Energy savings and higher volumetric loading rate achieved in the conventional anoxic–oxic process for sewage treatment by enhancing biomass retention in the secondary clarifier

Abstract

This is the first study to achieve a short HRT (∼2h for the A/O reactor), high MLSS (∼10gL−1), and high volumetric loading (∼3.7kg CODm−3d−1 and ∼0.6kg NH4-Nm−3d−1) in the A/O process for sewage treatment by enhancing biomass retention in the secondary clarifier (∼4h settling time), which we refer to as the high-performance A/O process (HP-A/O) in this paper. Over 258days of continuous operation, with a decrease in HRT from 12 to 2h, remarkable COD (95±3%), NH4+-N (98±2%), TN (79±5%), and TP (74±10%) removals were stably achieved, while the air requirement significantly decreased by 22%. The HP-A/O process offers advantages over the conventional A/O process (6–8h for A/O reactor, 3–5gL−1MLSS, and ∼1.0kg CODm−3d−1) for sewage treatment in terms of its lower energy consumption, smaller footprint and reactor requirements.