| The removal efficiency of aqueous humic acids by a single-stage activated sludge process and a two-stage activated sludge process was studied using synthetic wastewater, and the removal mechanism was explored by testing the element composition of the sludge, relative content of humic acids in sludge, sludge activity and the molecular weight distribution of humic acids in influent and effluent. In the single-stage activated sludge process, the removal efficiency of aqueous humic acids was keeping between 67%-84%, decreasing with the enhancement of humic acids content in the influent, and the different content of humic acids in the influent would not affect the removal efficiency of biodegradable organic matter. In the two-stage activated sludge process, the removal efficiency of humic acids in the first stage was 71.3%，better than that（60.1%） in second stage, and the removal efficiency of larger molecular humic acids was better than the smaller. Mechanism study indicated that humic acids was very difficult to be used by microorganism as carbon source, and removed by excess sludge discharge through adsorbed by activated sludge. |
