Organic matter removal under high loads in a fixed-bed sequencing batch reactor with peach pit as carrier

In this study, the evaluation of organic matter removal at high loads from synthetic wastewater was performed using a Fixed-bed Sequencing Batch Reactor (FSBR), in which peach pits were used instead of conventional carriers. The FSBR performance on organic matter removal at different organic loading rates (2-12 kg COD m^-3 d^-1) was significant. Organic matter removal efficiency was >90% at a loading rate less than 7.2 kg COD m^-3 d^-1. When the organic loading was 12 kg COD m^-3 d ^-1, organic matter removal in the FSBR and SBR reactors reached 71.84 and 56.57%, respectively, indicating that the FSBR performance is significantly higher than the SBR reactor. According to the higher efficiency of SBR with media, this comparison shows that bio-film bioactivity (7.06 ± 0.3 mg O₂ mg-VSS^-1 d^-1) is significantly higher than suspended biomass bioactivity (2.92 ± 0.149 mg O₂ mg-VSS ^-1 d^-1). As the OLR increased from 3.4 to 10 kg COD m ^-3 d^-1, the observed yield (Y_obs), the specific biomass growth rate (μ_overal) and the endogenous decay rate (k_d) increased from 0.018 to 0.02 g VSS g^-1 COD ^-1, 0.1 to 0.2 d^-1, and from 0.082 to 0.067 d ^-1, respectively, while the solid retention time (SRT) decreased from 40 to 19.8 d.