BIOLOGICAL NITROGEN REMOVAL FOR LONG-TERM LANDFILL LEACHATE BY USING MLE PROCESS

This study was conducted to investigate the effects of hydraulic loading rate and recycle ratio on biological denitrification and nitrification for leachate containing NH4+-N with high concentration about 1,500 ∼ 2,000 mg/L discharged from SUDOKWON landfill site. Pilot-scale MLE(modified ludzack ettinger) process was employed in this study. As a result of this examination, we found out that about 2.3 days in denitrification tank and 5.7 days in nitrification tank are the optimal HRT for obtaining the removal efficiency of about 80 % for T-N and 99% for NH4+-N at the conditions of recycle ratio of about 600 % and BOD/NH4+-N ratio of about 3.0. In addition, optimal recycle ratio for obtaining the maximum nitrogen removal efficiency while keeping proper microbes concentration in nitrification and denitrification tank was 200 % for external recycle and about 400% for internal recycle. The maximum removal rates for each load of T-N and NH4+-N were 0.055kgT-N/kgVSS/d and 0.07kgNH4+-N/kgVSS/d, respectively. The ratio of alkalinity consumed per T-N removed in this process (Δalkalinity/ΔT-N) was about 5.0.