Abstract:
The objective of the research is to compare the efficiency of nitrogen removal for on-site wastewater treatment in order to improve the recent system. The wastewater treatment system used in this research was the aerobic on-site package system. The experiment was divided into 4 phases. Phase 1, research was conducted under aerobic nitrogen removal and a maintenance of influent wastewater at the rate of 30 liters per day. Phase 2, the experiment was focused on the anoxic-aerobic system with a capacity of 40% for anoxic and 60% for aerobic. Phase 3, the experiment was set to increase the flow rate of wastewater up to 60 liters per day. Phase 4, additional of the media to 50% of tank volume was used. The synthetic wastewater with COD of 300 mg/l and TKN 30 mg/l were used for all experiments. Sludge Retention Time (SRT) was controlled at 10 days. The rate of return sludge and internal MLSS return flow rates were equal to that of the influent wastewater. Results indicated that the COD removal efficiency of this system in phase 1 to 4 were 92.48%, 97.18%, 95.40% and 96.85 %, respectively, and the total nitrogen removal efficiency were 77.51%, 83.30%, 91.16% and 92.75 %, respectively. The results also indicated that the addition of the anoxic zone and addition of media to the system leaded to an insignificant impact on the efficiency of the COD removal. However, it affected the nitrogen removal from the system while the nitrification process was not inhibited in all phases, and a denitrification process did not occur in the first phase. Based on the total nitrogen removal, result showed that the most effective mean of nitrogen removal was found in phase 4 through maximum nitrification rate and maximum denitrification rate of 0.164 mg. NH₃-N/mg. MLVSS-day and 0.31 mg. NO₃-N/mg. MLVSS-day, respectively. In conclusion, results suggested that modification of the recent system could be conducted by additional of an anoxic aerobic portion along with setting up the paddle and recycle pump to the system in order to increase anoxic condition and stimulate denitrification of the process