Aerobic Granular Sludge Start-up under Varying Wastewater Compositions - A Pilot Study at Ryaverket WWTP

Abstract

Aerobic granular sludge (AGS) is a promising technology for biological wastewater treatment that offers advantages over activated sludge treatment in terms of com pactness, energy efficiency and treatment performance. In this study, the start-up of three pilot scale AGS reactors at Ryaverket wastewater treatment plant was investi gated, where the effect of seeding culture and wastewater composition on granulation and treatment performance was evaluated. The reactors were operated with acti vated sludge or mature granules, and with raw or pre-sedimented wastewater. The results showed that nitrification and carbon degradation were effectively estab lished in all reactors, while denitrification and biological phosphorus removal were deficient, probably due to suboptimal operating conditions. The reactor with mature granules generally showed the best treatment performance, but overall, no reactor achieved sufficient treatment as the outgoing wastewater exceeded the limit val ues for total nitrogen and total phosphorus. The use of pre-sedimented wastewater was considered to be disadvantageous for biomass build-up due to the low substrate available. In addition, the results showed that starting with mature granules achieve better purification, which can also be established more quickly.