Volatile fatty acid (VFA) removal of anaerobically digested molasses wastewater (MWW) in aerobic sequencing batch reactor (SBR) and up-flow aerobic column reactor (UACR) under various hydraulic retention time (HRT)

Abstract

This paper analyses the removal of volatile fatty acid (VFA) of anaerobically digested molasses wastewater (MWW) in three different phases, which are acclimatization phase, aerobic sequencing batch reactor (SBR) phase and up-flow aerobic column reactor (UACR) phase. The UACR was modified from SBR by recycling the effluent to the influent tank for circulation purpose. The effect of hydraulic retention time (HRT) was determined during the operation of UACR. The influent tank was filled with 1.0, 2.0, 3.0, 4.0 and 5.0 L of anaerobically digested MWW which corresponds to HRT 14, 7, 4.7, 3.5, and 2.8 days. The operation of SBR achieved 85.4 ± 1.8 % of VFA removal at HRT 14 days. When modified to UACR, the VFA removal efficiency reached 85.5 ± 2.3 % at HRT 14 days. The VFA removal changed from 85.5 ± 2.3, 81.0 ± 0.4, 81.3 ± 2.2, 84.6 ± 5.1 to 87.4 ± 0.7 % in the UACR when the HRT decreased from 14 to 2.8 days. The UACR achieved optimum VFA removal at HRT 2.8 days and had greater performance when compared to SBR since it required shorter aeration time to obtain similar result.