Abstract: A small-scale experiment was accomplished to evaluate effect of the bio-ecological technology combining anaerobic biogas digestor- anoxic  tank-waterfall aeration tank-constructed wetland in the treatment of domestic sewage and effect of internal recycle ratio on denitrification and deodorization effectsfunction of the technology. Results reveal that when the ratio increases from 25% to 200%, the total nitrogen removal increaseds from 15.0% to 52.3%. However, when the ratio continuesd to increase to 300%, the removal rate decreaseds to 44.7%. Besides, it is noted that hydrogen sulfide is the main source of odor that must be controlled for deodorization. The increasing internal recycle ratio leads to improved hydrogen sulfide removal efficiency. When the ratio risesaised from 25% to 50%, 100%, 200% and up to 300%, the hydrogen sulfide removal rate went up from 23.7% to 30.8%, 54.7%、82.6% and 90.1％ in the anoxic tank. And at the same time, the rate increasesd with the concentrations of dissolved oxygen (DO) and nitrate (NO₃-) in the tank. The findings show that the combined technology performs the best when the internal recycle ratio in the system is adjusted to 200%.

Key words: the internal recycle ratio, denitrification, deodorization, combination process