Investigation of the use of aerobic granules for the treatment of sugar beet processing wastewater.

The treatment of sugar beet processing wastewater in aerobic granular sequencing batch reactor (SBR) was examined in terms of chemical oxygen demand (COD) and nitrogen removal efficiency. The effect of sugar beet processing wastewater of high solid content, namely 2255 ± 250 mg/L total suspended solids (TSS), on granular sludge was also investigated. Aerobic granular SBR initially operated with the effluent of anaerobic digester treating sugar beet processing wastewater (Part I) achieved average removal efficiencies of 71 ± 30% total COD (tCOD), 90 ± 3% total ammonifiable nitrogen (TAN), 76 ± 24% soluble COD (sCOD) and 29 ± 4% of TSS. SBR was further operated with sugar beet processing wastewater (Part II), where the tCOD, TAN, sCOD and TSS removal efficiencies were 65 ± 5%, 61 ± 4%, 87 ± 1% and 58 ± 10%, respectively. This study indicated the applicability of aerobic granular SBRs for the treatment of both sugar beet processing wastewater and anaerobically digested processing wastewater. For higher solids removal, further treatment such as a sedimentation tank is required following the aerobic granular systems treating solid-rich wastewaters such as sugar beet processing wastewater. It was also revealed that the application of raw sugar beet processing wastewater slightly changed the aerobic granular sludge properties such as size, structure, colour, settleability and extracellular polymeric substance content, without any drastic and negative effect on treatment performance.