Biological activated carbon (BAC) has been developed on the granular activated carbon by immobi-lization of selected and acclimated species of bacteria to treat the micro-polluted water. The BAC removal effi-ciencies for nitrobenzene, permanganate index, turbidity and ammonia were investigated. Effects of shock load-ing and SEM (Scanning Electron Microscope) observation on BAC were studied. Baekwashing and its intensity of BAC were also discussed. The results showed that BAC took short time to start up and recover to the normal condition after shock loading. The shock loading studies showed that the removal efficiency of BAC was not completely inhibited even at high concentration of nitrobenzene. Backwashing performed once every 10- 20 d,or an average of 15 d. Backwashing intensity was 12-14 L/( s·m2) with air and 3-4 L/( s·m2) with water.