation-rate kinetic models were used to describe solids degradation. The stability criteria utilized were: a hydrogen-sulfide index value of 60 days, a specific oxygen uptake rate of less than or equal to 2.0 milligrams oxygen/gram volatile solids/hour, and a biodegradable volatile solids reduction of 95 percent.; The results indicated that indirect measures of stabilization were not dependable to determine sludge stability. A direct measure of sludge odor and putrefaction potential would be a superior basis for stability determination. No single parameter or set of parameters was found to be satisfactory as a simple and quick measure of sludge stability. Several variables affected the detention time required to produce a stable sludge. The magnitude of the first-order decay coefficient was affected by several variables. The first-order and retardation-rate models were satisfactory in describing solids degradation for the waste activated and mixed primary/waste activated sludges evaluated, but not for primary sludges. Nitrification and nitrogen loss to the extents of 5-44 percent and 24-53 percent, respectively, were observed during stabilization.