Temperature phased anaerobic digestion (TPAD) was tested to stabilize the sewage sludge. The performance of TPAD was evaluated based on VS removal efficiency, biogas production and biochemical methane potential (BMP). TPAD system showed higher efficiency than the control in all the performances. The major treatment was occurred in the thermophilic reactor and the mesophilic reactor acted as the post-treatment. Accordingly, most methane was produced in thermophilic and its production was increased to 0.35 L/L/d as organic loading rate increased. However, there needed a counterplan for the enhancement of TPAD system because the methane productions per unit g V Sremoved were gradually decreased. Therfore, using serum bottle potential test, co-digestion of sewage sludge and food waste was examined. The food waste could supply the organic fraction which was insufficient in sewage sludge and also sewage sludge could dilute the excess fatty acids, ammonia, and sodium ions etc. which cause inhibition to the microbial activity in treatment of food waste. As a result, co-digestion enhanced the biogas production when properly mixed. Using linear and nonlinear regressions, the food waste input of 40% was preferable in thermophilic condition. In mesophilic condition, however, as the substrate concentration increasing from 1 to 4g VS/l, the optimal proportion of food waste decreased from 40% to 20%. Consequently, TPAD process and co-digestion strategy showed distinct improvement in anaerobic stabilization. And applying co-digestion with food waste to TPAD process could be expected to make more preferable result.
