Effect of Hydraulic Retention Time and Recycle Ratio on Anoxic/Oxic Bioreactor and Artificial Wetland Performance for Domestic Wastewater Treatment

In this study, the effect of Hydraulic retention time (HRT) and recycle ratios on anoxic/oxic Bioreactor and Artificial wetland Performance for domestic wastewater treatment were experimented. Chemical Oxygen demand (COD), Ammonium nitrogen (NH4+-N), Nitrate nitrogen (NO3--N) and Total phosphorus (TP) removal were examined. The temperature was maintained at 20 to 24 and pH ranges was 7.6 – 8.1. The result revealed average COD removal efficiencies of 47, 68, 74, 83 and 85% at HRT of 1.5, 4, 2, 3 and 5hrs, and recycle ratios of 3, 2, and 1. Average removal of NH4+-N was 78, 85, 88 and 89 % at HRT of 5, 3, 4 and 1.5hrs and recycle ratios of 1, 2, and 3. Average removal of NO3--N was 92, 94, 95 and 97% at HRT of 2, 1.5, 3, 5 and 4hrs and recycle ratios of 3, 1 and 2. The average removal of TP was 78, 85, 88 and 89% at HRT of 5, 3, 2 and 1hr with recycle ratios of 1, 2, and 3 respectively. The system removed up to 74.1, 85%, 94.4% and 85% of the COD, NH4+-N, NO3--N and TP at different HRT, recycle ratios and with proper pH control using external source of alkalinity. The optimum recycle ratio was found to be 3. The result revealed high removal performance at increasing HRT and recycle ratios.