Aerobic Granulation - Pilot Research in Aerobic Granular Sludge

Pilot Research in Aerobic Granular Sludge

Aerobic granulation technology for the application in wastewater treatment is widely developed at laboratory scales. The large-scale experience is still limited but different institutions are making efforts to improve this technology:

• Since 1999 DHV Water, Delft University of technology (TUD), STW (Dutch Foundation for Applied Technology) and STOWA (Dutch Foundation for Applied Water Research) have been cooperating closely on the development of the aerobic granular sludge technology (Nereda). In September 2003, a first extensive pilot plant research was executed at STP Ede, the Netherlands with focus on obtaining stable granulation and biological nutrient removal. Following the positive outcome together with six Dutch Water Boards the parties decided to establish a Public-Private Partnership (PPP)- the National Nereda Research Program (NNOP)- to mature, further scale-up and implement several full-scale units. As part of this PPP extensive pilot tests have been executed between 2003 and 2010 at multiple sewage treatment plants.

• From the basis of the aerobic granular sludge but using a contention system for the granules, a sequencing batch biofilter granular reactor (SBBGR) with a volume of 3.1m3 was developed by IRSA (Istituto di Ricerca Sulle Acque, Italy). Different studies were carried out in this plant treating sewage at an Italian wastewater treatment plant.

• The use of aerobic granules prepared in laboratory, as a starter culture, before adding in main system, is the base of the technology ARGUS (Aerobic Granules Upgrade System) developed by EcoEngineering Ltd.. The granules are cultivated on-site in small bioreactors called propagators and fill up only 2 to 3% of the main bioreactor or fermentor (digestor) capacity. This system is being used in a pilot plant with a volume of 2.7 m3 located in one Hungarian pharmaceutical industry.

• The Group of Environmental Engineering and Bioprocesses from the University of Santiago de Compostela is currently operating a 100 L pilot plant reactor.

The feasibility study showed that the aerobic granular sludge technology seems very promising (de Bruin et al., 2004. Based on total annual costs a GSBR (Granular sludge Sequencing Batch Reactors) with pre-treatment and a GSBR with post-treatment proves to be more attractive than the reference activated sludge alternatives (6-16%). A sensitivity analysis shows that the GSBR technology is less sensitive to land price and more sensitive to rain water flow. Because of the high allowable volumetric load the footprint of the GSBR variants is only 25% compared to the references. However, the GSBR with only primary treatment cannot meet the present effluent standards for municipal wastewater, mainly because of exceeding the suspended solids effluent standard caused by washout of not well settleable biomass.