The Nereda® aerobic granular biomass is an innovative wastewater treatment technology for biological nutrient removal that is considered to be a game-changing innovation offspring of the conventional activated sludge process (CAS).
Nereda® is currently applied at a dozen industrial and urban wastewater treatment plants, all showing significant improvements with regard to process stability, effluent quality (typically TN < 5 mg/l, TP <1 mg/l), and energy savings (>35%), compared to CAS processes.
Aerobic granular biomass has several advantages over conventional activated sludge flocs. These include excellent settling ability resulting in better biomass retention and higher biomass concentrations and the ability to withstand large variations in flow and load. As a result compact reactor design reduces plant footprints and total treatment costs significantly.
The Epe WWTP was designed and constructed by Royal HaskoningDHV in 2010-2011 Three Nereda® reactors handle flows of on average 8.000 m3/day and with peaks of 36.000 m3/d. The plant has to meet stringent effluent limits even at temperatures of 8°C. For start-up the influent to the Nereda® system was progressively increased to 100% over a period of four months, whilst granules were building-up within the bioreactors. This ‘granulation period’ included winter months with wastewater temperature well below 10°C. The full scale results showed not only the average but even the 95%ile figures meeting the stringent demands. Industrial discharges create large fluctuations in the feed, most notably pH-values frequently peaking above pH 10. Such peaks caused complete loss of nitrification in the CAS system. The Nereda®, showing remarkable process stability, was never influenced by these peaks. A key advantage of Nereda® is the reduced power consumption. At Epe, the introduction of the Nereda process reduced the energy consumption from 3.500 kWh/d to 2.000-2.500 kWh/d. A benchmark proves this to be >40% less compared to similar sized conventional plants in the Netherlands.
The Frielas WWTP is a 70.000 m3/d plant in Greater Lisbon, suffering from several operational constraints, especially bulking sludge. To validate the applicability of Nereda one of six CAS reactors was retrofitted into a Nereda® to run in parallel to the remaining five. The Nereda® proved to achieve a much better stability, better effluent quality (at 2,5 times the loading rate) and nearly 50% reduction in overall energy consumption (of which 35% through more efficient aeration). Additional benefits of Nereda® have proven to be its stability at high and fluctuating salinity and the high degree of recovery of biopolymers or alginate.
With tank-sizes similar to the world’s largest SBR tank volumes, the technology is mature and ready to be applied. It can meet stringent demands at appreciable lower CAPEX and OPEX, and smaller footprints than existing solutions (for more info: nereda@rhdhv.com).