Effect of Varying Solids Concentration and Organic Loading on the Performance of Temperature Phased Anaerobic Digestion Process

Abstract

The effect of varying total solids (TS) and volatile solids (VS) concentrations and organic loading on the performance of a temperature phased anaerobic digestion (TPAD) system treating a mixture of primary and waste activated sludges was evaluated. An optimum volatile solids destruction of 61.5% occurred at a feed concentration of 4.9% (corresponding to 3.8% VS concentration) in the system operated at a total detention time of 20 days. At a total solids concentration of 7.9% (5.8% VS concentration), the volatile solids destruction efficiency dropped to 52.5%. At all conditions (4.4 to 7.9% TS) the TPAD system was able to meet the requirements for Class A biosolids, including those for fecal coliform and volatile solids destruction. The effluent fecal coliform concentration never exceeded 628 most probable number (MPN)/g TS. Thermophilic biomass activity tests were run on both the thermophilic (55°C) and the mesophilic (35°C ) sludge. Biomass from the thermophilic reactor showed much greater activity at 55°C than at 35°C. However, significant activity was still present when the test was run at 35°C. Activity tests completed on samples from the mesophilic reactor also had high activities at 55°C, sometimes equal to the activity of the thermophilic biomass. These results suggest that the bacterial consortia in the TPAD system may be temperature-tolerant and not necessarily two distinct communities with two distinct temperature regimes as had been previously assumed. Water Environ. Res., 74, 142 (2002).

Upgrading of the anaerobic digestion of waste activated sludge by combining temperature-phased anaerobic digestion and intermediate ozonation

“…So far several studies on TPAD process have been reported (Schmit & Ellis 2001;Vandenburgh & Ellis 2002;Sung & Santha 2003), but no study was reported for treating WAS.…”

Anaerobic digestion of secondary residuals from an anaerobic bioreactor at a brewery to enhance bioenergy generation

“…Therefore, thermophilic AD (55°C) has been found to improve both biosolids and pathogen destruction over mesophilic AD (35-37°C) [3,36]. Thermophilic digesters have also been shown to better maintain high COD removal eYciencies after increases in organic loading than mesophilic digesters [14,22].…”

Energy and Resource Recovery from Sludge

“…♦ The disadvantages are (Han and Dague, 1997;Vandenburgh and Ellis, 2002) ♦ Higher energy required for thermophilic phase;…”