Feasibility Study of Applying Anaerobic Step-Feeding Mode for the Treatment of High-Strength Wastewater in Granular Sequencing Batch Reactors (GSBRs)

This study investigated the feasibility of applying an anaerobic step-feeding strategy to enhance performance granular sequencing batch reactors (GSBRs) in terms operational stability cultivated mature granules and nutrient removal efficiencies. Two identical 5 L were operated with a total cycle time 8 h. GSBRs high-strength synthetic wastewater (COD = 1250 ± 43, ammonium (NH4-N) 115.2 4.6, orthophosphate (PO4-P) 17.02 0.9 mg/L) for 360 days through three stages: (1) Cultivation, 125 (>2.1 mm); (2) Maturation, 175 (>3 (3) alternate feed loading R2 only 60 (anaerobic step-feeding). The granulation process, physical properties granules, nutrients, substrate recorded during entire period. For cultivation maturation stages, both followed fast single feeding mode by mixing, results indicated strong correlation between R1 due same working conditions. During stage, adopting high organic rate (OLR) at reactor start-up did not accelerate formation granules. Removal efficiency PO4-P was less than 76% period, while it exceeded 90% COD, higher 80% NH4-N without effect nitrite or nitrate accumulations simultaneous nitrification–denitrification. After changing filling only, there unexpected deterioration rapid disintegration matured (poor settleability) accompanied poor effluent quality content suspended solids because selection pressure short settling time. Consequently, operation under mixing favors stable long-term granule stability.