Aerobic Granular Biomass Technology: Recent Performance Data, Lessons Learnt And Retrofitting Conventional Treatment Infrastructure

Aerobic granular sludge has been extensively researched over the last two decades as a part of the search for more sustainable wastewater treatment solutions. Conventional activated sludge (CAS) systems have key disadvantages such as slow settling flocculent biomass necessitating large clarifiers and low reactor biomass concentrations (typically 3-5 kgMLSS/m3), large treatment system footprints and relatively high system energy usage. It has been shown at the lab, pilot and the full scale that aerobic granular sludge has distinct advantages, when compared to CAS systems, including improved settling characteristics, which in turn allows for higher biomass concentrations and hence more compact treatment systems. 

A co-ordinated research partnership in the Netherlands led to the development of the Nereda® technology – a full-scale application of aerobic granular sludge. Currently, over 30 full scale Nereda® plants are operational or under design/construction across 5 continents. The operational full-scale plants have met effluent requirements whilst achieving more sustainable wastewater treatment with key advantages outlined below (compared to similarly loaded activated sludge systems): 

• 25-75% reduction in treatment system footprints as a result of higher reactor biomass concentrations and the non-use of secondary settling tanks; 
• 20-50% energy usage reduction and;
• Associated capital and operational cost savings. 

This paper highlights the different Nereda® design configurations which have been developed to meet requirements at different sites across the world. Furthermore, results from several full-scale treatment plants are presented and the potential to extract a high-value reuse product (alginate) from Nereda® excess/waste sludge is discussed.