The characteristics of thermally regenerated activated carbon (AC) polluted with biological activated carbon (BAC) process were investigated. The results showed that the true micropore and sub-micropore volume, pH value, bulk density, and hardness of regenerated AC decreased compared to the virgin AC, but the total pore volume increased. XPS analysis displayed that the ash contents of Al, Si, and Ca in the regenerated AC respectively increased by 3.83%, 2.62% and 1.8%. FTIR spectrum showed that the surface functional groups of virgin and regenerated AC did not change significantly. Pore size distributions indicated that the AC regeneration process resulted in the decrease of micropore and macropore (D > 10 mu m) volume and the increase of mesopore and macropore (0.1 mu m < D < 10 mu m) volume in regenerated AC, which are benefit for water treatment. These results will provide a theoretical basis for the reuse of biological waste (spent AC) from BAC process. (C) 2014 Elsevier Ltd. All rights reserved.